50 years of D11

25 Sept 2022, 11:45 → 28 Sept 2022, 16:00 Europe/Paris

ILL4/rdc-1 - Amphi Chadwick (ILL4)

Thank you to all those who participated in the symposium dedicated to the 50 year anniversary of D11!

The 50th birthday of D11
A History of SANS at the Institut Laue – Langevin

In September 1972 the first user experiment was performed on D11, the archetype pin-hole SANS at the Institut Laue – Langevin. On the occasion of the 50th anniversary of D11 a symposium celebrated this achievement as a satellite meeting to the XVIII International Small-Angle Scattering Conference (SAS2022). 

The symposium took place as an in-person meeting from 26-Sep until 28-Sep 2022.

Attendees are invited to submit an article for a special issue to appear in The European Physical Journal E (EPJ E).

Deadline for article submission is October 31st 2022.

You can download the timelapse video of the upgrade work on D11 at the following link.

Sunday, 25 September

Reception and welcome buffet (from 5pm)

Monday, 26 September

Talks: Chair: Jacques Jestin

1 Science Director's Welcome

Speaker: Jacques Jestin

2 The 1980s and the first D11 modernistion program

D11 was conceived and designed by Konrad Ibel, Werner Schmatz and Tasso Springer and became operational in 1972 shortly after ILL’s first neutron beams became available. Soon after a high angle data bank (D11B) was added by Gernot Kostorz for studying diffuse scattering. The first few years were devoted to many pioneering experiments in the fields of polymers, materials, metallurgy as well as structural biology. In parallel rapid progress was made in software development (Ron Ghosh) although the fundamental design of the instrument remained constant. In the early 1980s at Oak Ridge Wally Koehler had built a 30m SANS instrument whose novel feature was having the 2-dimensional detector mounted on a trolley inside the tube. This was a major motivation for us to initiate a whole series of modifications to modernise D11. A new detector tube was installed with the detector moving inside on a trolley, the instrument control system underwent a major renewal, sample changers and beam stops were automated new sample environments introduced and old ones improved . In my talk I will attempt (within the constraints of 40 years memory) to describe the evolution of D11 in these early years and to show some examples of the data obtained.

Speaker: Peter Timmins (ILL retired)

3 D11, the stimulus for early biology at ILL

Following a period of strong development of the contrast variation method using H2O/D2O exchange on physical-chemical and readily available soluble protein samples,D11 hosted a number of challenging experiments in biology—in particular on protein-nucleic acid interactions. Important results were obtained on the inner structures of plant viruses, ribosomes and chromatin. A study of aminoacyl-tRNA synthetases interactions with their tRNA substrates established in-beam structural biochemistry on D11.

Speaker: Joseph Zaccai

4 Using X-ray and neutron scattering to analyze nanoparticles for drug and RNA delivery

Speaker: Heinrich Haas (BioNTech AG)

Coffee break + discussion

Talks: Chair: Peter Timmins

5 Polarised neutron scattering from dynamic polarised nuclei.

It was in September 1972 when Konrad Ibel and myself put a solution of sperm whale myoglobin into the sample chamber of D11. To our great surprise it was after a few seconds of irradiation by thermal neutrons – I think the A-selector was not yet in place – when a beautiful central peak of scattered neutron intensity emerged on the screen, the first picture of neutron small-angle scattering with D11.
The was also the beginning of neutron small-angle scattering from macromolecules in mixtures of heavy water, D2O, and H2O. The large difference in the scattering lengths of the isotopes 1H (=H) and 2H (=D) has been beneficial for studies of composite structures like membranes, nucleoproteins, lipoproteins and viruses. The demand of beam time largely exceeded the time available at D11.
At the same time Hayter, Jenkins and White (Physical Chemistry Laboratory Oxford) came up with a method using the spin dependence of the interaction of polarised neutrons with polarised protons. The variation of the scattering length b with proton polarisation largely exceeds that obtained with isotopic substitution. No echo for a long time.
About a decade later, a growing interest of neutron scattering from dynamic polarised bulk protons in macromolecules developed, mainly triggered by the introduction of glassy hydrogenous substances as polarized target material in high energy physics (reviewed by Niinikoski, 2013). The selective depolarisation of dynamically polarised proton spins or deuteron spins by the method of adiabatic fast passage (AFP) in specifically deuterated ribosomal particles has been extensively used in polarised neutron small-angle scattering in collaboration with CERN (Knop et al. 1986, Willumeit et al. 1996). This method which became known as nuclear spin contrast variation has also found numerous applications in structural studies on polymers (Koghi et al. 1987, Glättli et al. 1989, Kumada et al. 2010). This work was done outside the ILL.
What about the evolution of proton polarisation at the onset of microwave irradiation? The answer could be interesting with radical proteins, like tyrosyl doped catalase. The study of free radicals of different size would help to find an answer. On that substantially enlarged basis a Swiss-French-German collaboration was established. The polarised target facility from PSI was temporarily installed at the instrument D22 of the ILL. In fact, the results from solutions of free radicals were quite clear. The creation of a local proton polarisation in the vicinity of an unpaired electron is followed by its diffusion into the bulk. The barrier confining the domain of local polarisation is identical with the molecular surface of small free radical molecules dissolved in a deuterated solvent. With larger free radical molecules an intramolecular magnetic spin diffusion barrier cannot be ignored.
Now let us turn to catalase. This enzyme converts hydrogen peroxide incredibly fast into water and oxygen. Replacing one of the hydrogens of the H2O2 by CH3CO this derivative is accepted by catalase like H2O2 but treated in a quite different way: first, the response is slow and, second, after some intermediate steps, one of its amino acids, tyrosine, is converted to a tyrosyl radical. The number of tyrosyl radicals created in this way is small, typically less than one among the 500 amino acids of one of the four subunits of catalase molecule. The contribution of a small domain of reasonably strong polarised protons near a tyrosyl radical to the polarisation dependent scattering intensity is expected to be small. The direction of DNP has been changed several thousand times in order to obtain the polarisation dependent scattering intensity of only 1/1000 of the total intensity with a sufficient accuracy. The unpaired electron is probably that of the tyrosines fairly close to the centre of the catalase molecule (Zimmer et al. 2016).
A more sophisticated version of time-resolved neutron scattering using the inversion of the proton polarisation by AFP appears to confirm the existence of the tyr-369 radical in agreement with an earlier analysis of the EPR of tyrosyl doped catalase (Hautle et al. manuscript in preparation).

Speaker: Heinrich Stuhrmann (retired)

6 Small angle scattering: scaling cross-sections and widening the q-window to answer scientific questions

We will recap published and unpublished work initiated on D11, D17 and D1B with J.B. Hayter: what happens at low-q and high-q for common and uncommon ionic micelles made from self-assembled amphiphiles in a given solvent?

In the standard SAS range, the Hayter-Penfold decoupling procedure work well for all ionic micelles investigated as long as the chain length is not too short or too long.

As suggested by Luzzati, the absolute scale was crucial to go beyond wild shape fitting of a broad peak with unphysical parameters: from then, the micellar growth controlled by the area per molecule in the lateral equation of state was understood.

But there are still fully open questions, even after 50 years of active X-ray/neutron work on “simple” systems that were not fully understood last century, even for systems where an apparent implicit consensus on unproven facts are favored by the absence of absolute scale and comparison of the results with models.

We will give three examples:

• At high-q, in the range 0.4 Å$^{-1}$ to 0.6 Å$^{-1}$, there is only very few published work about localization of methyl end-groups and this only for saturated aliphatic chains.[1]

• At low-q, there is sometimes an elusive intensity upturn following $q^{-1}$ or $q^{-2}$:[2] this may be related to flexible necklaces of "flocculated" micelles with threadlike images in electron microscopy, common in the case of magnetic nanoparticles, as suggested by J.B. Hayter and R. Pynn.[3] Their domain of existence as a function of ionic strength is not yet identified.

• there are several observation of non-spherical micelles close to cmc. Theoreticians don’t believe experimentalists observations because it is contradictory with elastic theory. We suggest that taking the chain packing as well as the head elastic contributions with one parameter, and not only one with two unphysical bending constants of a molecular film, may solve this long-standing scientific problem.

As always, a broad q window and comparing data on absolute scaled with different predictive models lead to solid scientific progress beyond multiparametric fitting with or without Fourier transforming the data.

1. B. Cabane, R. Duplessix, and T. Zemb, J. Phys. France 46, 2161-2178 (1985), DOI: 10.1051/jphys:0198500460120216100
2. B. Hammouda, J Res Natl Inst Stand Technol. 2013; 118: 151–167, DOI: 10.6028/jres.118.008
3. W. A. Hamilton, P. D. Butler, S. M. Baker, G. S. Smith, John B. Hayter, L. J. Magid, and R. Pynn, Phys. Rev. Lett. 74, 335 (1995), DOI: 10.1103/PhysRevLett.72.2219

Speaker: Thomas Zemb

7 How SANS reveals the nanostructure and moisture interactions of wood cell walls

Wood is an abundant biological material with various technical applications ranging from sustainable building materials to advanced functional materials made of nanocelluloses. The structure of wood cell walls is hierarchical, consisting of well-oriented, elongated units from the molecular level to the macroscale. Our picture of the complex composite-like structure of wood cell walls and its interactions with water has become more accurate during the past decade, and results obtained with small-angle neutron scattering (SANS) have played an important part in this development.

SANS can be used to observe the structure of wood cell walls from the level of cellulose microfibrils (diameter 2-3 nm) to microfibril bundles (diameter 10-20 nm) and above. It detects the moisture-induced swelling of the microfibril bundles, which can be analysed using the WoodSAS model [1]. This model allows also determining the diameter of microfibril bundles in the wet state, without cutting the cell walls [2]. We have subsequently used SANS for in situ experiments investigating the drying behavior of wood [3] and the exchange of liquid water within the fibrillar structures [4]. All of these studies were based on SANS experiments carried out at D11.

References
[1] Penttilä, P.A., Rautkari, L., Österberg, M., Schweins, R. (2019) J. Appl. Crystallogr., 10.1107/S1600576719002012
[2] Penttilä, P.A., Altgen, M., Awais, M., Österberg, M., Rautkari, L., Schweins, R. (2020) Sci. Rep., 10.1038/s41598-020-77755-y
[3] Zitting, A., Paajanen, A., Rautkari, L., Penttilä, P.A. (2021) Cellulose, 10.1007/s10570-021-04204-y
[4] Penttilä, P.A., Zitting, A., Lourençon, T., Altgen, M., Schweins, R., Rautkari, L. (2021) Cellulose, 10.1007/s10570-021-04253-3

Speaker: Paavo Penttilä (Aalto University)

8 SANS Crystallography

Soon after the advent of High-Tc superconductors, it became clear that that important information could be obtained by observing the lattice of quantised flux lines in these and other unconventional and conventional superconductors. This meant that SANS scattering patterns contained Bragg peaks had to be analysed. I will compare the state of the art of early experiments with what is available today to investigate flux line lattices and other mesostructures, including Bayesian analysis and quasi-monochromatic (as on D11) versus TOF SANS techniques.

Speaker: Edward M Forgan

Lunch

Talks: Chair: François Boué

9 Hard problems in soft matter - a not quite random walk through 30 years of soft matter research with neutrons (remote)

The small-angle instruments at ILL have been instrumental for our soft matter research during the last 30 years. I will illustrate this with a number of research projects where SANS has been key in elucidating structural properties of various soft matter systems, covering diverse topics such as the formation of polymerlike micelles, the kinetics of the micelle-to-vesicle transition, gel structures formed in an arrested spinodal decomposition in solutions of globular proteins, and the response of soft microgels to high packing densities. Particular attention will be given to the importance of interdisciplinary interactions and the role of computer simulations when attempting to interpret and understand results obtained with complex soft matter systems.

Speaker: Peter Schurtenberger (Lund University)

10 Exploring the influence of nanoparticles on the polymer chain conformation: from solution to nanocomposites

Adding nanoparticles (NPs) to polymer solution or melt is an efficient strategy to improve the macroscopic polymer behavior (viscosity, mechanical reinforcement…) and design hybrid macromolecular materials with enhanced properties. Among the vast literature dealing with NPs and polymer, one fundamental question arises: do NPs modify the global and local polymer chain conformation? Such issue is highly relevant since chain conformation is a central concept in polymer science and its description is essential for understanding the physical and dynamical properties of polymers. While in solution there is a general consensus on chain collapse, it is more controversial in melt for which chain swelling, contraction or no perturbations have been observed.

Small-Angle Neutron Scattering (SANS) can directly answer this question thanks to the Zero Average Contrast (ZAC) method, which is an elegant approach to cancel out the scattering of the NPs by using an appropriate amount of hydrogenated and deuterated polymer in order to only measure the signal of a single polymer chain. Then, the analysis of the scattering spectra gives a radius of gyration from which we can deduce if the polymer contracts, swells or remains unperturbated in the presence of NPs. By investigating the behavior in both solution and melt, we can also figure out if there is a connection between chain conformation in solution with NPs and chain conformation in nanocomposites without solvent. During this talk, I will first present SANS results on both systems (polymer nanocomposites (PNCs) and polymer solution) and show the influence of NP size (from 1 nm to 20 nm), NP concentration and nature of NP/polymer interaction (attractive or repulsive) on the Rg evolution. Then, I will also address the influence of NPs on the chain deformation to get more insights into the mechanical reinforcement in PNCs. For the latter study the D11 spectrometer played a primordial role to access the stretched chain form factor.

Speaker: Nicolas Jouault (Sorbonne-Université, Laboratoire PHENIX)

11 Understanding dipeptide-based hydrogels

Small angle scattering is a really useful technique to understand the self-assembly of a range of N-functionalised dipeptides. These form micellar structures at high pH and gels at low pH. Gels with different properties can be formed by controlling the micellar species present prior to gelation, for example by changing the counter-ion, by the addition of salts or by a heat-cool cycle. To understand all of this, we have used small angle neutron scattering, for example using contrast matching approaches to understand the molecular packing and rheo-SANS to follow the gelation process with time.

Speaker: Dave Adams

12 Conference photo

Coffee break + discussion

Talks: Chair: Charles Dewhurst

13 Ever higher magnetic fields, ever larger magnetic structures (remote)

A magnetic field is one of the many tools that we can use to tune or adjust materials. In some cases, this is through the very direct coupling to atomic magnetic moments, giving rise to new structures. In other cases, the interaction is on the microscopic scale, for example, the rotation or growth of magnetic domains over a wide range of length scales. Some materials do not have direct magnetic degrees of freedom, but due to their shape can still respond to the direction imposed by a magnetic field. In this talk, I will show how this tool, the magnetic field can been used to control what appears in the small angle scattering domain.

Speaker: Elizabeth Blackburn (Lund University)

14 Multiscale micro-architecture of pore space in rocks: size, shape, deformation and accessibility (remote)

The interface between rock matrix and pore space in sedimentary rocks is rough over seven orders of magnitude of the linear scale, from sub-nanometers (nearly molecular) to centimeters. Since the early 1980's, pore-matrix roughness has often been described using the framework of Mandelbrot's fractal geometry and the corresponding mathematical formalism for correlation functions; this formalism has been applied to successfully model the power-law SANS and SAXS results for many types of sedimentary rocks (e.g. sandstones, shale, carbonates and coal). P.W. Schmidt first established the connection between pore-size distribution (as an alternative expression of roughness) and the power-law dependence of small-angle scattering intensity, and within a decade, the vast world of fractals in natural porous media was revealed.
Small-angle scattering is uniquely suited to microstructural geological applications, given its capacity to provide volume-average nano- and microstructural information, and its sensitivity to the chemical composition of pore content. In the early days, the crucial issue was the extent of the Q-range (hence the pore sizes). The capacity to study pore sizes was limited by the small-Q limit of the longest-base SANS instrument D11; this range was then greatly improved in 1997, following the construction of a Bonse-Hart type USANS instrument by M. Agamalian. Since that time, pore sizes ranging from sub-nanometeres to approximately 20 micrometers can be investigated using SANS-USANS. The capability of long base SANS instruments using wavelengths of ca. 5 Å to provide overlap with USANS data in the region around Q≈10-3 Å-1 has been crucial to the elimination of multiple scattering, a problem specific to strong scatterters (like most rocks), and inescapable for the modern lens-geometry and TOF SANS instruments. Technical developments resulting in low background noise of modern SANS detectors have enabled precise insight into the nano- and sub-nanometer scale regions, which led to the discovery of the ubiquitous phenomenon of gas condensation in the nano-pores of shales and carbonates. Similar results have been obtained for coal and aerogels.
A seminal step occured with the gradual development of SANS and USANS contrast matching capability, delivered by high pressure gas environmental cells, which offered significant progress compared to the use of deuterated liquids in earlier contrast matching experiments. This made it possible to independently characterise the total porosity, specific surface area and pore size distribution for porous spaces that are accessible and inaccessible to penetrating fluids (greenhouse gases in particular). Significantly, for a great majority of measured rocks, the roughness of the matrix - pore interface of the accessible pores turned out to be less accentuated than that of the inaccessible pores. This provided an interesting insight into the long-standing fundamental question of the origin and temporal persistence of porosity in rocks; in addition to the antisintering mechanism proposed by M. Cohen, the reactive transport of brine through the rock matrix likely plays a significant role. The recently added uniaxial stress capability enabled SANS and USANS measurements under simulated pressure conditions encountered in unconventional shales subjected to hydraulic fracturing. The results showed that the porosity response to simulated well-management is complex: it is both pore-size-dependent and thermal-maturity dependent. Armed with these capabilities, small angle neutron scattering has become a mainstream tool in petrology and geology on the nano- and microscale, applied in tandem with electron microscopy, gas adsorption measurements, mercury intrusion porosimetry and SAXS-USAXS .

Speaker: Andrzej Radlinski (University of Warsaw)

15 D11: a fantastic instrument for conservation, restoration and the study of ancient technologies in Cultural Heritage

Artefacts of interest in cultural heritage (CH) are often rare, precious, manifolds and complexes and their secrets are difficult to disclose.
The D11 instrument at Institut Laue Langevin (ILL) is a very unique instrument to investigate CH samples and their history. D11 uses: neutrons that are a no-destructive probe and the small angle neutron scattering (SANS) technique covering four decades in Q, i.e. it is able to investigate dimensions between the Å to some hundreds of microns, a very interesting range of investigation for complexes systems as those of interest in CH. Furthermore the fact that with neutrons we can investigate light elements and to use contrast methods to make in evidence some specific part of the systems makes D11 the best and very versatile instrument for these kind of studies. We will present here three applications of D11 to CH systems: a study on ancient paper to shade light on the mechanisms of the paper degradation [1]; a study of the porosity of ancient ceramic and how it is related to a specific technique of production and the historical context [2]; a study of the characteristics of nanoparticles of alkaline earth hydroxide to drive their production on large scale, for curative and preventive eco-friendly treatments of waterlogged wood [3].

References:
[1] M. Missori, C. Mondelli, M. de Spirito, C. Castellano, M. Bicchieri, R, Schweins, G. Arcovito, M. Papi and A. Congiu Castellano "Modifications of the mesoscopic structure of cellulose in paper degradation" Phys. Rev. Lett. 97 (2006) 238001
[2] Mondelli, C; Zorzi, S; Ricci, G; Galvan, V; Balliana, E; Schweins, R; E. Cattaruzza.
“Exploring the Porosity in Ceramics at the nm Scale: From Understanding Historical Ceramics to Innovative Materials Design” European journal of chemical physics and physical chemistry (2020) Vol. 21, Issue 10, 966-970
[3] G. Taglieri, V. Daniele, L. Macera, R. Schweins, S. Zorzi, M. Capron, G. Chaumat and C. Mondelli
“Sustainable Nanotechnologies for Curative and Preventive Wood Deacidification Treatments: An Eco-Friendly and Innovative Approach.” Nanomaterials (2020) Volume 10, Issue 9, 1744

Speaker: Claudia Mondelli (CNR-IOM-OGG)

16 Fighting Gravity on D11

To use the minimum q of a SANS instrument we require the longest collimation and detector distances combined with the longest wavelength. This combination maximizes how much gravity curves the neutron beam and how much the beam is spread due to the range of wavelengths. D11 is the only gravity limited SANS instrument in the world where at minimum q gravity prevents any transmission through the collimation above a certain wavelength and the beam also falls off the bottom of the detector. To solve these problems initially the use of a prism was employed providing a refracted angle to counter the fall in gravity. This worked in principle but suffered from absorption and scattering from the prism material and was limited to very small beams. Inspired by the horizontal reflectometer FIGARO, a reflective surface of one of the guides in the collimation was found to be able to undo the effects of gravity without the beamsize restriction. Combined with a lens, this allowed a minimum q of 7x$10^{-5} Ang. ^{-1}$ to be measured. A scientific example of a system that would profit from this minimum q will be presented.

Speaker: Robert Cubitt (ILL)

Poster session/Wine and Cheese evening

Tuesday, 27 September

Talks: Chair: Giovanna Fragneto

17 D11 & Small Angle Neutron Scattering – A Paradigm of ILL (remote)

D11 at the ILL Grenoble is an exceptional tool for diverse areas of European and worldwide science and technology. Its value stems from the pioneering work of Springer, Schmatz and Ibel, (1,2) and the quality of a sequence of “instrument responsibles”, technicians and users since 1972. Long wavelength, well collimated neutron beams has been a success everywhere. I will touch on some pleasant examples of our experiences:

1973 at the start of biological work- Collagen and Tobacco Mosaic Virus- with Andrew Miller and Peter Timmins,
1974 the first spin echo instrument- with Ferri Mezei, -
1979 the Deuxieme Souffle,
2009 Saving a Figaro experiment with Jared Raynes, Peter Lindner,
2015 Australian High Court re. what is an emulsion ?-with Andrew Jackson,
20o22 Current USANS from Emulsions on Kookaburra, ANSTO with Liliana de Campo, Kevin Galvin.

Many people have participated in other major work at ILL including John Hayter, Maurice Leslie, Graham Jenkin, Robert Thomas, Jeff Penfold, Ron Ghosh, Karen Edler. I am glad to acknowledge them.

(1) J. Mol. Bid. (1969) 41,231-236 Neutron Small-angle Scattering from Aqueous Solutions of Oxy- and Deoxyhaemoglobin R. SCHNEIDER, A. MAYER Physik-Department der Technischen Hochschule, Miinchen, Germany W. SCHMATZ, B. KAISER AND R. SCHERM Institut fiir Festktirper- und Neutronenphysik der Kernforschungsanluqe Julich, Germany (Received 15 November 1967, and in revised form 1 January 1969)
(2) Theory of a velocity focussing instrument for neutron small angle scattering” K Ibel, W. Schmatz, T Springer, Kernphysik und Kernchemie, Atomkernenergie 17, 13-18, 1971

Speaker: John W. White

18 Kinetics Pathways of Block Copolymer Self-assembly in Solution: transitions, logarithmical relaxations, molecular exchange and effect of crystallinity

Self-assembled systems are generally highly dynamic structures characterized by molecular exchange, fluctuations and fusion/fission and morphological transitions. Examples include micelles formed by synthetic surfactants and block copolymers as well as lipid membranes. Despite their importance in technological and biomedical applications, the kinetic pathways associated with the formation and molecular transport of such self-assembled nanostructures are generally poorly understood. Time-resolved small-angle X-ray/neutron scattering (TR-SAXS/SANS) is powerful technique [1] that allow non-equilibrium kinetic processes such as nucleation processes [2,4] and morphological transitions [3,5] to be followed with structural resolution over time scales starting from a few milliseconds. Neutrons have the additional advantage of facile contrast variation through H/D substitution schemes, which also allow equilibrium processes such as molecular exchange and diffusion to be studied without perturbation [1,6-8].
In this presentation we will address the basic kinetic pathways found in block copolymer micelles formed by amphiphilic self-assembly. We will address both equilibrium and non-equilibrium kinetics and argue that the understanding of kinetic pathways can be utilized to manipulate and design the physical properties of self-assembled systems. The mechanism of molecular exchange in block copolymer micelles that was tediously studied at D11 in the early 2000s and the rather dramatic effect of polydispersity will be discussed in detail . Furthermore, we shall discuss the role of confinement and crystallinity on the stability and molecular transport processes in semi-crystalline micelles [8,10] and telechelic polymer micelles [11,12] and discuss the relevance to biological systems and biomedical applications.

References
[1] R. Lund, L. Willner and D. Richter, Adv Polym Sci, 2013, 259, 51–158.
[2] R. Lund, L. Willner, M. Monkenbusch, P. Panine, T. Narayanan, J. Colmenero and D. Richter, Phys. Rev. Lett., 2009, 102, 188301.
[3] R. Lund, L. Willner, D. Richter, P. Lindner and T. Narayanan, ACS Macro Lett., 2013, 2, 1082–1087.
[4] G. V. Jensen, R. Lund, J. Gummel, M. Monkenbusch, T. Narayanan and J. S. Pedersen, J. Am. Chem. Soc., 2013, 135, 7214–7222.
[5] G. V. Jensen, R. Lund, J. Gummel, T. Narayanan and J. S. Pedersen, Angew. Chem. Int. Ed., 2014, 53, 11524–11528.
[6] R. Lund, L. Willner, J. Stellbrink, P. Lindner and D. Richter, Phys. Rev. Lett., 2006, 96, 068302.
[7] S.-H. Choi, T. P. Lodge and F. S. Bates, Phys. Rev. Lett., 2010, 104, 047802.
[8] T. Zinn, L. Willner and R. Lund, Phys. Rev. Lett., 2014, 113, 238305.
[9] T. Zinn, L. Willner, V. Pipich, D. Richter and R. Lund, ACS Macro Lett., 2015, 4, 651–655.
[10] König, N., Willner, L., Pipich, V., Zinn, T., & Lund, R. Phys. Rev. Lett, 2019. 122(7), 078001.
[11] König, L. Willner, N, Mahmoudi, V. Pipich and Lund, R Phys. Rev. Lett., 2020, 124, 197801.
[12] T. Zinn, L. Willner and R. Lund ACS Macro Lett., 2016 5(12), 1353-1356

Speaker: Reidar Lund

19 Electrostatic Self-Assembly in Solution: Structure, Function and Switching

With regard to the increasing need for sustainable energy, developing strategies to exploit solar energy become more and more important. Inspired by natural systems it is highly promising to self-assemble building blocks into functional supramolecular units.
Electrostatic self-assembly leads to nanoscale shapes ranging from spheres and cylinders over vesicles to networks. Key to a targeted structure design is to fundamentally understand structure directing effects. In this regard, crucial insight has been gained from small-angle neutron scattering (SANS) at D11@ILL, alongside with other methods such as static and dynamic light scattering (SLS, DLS), atomic force microscopy (AFM), spectroscopy, zeta-potnatial measurements and isothermal titration calorimetry (ITC). Structure directing effects encoding the supramolecular nanoscale structure, in particular the particle particle size and shape on a 10-100 nm level, will be discussed. In particular, thermodynamics and the interplay of interaction forces are key to connect the molecular building block features with the nanoscale assembly properties.
In addition, we describe light-triggered size and shape changes of electrostatically self-assembled supramolecular nanostructures, following different strategies. This route for the conversion of light into structural and mechanical effects is promising for applications in drug delivery, nanosensors and solar energy conversion.

Speaker: Franziska Gröhn (Friedrich-Alexander-Universität Erlangen-Nürnberg)

Coffee break + discussion

Talks: Chair: Stefan Förster

20 Dendrimers and Small-angle Neutron Scattering: History and Perspectives

Dendrimers are synthetic macromolecules having a defined architecture. Starting from a trifunctional monomer (generation 0), subsequent generations are connected to this initial core from which in a treelike structure results. Small-angle neutron scattering (SANS) has been extremely useful for the characterization of these molecules since it allows us to change the contrast through mixtures of deuterated and protonated solvents. In this way, SANS served for a full characterization of dendrimers set up of flexible [1] or stiff molecular units.[2, 3] Moreover, a SANS-study of flexible dendrimers with partially deuteration of the endgroups led to the unambiguous conclusion that these dendrimers have a dense core, that is, the endgroups fold back to a certain extend.[4] Another feature revealed by SANS in conjunction with modeling by molecular dynamics is the soft interaction of flexible dendrimers in solution.[5-7]
In this lecture we will review this work and its extension to more recent systems including DNA-based, charged dendrimers. We will demonstrate that, in the latter case, the generation number, the salt concentration and the flexibility between different generations serve as physical control parameters to tune the softness of the dendrimer interactions.[8] Finally, we will show how a combined effort between synthesis, theory and SAXS-measurements reveals that suitably engineered, hybrid dendrimers have recently led to the experimental verification of cluster crystals,[9] a novel state of matter, 20 years after its original theoretical prediction.[10]

1. Potschke, D.; Ballauff, M.; Lindner, P.; Fischer, M.; Vogtle, F., Analysis of the structure of dendrimers in solution by small‐angle neutron scattering including contrast variation. Macromolecules 1999, 32 (12), 4079-4087.
2. Rosenfeldt, S.; Dingenouts, N.; Potschke, D.; Ballauff, M.; Berresheim, A. J.; Mullen, K.; Lindner, P.; Saalwachter, K., Analysis of the spatial structure of rigid polyphenylene dendrimers by small‐angle neutron scattering. J Lumin 2005, 111 (4), 225-238.
3. Rosenfeldt, S.; Karpuk, E.; Lehmann, M.; Meier, H.; Lindner, P.; Harnau, L.; Ballauff, M., The solution structure of stilbenoid dendrimers: a small‐angle scattering study. Chemphyschem 2006, 7 (10), 2097-104.
4. Rosenfeldt, S.; Dingenouts, N.; Ballauff, M.; Werner, N.; Vogtle, F.; Lindner, P., Distribution of end groups within a dendritic structure: A SANS study including contrast variation. Macromolecules 2002, 35 (21), 8098-8105.
5. Likos, C. N.; Rosenfeldt, S.; Dingenouts, N.; Ballauff, M.; Lindner, P.; Werner, N.; Vogtle, F., Gaussian effective interaction between flexible dendrimers of fourth generation: A theoretical and experimental study. J Chem Phys 2002, 117 (4), 1869-1877.
6. Ballauff, M.; Likos, C. N., Dendrimers in solution: insight from theory and simulation. Angew Chem Int Ed Engl 2004, 43 (23), 2998-3020.
7. Rosenfeldt, S.; Ballauff, M.; Lindner, P.; Harnau, L., Structure and interaction of flexible dendrimers in concentrated solution. J Chem Phys 2009, 130 (24).
8. Jochum, C.; Adzic, N.; Stiakakis, E.; Derrien, T. L.; Luo, D.; Kahl, G.; Likos, C. N., Structure and stimuli‐responsiveness of all-DNA dendrimers: theory and experiment, Nanoscale 2019, 11, 1604.
9. Stiakakis, E.; Jung, N.; Adzic, N.; Balandin, T.; Kentzinger, E.; Rücker, U.; Biehl, R.; Dhont, J. K. G.; Jonas, U.; Likos, C. N., Self assembling cluster crystals from DNA based dendritic nanostructres, Nature Communications 2021, 12, 7167.
10. Likos, C. N.; Lang, A.; Watzlawek, M.; Löwen, H., Criterion for determining clustering versus reentrant melting behaviour for bounded interaction potentials, Physical Review E 2001, 63, 031206.

Speaker: Matthias Ballauff (Institut fuer Chemie und Biochemie, FU Berlin)

21 Evolution of a HP-SANS cell and its upgrade with a periodic pressure jump unit for soft matter studies

Motivated by the patented idea of using scCO2-microemulsions as a starting material for the production of polymer nanofoams [1], we developed a new high-pressure cell together with Ralf Schweins and Peter Lindner in 2006. We were able to demonstrate its functionality in a first test SANS experiment at D11 in March 2007. In this and a series follow-up experiments we could show that scCO2-microemulsions containing water, supercritical carbon dioxide and fluoro-surfactants show similar properties as “classical” water/oil microemulsions [2]. However, using carbon dioxide, one exiting feature of scCO2-microemulsions is, that the solvent quality of scCO2 and hence the overall microemulsion properties, are tuned simply by adjusting pressure. Moreover, due to its large sapphire windows, we were also able to use the HP-SANS cell to study the dynamics of scCO2-microemulsions using NSE [3]. Further, in another study, we discovered that substituting cyclohexane with small amounts of scCO2 allows significant reductions in environmentally harmful fluorinated surfactants. Applying systematic contrast variation SANS, we were able to relate this effect to the formation of a depletion zone of cyclohexane near the fluorinated amphiphilic film [4]. Last but not least, we upgraded the high-pressure SANS cell with a periodic pressure jump system as part of the TISANE project. By combining this unique setup with time-resolved SANS, we were able to elucidate not only the kinetics of pressure-induced structural changes in scCO2-microemulsions [5], but also unravel the swelling kinetics of N-n-propylacrylamide-based microgels using periodic pressure jumps [6].
[1] M. Schwan, L. G. A. Kramer, T. Sottmann, R. Strey, Phys. Chem. Chem. Phys, 12, 6247 (2010).
[2] M. Klostermann, T. Foster, R. Schwein, P. Lindner, O. Glatter, R. Strey, T. Sottmann, Phys. Chem. Chem. Phys. 13, 20289 (2011).
[3] O. Holderer, M. Klostermann, M. Monkenbusch, R. Schweins, P. Lindner, R. Strey, D. Richter, T. Sottmann, Phys. Chem. Chem. Phys. 13, 3022 (2011).
[4] Y. Pütz, L. Grassberger, P. Lindner, R. Schweins, R. Strey,T. Sottmann, Phys. Chem. Chem. Phys. 17, 6122 (2015).
[5] A. Müller, Y. Pütz, R. Oberhoffer, N. Becker, R. Strey, A. Wiedenmann, T. Sottmann, Phys. Chem. Chem. Phys. 16, 18092 (2014).
[6] O. Wrede, Y. Reimann, S. Lülsdorf, D. Emmrich, K. Schneider, A. J. Schmid, D. Zauser, Y. Hertle, A. Beyer, R. Schweins, A. Gölzhäuser, T. Hellweg, T. Sottmann, Scientific Reports 8, 13781 (2018).

Speaker: Thomas Sottmann

22 Structural evolution of temperature-responsive polysaccharide-block-polypeptide copolymers

Linking polysaccharides and polypeptides together leads to fully biocompatible copolymers with unique properties for healthcare applications: not only they are fully biodegradable, but also they offer specific recognition and docking properties to membrane receptors of biological cells. Moreover, the two blocks can respond to external stimuli, such as pH, temperature, or the presence of specific molecules. Although they are both hydrophilic, the solubility in water of the polypeptide block can differ from that of the carbohydrate part, leading to compartmentalized supramolecular aggregates such as core-corona spherical or cylindrical micelles, or vesicles.[1,2] Accordingly, they are ideal candidates as novel nano-carriers for drug delivery. This work reports a structural study performed by SANS in fall 2018 at the ILL on the D11 spectrometer, where we deciphered the phase behavior (in temperature and concentration) of diblock copolymers made of a thermosensitive elastin-like polypeptide (ELP) block,[3] tethered to various hydrophilic carbohydrate blocks: PEG, dextran, hyaluronan, and a short oligosaccharide (laminarihexose).[4]

[1] A. Carlsen, S. Lecommandoux, Curr. Opin. Colloid Interface Sci. 2009, 14 (5), 329–339.
[2] C. Bonduelle, S. Lecommandoux, Biomacromolecules 2013, 14 (9), 2973–2983.
[3] E. Garanger, S. R. MacEwan, O. Sandre, A. Brûlet, L. Bataille, A. Chilkoti, S. Lecommandoux, Macromolecules 2015, 48 (18), 6617–6627. [https://hal.archives-ouvertes.fr/hal-01370027]
[4] Y. Xiao, Z. S. Chinoy, G. Pécastaings, K. Bathany Katell, E. Garanger, S. Lecommandoux, Biomacromolecules, 2020, 21(1), 114–125. [https://hal.archives-ouvertes.fr/hal-02299856]

Speaker: Olivier Sandre (CNRS / Université de Bordeaux / Bordeaux INP)

23 Interpreting simultaneous small-angle neutron scattering and reflection from surfactant stabilised air-water foams

Air-in-water foams stabilised by surfactants and polymers have been the subject of much recent debate due to their ubiquitous occurrence, desirable or otherwise. When examining such hierarchically structured and dynamic materials using neutron techniques, the complex patterns observed are often discussed in terms of a superposition of on- and off-specular scattering and reflectivity arising from the air/water interfaces and any (self-assembled) structures within the sample. Here, we present such data from foams stabilised by surfactant multi-layers comprising sodium lauryl ether sulfate/sodium dodecylsulfate blends in the presence of multi-valent salts (AlCl3, CaCl2). Concurrently, we demonstrate how the absolute intensities, the incoherent backgrounds and the transmissions can be used to determine the thickness of the liquid films within the beam, and thence, the liquid volume fraction in the foam. Together with literature data, and with additional contrast variation data, we re-interpret our previously published data and highlight some correlations between surface structure / composition and foam stability.

Speaker: Peter Charles Griffiths

Lunch

Talks: Chair: Ralf Schweins

24 Small-angle scattering from proteins: Crowding conditions and phase transformations (remote)

Protein solutions can exhibit rather complex behavior, in particular at high concentrations, i.e. "crowding" conditions.
For a comprehensive understanding of the structures,
from the molecular level to oligomers to larger-scale structures arising, e.g., in phase separating systems,
small-angle scattering plays a crucial role. This is also the basis for the interpretation of the associated dynamics
as well we kinetic effects. We discuss examples for the crucial role of small-angle scattering, particularly for the kinetics of phase transformations such as liquid-liquid phase separation and phenomena related to crystallization.

Speaker: Frank Schreiber (University of Tübingen)

25 D11 and the microgel's softness, a long standing story with a bright future

In this talk, I will discuss the fundamental contribution of small-angle neutron scattering - in particular of D11 - in the understanding of the properties of both individual microgels and of the macroscopic properties of microgel suspensions. We will discuss the use of SANS for the characterisation of the architecture of individual microgels. Then we will focus on the use of contrast variation to determine the microgel bulk modulus and the response of individual microgels to crowding.

Speaker: ANDREA SCOTTI

26 Self-Assembly in Deep Eutectic Solvents

Deep eutectic solvents (DES) are promising novel solvents obtained through the complexation of a halide salt such as choline chloride with a hydrogen bond donor such as urea or glycerol, enabling them to be tuned for particular properties, including low toxicity and sustainability. They are of increasing interest to replace organic solvents in applications from synthesis to pharmaceutical formulations. We have found that polar DES will support amphiphile aggregation and so are undertaking a systematic study to correlate the unique hydrogen-bonded nanostructure of DES with surfactant phase behaviour in these solvents. We have used a range of scattering techniques, including small angle scattering and reflectivity as well as measurements of critical micelle concentration, rheology and thermal properties to study micellization in these media. These investigations have shown that DES can promote amphiphile self-assembly but alter surfactant phase behaviour significantly compared to that in water, offering control over micelle morphology, as the solvent components can be tuned to be interacting or non-interacting with the surfactant, altering the micelle shape. In ternary DES, containing both urea and glycerol as hydrogen bond donors, the interaction of cationic and anionic surfactant headgroups with these solvent components are strikingly different. In addition, despite the highly ionic nature of DES, surfactant counterion binding is also surprisingly important in controlling micelle shape, and the micelles appear to show electrostatic interactions as the surfactant concentration is increased. This presentation will discuss our results and try to draw conclusions on the important factors controlling amphiphile behaviour in these interesting novel solvents.

Speaker: Karen Edler (Lund University)

27 Micelle structure and composition: the contribution from SANS (remote)

Surfactant self-assembly is an important phenomenon in a wide range of processes and applications. SANS has played a central and key role in developing our understanding of surfactant self-assembly. From the early 1980’s D11 has been the leading and pioneering SANS instrument for such studies. Three key issues from some the early studies on D11, associated with micelle models, the complementarity of SANS and neutron spin echo, and the application of shear alignment, and which are still relevant and important to current studies, will be revisited. The contribution of more recent studies of mixed surfactant self-assembly will be reviewed, with a particular emphasis on three aspects: the role of surfactant molecular structure in manipulating the micelle structure, the complex evolution of structures that can arise in mixtures, and the emerging importance of biosurfactants.

Speaker: Jeff Penfold (ISIS, STFC and PTCL, Oxford)

Coffee break + discussion

Breakout session

Discussion of needs and prospects for SANS

Conference Dinner

Wednesday, 28 September

Talks: Chair: Bruno Demé

28 The use of SANS in optimising pharmaceutical formulation

Nanosuspensions are sub-micron-sized colloidal dispersions of nano-sized drug particles stabilised by surfactant and/or polymer. Nanosuspensions are of considerable interest as a means of solving the problems of poor water solubility and low bioavailability exhibited by many drugs, and which pose significant challenges for the preparation of a medicine for patient use. Despite the fact that there are an increasing number of commercially available nanosuspensions, it is still not possible to make a rational selection of the stabilising polymer/surfactant. To gain this understanding we have performed small-angle neutron scattering (SANS) measurements in combination with isotopic substitution of the aqueous solvent on a range of drug nanosuspensions wet-bead milled in the presence of a number of different hydrophilic polymers of varying molecular weight and, in some instances, in the presence of surfactant. The layer thickness and amount of the absorbed polymer was determined to be insensitive to the molecular weight of the various polymers indicating that the adsorbed layer was lying relatively flat on the various drug particle surfaces. In contrast, however, SANS studies revealed that the amount adsorbed and the thickness of the polymer layer was dependent on both the nature of the hydrophilic polymer and the nature of the drug. The insensitivity of the adsorbed polymer layer to polymer molecular weight has important implications for the production of nanoparticles, suggesting that lower molecular weight polymers should be used when preparing nanoparticles by wet-bead milling, since nanoparticle formation is then more rapid but with no likely consequence as regards the physical stability of the resultant nanoparticles.

Speaker: Jayne Lawrence

29 Isotropic and anisotropic SANS from polymer systems

I will try to tell you a story about our hour after hour life – with mixture of stress and pleasure to be by the side of this beautiful leading machine, building a special relationship as D11 co-users, with different colleagues along my career. It actually started here!
This should cover different science cases, where D11 was useful in different ways: polymer gels, stretched polymers/reptation, stretched networks/rearrangements, sheared solutions, nanocomposites (stretched also…), polyelectrolytes, electrostatic complexes…This implied several local contacts invaluable support, too: Radulf, Robert, Peter, Adrian, Isabelle, Sylvain, and Ralf...

Speaker: Fraançois Boué (Laboratoire Léon Brillouin)

30 Visualisation of morphological changes in Soft Matter Systems via SANS contrast variation at the D11

The striking difference in the scattering length density of H and D offers a chance to vary or tune the neutron scattering contrast of selected components in complex systems while retaining the chemistry of the systems. Such contrast variation in turn provides unique opportunities for structural analysis in the field of Soft Matter not accessible to other scattering techniques like for instance to investigate the structure of particles in distinct matrices or to analyse the shape and distribution of a component or compartment within a particle. The present contribution reports on three typical examples of a successful application of the concept of contrast variation carried out with D-11. The first example presents a model analysis on aspects of cellular crowding via an investigation of the impact small colloidal particles at variable concentration exert on the size and shape of macromolecules in dilute solution. SANS demonstrated for the first time that small colloids induce a shrinking of the coil dimensions of macromolecules.1 The second example presents an investigation of double hydrophilic block copolyelectrolytes forming micelles at high and low temperature. SANS could locate the two blocks within the micelles at either temperature and revealed full inversion of the micelles along the temperature variation.2 The third example, establishing the most recent project, presents a study on mixed micelles formed from DTAB as a typical cationic surfactant and an anionic azo-dyestuff. SANS succeeded to locate the dyestuff within the co-assembly of the two components.

1. Kramer, T.; Schweins, R.; Huber, K. Macromolecules 2005, 38, 9783-9793
2. Carl, N.; Prevost, S.; Schweins, R.; Houston, J. E.; Morfin, I.; Huber, K. Macromolecules 2019, 52, 8759−8770

Speaker: Klaus Huber (Professor at University of Paderborn)

Coffee break + discussion

Talks: Chair: Matthias Ballauff

31 Soft Quasicrystals - a D11 discovery

Quasicrystals are a peculiar state of order, which is fundamentally different from classical ordered crystalline states. Discovered in 1982 for MnAl-alloys, it has since then been found for more than 100 different metal alloys.

In a 2009 D11 summer nightshift we discovered a micellar phase showing an unusual SANS-pattern with 12-fold rotational symmetry. When published in 2011, it was the third ever reported non-metallic dodecagonal quasicrystalline phase. Non-metallic quasicrystals have since then been found also for block copolymers, nanoparticles, colloids, or fullerenes. This indicates that quasicrystals are a quite common state of matter.

We have since then shown by X-ray and neutron scattering experiments as well as MD-simulations that particles with soft repulsive interactions form a distinct set of two- and three-dimensional quasicrystalline states with 8-, 10- and 12-fold rotational symmetry. We investigated quasicrystals formed by block copolymers, nanoparticles and colloids covering length scales from 10 nm to 500 µm. We observe surprisingly good agreement between the predicted and observed quasicrystalline structures and their stability regions in 2D- and 3D-phase diagrams. We further show that all so far reported non-metallic quasicrystals including dendrons, star and block copolymers, nanoparticles, polymer-grafted nanoparticles, colloids, mesoporous silica as well as BaTiO3-, fullerene, and organo-framework monolayers can be derived from this set of quasicrystalline structures. Furthermore, we demonstrate a direct link between non-metallic quasicrystals derived from repulsive potentials and metallic quasicrystals derived from attractive potentials. We show that the existence of two intrinsic length scales is essential for the formation of both non-metallic and metallic quasicrystals, facilitating locally high coordination and thereby optimizing sphere packing.

Speaker: Stephan Förster (Forschungszentrum Jülich)

32 Contribution of SANS and particularly of D11 on the understanding of thermoreversible gelation

Being among the first users of D11, I will give during my talk an outlook of the topics I investigated with this SANS camera. My first use of D11 dates back to Mai 1975 for studying the chain conformation in a crystalline polymer, namely isotactic polystyrene (iPS). Unlike polyethylene, that was studied simultaneously by other group of scientists, iPS did not display any isotopic segregation so that the single chain behaviour could be determined. We showed that the chain conformation depends on the crystalline growth rate with respect to the polymer viscosity. The chains fold completely in single crystals grown from dilute solutions while there is an alternation of folded parts and amorphous part in the bulk state. Our studies in polymer thermoreversible gels displaying fibrillar morphology have shown that the chain possesses a persistence length much larger that observed in the usual flexible state. We could show that this is due to helical stabilization through the formation of polymer/solvent molecular compounds. We could further show that a larger persistence length appears as a prerequisite for the formation of polymer thermoreversible gels.
We also investigated hybrid polymer thermoreversible gels/self-assembled systems. We could highlight the encapsulation of a bicopper complex by polymer fibrils, or the sheathing of polymer fibrils by self-assembled nanotubes.

Some references

• J.M. Guenet A neutron scattering study of the chain trajectory in
  isotactic polystyrene single crystals. Macromolecules, 1980, 13, 387
• J.M. Guenet A neutron scattering investigation of the chain
  trajectory in thermoreversible gels. Macromolecules, 1987, 20 2874
• M. Klein, A. Brulet, J.M. Guenet Molecular structure in isotactic
  polystyrene thermoreversible gels. Macromolecules 1990, 23, 540.
• J.M. Guenet, A. Brulet, C. Rochas Agarose chain conformation in the sol
  state by neutron scattering Int. J. of Biol.Macromol. 1993, 15, 131
• D. Lopez, J.M. Guenet Encapsulation of filaments of a
  self-assembling bicopper complex in polymer nanowires. Eur. Phys. J.
  B 1999, B12, 405
• S. Malik, C. Rochas, J.M. Guenet Syndiotactic
  Polystyrene/Naphthalene intercalates: preparing thermoreversible
  fibrillar gels from a solid solvent Macromolecules 2005, 38, 4888
• D. Dasgupta, Z. Kamar, C. Rochas, M. Dahmani, Ph. Mesini, J.M. Guenet
  Design of hybrid networks by sheathing polymer fibrils with
  self-assembled nanotubules Soft Matter 2010, 6, 3576
• A. Boulaoued, J.-L. Bantignies, R. Le Parc, C. Goze-Bac, P. Mesini, T.-T.-T.
  Nguyen, A. Al Ouahabi, P. Lutz, J.-M. Guenet Hybrid fibrillar xerogel
  with unusual magnetic properties Langmuir 2016, 32, 13193

Speaker: Jean-Michel Guenet (CNRS Institut Charles Sadron)

33 SANS studies of polymer structure in nanocomposites

As compared to other techniques of analysis of nanostructures, small-angle neutron scattering has always been way better in terms of design of special contrast situations, and worse for statistics due to inherently low flux. SANS beamlines at ILL, and in particular D11 dedicated to soft matter studies, have allowed to keep the first advantage, while providing excellent experimental conditions respect to, including with respect to flux.
In this talk, I will present some recent studies of polymer structure in nanocomposites. Such materials have striking mechanical and dynamical properties, in particular the dynamics of the polymer close to the nanoparticles has triggered a large body of experimental and theoretical studies. The possible slow-down of the polymer corresponds to higher moduli, and the percolation of any hard phase, particles or slowed-down polymer, has a strong impact on the macroscopic mechanical properties. If one wishes to specifically characterize the structure of the polymer, SANS is one of the best options. By blending hydrogenated and deuterated chains, while matching the filler silica nanoparticles, we have recently provided evidence for chain-mass dependent bulk or interfacial segregation, and modelling and experimental results will be critically reviewed. In a second study, we have characterized the particle dispersion by small-angle scattering and reverse Monte Carlo modelling, and used it to improve the determination of the thickness of the polymer interfacial layer seen by broadband dielectric spectroscopy. Both the general nanoparticle dispersion and the characteristic time of this interfacial layer has been shown to be tunable by surface modification, paving the way for a precise control of mechanical properties of polymer nanocomposites in the future.

Speaker: Julian Oberdisse

34 Small Angle neutron Scattering and Polymer science (remote)

50 years ago, polymers were well established materials, but there were a number of crucial questions open to relate molecular to material properties. It was already 50 years since Herman Staudinger had proposed that plastics were composed of long chain molecules and 20 years since Paul J. Flory described long chain molecules as random walks where dimensions increase as the scare root of mass. Both of these won Nobel prizes for their work and it was accepted that the material properties of plastics such as elasticity and viscoelasticity were determined by their long chain nature. However no direct experimental evidence for Staudinger and Flory had been observed. It was understood that small angle scattering would provide the link if a labelling technique were available. Given the large content of hydrogen, deuteration would be ideal if SANS instruments could provide a high enough count rate. Enter D11 and in 1973 the random walk nature of a single polymer molecule in a melt was demonstrated by several groups. Rapidly afterwards SANS experiments showed many other examples of the molecular basis for plastic behaviour such as the deformation and then relaxation of molecules in stretched samples.

Speaker: Julia S. Higgins

Lunch

Visite Guide Hall