50 years of D11

Dendrimers and Small-angle Neutron Scattering: History and Perspectives

27 Sept 2022, 10:50

25m

ILL4/rdc-1 - Amphi Chadwick (ILL4)

Invited speakers Talks

Speaker

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

Description

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.