MPIP researcher in collaboration with L Gury, S. Kamble, D. Parisiand D. Vlassopoulos (IESL-FORTH, Greece) and J. Zhang, J. Lee, A. Abdullah, K. Matyjaszewski a nd M.R. Bockstaller (CMU, Pittsburgh, PA USA) found thatthe second virial coefficient, A2
displays an unexpected crossover behavior from the anticipated positive to unexpected negative values in a good solvent for the polymer grafts.
Understanding the effect of polymer brush architecture on particle interactions in solution is a requisite to enable the development of functional materials based on self-assembled polymer-grafted nanoparticles (GNP). Static and dynamic light scattering of polystyrene-grafted silica particle solutions in toluene reveals that the pair-interaction potential, inferred from the second virial coefficient, A2
, is strongly affected by the grafting density,σ, and degree of polymerization, N
, of tethered chains. In the limit of intermediate σ (~0.3-0.6 nm-2
) and high N
is positive and increases with N
in agreement with the good solvent conditions. In contrast, for high σ > 0.6 nm-2
and low N
displays an unexpected reversal to negative values, thus indicating poor solvent conditions. These findings are rationalized by means of a simple analysis based on a coarse-grained brush potential which balances the attractive core-core interactions and the excluded volume interactions imparted by the polymer grafts.. The effect of grafting density also illustrates the opportunity to tailor physical properties of hybrid materials by altering geometry (or architecture) rather than variation of the chemical composition.About the Project:
This project is funded by ERC SmartPhon (No. 694977).