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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 24: Poster Session I

CPP 24.45: Poster

Montag, 16. März 2020, 17:30–19:30, P3

Kinetics of shell collapse and aggregation in thermoresponsive PMMA-b-PNIPAM micelles revealed by time-resolved small-angle neutron scattering and fast pressure jumps — •Geethu P. Meledam¹, Chia-Hsin Ko¹, Shu-Hsien Huang¹, Bart-Jan Niebuur¹, Leonardo Chiappisi², Alfons Schulte³, and Christine M. Papadakis¹ — ¹TU München, Physik-Department, Garching, Germany — ²Institut Laue-Langevin, Grenoble, France — ³University of Central Florida, Orlando, U.S.A.

The amphiphilic diblock copolymer, poly(methyl methacrylate)-b-poly(N-isopropylacrylamide) (PMMA-b-PNIPAM) self-assembles into core-shell micelles in aqueous solution, and the thermoresponsive PNIPAM shell collapses upon heating through its cloud point. Here, we explore the kinetics of structural modifications and intermicellar interactions in PMMA-b-PNIPAM micelles during its phase transition by performing time-resolved small-angle neutron scattering (SANS) in combination with millisecond pressure jumps. Because of the fast equilibration in a pressure jump, we are able to observe different stages of micellar shell collapse and aggregation while undergoing phase transition. At high pressures, the micellar shell stays rather hydrated and the growth proceeds via diffusion-limited aggregation. On the contrary, at low pressures, a hydrophobic-driven micellar aggregation occurs due to the strong dehydration of the PNIPAM shell. In general, the strategy of combining time-resolved SANS with rapid pressure jump experiments provides an exclusive possibility to probe the initial stages of phase transitions in macromolecules.