Mechanism of Molecular Exchange in Block Polymer Micelles @ University of Minnesota
January 11, 2010 :: Highlight from IRG1
: Soohyung Choi, Frank Bates, Tim Lodge. University of Minnesota
Mr. Soohyung Choi, a graduate student co-advised by Professor Bates and Professor Lodge, investigated the molecular exchange dynamics in diblock copolymer micelles. Two pairs of structurally matched poly(styrene-b-ethylene-alt-propylene) (PS-PEP) were synthesized and dispersed in squalane, which is highly selective for the PEP block. Each pair includes polymers with fully deuterated (dPS-PEP) and normal (hPS-PEP) PS blocks. Since the neutron scattering intensity is proportional to the fraction of hPS in the micelles, the molecular exchange rate is measurable by the contrast matching technique in time-resolved small-angle neutron scattering measurements. Not only does temperature impact the exchange rate in a way consistent with polymer melt dynamics, increasing the core PS block length by 60% produces a remarkable 10,000-fold decrease in exchange rate due to the unfavorable interactions associated with ejecting a core block into the solvent. This work provides fundamental understanding of block copolymer micelle dynamics and the attainment of equilibrium structures, which are both relevant to a host of potential applications including drug delivery.
Related publication(s):
- Phys. Rev. Lett. 2010, in press
