Strong Variation of Micelle-Unimer Coexistence as a Function of Core Chain Mobility.

ABSTRACT: Polymeric micelles coexist in solution with unassembled chains (unimers). We have investigated the influence of glass transition temperature (T _g) (i.e., chain mobility) of the micelle core-forming blocks on micelle-unimer coexistence. We synthesized a series of seven PEG-b-P(nBA-ran-tBA) amphiphilic block copolymers (PEG = poly(ethylene glycol), nBA = n-butyl acrylate, tBA = tert-butyl acrylate) with similar molecular weights (12 kg/mol). Varying the nBA/tBA molar ratio enabled broad modulation of core block T _g with no significant change in core hydrophobicity or micelle size. NMR diffusometry revealed increasing unimer populations from 0% to 54% of total polymer concentration upon decreasing core block T _g from 25 to -46 °C. Additionally, unimer population at fixed polymer composition (and thus core T _g) increased with temperature. This study demonstrates the strong influence of core-forming block mobility on polymer self-assembly, providing information toward designing drug delivery systems and suggesting the need for new dynamical theory.

SUBMITTER: Carrazzone RJ 

PROVIDER: S-EPMC10004150 | biostudies-literature | 2021 Jul

REPOSITORIES: biostudies-literature