PEE–PEO Block Copolymer Exchange Rate between Mixed Micelles Is Detergent and Temperature Activated

Abstract

We examine the kinetics of polymer chain exchange between mixed block copolymer–detergent micelles, a system relevant to the synthesis of protein-containing biomimetic membranes. While chain exchange between block copolymer (BCP) aggregates in water is too slow to observe, and detergent molecules exchange between micelles on a time scale of nanoseconds to microseconds, BCP chains exchange between mixed detergent–polymer micelles on intermediate time scales of many minutes to a few days. We examine a membrane-protein-relevant, vesicle-forming, ultrashort polymer, poly(ethyl ethylene)20-poly(ethylene oxide)18 (PEE20–PEO18). PEE20–PEO18 was solubilized in mixed micelles with the membrane protein compatible nonionic detergent octyl-β-d-glucoside (OG). Using cryo-TEM and small-angle neutron scattering (SANS), we demonstrate complete solubilization of the polymer into micelles. Using time-resolved SANS (TR-SANS), we provide the first direct evidence that detergents activate BCP chain exchange and determine kine...