Conformation and aggregation behavior of poly(ethylene glycol)‐b‐poly(lactic acid) amphiphilic copolymer chains in dilute/semidilute THF solutions

Abstract

AbstractThe behavior of amphiphilic copolymer chains in a solvent is not the same as that of homopolymers. As an important synthetic biomaterial, poly(ethylene glycol)‐b‐poly(lactic acid) copolymers are often dissolved in tetrahydrofuran (THF) for study. Few studies have focused on the potential aggregation behavior and compact conformation of the amphiphilic macromolecules in a THF solution. In this study, a series of poly(ethylene glycol)‐b‐poly(lactic acid) diblock copolymers were synthesized and characterized using fourier‐transform infrared spectroscopy, nuclear magnetic resonance, thermogravimetric analysis, and gel permeation chromatography methods. The aggregation behavior of amphiphilic molecular chains in a THF solution was studied using dynamic light scattering and transmission electron microscopy. The results showed that the aggregation size in solutions at a concentration of 2.0 mg/mL is within the range of 50–250 nm. It was further demonstrated that molecular chains exhibit a compact conformation in a dilute THF solution, which leads to a comparatively larger deviation in the characterization of molecular weights using GPC method. Here, a model is proposed to elucidate the dynamic evolution between compact amphiphilic single chains and aggregates. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012