A random hydrophobic/pH-sensitive copolymer brush poly(polylactide methacrylate-comethacrylic acid)-b-poly(poly(ethylene glycol) methyl ether methacrylate) [P(PLAMA-co-MAA)-b-PPEGMA] was synthesized by the combination of activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) with ring opening polymerization (ROP). The chemical structure, molecular weight and polydispersity index were characterized by nuclear magnetic resonance hydrogen spectrum (¹H NMR) and gel permeation chromatography (GPC). The reaction conditions of polymerization were optimized and polymer products with controllable molecular weight and narrow distribution were obtained. The self-assembly behavior (micelle size, morphology and pH-sensitive properties) of the polymer brush was investigated by dynamic light scattering (DLS) and scanning electron microscopy (SEM). The P(PLAMA-co-MAA)-b-PPEGMA self-assembled micelles were sphere in morphology and with an uniform particle size. As the solution pH decreased from 7 to 3, the deionization of carboxyl groups of PMAA contributed to the shrinking of micelle structure, which made the micelle size decreased from 200～300 nm to about 150 nm. When the solution pH decreased to below 2, the surface charge of micelle became very small which resulting in the aggregation of micelles and the increase of micelle size.

Key words: pH-sensitive, polymer brush, self-assembled micelle, ARGET ATRP, ROP