Mixed molecular brushes with PLLA and PS side chains prepared by AGET ATRP and ring-opening polymerization

Brush macromolecules having poly(L-lactide) (PLLA) and poly(styrene) (PS) side chains were prepared on the backbone of partially esterified poly(2-hydroxyethyl methacrylate) (PHEMA) by using a combination of atom transfer radical polymerization (ATRP) and ring-opening polymerization. The number-average degrees of polymerization of PLLA side chains and PS side chains were determined by H-1 NMR spectroscopy, and the apparent molecular weights of the brush molecules were measured by gel permeation chromatography. The relationship between the crystallization of PLLA with PLLA and PS side chain lengths was investigated. Inside a brush molecule due to the unfavorable interaction between PLLA and PS two phases were formed. Brush molecules adsorbed on mica tend to make a starlike conformation; however, they change to a globular conformation after thermal treatment.