Poly(methylmethacrylate)-block-poly(N-hydroxyethylacrylamide) diblock copolymers: direct ATRP synthesis and characterization

Abstract

Diblock copolymers consisting of methylmethacrylate (MMA) and N-hydroxyethylacrylamide (HEAAm) polymer were successfully synthesized via direct two steps atom transfer radical polymerization (ATRP). At first, poly(methylmethacrylate) (PMMA) macroinitiators were prepared using methyl 4-(bromo-methyl) benzoate initiator and were used for synthesizing PMMA-b-PHEAAm block copolymers. PMMA homopolymers were synthesized in N,N′-dimethylformamide (DMF) using CuBr/2, 2′bipyridine catalyst system at 110 °C temperature in nitrogen atmosphere. Block copolymers were synthesized in mixture of DMF/water (8/2 v/v%) and in pure DMF in the presence of CuBr/1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA) catalyst system at 85 and 100 °C, respectively, while argon was used for deoxygenation and inert environment. Purification of block copolymers was conducted through dialysis against deionized water using a dialysis tubing (MWCO 3,500, cellulose membrane). Molecular weights of PMMA polymers (M n = 4,400, 6,200 and 8,400 Da) were determined by size exclusion chromatography using tetrahydrofuran (THF) as eluent. The chemical structure and actual copolymer compositions were determined using elemental analysis (EA), attenuated total reflectance infrared (ATR-IR) and proton nuclear magnetic resonance (1H NMR) spectroscopic analysis. Phase separation of diblock copolymers resulting in two glass transition temperatures as detected by differential scanning calorimeter (DSC) proves their amphiphilic behavior. Thermogravimetric analysis (TGA) also showed that diblock copolymer, with two-step decomposition has higher thermal stability than PMMA.