Synthesis of poly(3-hexylthiophene) based rod–coil conjugated block copolymers via photoinduced metal-free atom transfer radical polymerization

Abstract

The photo-mediated “metal-free” atom transfer radical polymerization approach has been investigated for the first time to polymerize methyl methacrylate, N,N-dimethylamino-2-ethyl methacrylate, 2-([4,6-dichlorotriazin-2-yl]oxy)ethyl methacrylate and a mixture of methyl methacrylate and 1-pyrenemethyl methacrylate from a regioregular poly(3-hexylthiophene) (P3HT) macroinitiator to produce well-defined rod–coil conjugated diblock copolymers, highly relevant for use as organic electronic materials without metal catalyst contamination. This was achieved using pyrene and a pyrenyl N-substituted phenothiazine (PPTh) as UV light photoredox catalysts. Spectral and chromatographic results revealed that the applied synthetic approach generated P3HT-based diblock copolymers in a controlled manner and with narrow molecular weight distributions (Đ ≤ 1.3). From a comparison of the efficiency of the photocatalysts, PPTh has shown advantages over pyrene, including much lower catalyst content and higher polymerization conversions.