Three-Arms PLA/PS Copolymer Based on 2,5-Dihydroxy-1,4-Benzoquinone

Abstract

This study focuses on preparation of hybrid block copolymers of polylactide (PLA) and polystyrene (PS) involving 2,5-dihydroxy-1,4-benzoquinone (DHBQ) as a dual initiator. At the first stage in the presence of AcONa 2,5-dihydroxy-1,4-benzoquinone opened the lactide ring resulting in the carboxylic end-group that further provides for the PLA chain growth. The polymerization proceeds at a moderate rate to high conversion degrees to form the polymers with well-defined molecular weight (MW) characteristics. The presence of an internal DHBQ fragment in the polymer was proven by IR, UV-VIS, NMR and MALDI-TOF techniques. Obtained polymer can be considered as macroquinone (MQ). The styrene polymerization initiated by MQ/Bu3B proceeds at a moderate rate leading to the formation of hybrid three-radial PLA/PS copolymer. During the copolymer formation linear increase of Mn with conversion as well as polydispersity decrease were observed. As evidenced by relatively low content of polystyrene in the copolymer (8.1 wt. %), the process has a good selectivity. The introduction of styrene units into the copolymer allows a 4-fold increase the E modulus in comparison with the homo-PLA.