Three-arms PLA/PS copolymer based on 2,5-dihydroxy-1,4-benzoquinone

This study focuses on the 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 opens the lactide ring, resulting in a carboxylic end group that further facilitates the growth of the PLA chain. 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 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-arms PLA/PS copolymer. Linear increase in M_n with conversion and polydispersity reduction were observed during copolymerization. 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 leads to a four-fold increase in E modulus compared to homo-PLA.