Synthesis, characterization and quantitative epoxidation-modification of a novel high-transparency S(SP)S symmetrical triblock copolymer with alternating mid-block by LAP method

Pure multi-block copolymers and deformed multi-block copolymers have unique applications in the field of high-performance thermoplastic elastomers, resins and rubber materials. For styrene (S) and conjugated 1,3-dienes (e.g. 1,3-pentadiene, P) monomers, living anionic polymerization (LAP) has significant advantages in precise control of molecular weight and its distribution and precise control of microstructure and the sequence distribution. Subsequently, the post-polymerization modification strategy including epoxidation can further expand the application field of such polymer materials. Herein, a series of novel symmetrical triblock copolymers of different compositions with homo-polystyrene as end-blocks and strictly alternating sequence as mid-block, poly(S)-b-poly(S-alt-P)-b-poly(S) (SSPS), were synthesized in cyclohexane by the classical three-step sequential feeding method using n-BuLi as initiator. The effect of the block ratio of SSPS triblock copolymer on impact strength, flexural strength and yield strength of transparent resin products was studied in detail. In addition, quantitative epoxidation post-polymerization functional modification was performed to obtain the novel triblock copolymer product which had a high-polarity and high-transparent thermoplastic resin with well-defined structure and quantitative degree of epoxidation (ED). All these novel copolymers before and after modification were characterized by 1H NMR, 13C NMR, FTIR, DSC and GPC.