Design, synthesis and characterization of polyisobutylene-based semicrystalline ternary ABC linear triblock copolymers.

摘要

The design, synthesis, and characterization of novel semicrystalline ternary ABC linear triblock copolymers have been studied. Specifically, glassy(A)- b-rubbery(B)-b-crystalline(C) linear triblock copolymers, where A block is poly(α-methylstyrene) (PαmeSt) (T _g = ∼160°C), B block is rubbery polyisobutylene (PIB) (T_g = ∼–70°C), and C block is polypivalolactone (PPVL) (T_m = 220∼230°C), have been prepared via the combination of living cationic sequential block copolymerization and site-transformation from living cationic to anionic ring-opening polymerization (AROP).; The synthesis of poly(αMeSt-b-IB) block copolymers via living cationic sequential block copolymerization was investigated using the adduct of the olefinic αMeSt dimer and HCl (DiαMeSt·HCI) as an initiator in the presence of 2,6-di-tert-butylpyridine (DTBP) in methylcyclohexane (MeChx)/methylchloride (MeCl) (60/40 v/v) at −80°C.; The synthesis of poly(IB-b-PVL) diblock copolymers consisting of rubbery (PIB)/crystalline (PPVL) block segments was accomplished by means of transformation of living cationic polymerization of IB to AROP of PVL. First, PIB with ω-carboxylate potassium salt was prepared by capping living PIB with 1,1-diphenylethylene (DPE) followed by quenching with 1-methoxy-l-trimethylsiloxy-propene, and hydrolysis of ω-methoxycarbonyl end groups. The PIB ω-carboxylate potassium salt was successfully used as a macroinitiator for the AROP of PVL in tetrahydrofuran, leading to poly(IB-b-PVL) copolymers.; The same methodology mentioned above was applied for the synthesis of poly(PVL-b-IB-b-PVL) triblock copolymers, except that a difunctional initiator, 5-tert-butyl-1,3-bis-(1-chloro-1-methylethyl)benzene (tBuDiCumCl), was used for the polymerization of IB in the first step.; The synthesis of poly(αMeSt-b-IB-b-PVL) linear triblock copolymers has been accomplished, for the first time, taking advantage of living cationic sequential polymerization and site-transformation technique used previously in the synthesis of poly(αMeSt-b-IB) copolymers and poly(IB-b-PVL) copolymers, respectively.; These novel ABC (glassy-b-rubbery-b-crystalline) linear triblock copolymers may serve as key model macromolecules to provide a deeper insight into how the competition of the microphase separation, the crystallization, and the glass transition affect self-assembly of block copolymers in a nanometer length scale.