Chemistry and Rheological Behavior of Cross-Linked Liquid Crystal Polyarylate with a Mixed End-Capping Strategy

Liquid crystal thermosets (LCTs) terminated with a phenylethynyl group (PEPA) have attracted extensive attention because their tunable processability is superior to thermoplastic liquid crystal polyarylates (LCPs). However, the high curing temperature and low curing rate of PEPA restrict regulation on the performance of cured LCTs. To address above challenges, the bis- or mixed end-cappers with inner and outer ethynyl groups were utilized to terminate LCP. The curing temperature was decreased from 370 to 320 °C by introducing high reactive 3-ethynylaniline (EA) and derivatives as end-cappers. Meanwhile, the cured LCT exhibited a high storage modulus (∼30 MPa) at a rubbery plateau (400 °C) due to a highly cross-linked network (cross-linking density = 3131.9 mol·m–3). Moreover, appropriate mixed end groups could realize a similar curing rate (∼500 Pa·s·min–1) to their highly reactive counterparts. Consequently, rheological measurements were innovatively conducted to understand the curing mechanism of diverse end cappers, which would inspire new strategies to develop high-performance thermosets.