High Performance Thermosetting All-aromatic Liquid Crystalline Poly(esterimide)s And Their Triple-shape Memory Effect

All-aromatic main chain thermotropic liquid crystalline polyesters(TLCPs)are attractive for their excellent chemical resistance,high thermal stability and outstanding mechanical properties,which exhibit great potentials in cutting-edge fields with harsh requirements on high performance,such as aerospace,electronics and petroleum exploration fields.However,existing TLCPs both on performance and synthesis methods have major drawbacks,which respectively reflect that poor processability,can not be dissolved in almost all ordinary solvents,their melting point is so high that is close to the decomposition temperature,low glass transition temperature,their polymerization temperature is so high.Therefore,how to develop a facile strategy to synthesize TLCPs at medium-low temperature and endowing TLCPs with good processability and high thermal resistance is a subject which has important research significance and practical value.This is the target of our project reported herein.The main contents include the following two aspects.Firstly,a new solution polymerization based on direct esterification under 120 °C is developed,two new reactive all-aromatic thermosetting liquid crystalline poly(esterimide)s(LCPEI-1 and LCPEI-2)terminated with 3-ethynylaniline(3-EA)and imide monomer(IM)with kinked structure added into main chain were synthesized.On the basis,their structures and properties were compared with two control samples without 3-EA end groups(LCPEI-1-c and LCPEI-2-c).The results indicate that LCPEI-1 and LCPEI-2 not only show low Tm,low melting viscosity(|η*|)and good solubility in solvent,their cured samples also have high Tg and high storage modulus(E’),whereas control samples,even treated with similar thermal history as curing procedure for LCPEI-1 and LCPEI-2,have poor comprehensive performances.simultaneously employing non-linear aromatic monomer and reactive end-groups is capable of obtaining liquid crystalline poly(esterimide)s(LCPEIs)with good processability and high thermal resistance.The new solution polymerization temperature is 120 °C,overcoming bottlenecks of traditional melt and solution polymerizations(310 °C).Secondly,LCPEIs with good processability and high thermal resistance have attracted more attention due to they could potentially offer unique opportunities in many applications.Besides,in order to solve the problem of triple shape memory polymers(low Tg).A new thermosetting resin with high Tg and triple-shape memory effect was prepared by blending LCPEI-1 with epoxy resin(EP).The cure reactive,thermomechanical properties,thermal resistance and triple-shape memory effect of EPEAEI have been systematically investigated.The results indicate that EPEAEI has two Tg(93 °C 和 218 °C)and triple-shape memory effect,both shape recovery(Rr)achieve 100% when deformation temperature(Tprog)are 173 °C and 248 °C,respectively.Meanwhile,compared with LCPEI-1,EPEAEI has lower cure temperature and similar thermomechanical properties;besides,EPEAEI has higher thermal resistance than EP.