| Soft matters such as liquid crystalline polymers(LCPs)and polymeric gels have been successfully constructed through self-assembly.Generally,main-chain LCPs(MCLCPs)features strong anisotropy in the direction of main chain,excellent mechanical properties and simple structures.Polymeric gels possess good self-supporting abilities and controllable macroscopic properties.However,it remains a challenge to endow the polymers with liquid crystal(LC)and gel behaviors at the same time due to the differences between their selfassembly processes.Thus,the investigation on the relationship between structure and performance not only helps to understand the self-assembly behaviors,but also provides the theoretical guidance in constructing new functional materials.In this thesis,a series of MCLCPs with pendent amide groups have been designed and synthesized,and the effect of the content of amide groups on liquid crystal and gel behaviors has been studied systematically.Then,the photo-responsive and photo-luminescent properties of the gels can be endowed by introducing the photo-responsive groups and aggregation-induced emission-active(AIE-active)groups into MCLCP gelators,respectively.Meanwhile,the effect of the AIEgen configuration on the liquid crystal behavior,gelation ability and related functions of polymers has been investigated,too.The details are given as follows:(1)A series of MCLCPs named as Px with different content of pendent amide groups were synthesized through melt poly condensation,where x was the content of pendent amide groups.Px gradually transformed from crystalline polymers to LCPs when x value increased.In the absence of amide pendent groups,i.e.,x=0,P0 formed a gel with a minimum gelation concentration(MGC)of 7.0 wt%in THF via π-π stacking interaction.P28 was unable to form gel due to weak π-π stacking and hydrogen bonding.As x increased from 36 to 100,the MGC values of Px in THF decreased from 6.0 wt%to 2.0 wt%.Moreover,P100 gel exhibited excellent mechanical property and could afford a pressure of～2.6×105 Pa.(2)The photo-responsive Azo-mLCP was prepared by constructing azobenzene group into MCLCP with pendent amide groups.Azo-mLCP formed gel with a MGC of 6.5 wt%in dioxane by hydrogen bonding between amide groups and π-π stacking between azobenzene groups.The gel-to-sol transition could be effectively triggered by a partial trans-to-cis conversion of azobenzene.Upon subsequent visible light irradiation,the AzomLCP gel formed again.Moreover,Azo-mLCP gel exhibited a good self-supporting ability with a storage modulus higher than 104 Pa when the content of Azo-mLCP was more than 7.5 wt%.(3)Two luminescent polymers with a single configuration,E-PM7 and Z-PM7,were designed and synthesized based on different tetraphenylethylene(TPE)configuration.The effects of configuration on liquid crystal and AIE behaviors were studied.E-PM7 showed two coexisting phases of smectic and rectangular liquid crystalline phases,whereas Z-PM7 was amorphous because of the more serious nonlinear "defects" of Z-units.Z-PM7 showed more obvious AIE behavior than E-PM7.Moreover,the fluorescent patterns of LCP E-PM7 were printed on a flexible PET film and a glass substrate through the photocyclization of TPE units upon UV irradiation.(4)In combination with pendent amide group and TPE,main-chain liquid crystalline copolyester gelators with liquid crystal,gelation and emission properties were designed.Both E-P20 containing single E-units and Z-P20 containing single Z-TPE units could form smectic liquid crystal,but E-P20 possessed a wider temperature range of liquid crystal and a narrower layer distance.Driven by the hydrogen bonding between the pendent amide groups,E-P20 and Z-P20 formed gels with MGC values of 10.0 wt%and 4.0 wt%in ethyl acetate,respectively.The AIE properties of Z-P20 gel were better than E-P20 gel because the intramolecular motion in Z-P20 was more restricted during the aggregation process.Moreover,in comparison with E-P20 gel,Z-P20 gel has better mechanical properties. |
PDF Full Text Request