| Coumarin is a type of photo-crosslinking photoresponsive material,which can undergo reversible photodimerization and depolymerization reactions.In addition,mesogen-jacketed liquid crystalline polymers have the characteristics of simple synthesis,solution processing,and the main chain rigidity and stable liquid crystallinity.Therefore,in this paper,two coumarin groups with light response characteristics are introduced into the side chain of mesogen-jacketed liquid crystalline polymers.It is expected to obtain a class of functional mesogen-jacketed liquid crystalline polymers with light-responsive properties.In this paper,a class of coumarin-containing polymer PCO and two types of copolymers PCO-PSP and PCO-PMMA are obtained through simple synthesis;and the liquid crystallinity and stimulus response characteristics of the above homopolymers and copolymers are studied.The details are as follows:1.We design and synthesize a class of mesogen-jacketed monomers containing coumarin groups MCO,then the monomers undergo free radical polymerization to obtain a class of coumarin-containing polymers PCO.The structures of monomers and polymers are confirmed by 1H NMR,MALDI-TOF MS and FT-IR,and the molecular weights of the polymers are determined by GPC.Then the thermal stability is studied by TGA,and it is found that the 5% thermal weight loss temperatures of the polymers PCO-4 and PCO-6 are both above 340?,which show good thermal stability.The optical properties were analyzed by ultraviolet absorption spectroscopy(UV)and fluorescence emission spectroscopy(PL).The results show that after the irradiation of 365 nm ultraviolet light,the maximum absorption intensity of polymers in polar solvent at 320 nm decreases,and the fluorescence intensity at 390 nm decrease sharply,indicating that the coumarin part has undergone a photodimerization reaction.In addition,the light response degree of polymers is greater than that of monomers.Through differential scanning calorimeter DSC and polarized light microscope POM research,it is found that polymers show stable liquid crystallinity.Through the study of one-dimensional X-ray diffraction WAXD,the phase structure is speculated as hexagonal columnar phase.2.Polymer PCO-PSP is obtained by free radical copolymerization of coumarin monomer MCO and spiropyran-containing vinyl monomer MSP.The structure and composition ratio are confirmed by 1H NMR,FT-IR,EA,etc.and the molecular weight of the copolymer is tested by GPC.Then its thermal stability is tested with TGA,and its 5% thermal weight loss temperature is above 290 ?;under the irradiation of ultraviolet light at 365 nm,the ultraviolet absorption peak at 324 nm of the copolymer PCO-PSP with the increase of ultraviolet irradiation time The continuous decrease indicates that coumarin has undergone photodimerization,and a new ultraviolet absorption peak appears at 560 nm.This is the absorption peak of spiropyran from SP isomerization to MC state,and the powder photograph of the copolymer exposed to ultraviolet radiation means that solid-state photochromism is achieved;the copolymer film changes from colorless to yellow under acid stimulation,and can return to its original state under amine stimulation.3.A class of copolymers PCO-PMMA are obtained by free-radical copolymerization of coumarin monomer MCO with different proportions of methyl methacrylate monomer MMA.The structure and composition ratio are confirmed by 1H NMR,FT-IR,EA,etc.and the molecular weight of the copolymer is tested by GPC.The 5% weight loss temperatures of the copolymers are above 260?;UV and PL test results show that the copolymer has light response characteristics.Under the irradiation of 365 nm ultraviolet light,the ultraviolet absorption peak at 324 nm continuously decreases,and the fluorescence intensity at 400 nm also decreases accordingly.Moreover,with the increase of MCO content,the degree of photoresponsiveness increases.The copolymers PCO-PMMA also show good solubility. |
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