Preparation And Photoresponsive Performance Of Poly(ether Sulfone)s Containing Azobenzene In The Main Chain

Azobenzene-containing polymers have been extensively studied due to the well photoresponsive properties of the azobenzene groups.In recent years,the research on the photoinduced deformation of azobenzene-containing polymers have attracted considerable attention.Among the photoinduced deformable azopolymers,the aliphatic azobenzene-containing liquid crystal polymers have been systematically studied,but the problem of their poor thermal performance still exists,which limits their use in high-temperature environments.Introducing azobenzene into high performance polymer systems is an effective method to solve the above-mentioned problems.Poly(ether sulfone)s is a high performance polymer with good thermal stability.Azobenzene-containg poly(ether sulfone)s showed photoinduced deformable performance.However,there are few studies on the photoinduced deformable properties of azobenzene-containg poly(ether sulfone)s,and the related influence laws need to be further enriched.In this paper,a series of poly(ether sulfone)s containing azobenzene groups in main chain were prepared.The thermal properties and the photoresponsive properties of the poly(ether sulfone)s were investigated.A new type of azobenzene-containing compound,4,4'-dihydroxybiazobenzene,was designed and synthesized.A novel poly(ether sulfone)s containing azobenzene groups in main chain was prepared based on 4,4'-dihydroxybiazobenzene.In order to study the effect of structure of azobenzene on the polymer performance,an azobenzene-containing poly(ether sulfone)s was prepared based on4,4'-dihydroxydiazophenyl.Both of the polymers showed good thermal stability(T_d5>410?)and high glass transition temperature(Tg>190?).The study of the photoinduced isomerization behavior showed that the time required for the bending angle to reach 90°is Azo-PES-1>Azo-PES-2.Therefore,as the rigidity of the azobenzene groups increased,the photoinduced isomerization rate and the degree of the polymer decreased.The study of the photoinduced deformation behavior showed that with the rigidity of the azobenzene group increased,the photoinduced deformation rate and maximum bending angle of the polymer decreased;with the thickness of the polymer films increased,the photoinduced deformation rate of the polymer decreased;with the increase of the excitation light intensity,the photoinduced deformation rate of the polymer increased.Four kinds of poly(ether sulfone)s containing azobenzene groups in the main chain with different segment structures were synthesized.All of the azobenzne-containing poly(ether sulfone)s had good thermal stability(T_d5>390?)and higher glass transition temperature(Tg>200?).The deformation rate of the polymer is APES-1>APES-2>APES-3>APES-4.Therefore,the study of the photoinduced deformation behavior showed that with the free volume of the polymers increased,the photoinduced deformation rate of the polymer decreased;with the segment flexibility of the polymers increased.Under non-polarized laser irradiation,the polymer film bent to the excitation light.However,under polarized laser irradiation,the polymer film bent away from the excitation laser.The phenomenon under polarized laser irradiation,which is different from under non-polarized laser irradiation,can be attributed to the competition between photoinduced orientation and photoinduced isomerization.When polarized laser was incident on the polymer films,both of the photoinduced orientation and photoinduced isomerization could occur.The photoinduced bending rate and maximum bending angle of the polymer film under 442 nm non-polarized laser excitation were larger than that under 532 nm non-polarized laser excitation,respectively.As the ambient temperature increased,the photoinduced deformation rate increased.