Preparation And Stimuli-Responsiveness Properties Study Of Azo-Containing Polymer Materials

Stimuli-responsive polymers have attracted much attention because of their properties/functions to produce intelligent responses to external stimuli.These external stimuli include light,heat,magnetism,humidity,p H,etc.Among them,light as a clean energy,has the advantages of remote control,clean and pollution-free.Azobenzene,as a typical photosensitive group,can undergo reversible photoisomerization behavior under specific wavelength light induction,thus endowing azobenzene polymer materials with photoregulation in terms of physical and chemical properties such as surface roughness and wettability,which has broad application prospects in the design and construction of smart materials.At the same time,in many application scenarios,the single external stimulus response of materials is often difficult to meet the actual needs,so the exploration and development of azo-containing polymer system with multiple stimulus response has become one of the hot research topics in the field of polymer materials.Based on the chain structure regulation of azobenzene polymers,main chain,side chain and crosslinked azobenzene polymers were prepared,and their stimulus response was systematically characterized and their application potential was preliminarily explored.The details are as follows:（1）In chapter 1,4,4’-dihydroxyazobenzene（DHAB）was introduced into polyurethane system as a stimulus responsive component,and a main chain azobenzene polymer with double photoacid stimulus response was prepared by addition polymerization.The structure of the polymer was confirmed by FT-IR,¹H NMR and UV-vis analysis.Based on the excellent light response characteristics of azobenzyl groups and the surface wrinkling mechanism,the influence of light on the dynamic regulation of surface wrinkle morphology of different azobenzyl polymer films/base systems was investigated.The results show that visible light exposure causes the photoisomerization of azophenyl groups in the polymer membrane layer,which leads to the release of stress,thus realizing the dynamic regulation of the surface wrinkles of the membrane/base system.Further,by means of copper mesh selection exposure,the controllable construction of a series of high level wrinkle patterned surfaces is realized and its application in information storage is explored.Based on visual color switching（<20 s）triggered by reversible protonation/deprotonation ofβ-nitrogen atoms of azophenyl groups in azo-polyurethane,simple impregnation was used to prepare acid-base response smart fabrics.Rapid and reversible color transformation between yellow and orange-red on fabric surface was achieved by TFA/Et₃N stimulation.Write/erase patterns on the surface of smart fabric with the help of mask.The results show that functional fabrics have high resolution,good acid and alkali resistance and fatigue resistance,and show good application prospects in information storage,vision sensor and other fields.（2）In chapter 2,the acid stimulated response side chain suspension triblock azobenzene copolymer was prepared by cationic ring-opening copolymerization.The formation mechanism of the polymer was studied in detail,and the structure and properties of the polymer were characterized by ¹H NMR,FT-IR and UV-vis.Secondly,the intelligent fabric surface modified by copolymer solution was constructed.The information storage stability,p H resistance and cycling stability of the functional fabric surface were investigated systematically.The results show that the surface of the functional fabric has good chemical stability and fast reversible color switching performance.Due to the rapid protonation of azophenylβ-nitrogen atoms in the copolymer induced by TFA stimulation,a rapid yellow to orange-red color switch occurs on the surface of the smart fabric.At the same time,a series of high resolution patterned surfaces are constructed with the help of the selection exposure system.（3）In chapter 3,a crosslinked azobenzene polymer film（CLCP）with photostimulus response and environmental stimulus response was designed and synthesized.The surface wettability of the CLCP film changed from hydrophobic to hydrophilic under UV stimulation.In addition,moisture stimulation could cause macroscopic deformation of the CLCP film.Further,ATR FT-IR spectroscopy was used to study the moisture sensitive mechanism of CLCP membrane,The comparison experiment showed that the introduction of azophenyl groups in the polymer chain structure had hydration with water vapor.,the surface volume of the CLCP membrane expanded,and finally due to the asymmetric volume expansion of the inner and outer sides of the membrane,the macro deformation was generated.As a kind of flexible actuator,CLCP film can complete different movements such as turning,twisting,spiraling and recovering under the stimulation of moisture.With the increase of relative humidity（RH）,the flexural curvature of CLCP membrane increases.When RH is 95%,the maximum stable flexural curvature of CLCP membrane reaches 2.1 cm^-1.Through patterning design,an"artificial inchworm"device with biomimetic significance was developed,with a crawling rate of 34 mm/min.Finally,by designing and assembling CLCP membrane into"bionic flower"and"artificial muscle",the potential application of CLCP membrane in intelligent flexible driving devices is preliminarily explored.