Preparation Of Azophenyl Photoinduced Phase Chnange Polymer And Its Application In The Filed Of Smart Aghesives

Reversible adhesives which are a new class of smart adhesives with switchable adhesion strength are considered to be an important strategy to solve the problems of separation and recycling of adhesives in some specific service environments.Due to the different mechanical properties of materials between solid state and liquid state,smart materials with controllable phase transition were widely applied in reversible adhesives.As the most typical photoresponsive compounds,azobenzene and its derivatives can convert conformation reversibly between cis configuration and trans configuration irradiated by under different wavelength light.As is well known,the glass transition temperature（T_g）or the melting point（T_m）between the two conformations of azobenzene derivatives is obviously different.When the T_g/T_m of the cis isomer is lower than room temperature and the T_g/T_m of the trans isomer is higher than room temperature,azobenzene derivatives possesses photoinduced reversible solid-to-liquid phase transition at room temperature,which provides a theoretical basis for azobenzene based reversible adhesives.Due to the strong H aggregation between the azobenzene moiety in polymer chains,the adhesion strength is greatly reduced（<4.0 MPa）,which prevents further development of azobenzene based reversible adhesives.In this paper,two kinds of azophenyl copolymers with photoinduced phase transition have been designed and synthesized to improve the adhesion strength of azobenzene based reversible adhesives.We have investigated the photoresponsive property,photoinduced phase transition property and photoswitchable adhesion property.And then,we have elucidated the structure-function relationship between polymer structure and adhesion performance to provide a theoretical basis for azobenzene based reversible adhesives with high adhesion strength.A series of photoinduced liquefied two-componentazophenyl copolymers（PNY-Azos）with different azobenzene moiety contents have been designed and synthesized via free radical polymerization.We have investigated the photoresponsive property,photoinduced phase transition property of PNY-Azos,and elucidated the structure-function relationship between polymer structure and adhesion performance.The H aggregation between polymer chains has been reduced by introducing commercial acrylates.At the same time,the adhesion strength of PNY-Azos has been improved due to the increase of supramolecular interactions（H bonding）and entanglement between polymer chains,which provides theoretical basis for the design of photo-controlled reversible adhesives based on two-component azophenyl copolymers.Furthermore,a series of three-component azophenyl copolymers（PNIM-Azos）with different azobenzene contents have been designed and synthesized to increase the adhesion strength by introducing more heteroatoms into the polymer chains.We have also investigated the photoresponsive property,photoinduced phase transition property and photoswitchable adhesion property.The adhesion strength of PNIM-Azos glued glass substrates has been increased to 11.3 MPa by introducing commercialized N-isopropylacrylamide and 2-methoxyethyl acrylate with O and N heteroatoms based on the enhanced entanglement and H bond effects in the polymer chains,which provides a theoretical basis for azobenzene based reversible adhesives with high adhesion strength.