Some of azobenzene-based low-molecular-weight compounds and polymers exhibit reversible solid–liquid

phase transition upon UV and visible light irradiation. Such materials possess multi-azobenzene side chains

connected to their backbone with relatively long methylene spacer, and thus, upon UV irradiation, the material

with cis-azobenzene moiety become liquid due to its glass transition temperature below room temperature.

The phase transition materials can be used for reversible adhesives that can bond and debond two substrates

on demand. The photochemical process has unique features such as athermal, contactless, and spatio-seletive

activation, although the one of the two substrates must penetrate irradiating light. In this review, azobenzenebased

solid–liquid phase transition materials are reported with a focus on the relationship among the chemical

structure, solid–liquid phase transition behavior, and reversible adhesive ability.

An epoxy resin having an amide structure（ DGBA） was synthesized and the physical properties of a cured

polymer obtained by curing with 4,4’-dihydroxydiphenyl ether（ DHDE） were evaluated. DGBA gave a crystalline

cured polymer with a melting point of 202.9℃, which was 15.5℃ higher than that of epoxy resin having

a diphenylene ether structure（ DGDE）. The Tg of the DGBA polymer in the DMA measurement was 133.2℃,

which was 37.3 ℃ higher than that of the DGDE polymer. The DGBA polymer had a significantly low thermal

expansion coefficient of 2.7×10-5℃-1, and the thermal conductivity is 0.29 W/m･K, which is 1.45 times that of

the bisphenol A type polymer.

For the study of the mechanism behind the adhesion phenomena, the adhesion interfaces were analyzed

by electron microscopy. Especially, scanning transmission electron macroscopy（ STEM） with energy dispersive

X-ray spectrometry（ EDX） and electron energy loss spectroscopy（ EELS） were performed for the local

chemical analysis of interfaces. Moreover, STEM-tomography was employed for the three-dimensional analysis

of interfaces. Polymer/metal joints obtained by injection molding, polymer/polymer interfaces formed via

interdiffusion, and polymer/metal bonded interfaces by hot-pressing were investigated. We have found the

common events that were occurred in the failure both of metal/polymer and polymer/polymer interfaces.

Linear low-density polyethylene（ LLDPE） / polyamide 6（ PA6） / compatibilizer blends are interesting as

the model blends of recycled multilayer films.　The aim of this study was to evaluate influences of compatibilizers

on morphology and mechanical properties of LLDPE / PA6 / compatibilizer blends.　The used compatibilizers

have approximately the same content of polar maleic anhydride and different types of non-polar main

chain each other.　The compatibilizers minimized the size of PA6 particles in the LLDPE and improved impact

strength significantly.　Maleic anhydride grafted polystyrene-block-poly（ethylene-butene）-block-polystyrene

（SEBS） showed remarkable performance in regard to minimization of PA6 particle size and improvement of

the impact strength.　Because the malic anhydride content was almost same among these compatibilizers, it

was estimated that chemical structure of main chain of the compatibilizer influenced PA6 particle size and impact

strength of the blends.