The
development and utilization of switchable adhesives are considered
to be an essential target to solve the problems of their separation
and recycling in some specific service environments, such as the preparation
or repair process of electronic devices. Intelligent materials with
controllable phase transition are utilized to fabricate switchable
adhesives because of the significantly diverse adhesion strengths
in different phase states. Photoresponsive azobenzene and its derivatives
usually possess different melting temperatures (T
m) or/and glass transition temperatures (T
g) of the cis–trans isomers, which are beneficial
to making the photoinduced solid–liquid phase transition for
switchable adhesive application possible. Here, a novel three-component
azo-copolymer (PNIM-Azo) with fast and reversible photoinduced solid–liquid
phase transition has been designed and synthesized. PNIM-Azo possesses
reversible bonding/debonding processes, resulting from the different
adhesion strengths between trans-configuration PNIM-Azo in the solid
state and cis-configuration in the liquid state. Moreover, by incorporating
commercialized 2-methoxyethyl acrylate and N-isopropylacrylamide
with O and N heteroatoms into the copolymer, the trans-configuration
PNIM-Azo possesses the highest adhesion strength (∼11 MPa between
two glass substrates) among all of the reported azobenzene-based switchable
adhesives, which could be attributed to the increase in the entanglement
effect because of the H-bond in the polymer chains formed by introducing
heteroatoms. Our synthesized PNIM-Azo copolymer provides an alternative
for designing and developing switchable adhesives with high adhesion
strength for some electronic production processes.
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