Programmed Main-Chain Scission in Aqueous Media toward UV-Curable, Dismountable Acrylic Coatings and Adhesives

Abstract

We recently reported that alternating sequences of a silyl-protected alcohol monomer and a cyclic ketene acetal functioned as cleavable sites upon treatment with aqueous acetic acid, although several hours were required to achieve a substantial decrease in molar mass. Here, hydrophilic acrylamide comonomers were introduced as third monomers to accelerate main-chain scission (MCS) in aqueous media. Incorporation of N-methoxymethyl acrylamide markedly accelerated MCS, despite decreasing the expected frequency of the cleavable alternating sequences. A terpolymer containing N,N-dimethylacrylamide also underwent faster MCS than the corresponding binary copolymer, although its MCS was slower than that of the N-methoxymethylacrylamide-containing terpolymer, consistent with its lower incorporation of the cyclic ketene acetal. These results demonstrate that efficient MCS in aqueous media is governed by a balance between accessibility of the polymer to the reaction medium and incorporation of cleavable sequences. This molecular design was further translated into UV-cured coatings and adhesives formed by in situ photoinitiated radical polymerization. The resulting adhesives exhibited sufficient adhesion and enabled dismounting upon immersion in aqueous acetic acid. Furthermore, the introduction of permanent cross-links improved the chemical and thermal stability of the adhesives while retaining acid-triggered dismountability. These results highlight the importance of designing not only the local sequences responsible for bond cleavage but also the surrounding repeat units that control their accessibility, thereby enabling molecular-level control of MCS to be translated into macroscopic dismounting behavior.