Desilylation-Triggered Degradable Silylacetal Polymers Synthesized via Controlled Cationic Copolymerization of Trimethylsilyl Vinyl Ether and Cyclic Acetals

Abstract

Silylacetal was demonstrated to function as a promising cleavable moiety for preparing polymers degradable via desilylation under diverse, mild conditions. The silylacetal moieties were installed in the main chain of the polymers via the controlled cationic copolymerization of trimethylsilyl vinyl ether (TMSVE) and a cyclic acetal under appropriately designed conditions. Importantly, desilylation reactions of the silylacetal units occurred under weak acid, base, or fluoride ion conditions, which triggered the degradation of the polymer via the spontaneous cleavage of the unstable hemiacetal moieties generated by the desilylation. Moreover, silylacetal moieties were successfully incorporated at the desired positions in the main chain via the addition of a small portion of TMSVE during the controlled cationic copolymerization of a vinyl ether and cyclic acetal. The strategy devised in this study will allow the design of elaborate polymers that undergo degradation triggered by various stimuli.

Controllable Degradation of Polyurethane Thermosets with Silaketal Linkages in Response to Weak Acid

“…Following this idea, mild degradability is anticipated if PU networks could be incorporated with hydrolyzable bonds in response to mild conditions. Among cleavable linkages, silaketal, usually applied as the protector for the hydroxyl group, is adequate to achieve controllable bond formation and fragmentation under different acid/base environments. − In general, silaketal is usually prepared from the condensation reaction between chloroalkylsilane and hydroxyl groups in the presence of a Lewis base, and the silaketal linkages can be further hydrolyzed under mild acidic conditions . It is noteworthy that the reaction activity of silaketal hydrolysis varies concomitantly with the change of alkyl substituents on silicon atoms, and the acidity of the environment also dominates the hydrolysis rate. , In that case, introducing silaketal linkages with different alkyl substituents into thermosetting PU materials will be a feasible approach to regulate the degradation rate as well as accomplish moderate recyclization …”

Recent Advances in Sequence‐Controlled Ring‐Opening Copolymerizations of Monomer Mixtures

“…The newly generated hydroxy group could then efficiently induce the subsequent ring‐opening anionic polymerization of LA to a diblock copolymer. In addition, cyclic acetals could also copolymerize with various vinyl ethers and styrene derivatives to form alternating or random copolymers, depending on the substituents on the cyclic acetals (Scheme 7e) [147,148] . Additionally, cyclic acetals can be prepared in‐situ from epoxides and aldehydes, which can further copolymerize with vinyl ethers, catalyzed by SnCl 4 , to form alternating copolymers with M n s∼12.4 kDa and Đ s of 1.5 (Scheme 7f) [149] …”

Rapid and Selective Photo‐degradation of Polymers: Design of an Alternating Copolymer with an o‐Nitrobenzyl Ether Pendant

“…Based on these analyses and the results of the model photo-degradation experiment, we propose that the photo-degradation of the alternating copolymer is presumably induced by cleavage of the hemiacetal intermediates generated via the photo-deprotection of the oNBn pendants (Figure 3D), which is similar with the desilylation-triggered degradation of silylacetal polymers. [52] As the produced βhydroxy aldehyde compound 4 is easily dehydrated into a derivative of cinnamaldehyde, which is a valuable compound for the perfume industry and a useful monomer, [53] there is a possibility of developing an upcycling system through optimization of the degradation conditions.…”