Degradable, Ultraviolet‐Crosslinked Pressure‐Sensitive Adhesives Made from Thioester‐Functional Acrylate Copolymers

Abstract

Pressure‐sensitive adhesives (PSAs) are made from soft, irreversibly lightly crosslinked polymers. Even after removal from surfaces, they retain insoluble networks which pose problems during the recycling of glass and cardboard. Herein, degradable PSAs are presented that provide the required performance in use but have networks that can be degraded after use. A series of copolymers was prepared through radical copolymerization of n‐butyl acrylate, 4‐acryloyloxy benzophenone (ABP) photo‐crosslinker, and dibenzo[c,e]oxepin‐5(7H)‐thione (DOT) to provide degradable backbone thioesters. The optimum tack and peel strengths were found for molar contents of 0.05 mol% ABP and 0.25 mol% DOT. Degradation of the backbone thioesters through aminolysis or thiolysis led to the full dissolution of the networks, loss of adhesive properties of films (decreases in the measured tack and peel strengths), and the quick detachment of model labels from a substrate. Inclusion of DOT into PSAs offers a viable route toward degradable and recyclable packaging labels.

Ring-opening terpolymerisation of phthalic thioanhydride with carbon dioxide and epoxides

“…46 Elsewhere, the statistical incorporation of thioester links into the polymer main chain of polyacrylates caused susceptibility to degradation by aminolysis and we found the same to be the case for our ROTERP terpolymers. 47 Subjecting a PTA/CO 2 /CHO terpolymer (Table 1 run #10) to methanolic ammonia for 48 h leads to its complete degradation into oligomers with M n < 1 kg mol −1 . In contrast, the all-oxygen counterparts from either CO 2 /CHO or PA/CHO ROCOP do not degrade under identical conditions.…”

Plenty of Space in the Backbone: Radical Ring‐Opening Polymerization

“…An advantage of embedding thioesters in the polymer main chain rather than esters is that they can be degraded under a variety of conditions, such as methanolysis, aminolysis, thiol‐thioester exchange [33,96] . Synthesis of biodegradable 3D printable resins, [97] adhesives [98] and drug delivery [99,100] using thionolactones has been reported. Furthermore, the design of amine bearing CKAs Even though hydrolytic degradability is a most desirable property for polymers in both industrial and biomedical applications, embedding more complex functionalities in the polymer backbone might be the key to synthesizing sophisticated smart materials that are not only degradable, but also stimuli responsive.…”

Insertion of Degradable Thioester Linkages into Styrene and Methacrylate Polymers: Insights into the Reactivity of Thionolactones

“…The glutathione-triggered degradation of DOT-derived backbone thioesters is promising for the intracellular delivery of drugs . DOT has also been used to produce degradable gels, networks, , and pressure-sensitive adhesives . Additionally, the stability of DOT in the presence of water (contrary to the hydrolytically labile cyclic ketene acetals) has enabled the heterogeneous synthesis of degradable particles under aqueous emulsion conditions. , …”