On-Demand Degradation of Thioester/Thioketal Functions in Vinyl Pivalate-Derived Copolymers with Thionolactones

Abstract

Copolymers containing thioester and thioketal groups were obtained by copolymerization of five-to sevenmembered ring thionolactones (TLs) with vinyl pivalate (VP). With the help of a degradation study on thioester and thioketal model compounds, we report the orthogonal reactivity of such incorporated links with thioesters being selectively cleaved by aminolysis and thioketals by peroxides. Orthogonal stepwise degradation of poly(TL-co-VP) copolymers was achieved using isopropylamine and benzoyl peroxide as shown by SEC. Bleach was identified as a universal agent for accelerated degradation. A good correlation between oligomer length after degradation and estimated polymer mass loss is also reported.

Synthesis of Degradable Polyethylene and Poly(ethylene-co-vinyl acetate) by Radical Co- and Terpolymerization of Ethylene, ε-Thionocaprolactone, and Vinyl Acetate

“…However, due to the difficulty of obtaining accurate molar masses for PE samples, it would be unwise to draw any firm conclusions from these results. It is also worth mentioning that the small amount of thioketal closed form (see Figure S14) does not degrade under the conditions employed …”

“…In the literature, ring retention was observed during the TCL copolymerization with vinyl esters. ,,, In these works, the ratio of TCL closed /TCL opened depends on both the overall monomer concentration and temperature. In bulk copolymerization with vinyl pivalate (VPi), the fraction of TCL closed units decreases from 34% at 70 °C to 15% at 100 °C . Also, bulk copolymerization of TCL with VAc leads to 35–45% of TCL closed at 70 °C, whereas in dilute solution, exclusively ring-opening polymerization is observed .…”

“…The presence of some TCL closed in copolymerization with ethylene, even though the polymerizations take place in dilute solution, may be explained by the lower steric bulk of ethylene compared to that of VAc, which facilitates its reaction with the ring-closed macroradical. We note that while ring retention can be considered to be a side reaction, the resulting thioketal groups are also sensitive to oxidative hydrolysis and could contribute to the backbone degradation …”

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

“…Additional thionolactones have since been reported, including DOT derivatives, ω-thionoalkanolactones − compatible with vinyl esters, and thionolactones derived from lactide, , and isochromanone . But there remain problems with fast and efficient homopolymerization, and there has been no report of copolymerization of a thionolactone with methacrylates.…”

Ring-opening polymerization of β-thiobutyrolactone catalyzed by phosphazenes

“…18 Also, more generally, PTEs prepared by ROP of cyclic thiolactones are currently attracting renewed attention given their inherent valuable properties in homopolymers as well as in copolymers, especially in relation to their degradation ability. 15,19–22…”