Alternating Sulfone Copolymers Depolymerize in Response to Both Chemical and Mechanical Stimuli

Abstract

This work describes the depolymerization of poly(vinyl acetate-alt-sulfur dioxide) (PVAS) as initiated by chemical and mechanical stimuli. In recent years, macromolecules that are able to depolymerize in response to specific stimuli have been highly sought because of their ability to amplify signal for sensing and drug delivery. Examples include self-immolative polymers from alkoxyphenol derivatives and polyaldehydes. We show here that alternating copolymers of sulfur dioxide and vinyl acetate are able to undergo similar depolymerization into their monomer components in response to various chemical and mechanical stimuli. Certain vinyl monomers such as vinyl acetate are able to polymerize with sulfur dioxide in a perfectly alternating manner, and the resulting copolymer possesses a low ceiling temperature. We show that this polymer is able to break down into its monomer components when subjected to UV/acetone, various Reactive Oxygen Species (ROS), and ultrasonication. In the case of UV, the acetone reacted via a Norrish reaction to produce free radicals that caused clean monomer production. For ROS, the polymer showed reactivity to both oxidizing and radical-containing ROS. Through kinetic studies, these polymers were shown to proceed via a two-part, first-order kinetic model with a fast initiation phase and a slow depolymerization phase. Finally, the polymers were subjected to probe ultrasonication, and depolymerization occurred as well. Most tellingly, the polymer again showed a fast initiation step and continued to depolymerize even after ultrasonication stopped. This class of polymers shows potential for drug delivery in response to both endogenous chemical and externally-applied mechanical cues.

Reflections on the Evolution of Smart Polymers

“…PPAs, PGs and POSs have been known since the 1960s to 1970s as PPAs and POSs were investigated as resists for lithography applications, and PGs were studied as degradable detergent builders . Recent advancements in their polymerization chemistry and end‐capping have enabled their depolymerization to be triggered by specific stimuli such as light, acid, oxidizing and reducing species, and even combinations of these stimuli . As these low T c polymers depolymerize back to the monomers from which they were prepared, their depolymerization is in principle reversible.…”

“…[63] Recent advancements in their polymerization chemistry and end-capping have enabled their depolymerization to be triggered by specific stimuli such as light, acid, oxidizing and reducing species, and even combinations of these stimuli. [64][65][66] As these low T c polymers depolymerize back to the monomers from which they were prepared, their depolymerization is in principle reversible. In contrast, another class of SIPs, first introduced in 2008, [67] depolymerizes to small molecules that differ from the monomers from which they were initially prepared.…”

Kinetics and mechanism of the thermal degradation for the synthesis of poly(norbornene sulfone)s by two different polymerization methods

“…Three-dimensional diffusion (Jander equation) D 4 1 À 2α stretch at 1300 cm À1 and symmetric stretch at 1135 cm À1 . [22] The bicycle (2,2,1) heptane and cis-bicyclo (3,3,0) octane indicate absorptions in the 921 cm À1 region.…”

Controlled aqueous polymerization of acrylamides and acrylates and “in situ” depolymerization in the presence of dissolved CO2

“…[4][5][6][7] In an attempt to overcome these limitiations, research has focused on the formation of polymeric materials derived from reformable monomers and the synthesis of stimuli responsive polymers. [8][9][10] Indeed, Zhu et al recently reported the low temperature (0°C) depolymerization of poly(N-isopropyl acrylamide) (pNIPAm) in aqueous media. 11 In this work, depolymerization was achieved by the addition of either TEMPO or 1,4-benzoquinone, which was proposed to proceed via abstraction of the terminal halide.…”