Fully degradable polymer networks from conventional radical polymerization of vinyl monomers enabled by thionolactone addition

Abstract

We report the preparation of degradable polymer networks by conventional free radical copolymerization of n-butyl acrylate with a crosslinker and dibenzo[c,e]oxepane-5-thione (DOT) as a strand-cleaving comonomer. Addition of only 4 mol% of DOT imparts the synthesized networks with full degradability by aminolysis, whereas gels with less DOT (2 mol%) cannot be degraded, in excellent agreement with the recently proposed reverse gel-point model. Importantly, even though DOT significantly slows down the polymerization and delays gelation, it has a minimal effect on physical properties of the networks such as shear storage modulus, equilibrium swelling ratio, glass transition temperature or thermal stability.

Degradable linear and bottlebrush thioester-functional copolymers through atom transfer radical ring-opening copolymerization of a thionolactone

“…A recent study concluded that chain transfer to the lactone was not significant during free radical polymerization. 30 In agreement, we found that the addition of up to 20 mol-% of lactone (2) to ATRPs of PEGA in toluene did not cause observable chain transfer, see Figure S1.…”

Thiocarbonyl chemistry in polymer science

“…67 TARO monomers have also found a use in producing degradable cross-linked materials through uncontrolled radical polymerization. 68,71 Incorporation of only 4 mol% of DOT into acrylate-based networks led to the ability to completely degrade the insoluble materials. The low incorporation allowed for the retention of the physical properties of the network, compared to non-degradable controls, and 3D-print some of the structures.…”

“…Conversely, thiocarbonyl fluoride (F 2 CvS) and thiocarbonyl chlorofluoride (ClFCvS), which do not have β-bonds, undergo radical polymerization of the CvS bond, see Scheme 13A. 75 Although the thiocarbonyl Low rate; yields oligomers only Methyl acrylate 63 Thiocarbonyl species is incorporated at a faster rate than the vinyl comonomer mPEG acrylate 63,66,67 n-Butyl acrylate 68,69 t-Butyl acrylate 64 Acrylamide 66 Homopolymerization 73 Low yielding…”

Radical ring-opening polymerization of sustainably-derived thionoisochromanone

“…shown to ring-open in previous rROP reports (see Figure S19). 21,27,28,[30][31][32][33] Next, full reaction coordinates with Gibbs free energy profiles were investigated (Figure 3). To begin, the isobutyronitrile radical generated 1 kcal/mol and an exergonicity of 5.9 kcal/mol.…”

“…For example, thionocaprolactone (thCL, Figure 1B) copolymerizes with vinyl acetate and cyclic ketene acetals but remains undisturbed when subjected to acrylates or acrylamides. 25,26 Alternatively, relatively well-studied dibenzo[c,e]oxepane-5-thione (DOT, Figure 2B) has copolymerized successfully with acrylates, 21,[27][28][29] acrylamides, 30 N-functional maleimides, 31 and styrenics 32,33 but remains inert in copolymerizations with vinyl acetate. 21,31 The styrene-co-DOT systems published to date are susceptible to degradation under specific conditions, yet traditional degradation methods, such as aminolysis, are unable to degrade p(S-co-DOT).…”