Mid-chain degradable polymers can be prepared by atom transfer radical polymerization from difunctional initiators that include triggers for the desired stimuli. While many difunctional initiators can respond to reducing conditions, procedures to prepare difunctional initiators that respond to oxidizing conditions are significantly less available in the literature. Here, a difunctional initiator incorporating an oxidizable boronic ester trigger was synthesized over four steps using simple and scalable procedures. Methyl methacrylate was polymerized by atom transfer radical polymerization using this initiator, and the polymerization kinetics were consistent with a controlled polymerization. The polymer synthesized using the difunctional initiator was found to decrease in molecular weight by 58% in the presence of hydrogen peroxide, while a control experiment using poly(methyl methacrylate) without a degradable linkage showed a much smaller decrease in molecular weight of only 9%. These observed molecular weight decreases were consistent with cleavage of the difunctional initiator via a quinone methide shift and hydrolysis of the methyl ester pendent groups in both polymers, and both polymers increased in polydispersity after oxidative degradation.
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Facile synthesis of polyperoxides with intermolecular peroxy bonds as macroinitiators for free radical graft copolymerization
A facile synthetic strategy to prepare a new type of on-chain polyperoxide bearing intermolecular peroxy bonds is reported. Polyketone from the copolymerization of ethylene and carbon monoxide was quantitatively transformed into amorphous and powdery polyperoxide using aqueous hydrogen peroxide at room temperature. This synthetic pathway allowed the highly selective and complete conversion of carbonyl groups into intermolecular peroxy groups that can initiate free radical graft copolymerization without generating fragmentary alkoxyl radical species. The thermal properties of polyperoxide were characterized by differential scanning calorimetry and thermogravimetric analysis, and the polyperoxide was further ap-plied as a macroinitiator to prepare densely grafted copolymers, polyethylene-g-poly(4-methyl styrene) and polyethylene-g-poly(methyl methacrylate), via grafting from approach.
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- Award ID(s):
- 2023955
- PAR ID:
- 10574195
- Publisher / Repository:
- ChemRxiv
- Date Published:
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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