Six-Membered Cyclic Carbonate Having Styrene Moiety as a Chemically Recyclable Monomer. Construction of Novel Cross-Linking-De-Cross-Linking System of Network Polymers

This article deals with (1) synthesis and anionic polymerization of a six-membered cyclic carbonate having styrene moiety, (2) anionic depolymerization of the obtained polymer, (3) radical cross- linking of the obtained polymer, and (4) anionic de-cross-linking of the cross-linked polymer. The monomer 5-ethyl-5-((p-vinylphenyl) methoxymethyl)-1,3-dioxan-2-one (St6CC) underwent anionic polymerization with potassium tert-butoxide (t-BuOK) as an initiator in THF to afford the corresponding polycarbonate (poly(St6CC)). It was confirmed that this polymerization was equilibrium polymerization by the relationships between the polymerization temperature and monomer conversion. Poly(St6CC) underwent anionic depolymerization with t-BuOK (5 mol % vs polymer repeating unit) as a catalyst in THF (0.1 M) at 20 °C for 24 h to recover St6CC in 60% yield. Treatment of poly(St6CC) with a radical initiator afforded the cross-linked polymer. Employment of styrene as the comonomer satisfactorily afforded the corre- sponding cross-linked polymer. It underwent anionic de-cross-linking with t-BuOK (10 mol % vs polymer repeating unit) in THF at 50 °C for 24 h to afford a THF-soluble polymer. The yield of the THF-soluble part increased as the styrene composition in the cross-linked polymer increased. It was suggested that the de-cross-linking efficiency depended on the cross-linking density.