Anionic ring-opening polymerization of -thionocaprolactone was examined. When organolithiums, Grignard reagents, and lithium tert-butoxide were used as the initiators, the corresponding polythiocarboxylic-O-ester was selectively formed. When potassium tert-butoxide and 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU) were used, the corresponding polythiocarboxylic-S-ester was predominantly formed. The monomer conversion and M n of the obtained polymer increased with the polymerization temperature. Elongation of polymerization time resulted in decrease of the polymer yield and Mn. The polymerization in tetrahydrofuran (THF) proceeded faster compared with the polymerization in toluene. Formation of a cyclic dimer was observed in the polymerization in THF.

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SUMMARY: Radical polymerizations of methacrylate-and styrene-based bicyclo orthoesters (BOEs), and their copolymerization with methyl methacrylate and styrene were carried out with 2,29-azoisobutyronitrile (AIBN, 5 mol-%) as an initiator in N,N-dimethylformamide (DMF, 2 M) at 708C for 15 h to afford the corresponding polymers in 64 -96% yields having BOE moieties in the side chains. Crosslinking of the polymers was carried out in the presence of BF 3 N OEt 2 (3 mol-%) as a cationic catalyst in CH 2 Cl 2 . The yield of the crosslinked polymer increased with increasing initial concentration of the polymer and increasing crosslinking temperature. Decrosslinking of the crosslinked polymers was carried out in the presence of trifluoroacetic acid (TFA, 5 mol-%) as a cationic catalyst in CH 2 Cl 2 to regenerate the starting linear polymers. The recovery of the starting linear polymer increased with decreasing concentration of the initially crosslinked polymer and with increasing decrosslinking temperature.

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