Copolymerization of lipoic acid with 1,2-dithiane and characterization of the copolymer as an interlocked cyclic polymer

Copolymerization of lipoic acid (LPA) and 1,2-dithiane (DT) and characterization of the resulting product were investigated. The copolymerization induced readily to give high-molecular-weight polymers in high yields. The difference in the polymerization reactivity between the two monomers may originate from the strain energies of the monomers. The mechanical properties of poly(LPA-co-DT) demonstrated that the polymers contains polycatenane structures. The molecular weight entanglement (M-e) of poly(LPA-co-DT) estimated from a dynamic viscoelasticity measurement was in good agreement with the half value of the molecular weight of a noninterlocked cyclic polymer estimated from the photodecomposition of poly(LPA-co-DT).