AbstractThe carbonates and oxides of zinc and cadmium polymerize propylene sulfide to elastomeric materials, but with the addition of ammonia low molecular weight polymers are produced. The effect of the ammonia is to react with some of the propylene sulfide to give aminopropanethiol, which will itself polymerize monomer by a stepwise reaction or, after reaction with the metal carbonate, form a metal bis(aminopropanethiolate) which is an active initiator. Chemical and spectroscopic examination of these polymers shows them to be essentially bifunctional, with one NH2and one SH terminal group. There is, however, evidence to suggest that further reaction of monomer occurs with the terminal amine groupings to give polyfunctional compounds. From the relative proportions of ammonia, zinc carbonate, and monomer, the rate of polymerization, molecular weight, and degree of endgroup coordination with catalyst residue can be controlled as desired. Due to the highly reactive endgroups, the polymers are readily crosslinked with epoxy resins, aziridinyl compounds, and hexamethoxymethylene melamine to give useful products exhibiting high solvent resistance.
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