Mechanical relaxations in episulfide network polymers

A variety of condensation network polymers have been prepared by the reaction between amine, episulfide, and epoxide monomers. The mechanical relaxations occurring in these systems have been examined using a torsion pendulum and the role of hydrogen bonding in the mechanism of the β relaxation is shown to be insignificant. The chemical reaction between amine and episulfide groups has been investigated by IR spectroscopy and is shown to parallel the reaction between amine and epoxide groups. However, steric and electronic factors are suggested to decrease the extent of reaction when aromatic amines are involved. In the case of networks prepared from blends of episulfide and epoxide monomers, measurements of the gel time, together with the mechanical behavior around the glass transition, indicate that either interpenetrating or two-phase networks are formed. This is postulated to be a consequence of the high reactivity of the episulfide ring compared to the epoxide ring. The blending of small amounts of episulfide monomer with the epoxide monomer prior to curing may provide an effective method for lowering gel times without reducing the crosslink density and its dependent physical properties.