Heterogeneous networks of polyisoprene/polyvinylethylene

High cis, 1,4-polyisoprene (PI) and polyvinylethylene (PVE) form a miscible blend, having a lower critical solution temperature (LCST). Networks of this blend were prepared by crosslinking with organic peroxide or by sulfur vulcanization. The very different reactivity of the two polymers leads to a disparity in the crosslinking, especially for sulfur curing-networks of PI can be formed without substantial reaction of the PVE. When the sulfur vulcanization is carried out at ca. 130 °C or higher (above the LCST), the polymers phase separate, yielding a PI network with PVE domains. Curing at lower temperatures maintains the miscible morphology, and a homogeneous blend network is obtained.