A series of liquid chloroprene-methacrylic acid copolymcr (CP--co-MAA) modified epoxy resin (ER)/poly (butyl methacrylate) (PBMA). semi-IPN were synthesized. Some physical properties were investigated. DSC diagrams showed two indistinct and inward endothermal transitions corresponding to the transitions of two networks in the semi-IPN system. By observing morphology with SEM technique it shows that there is a multiphase structure

in which CP-co-MAA's. domain sizes arc about 0.10--0.80μ. With increasing C/E ratio

the domain sizes are getting smaller

which is due to effect of mixing network of CP-co-MAA promoting entanglement and interpenetrating of PBMA and CP-co-MAA- ER network.In most of the semi-IPN's compositions

ER phase readily maintains its phase continuity while PBMA phase presents a band shape structure.Consequently

crosslinking network keeps in its continuous phase more readily than uncrosslinking one

thus it influences dominantly on the physical properties.