Molecular factors affecting the miscibility behavior of cycloolefin copolymers

The mutual miscibility diagram is determined for binary blends of two ethyl ene/norbornene random copolymers, and their monomer sequence distribution i s investigated by C-13 NMR spectroscopy. The miscibility changes abruptly a t a norbornene content of 50% where NMR measurements indicate a change in m icrostructure. When both copolymers have a norbornene content higher than 5 0%, all blends are miscible within the composition ranges available. A simp lified version of the lattice cluster theory (LCT) is applied to this syste m. The computations indicate that the chain stiffness (arising from the rig idity and steric interactions of the norbornene units) exerts significant i nfluence on the miscibility of these blends. Experimental miscibility diagr ams agree reasonably with the LCT predictions.