The free-radical copolymerization of donor, acceptor and neutral monomers to ternary copolymers is studied. It is shown that the composition of the ternary copolymers can be calculated from their monomer feed, in case the reactivity ratio (r) values of the three binary subsystems are known. The calculation based on the copolymer equation only considers really existing propagation steps.

The miscibility in blends of poly(2,6-dimethylphenylene oxide) (PPO) with random or block copolymers of styrene and methyl methacrylate (MMA) was studied by light microscopy and glass transition temperature measurements. Blends of PPO and the random copolymers were found to be miscible up to a copolymer content of 18 wt.-% MMA. The transition from miscibility to immiscibility in these blends is independent of temperature in the range 100 to 350 "C. From these data, the segmental interaction parameter between units of the homopolymer and MMA, x~~,~~~ is estimated to be about 0,5. Blends of PPO and the block copolymers of styrene and MMA used behave essentially as the corresponding homopolymers in terms of miscibility.

Using the suitable terpolymerization equations for the copolymerization of donor‐acceptor copolymer systems no ternary azeotrope could be calculated. Copolymerization reactivity ratios taken from literature show that there is no chance to find an azeotrope.