COPOLYMERS IN DILUTE-SOLUTION .1. PRELIMINARY-RESULTS FOR STYRENE-METHYL METHACRYLATE (REPRINTED FROM J-POLYMER-SCIENCE, VOL 16, PG 517-530, 1955)

The dilute solution properties of copolymers are briefly discussed in relation to those of the parent homopolymers. It is shown that copolym er molecules are usually more expanded in solution than would be expec ted from the averaged behavior of the pure polymers, because of repuls ive interactions between the unlike monomer units. A thermodynamic par ameter chi(AB) characterizing these interactions can be derived from m easurements of the dilute solution properties of copolymers. In favora ble cases this parameter can be independently evaluated from studies o f ternary systems composed of the two parent homopolymers and a solven t, thus allowing prediction of the behavior of the copolymer. Light sc attering and viscosity measurements on fractions of approximately equi molal copolymers of styrene and methyl methacrylate are presented and analyzed. The values of chi(AB) deduced from the results in two solven ts agree satisfactorily with each other, but are somewhat larger than those earlier obtained from measurements on ternary systems.