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Dilute solution properties of styrene–acrylonitrile and styrene–methyl methacrylate copolymers. I. Intrinsic viscosity–molecular weight relations

1976; Wiley; Volume: 14; Issue: 4 Linguagem: Inglês

10.1002/pol.1976.180140414

1542-9385

C. Rami Reddy, V. Kalpagam,

Surfactants and Colloidal Systems

Abstract Styrene–acrylonitrile (St–AN) copolymers of three compositions—27.4 mole‐% (SA 1 ); 38.5 mole‐% (SA 2 ); and 47.5 mole‐% (SA 3 ) acrylonitrile—and styrene–methyl methacrylate (St–MMA) copolymer (SM) of 46.5 mole‐% methyl methacrylate were prepared by bulk polymerization at 60°C with benzoyl peroxide as the initiator, and were then fractionated. The molecular weights of unfractionated and fractionated samples were determined by light scattering in a number of solvents. The [η] versus M̄ w relations at 30°C were established for SA 1 , SA 2 , SM, and polystyrene (PSt) in ethyl acetate (EAc), dimethyl formamide (DMF), and γ‐butyrolactone (γ‐BL), and for SA 3 in methyl ethyl ketone (MEK), DMF, and γ‐BL. Second virial coefficients A 2 and the Huggins constant were determined. From values of A 2 and the exponent a of the Mark–Houwink relation it is seen that the solvent power for samples SA 1 , SA 2 , and PSt is in the order EAc < γ‐BL < DMF, while for sample SA 3 the solvent power is in the order MEK < γ‐BL < DMF. The solvent power decreases with an increase in AN content. The solvent power of the three solvents used for SM copolymer sample is practically the same within experimental errors. From the a values it is concluded that in a given solvent the copolymer chains are more extended than the corresponding homopolymers.