Solution properties of poly(butyl methacrylate-co-acrylonitrile)

Abstract

Poly(buty1 methacrylate-co-acrylonitrile) of 1:1 molar composition has been prepared by bulk polymerization process using 2,2'-azoisobutyronitrile (AIBN) as the initiator and fractionated using ethyl methyl ketone and methanol as the solvent and the precipitant respectively. The identical value of the refractive index increments (dn/dc) of these fractions indicated their homogeneity in chemical composition. The dilute solution properties of these fractions in N,N-dimethylformamide (DMF), ethyl methyl ketone (MEK), and acetone have been investigated employing light-scattering, osmometry and viscometry techniques. The following Mark-Houwink relationships have been established at 25°C: DMF:[η]=1,538·10 hypehn;2·M̅_W^0.73 MEK:[η]=7,096·10 hyphen;2·M̅_W^0.56 Acetone:[η]=7,852·10 hyphen;2·M̅_W^0.72. The unperturbed dimensions for the copolymer have been evaluated and compared with those for the constituting homopolymers. A solvent dependence of the unperturbed dimension has been observed. The steric factor, σ, was found to be 2,64 in DMF and 2,48 in MEK for poly(buty1 methacrylate-co-acrylonitrile) compared to a value of 2,20 for poly(acrylonitri1e) in DMF, and 2,09 for poly(buty1 methacrylate) in MEK which suggests the greater stiffness of the copolymeric chain compared to the constituting homopol ymers.