Solution Properties of the Methyl Methacrylate-Acrylonitrile Copolymer

Abstract

Abstract Short-range interactions between chain units of random copolymers in solution may be influenced by the characters of the pendant side groupes or, more precisely, by the dipole moment of the substituent. In those experiments the steric factor was derived for a random copolymer composed of methyl methacrylate and acrylonitrile from the relation between the limiting viscosity number and the molecular weight. Mark-Houwink relations were obtained in N,N′-dimethylformamide (DMF) and in methyl ethyl ketone (MEK) at 30°C for the copolymer containing 0.48 mol fraction of acrylonitrile, and for polymethyl methacrylate (PMMA) for the sake of comparison: [η]=4.61×10−4M0.65 for the copolymer in DMF [η]=1.70×10−4M0.65 for PMMA in DMF [η]=1.26×10−3M0.52 for the copolymer in MEK With the Stockmayer-Fixman expression, these correlations become, respectively: [η]=213×10−5M1⁄2+12.4×10−7M [η]=78.2×10−5M1⁄2+5.05×10−7M [η]=163×10−5M1⁄2+1.05×10−7M The unperturbed mean square end-to-end distance, 〈L2〉0, determined from the first term of the latter expressions, together with the 〈L2〉0f value calculated by assuming the completely free rotation, gives the steric factor of σ=(〈L2〉0⁄〈L2〉0f)1⁄2 2.59±0.01 from the DMF solution; this factor is larger than that for polymethyl methacrylate (2.11±0.08),, and that for polyacrylonitrile (2.20+0.05). The steric parameter derived from the MEK solution is 2.37±0.05 for this co-polymer; this value does not agree with the value obtained from the DMF solution. In both cases, it may be concluded that the dimensions of the copolymer between acrylonitrile and methyl methacrylate are influenced by the electrostatic interactions between nitrile groups of acrylonitrile units and methoxy-carbonile and/or methyl groups of methyl methacrylate units. The second virial coefficient in MEK obtained from the light scattering measurements also has a larger value for this copolymer than for polymethyl methacrylate. This tendency of copolymers to show a larger second virial coefficient seems to be an essential characteristic of some copolymers.