The characteristic ratio of poly(methacrylic acid) in organic solvents

Parameters of the Mark‐Houwink equation for poly(methacrylic acid) (PMAA) in methanol at 25°C, [η] = 0,0224 · M0,679, were determined and found to differ markedly from those reported earlier for 26°C. The value of the exponent along with the high value of the second virial coefficient confirms that near to 25°C methanol is not a theta‐solvent for PMAA. By employing extrapolation according to Tanaka, the characteristic ratios C of PMAA in methanol (C = 12,0) and in 2‐ethoxyethanol (C = 9,7) were determined from viscosity data at 25°C. The unperturbed dimensions of PMAA depend on the solvent used. They are larger in organic solvents than in water, but the difference is not so high as assumed before. By using the Stockmayer‐Fixman extrapolation, the characteristic ratio for PMAA in 2‐ethoxyethanol was determined at 70°C, i.e. at a temperature not too far from theta‐conditions (Θ = 65°C, C = 8,2). A comparison with the value for 25°C shows that the unperturbed dimensions of PMAA decrease with increasing temperature.