A polymethyl methacrylate polymer, prepared by the emulsion technique, was fractionated three times to obtain essentially homogeneous fractions. The intrinsic viscosities and weight average molecular weights were determined in an ideal solvent at 23°C. and in nonideal solvents at 25°C. The constants K and a in the conventional modified equation [η] = KMa were determined. The intrinsic viscosity in an ideal solvent was found to fit closely over the molecular range studied with the relation [η]θ = KM1/2. Light scattering measurements giving root‐mean‐square distance between ends of a polymer chain were carried out. It was shown that these results support both Kuhn's relation (r̄2)1/2 ≈︁ M0.50 and Flory's relation (r̄2)3/2 = M[η]/2.1 × 1021 in an ideal solvent. In a nonideal solvent only Flory's relation was found to be in agreement with the experimental results. The values of volume expansion factor α3 ratios A2M italicw2/(r̄2)3/2 and A2Mw/[η] in a nonideal solvent and the value of the ratio [η]/M1/2 in an ideal solvent showed that the polymer molecules were expanded beyond their random flight dimensions in a nonideal solvent.
Section, Picatinny Arsenal, Dover, New Jersey 471 472 S. N. CHINAI, A. T,. RESNICK, H. T. LEE and then xith \Yuter. hours.The polymer tvas finally drird at G 0 C . for 24 The yield of poly-n-octyl methacrylatc polymer ivas 87%. FractionationThe fractional precipitation procedure, combined with lowering the temperature from 30' to 20°C., was used in the fractioiiatioii of poly-n-octyl methacrylate from a 3yo benzene solution, with the use of methanol as a precipitant. The original heterogeneous sample ~vab divided into five fractions a t the end of the first fractionation. Of these, only three fractions were subjected to the first refractionation from a o.5y0 benzene solution.This resulted in 12 subfractions. Of these 12 subfractions, 11 were subjected to the second refractionation from a 0.1% benzene solution. Only the first fraction from each of these 11 subfractions was recovered. This procedure resulted in 11 fractions which were more homogeneous with respect to molecular might than the original material. The fractions were rendered free from solvent by the frozen-benzene technique.
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