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.
Poly‐n‐butyl methacrylate prepared by the emulsion technique was fractionated three times by the fractional precipitation procedure to obtain eight fractions. Relationships between viscosity and weight‐average molecular weight were obtained in both an ideal solvent, isopropanol, and a nonideal solvent, methyl ethyl ketone. These relationships are represented by equations:
The effect of the size of the pendant groups (‐methyl, ‐ethyl, and n‐butyl ester) on the degree of extension of macromolecules in ideal solvents is discussed. It was found that the degree of flexibility of the macromolecule increases as the size of the pendant group increases. These results are believed to be due to the short‐range interference effect of the solvent molecule on the degree of free rotation of the macromolecule.
Poly‐n‐hexyl methacrylate prepared by the emulsion technique was fractionated three times by the fractional precipitation procedure to obtain eight fractions. Relationships between viscosity‐ and weight‐average molecular weight were obtained in both an ideal solvent, isopropanol, and a nonideal solvent, methyl ethyl ketone. These relationships are represented by equations:
The effect of the size of the pendant groups (‐methyl, ‐ethyl, n‐butyl and ‐n‐hexyl ester) on the degree of extension of macromolecules in ideal solvents is discussed. It was found that initially as we progress from polymethyl to poly‐n‐butyl methacrylate the degree of flexibility of the macromolecule increases as the size of the pendant group increases. These results are believed to be due to the short‐range interference effect of the solvent molecule on the degree of free rotation of the macromolecule. However, it was found that poly‐n‐bexyl methacrylate chains have considerably greater chain extension than any of the other three polymers. This expansion of poly‐n‐hexyl methacrylate chains ia a result of the steric effect of large pendant units.
A polyethyl methacrylate polymer, prepared by the emulsion technique, was fractionated three times to obtain ten fractions. The intrinsic viscosity‐molecular weight relations were established in an ideal and in a nonideal solvent at 23°C. Light scattering measurements giving polymer dimensions were compared with the viscosity theories advanced by Debye‐Bueche, Kirkwood‐Riseman, and Flory‐Fox. The calculated values of the effective bond length b for polymethyl methacrylate and polyethyl methacrylate show that polymethyl methacrylate chain has greater hindrance to rotation than the polyethyl methacrylate chain. The results are explained by consideration of the free volume occupied by the solvent molecules.
The complex dielectric constant of a pure molecular weight fraction of poly‐n‐hexyl methacrylate and of poly‐n‐octyl methacrylate was determined over a frequency range of 30 to 3 × 105 cycles/sec. and a temperature range of −66 to 106°C. and −61 to 81°C., respectively. The data indicate the presence of two transition regions, with the transitions being further apart with increasing side chain length. Examination of the data showed that superposition was not possible using the usual superposition schemes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.