Properties of dilute polymer solutions I—Osmotic and viscometric properties of solutions of conventional polymethyl methacrylate

Abstract

This is the first report of a series on the properties of dilute solutions of conventional polymethyl methacrylate designed to characterize the chain length and its distribution, the intramolecular chain interactions and the thermodynamic interactions with solvent and their effects on the chain dimensions, and to establish the accuracy and reproducibility of such data. Herein [η] M ̄ n relations in benzene at 30° are established for both fractionated and unfractionated polymers from ebulliometric determinations in benzene for M̄ n from 200 to 6 × 10 3 and from osmotic pressure measurements in two or more solvents for M̄ n from 10 4 to 7 × 10 5. Evidence is presented that the values of M̄ n so obtained are generally accurate and reproducible within an uncertainty of three per cent. The observed curvature and its molecular weight dependence in osmotic pressure/concentration relations is in general accord with theoretical expectation. The identity of [η] M ̄ n relationships found for unfractionated polymers prepared both with and without added chain transfer agent indicates that both have the same molecular weight distribution and that disproportionation is the predominant mode of termination of methyl methacrylate radicals at 60°.