Polyethylmethacrylate in dilute solution

Abstract

Polyethylmethacrylate (PEM) was prepared by bulk polymerization and fractionated using acetone/acetone-water (2:1 V/V) mixture. The solution properties of fractionated as well as unfractionated polymers were investigated in various solvents (ethylacetabte, toluene, ethylacetate-ethanol) by light scattering and viscosity at 35°C. Osmotic pressure measurements were also carried out on selected polymer samples for the evaluation of width of distribution. [η]-M_w and (r²)^½-M_w relationships for these systems were established. Ethylacetate was found to be a bad solvent compared to toluene and methylethyketone. In the case of unfractionated PEM, the parameters like [η]^⅔M^⅓, M_w/[Φ], and φ were corrected for molecular weight heterogeneity assuming SCHULZ-ZIMM distribution. For the evaluation of FLORY's constant K, and the unperturbed dimension (r⁰₂)^½ of the polymer, FLORY-FOX, KURATA-STOCKMAYER, and STOCKMAYER-FIXMAN methods were employed. The K and (r⁰₂)^½ values evaluated from the FLORY-FOX method were almost similar to those measured in a θ solvent, while the other two methods yielded higher values. A comparison of the measured (r²)^w_½ and that calculated from KIRKWOOD-RISEMAN and DEBYE-BUECHE theories indicated the polymer coil as conforming to a statistical chain. The molecular weight dependence of A₂, the second virial coefficient, for PEM/ethylacetate was established and the value of A₂ compared well with that calculated from OROFINO-FLORY equation.