Abstract
Dilute solutions of narrow distribution poly(methyl methacrylate) (PMMA) samples in the poor solvents, 2-ethoxyethanol and acetonitrile, are studied by dynamic and static light scattering and viscometry. Theta temperatures at 37,8°C and 32,3°C, respectively, are found, where the constants KΘ of the Mark-Houwink-Sakurada relation are 5,6 · 10−2 cm3/g and 4,0 · 10−2 cm3/g. This implies that the unperturbed dimensions of PMMA molecules in 2-ethoxyethanol are greater by 12% than in acetonitrile. The hydrodynamic radii in the two solvents and the radii of gyration in acetonitrile are found to decrease smoothly with decreasing temperature passing the theta temperatures. Data treatment according to the thermal blob model shows that the macromolecular coils, still close to Gaussian statistics, move toward the excluded volume regime above the theta temperature Θ and toward the collapse regime below Θ.
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