β Scribed by Peng Wei Zhu; Donald H Napper
No coin nor oath required. For personal study only.
The coil-to-globule transitions of fractionated poly(N-isopropylacrylamide) chains attached to electrosterically stabilized polystyrene latex particles were studied for molecular weights ranging from 3 Γ 105 to 2 Γ 10 6. The shapes of the transitions proved to be a sensitive function of the polymer molecular weight: the component of the transition that occurred under better than 0-solvency conditions increased significantly (from 30 to 80%) as the molecular weight was decreased by an order of magnitude; concomitantly, the component that occurred under worse than 0-solvency conditions was substantially decreased. Studies carried out with 13C NMR supported the hypothesis that these two types of transitions were phenomenologically different. The transitions in worse than 0-solvents can be attributed to the strong attractive binary interactions that characterize worse than 0-solvents, whereas the transitions in better than 0-solvents arose from the weaker attractive many-body interactions, i.e. n-clustering. Simple scaling law considerations imply that the component of the coil-to-globule transitions arising from n-clusters should decrease with increasing molecular weight of the interfacial polymer, in conformity with the experimental data.
π SIMILAR VOLUMES
The coil-to-globule transition of two poly( N-isopropylacrylamide) (PNI-PAM) ionomers with different ionic contents (0.8 and 4.5 mol %), but similar weight average molar masses, in deionized water was investigated by a combination of static and dynamic light scattering. In spite of the large differe
A high molar mass polycation poly(methacryloylethyl trimethylammonium methylsulphate), PMETMMS, dissolved in mixtures of water and acetone, was studied using light scattering during the reversible coil-to-globule transition. When the mass fraction of acetone in the solvent mixture, β₯, is higher than