A newly designed viscometer was used to measure the viscosity of polymer solutions under high-temperature and low-shear-rate conditions. Rheograms of dilute and concentrated scleroglucan solutions were determined in the range of temperatures between 30 and 150°C. Rheological behaviour was correlated with macromolecule structural parameters. Intrinsic viscosity values versus temperature were analysed on the basis of Yamakawa's theory of semirigid chains. As the temperature increased, local molecular rigidity decreased. An Arrhenius equation form was found for the persistence length variation versus temperature. An apparent activation energy of 7.5 kJ mol-1 (1.8 kcal mol-1) was determined. This value was of the same order of magnitude as the hydrogen bond energy that stabilizes the scleroglucan triple-helix structure. On considering a model of rod particles, the scleroglucan molecule behaves like a rod-like polymer up to 130°C.
Посилання на статтю:
Studies on scleroglucan conformation by rheological measurements versus temperature up to 150°C / C. Noi'k* and J. Lecourtier // Polymer. – 1993. – Vol 34. – P. 150-157.