Part A
The spin-lattice relaxation time and the nulcear Overhauser enhancement were measured using Bruker AM 300 spectrometer operating at 75.5 MHz for $^13C$ to investigate the molecular motional characteristics and its tacticity effect for tactic poly(2-hydroxyethyl methacrylate) (PHEMA) as a function of temperature in dimethyl sulfoxide and methanol solvents. The observed relaxation data have been analyzed for both backbone motion and methyl internal rotation according to the log-$x^2$ distribution model and the diamond-lattice model. The correlation times thus obtained thus obtained for the molecular motions show that isotactic PHEMA is more flexible than syndiotactic counterpart. The syndiotactic PHEMA seems to have intramolecular hydrogen bonding which restricts the motion of C-2 carbon at temperatures below 35℃, whereas isotactic one indicated no hydrogen bonding at all temperatures examined in this study. The methyl group of isotactic PHEMA shows a greater degree of freedom for the internal rotation than that of syndiotactic one.
Part B
The unperturbed dimensions of isotactic PHEMA were evaluated from intrinsic viscosity measurments in water, ethanol, 1-propanol, 2-propanol, and 2-butanol under θ conditions over the temperature range of 3.7 - 32.1℃. The smallest value of unperturbed dimensions ($K_θ$) and the largest negative temperature dependence of unperturbed dimensions and the polymer-solvent interaction parameter (B) were obtained in aqueous θ solvent relative to the corresponding organic θ solvents. The temperature coefficient of the unperturbed dimensions, dln<$r^2_0$/dT, obtained in this study has a negative value of $-1.44×10^{-3}$ $deg^{-1}$ under chemically similar θ solvents such as ethanol, 1-propanol, 2-propanol, and 2-butanol where specific solvent effects are eliminated or minimized. Both the entropy of dilution and enthalpy of dilution show the negative values for water, methanol, and t-butanol, whereas the positive ones for ethanol, 1...