Dilute solution properties of tactic poly(2-hydroxyethyl methacrylate)

Abstract

PART A Dilute Solution Properties of Tactic Poly(2-Hydroxyethyl Methacrylate) Isotactic and syndiotactic poly(2-hydroxyethyl methacrylate) (PHEMA) have been prepared. Intrinsic viscosity-molecular weight relationships were established for the isotactic and syndiotactic PHEMA in N,N-dimethylformamide (DMF) at 25$^\circ$C by solution viscometry and light scattering. The unperturbed dimensions and interaction parameters have been examined in DMF, water, methanol, ethanol, and water-methanol (1:7 by volume) mixture for isotactic PHEMA and DMF, methanol, and water-methanol (1:7 by volume) mixture for syndiotactic PHEMA using the Stockmayer-Fixman representation. The results suggest that the compact random coil structure for isotactic PHEMA occurs in water solvent and isotactic PHEMA is more highly extended in polar solvents. PART B Effect of Ureas on the Viscometric Behavior of Water Soluble Isotactic Poly(2-Hydroxyethyl Methacrylate) Isotactic poly(2-hydroxyethyl methacrylate) (PHEMA) is soluble and has the compact random coil structure in water solvent. The effect of six ureas (thiourea, urea, methylurea, ethylurea, 1.3-dimethylurea, and tetramethylurea) on the viscometric behavior of aqueous solutions of isotactic PHEMA as a function of urea concentrations at 25$^\circ$C has been investigated. The compact random coil structure is found to disappear as ureas are added. The result is discussed in terms of water structure-breaking and -making of solutes, and hydrophobic interactions between hydrophobic groups. In addition, experiments were performed with aqueous isotactic PHEMA solution at four different temperatures. The temperature-dependant conformational behavior of isotactic PHEMA in pure water presents that the most compact conformation is occured at 20$^\circ$C among four different temperatures.