A study of the shearing and crosslinking of hydroxypropyl cellulose, a liquid crystal polymer, and its permeability as a hydrogel membrane

This work is a study of the structure and properties of solutions of hydroxypropyl cellulose (HPC) and its films crosslinked under various conditions. Temperature, concentration and shear flow field were found to be important parameters in the formation of HPC mesomorphic structures.; Photoinitiated crosslinking of HPC solutions in both the isotropic and liquid crystalline states preserved their structures permanently. The crosslinked HPC films have much better thermal properties than the uncrosslinked ones. Higher tensile modulus and strength were obtained from films crosslinked in the liquid crystalline state compared to those crosslinked in the isotropic state or to uncrosslinked films.; A shear-crosslinking device was used to prepare crosslinked films from different concentration solutions and under various shear conditions. X-ray diffraction measurements reveal that these HPC films show a nematic liquid crystal structure when the solution concentration is above the critical concentration. The molecular chain direction in the nematic LC films is parallel to both the surface of the film and the shear flow direction. The degree of orientation has been quantitatively expressed using Herman's orientation function. Band texture formation and loss, and degree of orientation were interpreted in terms of the competition between orientation and relaxation processes of the rigid-rod polymers. This further clarifies the conflicting reports in the literature regarding the origin of the band texture and its relationship to the orientation.; Permselectivity of HPC membranes crosslinked in the isotropic or liquid crystalline states was characterized by using small organic penetrants and long chain macropenetrants. The diffusivities decrease as the interaction between penetrant molecules and membranes increases, and with the increase of the effective size of the penetrants. The molecular weight cut-off of the membranes corresponds to a radius of gyration between 14 A and 22 A.; Phenyl urethane ended polyethylene glycols were synthesized and used to study the effect of penetrant concentration. Phenyl urethane ended polyethylene glycols at low concentration have higher permeability and diffusion coefficients and smaller partition coefficients compared to the corresponding PEGs.; When the volume fraction of macropenetrants in the membrane is calculated, it shows strong absorption of PEGs onto the membranes whereas phenyl urethane ended PEGs have less absorption.