Preparation and morphological characterization of diacetylene-containing coploymers.
Koh, Cheok Poh.
Date of Issue1999
School of Materials Science and Engineering
Polyurethane-diacetylene copolymers were synthesized from three basic monomers: 4,4'- Dissocyanodiphenylmethane (MDI), 2,4-hexadiyne-l,6-diol (HDD) and a poly(propylene glycol) (PPG425/PPG725) via solution polymerization. By varying the diacetylene contents and the molecular weights of the poly(propylene glycol), copolymers with different physical and thermal properties were produced. Thermal analyses revealed a two phase domain morphology in which diacetylene-urethane (HDD/MDI) hard segments are well dispersed throughout a continuous amorphous poly(ether-urethane) (PPG/MDI) matrix. Thermogravimetric Analysis were applied to investigate the thermal stabilities of the as-synthesized copolymers. Experimental study was carried out to investigate the effects of solvent, reaction time and temperature on the average molar masses and molar mass distribution of the as-prepared copolymers using Gel Permeation Chromatography. Raman, X-ray diffraction and thermal techniques were used to probe the effects of casting solvent on the hard segment domains ordering. It is found that the reactivity of the copolymers is greatly affected by the casting solvent. It is assumed that the paracrystalline state of the hard segment phase represents a state of two-dimensional order reminiscent that of smectic and nematic liquid crystal. The effects of thermal induced residual strain on the optical properties of poyurethane-diacetylene copolymers have been studied using Raman Spectrocopy. Experiments were carried out to determine the tensile and compressive strain dependence of the Raman frequency of the C=C triple bond stretching band in the copolymer.