Synthesis and characterization of polyurethane ionomers, blends and urethane-urea aerogel hybrids.

摘要

The chemical and physical properties of alkali, alkaline metal and selected transition metal polyurethane ionomers were investigated. A new synthesis was developed for carboxylated polyurethane anionomers, and it was employed to synthesize a range of ionomers. Thus, a series of polyurethane ionomers was prepared in which the molecular weight of a constituent diol, the concentration of carboxylic acid sites, and the nature of the cations was varied. The analogous materials with equivalent nominal stoichiometries were synthesized by the standard method of preparing the acid-form polymer and of replacing the protons for metal ions.; The novel synthesis employs a multiphase reaction between isocyanate-terminated prepolymers and solid, anhydrous microcrystalline metal salts of a carboxylic acid diol. This required the development of new synthesis of these starting materials. The materials studied are based on polyether diols, acid-containing diols and a saturated diisocyanate. The novel synthesis is more than twenty times as fast as the standard method under the same conditions.; The spectroscopic and mechanical properties of the polyurethane ionomers synthesized in both ways were studied and contrasted. Those prepared by the new method have greater spatial homogeneity, resulting in lower scattering loss in the ultraviolet-visible range. They also exhibited values of E ′ (the real elastic modulus) that are as much as an order of magnitude greater than those made by the standard method. In addition, the temperature dependence of Fin the −25 ∼ +75°C range is remarkably low.; Studies of the structural properties by infrared spectroscopy, small angle x-ray scattering, thermal analysis, gel permeation chromatography and scanning electron microscopy were used to elucidate their molecular structures and intermolecular interactions. The rates of key synthetic reactions and the thermal stability of the metal containing polyurethane ionomers were studied by thermal analysis.; The polyurethane ionomers synthesized in this work were combined with, sulfonated polystyrene, and poly(ethylene-co-acrylic or methacrylic acid) polymers, their partially neutralized ionomers, and thermoplastic polyurethanes. It was found that polyurethane anionomers synthesized by the new method were miscible with these polymers through the composition range. Several series of these blends were studied using mid- and far-infrared spectroscopy to investigate molecular interactions that lead to the miscibility.; Isocyanate-containing molecules were reacted with chitosan silica aerogels. It was discovered that -NCO groups of the diisocyanate HMDI reacted selectively with amine groups in the presence of large excesses of -OH groups from alcohol, silica, and water. This study leads to the possibility of attaching nanoscale aerogel particles to substrates, to one another, and to additional molecules of interest.