Mark–Houwink–Sakurada constants for carboxylated segmented polyurethane

Abstract

Carboxylated polyurethane (PEUA) based on methylene-bis-4,4′-phenyl isocyanate, poly(propylene oxide), and 2,2′-hydroxymethyl propionic acid were synthesized. The effect of temperature on the extension stage of the polymerization reaction as well as that of the concentration of reagents on the molecular weight of PEUA were investigated by means of gel permeation chromatography (GPC). The best conditions for obtaining the highest molecular weight polymer correspond to the chain extension reaction temperature of 50°C and to a polymer concentration of 50% w/v. The obtained polymers have been characterized by 13C-NMR, Fourier transform infrared spectroscopy and differential scanning calorimetry. It was seen that, in the reaction conditions adopted, the formation of ureic groups does not occur and that the increase of molecular weight causes a lower mobility of the chains, as evidenced by a small increase of T g. The values of the PEUA Mark–Houwink–Sakurada constants in tetrahydrofuran (THF) at 25°C, determined by GPC and viscosity measurements, indicate that the polymer chain in THF is characterized by a high flexibility.