Effect of Hard Segment Molecular Weight on Dilute Solution Properties of Ether Based Thermoplastic Polyurethanes

A systematic study was conducted on the effect of hard segment molecular weight (or length) on solution and bulk properties of ether based thermoplastic polyurethanes (TPUs). The purpose of this study is to provide a roadmap to deliver the desired end-use performance of a polyurethane product based on the optimal design of the starting materials. In this paper, we report our findings on the effects of hard segment molecular weight on properties of a dilute solution of TPUs in N, N-dimethyl formamide (DMF). The molar feed was used to determine the molecular weight of the hard segment. Then, the weight fraction of the hard segment is determined by calculating the ratio of the molecular weight of the hard segment to the number average molecular weight of the TPU determined by Gel Permeation Chromatography. It was found at low hard segment weight fraction there is a significant impact on the weight average molecular weight and molecular weight distribution, intrinsic viscosity, critical concentration, hydrodynamic diameter, polymer-solvent interaction parameter and second virial coefficient. However, at high weight fractions at around 0.4, the impact is minimal. Furthermore, the weight fraction has a minimal impact on number average molecular weight, and the expansion parameter in the Flory-Huggins analysis.