Synthetic scheme to improve the solid content of biodegradable waterborne polyurethane by changing the association relationships of hydrophilic fragments.

A synthetic method was developed to prepare biodegradable waterborne polyurethanes (BHPUs) with a high solid content by introducing different molecular weights of poly(ethylene glycol) (PEG) into poly(ε-caprolactone) (PCL)-based polyurethanes. PCL is a semi-crystalline polymer that can be degraded in lipase to prepare biodegradable waterborne polyurethanes. The biodegradability of BHPUs was evaluated, and the results showed that BHPU samples could be degraded in a solution of phosphate-buffered saline (PBS)/lipase but not in PBS. Two different synthesis routes were used to prepare the BHPUs, which resulted in different association relationships between the ionic hydrophilic polymer dimethylol propionic acid (DMPA) and a nonionic hydrophilic polymer (PEG). The influence of the association relationship between DMPA and PEG on the solid content and other BHPU properties was investigated. The results showed that the method of associating all PEG molecules with DMPA increased the crystallization, tensile properties, and water and soil repellency of the BHPU samples. The solid content of the BHPU samples increased from 41% to 52.7%. In addition, PEG with molecular weights of 400 g mol and 1000 g mol had the best effect on the dispersibility and stability of BHPU samples when incorporated into a polyurethane backbone.