Effects of Internal\nEmulsifiers on Anionic Waterborne\nPolyurethanes for Breathable Membranes: Experimental and Computational\nStudy

Recently,\ntraditional solvent-based polyurethanes have\nincreasingly\nbeen replaced with waterborne polyurethanes (WPUs) to adopt greener\nsynthesis methods that avoid VOCs emissions. In the synthesis of WPUs,\nwhere polymerization occurs in water, the role of emulsifiers that\nenable the dispersion of polyurethane is a crucial factor that determines\nthe properties and functionality of WPUs. This study employed both\nexperimental and computational simulation approaches to investigate\nthe effect of the chemical structure and concentration of internal\nemulsifiers on the dispersibility and physical properties of anionic\nWPUs. As the concentration of internal emulsifiers increased, the\nhydrophilicity and breathability of the WPUs films improved, while\nwater resistance declined. However, higher emulsifier concentrations\nled to reduced thermal stability, lower elongation at break, and decreased\nmolecular weight of the films. Unlike dimethylolpropionic acid (DMPA),\ndimethylolbutanoic acid (DMBA) enabled the formation of stable polymer\ndispersions with smaller particle sizes at lower concentrations and\nfacilitated the production of less hydrophilic films. Dissipative\nparticle dynamics simulations revealed that WPUs utilizing DMPA dispersed\nmore uniformly in water than those using DMBA.