Supramolecularly Reinforced Films from Polyurethane–Urea Dispersions Containing the Tris-Urea Motif

Abstract

Because of the drive toward more green and sustainable processes for polymer synthesis, there is a growing desire to avoid solvent-borne polymer systems where possible and exchange for waterborne alternatives. Here, it isdemonstrated that the use of carbohydrazide as a chain extender of polyurethane prepolymers dispersed in water leads to the generation of polyurethane–urea dispersions that are supramolecularly reinforced by the tris-urea motif. Despite being incorporated as a small percentage of the total formulation by weight, films cast from polyurethane–urea dispersions that incorporate the tris-urea motif allow for more than an order of magnitude increase in Young’s modulus and an order of magnitude increase in tensile strength without any compromise in the elongation at break. It is also demonstrated that the tris-urea group provides better mechanical strength than a chemically cross-linked structure and also undergoes stress relaxation on a longer time scale. Furthermore, DMTA measurements demonstrate that the increased strength of supramolecular hydrogen bonding interactions increase the mechanical stability at elevated temperatures. The improvement in mechanical properties shown by tris-urea containing polyurethane–urea dispersions should allow for the use of waterborne systems where previously only solvent-borne polymers have been used.

Mechanically Robust Skin-like Poly(urethane-urea) Elastomers Cross-Linked with Hydrogen-Bond Arrays and Their Application as High-Performance Ultrastretchable Conductors

“…As shown in Figure S1b, the CO absorption bands in PU-ASC can be deconvoluted into six subpeaks, which correspond to free CO in ester carbonyl (1736 cm –1 ), free CO in urethane (1730 cm –1 ), hydrogen-bonded CO in urethane (1705 cm –1 ), and ASC groups (1673, 1658, and 1642 cm –1 ). ,,, The density functional theory (DFT) results indicate that the hydrogen-bonded ASC and urethane groups aggregate into hydrogen-bond arrays with hierarchical structures, including dimers, trimers, and even larger aggregates (refer to the binding energy calculations in the Supporting Information). , The hydrogen-bond arrays are less-ordered because the asymmetric structure of IPDI and the bulky benzene ring in IPDH interfere in the dense stacking of the urethane and ASC moieties . The WAXD pattern of the PU-ASC elastomer exhibits a broad diffraction peak at 19.5°, indicating that PCL segments are found in the amorphous structure (Figure S4a).…”

Polymer Colloids: Current Challenges, Emerging Applications, and New Developments

“…Besides acrylates and epoxy waterborne systems, polyurethane dispersions containing dynamic bonds have been also investigated in the literature. 258 Due to the inherent incompatibility of isocyanate groups with water, polyurethane-based dispersions are almost exclusively prepared by first generating a polyurethane containing a stabilizing diol most commonly dimethylolpropionic acid (DMPA) and dispersing this in water after the polyurethane is neutralized with a base, commonly triethylamine (TEA). Irusta et al exploited this chemistry to incorporate different chain extenders to provide dynamic behavior.…”

Surfactant-free latexes as binders in paint applications

“…Later, the solvent evaporates releasing volatile organic compounds. As environmental regulations have imposed severe restrictions to the use of coalescent agents, multiphase polymer particles [3][4][5][6][7][8] and crosslinking using covalent [9][10][11][12], ionic [13], and hydrogen [14,15] bonds are used to overcome the film formation paradox.…”