Synthesis of Gemini Quaternary Ammonium Salts with Varying Hydroxyl Group Numbers and Their Application in the Preparation of Novel Cationic Waterborne Polyurethanes

Abstract

Due to their excellent hydrophilicity, antibacterial properties, and molecular designability, quaternary ammonium salts (QAS) have attracted considerable interest. In this study, four Gemini quaternary ammonium salts (GQAS-1, GQAS-2, GQAS-3, and GQAS-4), each containing two quaternary ammonium groups and varying numbers of hydroxyl groups, were designed and synthesized as hydrophilic chain extenders. These were subsequently used as chain extenders in cationic waterborne polyurethanes (WPUs). The WPUs were prepared using isophorone diisocyanate (IPDI), polybutylene glycol (PTMG), 1,4-butanediol (BDO), and GQAS-1, GQAS-2, GQAS-3, or GQAS-4. The results show that GQAS-4, which contains five hydroxyl groups, significantly enhances the performance of the resulting WPU. The WPU modified with GQAS-4 exhibits excellent emulsion stability. The five hydroxyl groups in GQAS-4 alter the crosslinking degree of the WPU molecular structure, endowing the film with a tensile strength of up to 5.4 MPa. Furthermore, when the GQAS-4 content is increased to 8.6%, the tensile strength of the film reaches 9.4 MPa. In addition, the incorporation of GQAS-4 substantially increases the glass transition temperature and thermal stability of the WPU films. This work provides a new synthetic approach and establishes a research foundation for the development of novel WPU coatings with antibacterial properties, heat resistance, and high mechanical performance.

Graphical Abstract