Physicochemically Tunable Hyperbranched Polyglycerol Copolymerized with Functional Aziridine As a Versatile, Multivalent Cross-Linker for Waterborne Acrylic Adhesives

Abstract

In order to comprehensively control the adhesion and cohesion of waterborne adhesives, it is important to develop and implement cross-linkers that are capable of controlling the cross-linking density as well as physical interaction with aqueous adhesive polymers. Herein, an aqueous-soluble, multifunctional polymeric cross-linker for waterborne acrylic adhesive is developed by functionalizing acrylic hyperbranched polyglycerol (HPG) with various functional moieties, namely, sulfate, trimethylammonium chlorate, phenyl, and n-butyl, by copolymerizing glycidol with N-functionalized aziridine ("F-AziAHPG"). The effect of the type of ring-opening polymerization and cationic and anionic mechanisms is explored to optimize the molecular weight, dispersity, and conversion of both monomers. Owing to the multivalency of hydroxyl groups on HPG, the type and degree of substitution of functional groups could be broadly tuned by varying the monomer ratio, independent from conjugation of acrylic groups for cross-linking. Mechanical and adhesive properties, as analyzed by rheometry, thermogravimetry, and lap-shear test, demonstrate the intricate control of adhesion and cohesion of the waterborne acrylic adhesives by F-AziAHPG cross-linkers.