Synthesis and Characterization of a Novel Kind of Water-Soluble Macromolecular Photoinitiators and Their Application for the Preparation of Water-Soluble Branched Polymers

The water-soluble polymers with a well-defined branched structure have received intensive attention due to their better solubility and shearing resistance than conventional linear polymers. In this contribution, a novel type of water-soluble macromolecular photoinitiators (macro-PIs) was specially designed and synthesized, which can serve as efficient multifunctional initiators for the preparation of water-soluble branched polymers. Photoinitiator groups were incorporated into the side chain of poly(styrene-alt-maleic anhydride) (PSM) via esterification of anhydride groups with 2-Hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959). The as-formed esterification products were further hydrolyzed to obtain water-soluble macro-PIs, designated as PSM-2959. The chemical structure of PSM-2959 was characterized by proton nuclear magnetic resonance (¹H NMR), Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–vis), and water-soluble macro-PIs with controllable content of photoinitiator groups were successfully obtained. Furthermore, photoinduced polymerization of acrylamide was performed using PSM-2959 as photoinitiators, and the experimental results demonstrated that PSM-2959 displayed an excellent photoinitiating property. More importantly, the as-prepared polyacrylamide with a branched structure showed good solubility and unique rheological property. The present work provided a facile and scalable method for the synthesis of macro-PIs with excellent water solubility and remarkable photoinitiating efficiency, which have potential applications as effective photoinitiators for preparing water-soluble polymers with a well-defined branched structure.