Multifunctional PMMA144- b -PDMAEMA51/TiO2 Nanocomposites for Efficient Dye Removal and Antibacterial Applications: Experimental and DFT Insights

In this study, poly(methyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate) (PMMA-b-PDMAEMA), an amphiphilic block copolymer containing various chain lengths of a pH- and temperature-responsive PDMAEMA segment, was synthesized via atom transfer radical polymerization (ATRP). A PMMA-Br macroinitiator was first prepared by polymerization of methyl methacrylate using butyl 2-bromoisobutyrate (BuBriB) and a CuBr/2,2′-bipyridine catalytic system, and then the chain was extended with further batch polymerization of DMAEMA using the PMMA-Br macroinitiator. TiO2 nanoparticles were synthesized by the sol–gel method, and they were incorporated into the block copolymer through solvent casting to obtain PMMA-b-PDMAEMA/TiO2 nanocomposites. The synthesized copolymers and nanocomposites were comprehensively characterized by GPC, FTIR, 1H NMR, TGA, DSC, SEM, and XRD. The polymer nanocomposite containing 10% TiO2 achieved over 96% removal of methylene blue (MB) within 70 min at pH 7 under visible LED irradiation in the presence of NaBH4. In addition, it exhibited significant antibacterial activity, producing inhibition zones of 24.75 mm against Shigella sonnei (S. sonnei) and 23.25 mm against Staphylococcus hemolyticus(S. hemolyticus) at a dose of 45 μg. Density functional theory (DFT) calculations further elucidated the interactions between TiO2 nanoparticles and PMMA-b-PDMAEMA, the adsorption mechanism of methylene blue, and the interactions of the nanocomposites with bacterial cell proteins. These findings demonstrated that PMMA-b-PDMAEMA/TiO2 nanocomposites are promising multifunctional materials for environmental remediation by combining efficient dye adsorption with antibacterial activity. The novelty of this work lies in the development of a multifunctional PMMA-b-PDMAEMA/TiO2 nanocomposite that combines the mechanical stability, pH-responsive behavior, dye adsorption, and antibacterial properties of the prepared nanocomposites on a single platform for environmental remediation.