A new photoactivable material based on polyethylene imine with allyl functions (A-PEI monomer) was synthesized to develop new hydrogel. The water-based photoinitiating system consisting of anthraquinone-2-sulfonic acid (AQS) and N-methyldiethanol amine (MDEA) was studied by laser flash photolysis and electron paramagnetic resonance. LED@385 nm exposure of this combination of AQS with MDEA in aqueous medium has led to the formation of α-aminoalkyl radicals which were able to cross-link the acrylamide and A-PEI to generate new antibacterial materials in reduced time and under air. Interestingly, the addition of the multifunctional A-PEI monomer to acrylamide derived monomers has led to faster gel formation and an increase of the instantaneous G’ modulus value. The resulting hydrogel containing quaternary ammonium groups on its surface has demonstrated excellent anti-adherence and biocide properties against Escherichia coli and Staphylococcus aureus.