ABSTRACTHomopolymerization of chloro-substituted N-phenyl maleimide monomer at ortho N-OCPMI, meta N-MCPMI, and para N-PCPMI was performed at 70°C in DMF using benzoyl peroxide as a free radical initiator. The average molecular weight of all homopolymers, namely, H-OCPMI H-MCPMI and H-PCPMI by gel permeation chromatography was found to be 1,806, 2,464, and 4,542 with PDI 1.07, 1.09, and 1.11. The controlled poly dispersity index by conventional free radical polymerization is achieved. The thermal analyses reveal that the initial decomposition temperatures for all types of homopolymers are close to each other. On increasing heating rates, the activation energy (ΔE*),entropy of activation (ΔS*), enthalpy of activation (ΔH*), and Gibbs free energy (ΔG) increase for all types of homopolymers. The homopolymer of para chloro-substituted of N-phenyl maleimide, H-PCPMI has the highest thermal stability. All the synthesized monomers and homopolymers are found to show an excellent antimicrobial activity. Activity index is also evaluated.