Preparation and characterization of some new antimicrobial thermally stable PVC formulations

Abstract

Novel three biologically active itaconimido thiourea derivatives (DI, DII and DIII) were synthesized via reaction of N-[4-(isothiocyanatecarbonyl)phenyl] itaconimide with either aniline, p-toluidine or p- amino benzoic acid, respectively. The radical polymerization of DI, DII and DIII in dimethyl sulfoxide using azobisisobutyronitrile initiator was successfully performed to produce three polymers that were denoted as PI, PII and PIII, respectively. Their chemical structures were confirmed by elemental analyses, FTIR, 1H-NMR and mass spectra. They showed a high potency for growth inhibition of E. faecalis, S. epidermidis, E. coli, A. niger, C. neoformans and C. tropicalis. This is not only illustrated by their high inhibition zone diameters but also by their low minimum inhibitory concentrations. Some of them showed activities better than the reference drug Amphotericin B against all the tested fungi. DIII and PIII were safe on normal fibroblast cells of the lungs of the human (MRC-5 cells) through their evaluation using cytotoxic activity measurement. The thermal stability of PVC in the presence of DI–DIII and their polymers PI–PIII was evaluated. In comparison with DBLC, Cd–Ba–Zn stearate and n-OTM as reference stabilizers, DI–DIII and PI–PIII greatly stabilize PVC against thermal degradation. This is evidenced by increased initial decomposition temperatures and decreased weight losses at particular temperatures. It was found that the substituent group having an electron releasing nature that incorporated into DII and PII enhances their performance for PVC stabilization. DI–DIII and PI–PIII achieve a lower degree of discoloration and molecular weight alteration of PVC than the industrial stabilizers.