Synthesis, characterization and reactivity ratios of copolymers and terpolymers

The thesis investigates synthesis, characterization, reactivity ratio determination and thermal studies of N-vinyl-2-pyrrolidone based copolymers and terpolymers. N-vinyl-2-pyrrolidone-co-methyl methacrylate, N-vinyl-2-pyrrolidone-maleic anhydride-methyl methacrylate, and N-vinyl-2-pyrrolidone-maleic anhydride-styrene terpolymers were synthesized using Ti(III)/DMG redox initiator and AIBN thermal initiator. The synthesized polymers were characterized by using FTIR, 1H-NMR, 13C-NMR and spectroscopic methods. Thermal studies were done on the polymers for finding the degradation temperature and glass transition temperature using TGA and DSC analytical techniques. The structure and arrangements of monomers in the polymers were studied using Fineman-Ross, Kelen-Tudos and Extended Kelen-Tudos methods. The microstructure of the polymer was determined using the reactivity ratio calculation. For imparting efficient anti-bacterial activity, the synthesized terpolymer was grafted with antibacterial agents like para amino benzoic acid and 2,4-dichloro phenol anti-bacterial agents. Chapter 1 gives an introduction to the thesis and covers the literature review in the specific research area. In chapter 2, redox copolymerization of N-vinyl-2-pyrrolidone (NVP) with methyl methacrylate (MMA) was carried out using titanium(III)–dimethylglyoxime [Ti(III)-DMG] redox initiator in aqueous sulphuric acid-alcohol media. The resulting copolymer was characterized by FTIR, 1H-NMR, 13C-NMR spectroscopic methods and elemental analysis. Thermal properties of the copolymer were determined by differential scanning calorimetric technique (DSC) and thermogravimetric analysis (TGA). The reactivity ratios of the monomers were computed by Fineman-Ross (F-R), Kelen-Tudos (K-T), and extended Kelen-Tudos (EK-T) methods at lower conversion. The reactivity ratios obtained r1 (MMA) 2.5 and r2 (NVP) 0.03 showed richer content of MMA than NVP in the copolymer having extreme ideal behaviour. The distribution of monomer sequence along the copolymer chain was calculated using a statistical method based on reactivity ratios. Ti(III)-DMG redox initiator showed increased addition of NVP to MMA during copolymerization. In chapter 3, series of poly (N-vinyl-2-pyrrolidone-maleic anhydride-styrene) terpolymer have been synthesized using titanium(III)-dimethylglyoxime redox initiator system. The usage of redox initiators in the terpolymerization was limited; hence it had to be considered as a new approach. The reactivity of the monomers was studied by well accepted Kelen-Tudos, Finemann-Ross linear methods and compared with the nonlinear RREVM method. The results also suggested that RREVM method is the most reliable and superior method for the estimation of reactivity ratios. The reactivity ratios for the terpolymer (r1 0.99 and r2 0.05) obtained from RREVM method showed that the N-vinyl pyrrolidone-maleic anhydride complex was more predominant than styrene in the terpolymer, and the complex had more attraction towards self than styrene. The microstructure determination study depicts that alternating polymer can be prepared by increasing the styrene feed content. The resonance factor and the polarity of the complex were calculated and found to be 5.01 and 0.93 respectively; which were different from that of the individual monomers. These calculations would help in predicting the association of monomers during copolymerization. It was observed that the glass transition temperature for the terpolymer increased as the complex ratio in the terpolymer increases. The terpolymer is thermally stable up to 323°C. In chapter 4, the synthesis of Poly (N-vinyl pyrrolidone-maleic anhydride-methyl methacrylate) using azobisisobutyronitrile in 1,4-dioxan solvent was described. The polymers with different composition could be successfully synthesized and characterized using FTIR, 1HNMR, 13NMR, TGA and DSC techniques. The monomer-monomer interactions were studied using Finemann-Ross and Kelen-Tudos methods of calculating the reactivity ratio. The reactivity ratios r1 and r2 with respect to methyl methacrylate and N-vinylpyrrolidone-maleic anhydride complexomer are found to be 6.05 and 0.06 respectively. It showed that methyl methacrylate had greater reactivity than N-vinyl-2-pyrrolidone-maleic anhydride complex, i.e., the terpolymer contained methyl methacrylate in higher ratio. The thermal stability of poly (N-vinyl pyrrolidone-maleic anhydride-methyl methacrylate) was 165 °C and the glass transition temperature was found to increase from 153 °C to 182 °C as MMA concentration increase. Chapter 5 deals with the synthesis of poly (N-vinyl-2-pyrrolidone-maleic anhydride-styrene) terpolymer using AIBN initiator with acetone as solvent. Grafting of the terpolymer with antibacterial agents para aminobenzoic acid and 2,4-dichlorophenol to introduce bactericidal activity to the terpolymer was carried out. The terpolymer and the grafted polymers were characterized by FTIR, 1H-NMR, and 13C-NMR spectroscopic methods. Thermal properties were determined by differential scanning calorimetric technique and thermogravimetric analysis. The glass transition temperatures were observed to be 111 °C (terpolymer), 150 °C (VMS-G-PABA) and 130 °C (VMS-G-DCP). Terpolymer started degradation at 288 °C and grafted terpolymers at 104 °C (VMS-G-PABA) and 129 °C (VMS-G-DCP) respectively. The anti-bacterial activity of grafted terpolymers was evaluated by the shake flask method against gram positive and gram negative bacteria E. coli and S. epidermidis. The grafted terpolymers showed effective inhibition against both the bacteria, the minimum inhibition concentration was observed as 75 μg/mL and 80 μg/mL for VMS-G-PABA and 50 μg/mL for VMS-G-DCP against E. coli and S. epidermidis respectively. The new polymers showed 90 % bacterial growth inhibition at 200 μg/mL. In chapter 6, well defined network structured PVP-T-PHEMA hydrogels were synthesized and characterized. The study demonstrates the synthesis of well-defined network structured hydrogels using the template polymerization method. In this work, we have polymerized hydroxyethyl methacrylate in the presence of poly (N-vinyl-2-pyrrolidone) using potassium persulphate as initiator. The resulting template polymer was characterized using spectroscopic methods and the structural morphology was studied using SEM analytical techniques. In addition, the thermal properties of the template polymer were understood by TGA analysis. Similarly, the swelling property and water content of the hydrogels were also studied in connection with the hydrogel formation.