Preparation and Characterization of Antibacterial Guanidine-Based Polymeric Material

Abstract

Within the scope of this thesis study, guanidine-based cotton fabrics with antibacterial properties have been prepared for applications in food packaging, textiles, and the medical field. To impart antibacterial properties to the cotton fabrics, the antibacterial polymer poly(hexamethylene guanidine) hydrochloride (PHMG) was synthesized through the polycondensation reaction of hexamethylenediamine and guanidine hydrochloride monomers, and then the fabrics were modified with PHMG. Two different approaches were studied for the antibacterial modification of cotton fabrics. In the first approach, the direct and peroxide grafting techniques were initially performed to graft PHMG polymer onto the cotton fabrics without using additional chemical materials. However, these methods did not provide the desired modification. In the second approach, grafting studies were conducted using different radiation-induced graft polymerization methods with glycidyl methacrylate (GMA) and acrylic acid (AAc) monomers to functionalize the cotton fabrics for subsequent modification with PHMG. Since convenient results were not obtained from the GMA grafting studies with the conditions applied during trials, the studies to functionalize the cotton fabrics were continued with AAc monomer. Cotton fabrics were irradiated at a dose of 30 kGy using a gamma radiation source in the presence of oxygen, and then treated with aqueous solutions of AAc monomer. AAc grafting studies were performed with AAc aqueous solutions at concentrations of 20%, 30%, and 40% (v/v), at a reaction temperature of 65°C and a reaction time of 3 hours. Cotton fabrics with antibacterial activity were prepared by a chemical coupling reaction of the carboxyl groups present in cotton fabrics grafted and functionalized with AAc and the amino functional groups of the PHMG polymer through amide bonds. Firstly, the carboxyl groups in the AAc-grafted cotton fabrics were activated using the DMTMM coupling reagent. Then, the fabrics were combined with a 10% (w/v) aqueous solution of PHMG and allowed to react at room temperature for approximately 18 hours. As a result, cotton fabrics modified with PHMG polymer were obtained. Based on the conducted studies, the optimum grafting conditions were determined as 30% (v/v) concentration of AAc aqueous solution, 65°C reaction temperature, and 3 hours reaction time. The average grafting yield for fabrics prepared under these conditions was determined as 13.8%, while the corresponding average modification efficiency (coupling yield) of PHMG modification was 19.6%. The chemical structure, elemental composition, and molecular weight of the synthesized PHMG polymer were investigated using FTIR, NMR, elemental analysis, and MALDI-MS. The antibacterial properties were examined using agar well diffusion and broth dilution methods. As a result of the broth dilution test, the MIC values obtained from the test tubes were 8 mg/L for E. coli and 4 mg/L for S. aureus. On the other hand, the MIC values determined from the agar plates were 64 mg/L for E. coli and 16 mg/L for S. aureus. For the final materials, PHMG-modified cotton fabrics, the presence of covalent amide bonds in the structure upon PHMG modification was confirmed by FTIR analysis via the peaks observed at 1633 cm-1 and 1550 cm-1 on the FTIR spectrum. The elemental analysis was carried out to obtain the final composition of elements within the cotton fabrics after PHMG modification. The surface morphology of the fibers in the prepared fabrics was observed using SEM, and the antibacterial properties were investigated using the agar diffusion test. The antibacterial activity of the PHMG-modified cotton fabrics was confirmed through the qualitative agar diffusion test.