Abstract:
Metal containing polymers have gained much attention in recent years for their antimicrobial properties and few of these polymers are derived from the renewable resources. In view of the growing production of glycerol owing to the implementation of the biodiesel 10% blend (B10) programme in our country, the production of glycerol as the byproduct of the biodiesel is expected to be increased. This study is aimed to synthesise a novel and value-added cobalt-conjugated poly(glycerol adipate) (Co-PGA) with antimicrobial properties for polyurethane coating. Poly(glycerol adipate) (PGA) was first synthesised by polycondensation of glycerol with adipic acid at molar ratio of 2:1 and reaction temperature of 180°C and 210°C to produce PGA with different physico-chemical properties such as OHV, AV, and Mw. Cobalt was then incorporated into PGA at 150 °C and the reactions were monitored by acid value and hydroxyl value determination. The chemical structure and weight average molecular weight of the Co-PGA were characterised by FTIR, 13C-NMR and GPC. The cobalt contents of the synthesised Co-PGA were determined by ICP-MS. PGA retaining with acid value >35 mg KOH/g sample was able to incorporate up to 5%w/w of cobalt into the Co-PGA polymer. The incorporation of cobalt demonstrated additional catalytic effect on producing hyperbranched Co-PGA and increased the degree of branching of the incorporated PGA8 from 25.1 to 59.3%. Co-PGA8 to Co-PGA10 with 4.4-5%w/w of cobalt contents showed inhibition against E. coli (MIC50 at 675 μg/ml), S. aureus (MIC50 at 450 μg/ml ), P. aeruginosa (MIC50 at 112.5 μg/ml), and C. albicans (MIC50 at 56.25μg/ml) in resazurin broth microdilution study. Co-PGA10 incorporated with 5%w/w of cobalt content was used as an active antimicrobial agent to blend with blank PGA and commercial polyols, i.e. PEG 6000 and PCL 2000 and reacted with isophorone diisocyante for the preparation of polyurethane (PU) coating. The antimicrobial properties of the PU coatings prepared by 0.5-35%w/w of the synthesised Co-PGA10 were investigated using disk diffusion test. The PU coatings demonstrated antimicrobial activity against E. coli, S. aureus, B. subtillis and C. albicans. Among all the tested strains, C. albicans was the most susceptible strain to Co-PGA10 and Co-PGA10 prepared PU coating in both broth microdilution and disk diffusion test. The Co-PGA exhibited promising antibacterial and antifungal properties and can be potentially applicable as active antimicrobial agents in protective coating of medical devices.
