Lactide oligomers modified with linear polyethyleneimine for antibacterial coatings

Lactide oligomers were synthesized in the presence of glycidol via ring opening solution polymerization and used in the addition reaction with linear polyethyleneimine (L-PEI). Detailed analysis of the lactide oligomers was conducted using 1 H NMR, GPC and MALDI-ToF. L-PEI with different molecular weight (2.5 and 4.0 kg mol −1 ) was introduced to the addition reaction with lactide oligomers. The obtained copolymers were modified with various 1-bromoalkanes and their percentage of grafting as well as antibacterial properties of the final product against Escherichia coli were studied. The product with the highest grafting level was obtained in the presence of bromobutane, regardless of the L-PEI : PLA ratio used, and displayed potent antimicrobial activity both as a polymer film and in the blend with commercial polylactide. Inhibition of bacterial growth was observed at a concentration of 30 wt% of the copolymer grafted with 1-bromooctane and 1-bromodecane in the polylactide blend. In this case the total wt% of PEI in the blend was 1.1%. Antibacterial polylactide film composed of commercial PLA and block copolymer of lactide and linear polyethyleneimine (L-PEI) has been prepared. To observe complete inhibition of bacterial growth only 1.1 wt% of linear L-PEI is required.