Structure-activity relationship of antibacterial bio-based epoxy polymers made from phenolic branched fatty acids

In order to study the structure-activity relationship of antibacterial bio-based epoxy polymers made from phenolic branched fatty acids (phenolic BCFAs), a series of curing agents (i.e., phenolic BCFA-amides (phenolic BCFAAs)) were prepared from phenolic BCFAs and polyamines at 90 ?C and 160 ?C. Those phenolic BCFAs were made from phenol, thymol, carvacrol, and creosote, respectively, while the polyamines were ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and hexamethylenediamine (HDA). The prepared curing agents were then used to make different antimicrobial bio-epoxy polymers with a commercial epoxy resin, diglycidyl ether of bisphenol A (DGEBA). All the monomers were thoroughly characterized by Fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (NMR). Two bio-epoxy polymers, phenol-BCFA (EDA) and creosote BCFA (EDA), were found to be most active against both Gram-positive and Gram-negative bacteria. The leaching experiments on the phenolBCFA (EDA) showed no signs of small molecules (i.e., biocides) leaking out of the polymer to inactivate the bacteria. Most importantly, the reusability study indicated that the polymer was inherently antibacterial and maintained its efficacy for at least three uses. This study presents important findings on the antimicrobial activity of individual phenolics, polyamines and molecular weights of the curing agents, and the evidence demonstrates that the amphiphilicity contributes to the key impact of the antimicrobial activity of the bio-epoxy polymers.

Automated summary

The study investigated the structure-activity relationship of antibacterial bio-based epoxy polymers made from phenolic branched fatty acids by preparing curing agents from phenolic BCFAs and polyamines. The bio-epoxy polymers, especially phenol-BCFA (EDA) and creosote BCFA (EDA), demonstrated significant antimicrobial activity against a broad range of bacteria, indicating their potential as inherently antibacterial materials. The study also highlighted the importance of amphiphilicity in contributing to the antimicrobial activity of the bio-epoxy polymers.