Betaine ester-shell functionalized hyperbranched polymers for potential antimicrobial usage: Guest loading capability, pH controlled release and adjustable compatibility

Betaine ester-shell functionalized hyperbranched polyethylenimines (BEHPEI) were synthesized by Menschutkin reaction between per-N-methylated polyethylenimine (MeHPEI) and alkyl bromoacetate. BEHPEI could play dual antimicrobial roles that were, the betaine ester-shell acted as contact-based antibacterial polycations and the drug-loaded BEHPEI could controllably release the drugs due to the cleavage of the betaine ester groups under weak alkaline condition. The BEHPEI exhibited high transport capacities that per gram of BEHPEI could encapsulate 0.24-2.67 g of dyes or drugs. The model drug release experiment employing methyl orange (MO) showed that the drug release of MO-loaded BEHPEI complex occurred slowly in weak alkaline solutions and the release rate was controlled by varying pH, while the complex kept very stable under weak acid condition (pH = 3.0-7.0). BEHPEI generated from long chain alkyl bromoacetate was compatible with organic resins implying the possible usage in antimicrobial fibers and coatings. Another BEHPEI obtained from short-chain alkyl bromoacetate was water soluble and maybe used in lotion formula. The hydrolysis of BEHPEI afforded zwitterionic shell.