Thermal deprotection: a sustainable and efficient strategy for synthesising α-polylysine adsorbents†

Abstract

α-Polylysine (PLys) is a versatile, renewable, and biodegradable polymer with extensive amine functionality and water-solubility, making it an ideal candidate for critical applications such as heavy metal adsorption and beyond. However, conventional synthesis of linear PLys relies on toxic reagents for side-chain deprotection, raising environmental and safety concerns that hinder its commercial scalability and sustainability. In this work, we introduce a groundbreaking, environmentally friendly method for PLys production using thermal deprotection of fluorenylmethyloxycarbonyl (Fmoc)-protected PLys. This innovative approach eliminates the need for hazardous deprotection agents, offering a greener and more cost-effective alternative. Beyond the synthesis of homopolymeric PLys, we extend this method to create α-polylysine-b-poly(ethylene glycol) (PEG-b-PLys) block copolymers using thermal deprotection, showcasing their superior performance in removing Pb²⁺ ions from aqueous solutions. Our results not only advance sustainable polymer synthesis but also demonstrate the potential of thermally driven deprotection to revolutionise wastewater treatment technologies and expand the scope of PLys applications in environmental remediation and other critical industries.