Synthesis of hyperbranched polyethylene-graft-poly[3-ethyl-3-(methacryloyloxy)methyloxetane] via chain walking polymerization and ATRP for cationic photo-curing on membrane surface

Polyethylene is among the most widely-used coating materials due to the excellent physical and mechanical properties. However, the chemical inertness and poor solubility limit the application of polyethylene in coating. In this study, hyperbranched polyethylene-based graft copolymers containing functional oxetane groups (HBPE-g-POXMA) were synthesized via chain walking polymerization (CWP) and atom transfer radical polymerization (ATRP) in tandem. Macroinitiators were first synthesized via CWP of ethylene and trimethyl(undec-10-en-1-yloxy) silane following deprotection and esterification reaction. Subsequent ATRP of 3-ethyl-3-(methacryloyloxy) methyloxetane was performed to yield functional polyethylene with controlled molecular weight (MW), relatively narrow MW distribution, good solubility in organic solvents as well as pendant oxetane groups for photopolymerization. Finally, cationic photo-curing of HBPE-g-POXMA was conducted to build crosslinked polyethylene layers on polypropylene membrane surface. The composite membrane showed a narrow pore size distribution (0.03–0.63 μm) and an average pore size of merely 0.31 μm, which exhibited a retention ratio of over 90 % for different dyes. The strategy developed in this study could provide a synthetic route to hyperbranched polyethylene for functional coating via cationic photo-curing.