Preparation of hydrophilic HDPE porous membranes via thermally induced phase separation by blending of amphiphilic PE-b-PEG copolymer

Hydrophilic and anti-fouling HDPE/PE-b-PEG microporous membranes were prepared by blending high density polyethylene (HDPE) and amphiphilic copolymer polyethylene-block-poly(ethylene glycol) (PE-b-PEG) through the liquid–liquid thermally induced phase separation (L–L TIPS) process. Compared with pure HDPE membrane, HDPE/PE-b-PEG blend membranes exhibit larger water permeation flux due to the segregation of the hydrophilic PEG segments at the membrane surface, which was confirmed by X-ray photoelectronic spectroscopy (XPS) and contact angle measurements. The further investigation of the effects of PE-b-PEG content on the phase diagram of the HDPE/PE-b-PEG/DPE mixture system and membrane morphology showed that with increasing PE-b-PEG content, the cloud point of ternary system shifted to the higher temperature, while crystallization temperature did not change too much. Meantime, HDPE/PE-b-PEG membranes with higher PE-b-PEG content exhibited larger pore size, which is in consistent with the increased water flux. The improved separation performance and morphology of HDPE/PE-b-PEG membranes were explained by the viewpoint of droplet growth kinetics of L–L TIPS, i.e. the faster droplet growth rate and the longer droplet growth period result in the bigger droplet volume in HDPE/PE-b-PEG system, and thus the larger pore size in HDPE/PE-b-PEG membrane.