Reduction of fouling on poly(lactic acid) hollow fiber membranes by blending with poly(lactic acid)–polyethylene glycol–poly(lactic acid) triblock copolymers

Several poly(lactic acid) (PLA)–polyethylene glycol (PEG)–PLA triblock copolymers with PLA segments of different molecular weights were synthesized by ring-opening anion polymerization and used as hydrophilic additives for PLA hollow fiber membranes. PLA hollow fiber membranes were prepared via the non-solvent induced phase separation method. The effects of PLA–PEG–PLA copolymer addition on the membrane morphology and characteristics were evaluated by scanning electron microscopy, X-ray photoelectron spectroscopy, elemental analysis, and water contact angle measurements. The residual ratio of the PLA–PEG–PLA copolymer with the largest PLA molecular weight was almost 100%, while it was only about 10% for PEG. Addition of the PLA–PEG–PLA copolymer, which showed a high residual ratio in the membrane, effectively improved the hydrophilicity of the PLA hollow fiber membrane. Fouling experiments using bovine serum albumin and humic acid solutions revealed that the anti-fouling properties of the PLA hollow fiber membranes were remarkably improved by blending with the PLA–PEG–PLA copolymers.