Abstract:
Stimuli-responsive membranes play an important role in the fields of biomedicine, food and chemical
industries, and environmental applications, including separation of water–oil emulsions. In this study, we
present a method to fabricate pH-sensitive membranes using UV-initiated RAFT graft copolymerization
of styrene (ST) and acrylic acid (AA) on poly(ethylene terephthalate) (PET) track-etched membranes
(TeMs). The optimization of polymerization conditions led to successful grafting of polystyrene (PS) and
poly(acrylic acid) (PAA) onto PET TeMs, resulting in membranes with stable hydrophobicity and pH
change responsiveness. The membranes show a contact angle of 65° in basic environments (pH 9) and
97° in acidic environments (pH 2). The membranes were characterized by atomic force microscopy
(AFM), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX),
thermogravimetric analyses (TGA), Fourier transform infrared spectroscopy (FTIR), contact angle (CA)
methods. The PET TeMs-g-PS-g-PAA exhibited good performance in separating water–oil emulsions
with a high efficiency of more than 90% and flux for direct chloroform–water 2500 L m−2 h−1 and
reverse emulsions of benzene–water 1700 L m−2 h−1
. This method of preparing stimuli-responsive
membranes with controlled wettability and responsiveness to environmental pH provides versatility in
their use in separating two types of emulsions: direct and reverse.
