Formation of Water-Channel by Propylene Glycol into Polymer for Porous Materials

In this study, a porous membrane with a cellulose acetate (CA) matrix was fabricated using propylene glycol with a water pressure treatment without a metal salt as an additive. The water pressure treatment of the fabricated CA membrane with propylene glycol yielded nanopores. The nanopores were formed as the additives in the CA chains led to plasticization. The weakened chains of the parts where the plasticization occurred were broken by the water pressure, which generated the pores. Compared to the previous study with glycerin as an additive, the size of the hydration region was controlled by the number of hydrophilic functional groups. When water pressure was applied to the CA membrane containing propylene glycol as an additive, the hydration area was small, so it was effective to control the pore size and the number of nano pores than glycerin. In addition, the number of nanopores and pore size could be easily adjusted by the water pressure. The porosity of the membrane was increased owing to the trace amount of propylene glycol, confirmed by scanning electron microscopy (SEM) and porosimetry. The interaction between the CA and propylene glycol was verified by Fourier-transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). Consequently, it was the optimum composition to generate pores at the CA/propylene glycol 1:0.2 ratio, and porosity of 69.7% and average pore diameter of 300 nm was confirmed. Since it is a membrane with high porosity and nano sized pores, it is expected to be applied in various fields.