Seong Yong Ha

Gas permeation of poly(amide-6-b-ethylene oxide) copolymer

Abstract Block copolymers exhibit a different gas permeation behavior from that of homopolymers. In the diffusion process, the fraction of impermeable regions in the block copolymer decreases the diffusivity and the permeability. As the amount of impermeable regions in the block copolymer increases, the flow paths for the gas diffusion are restricted. Poly(amide-6-b-ethylene oxide) (PEBAX®) copolymer consists of a regular linear chain of rigid polyamide for hard segment interspaced with flexible polyether for soft segment. PEBAX® copolymer shows a typical permeation behavior of rubbery polymers. The permeability of CO2 increases with the pressure originating from the increment of the sorbed CO2 amounts. PEBAX® copolymer shows the high permeability and the high selectivity for polarizable/nonpolar gas pairs. Particularly, the selectivity of CO2 over N2 is 61 and that of SO2 over N2 is 500. For small and nonpolar gases (i.e. He, H2, O2 and N2), the permeability decreases with increasing the molecular size or volume of gases. On the other hand, for polarizable and larger gases (i.e. CO2 and SO2), it shows the high permeability. The high permeability and permselectivity of PEBAX® copolymer are attributed of polarizable gases to polyether segment in PEBAX®.

Percolation behavior of gas permeability in rigid-flexible block copolymer membranes

Abstract Transport of permeates through copolymer membranes with rigid and flexible block was investigated based on the percolation concept. In terms of the morphology, the percolation approach provided a rationale for the property of gas permeation behavior of block copolymer consisting of the rigid amideimide block and the flexible siloxane block. The permeability of oxygen through poly(amideimide)siloxane (SPAI) membranes containing different siloxane contents showed a peculiar permeation behavior, indicating that there existed a percolation threshold of the gas permeation at around 0.2–0.3 volume fraction of SPAI. At above the threshold volume fraction, the gas permeability of this block copolymer was proportional to the probability of spanning siloxane phase. We confirmed that an addition of flexible domains in the rigid matrix enhanced the rate of gas permeation, and the permeability of SPAI obeyed a simple power law above and near the percolation threshold. In order to inspect the present system, the percolation concept was reinterpreted to elucidate the change of gas permeability through polymeric membranes with rigid and flexible block.

Preparation of poly(amideimide siloxane) from trimellitic anhydride chloride, oxylene diamine and oligo(dimethylsiloxane) diamine

Abstract A novel poly(amideimide siloxane) block copolymer was prepared from oligo(dimethylsiloxane), trimellitic anhydride chloride and oxylene diamine using trimethylsilyl chloride as the reaction activator. Trimethylsilyl chloride enhanced the reactivity of oligo(dimethylsiloxane), resulting in a higher yield and viscosity of the product. The high reactivity of N -trimethylsilylated siloxane diamine stems from the silicon σ—π effect, and a nucleophilic addition—elimination reaction is proposed. The addition of a small amount of N -methylpyrrolidone in tetrahydrofuran led to a higher yield. The temperature of 10% weight loss for the product exceeded 355°C according to thermogravimetric analysis data. A transient change in the contact angle of water on the sample surface was observed, suggesting surface segregation of the hydrophobic component in the polymer.