Short Report 1: Functionalized Membrane Development in Yamaguchi Group

Membrane technology has drawn numerous attention because it can be an alternative to reduce energy consumption1. Many researchers had made functionalized membranes to achieve some goals in separation process or to mimic the nature.

In 1991, Yamaguchi et al proposed a new concept of pore-filling membrane. HDPE was used as hard porous substrate and filled by poly(methyl acrylate). Swelling of poly(methyl acrylate) can be restricted due to mechanically stable HDPE matrix2. Pore-filling membrane concept was shown in figure 1. Grafting process itself had been reported successfully using Plasma-induced graft polymerization (PIGP) method234567. This method is convenience to treat thermally labile monomer because its mild thermal conditions on acidic environment4. Grafted copolymer composition as well as its solubility can be regulated by monomer composition variation6.

Figure 1. Concept of Pore- Filling Membrane2

Ulbricht et al reported on 1997 that pore-filling concept had been successfully applied to polyacrylonitrile (PAN) asymmetric membrane for pervaporation process8. His group was using UV irradiation instead of plasma. Pore-filling membrane also can be prepared using inorganic substrate like porous glass9.

Ten years after the first paper about pore filling membrane, the concept was employed on hollow fiber membrane10,11 and microcapsule12. Not just for pervaporation, in 2005 Yamaguchi et al were successfully demonstrated the capability of pore-filling membrane to do Reverse Osmosis process. It can be achieved using crosslinked grafting polymer13.

The further development of pore filling membrane was smart responsive gating membrane. The idea was to create something like a door in substrate pores than can be open or closed depend on the stimuli. Other work by Yamaguchi et al showed that copolymer N-isopropylacrylamide (NIPAM) -- benzo[18]crown-6-acrylamide (BCAm) grafted on porous HDPE substrate can response Ba2+ ion3. This concept of ion-gating membrane can be modelled using some governing equations14.

The same group then developed biomolecule-recognition gating system to responds signals of biomolecules by using of biorecognition cross-linking and polymer phase transition on same porous substrate15. Some improvements were made to the responsive polymer or the “door” of the gating membrane. NIPAM as primary backbone of the “door” was combined with β-cyclodextrin16 and DNA17 to broaden its capability to sense variety of molecules. The gating membrane can also be modified in order to respond pH using ion- recognition polyampholyte like poly(acrylic acid-co-crown ether)5.

Other example of functionalized membrane is using ceramic membrane for gas separation. Yamaguchi et al demonstrated the great potential of zeolitic-imidazolate frameworks (ZIF)-8 to be used as a material for the membrane separation of propylene/propane on the basis of their diffusivity difference1.

References

1. Hara, N. et al. Diffusive separation of propylene/propane with ZIF-8 membranes. J. Memb. Sci. 450, 215–223 (2014).2. Yamaguchi, T., Nakao, S. & Kimura, S. Plasma-graft filling polymerization: preparation of a new type of pervaporation

membrane for organic liquid mixtures. Macromolecules 24, 5522–5527 (1991).3. Yamaguchi, T., Ito, T. & Sato, T. Development of a Fast Response Molecular Recognition Ion Gating Membrane. J. Am.

Chem. Soc. 4078–4079 (1999).4. Chi, X., Ohashi, H. & Yamaguchi, T. Plasma-Induced Graft Polymerization Inside Pores of Porous Substrates Assisted by an

Infiltration Agent in Acidic Conditions. Plasma Process. Polym. 11, 306–314 (2014).5. Ohashi, H., Ebina, S. & Yamaguchi, T. Logistic gate-like permeable property of gating membrane with ion-recognition

polyampholyte. Polymer (Guildf). 55, 1412–1419 (2014).6. Yamaguchi, T., Nakao, S. & Kimura, S. Design of pervaporation membrane for organic-liquid separation based on

solubility control by plasma-graft filling polymerization technique. Ind. Eng. Chem. Res. 32, 848–853 (1993).7. Yamaguchi, T., Yamahara, S., Nakao, S. & Kimura, S. Preparation of pervaporation membranes for removal of dissolved

organics from water by plasma-graft filling polymerization. J. Memb. Sci. 95, 39–49 (1994).8. Ulbricht, M. & Schwarz, H.-H. Novel high performance photo-graft composite membranes for separation of organic

liquids by pervaporation. J. Memb. Sci. 136, 25–33 (1997).9. Kai, T., Yamaguchi, T. & Nakao, S. Preparation of Organic/Inorganic Composite Membranes by Plasma-Graft Filling

Polymerization Technique for Organic-Liquid Separation. Ind. Eng. Chem. Res. 39, 3284–3290 (2000).10. Kai, T. Preparation of hollow-fiber membranes by plasma-graft filling polymerization for organic-liquid separation. J.

Memb. Sci. 170, 61–70 (2000).11. Yamaguchi, T., Suzuki, T., Kai, T. & Nakao, S. Hollow-fiber-type pore-filling membranes made by plasma-graft

polymerization for the removal of chlorinated organics from water. J. Memb. Sci. 194, 217–228 (2001).12. Chu, L. Preparation of thermo-responsive core-shell microcapsules with a porous membrane and poly(N-

isopropylacrylamide) gates. J. Memb. Sci. 192, 27–39 (2001).13. KAI, T. et al. Development of crosslinked plasma-graft filling polymer membranes for the reverse osmosis of organic

liquid mixtures. J. Memb. Sci. 265, 101–107 (2005).14. Ito, T., Ohashi, H., Tamaki, T. & Yamaguchi, T. Mathematical modeling of molecular recognition by an ion-gating

membrane oscillator. J. Memb. Sci. 448, 231–239 (2013).15. Kuroki, H., Ito, T., Ohashi, H., Tamaki, T. & Yamaguchi, T. Biomolecule-recognition gating membrane using biomolecular

cross-linking and polymer phase transition. Anal. Chem. 83, 9226–9 (2011).16. Ohashi, H., Abe, T., Tamaki, T. & Yamaguchi, T. Influence of spacer length between actuator and sensor on their mutual

communications in poly(N -isopropylacrylamide-co -??-cyclodextrin), an autonomous coordinative shrinking/swelling polymer. Macromolecules 45, 9742–9750 (2012).

17. Sugawara, Y., Tamaki, T., Ohashi, H. & Yamaguchi, T. Control of the poly(N-isopropylacrylamide) phase transition via a single strand–double strand transformation of conjugated {DNA}. Soft Matter 9, 3331–3340 (2013).