Polymer Communication Synthesis and helix-sense-selective polymerization of a novel phenylacetylene having a trisiloxanyl group and two hydroxyl groups and enantioselective permeability of the resulting chiral polymeric membrane: Effect of the trisiloxanyl group on the polymerization and enantioselective permeability Lijia Liu a , Yoshiyuki Oniyama a , Yu Zang a , Shingo Hadano c, d , Toshiki Aoki a, b, c, d, * , Masahiro Teraguchi a, b, c , Takashi Kaneko b, c , Takeshi Namikoshi c, d , Edy Marwanta d a Department of Chemistry and Chemical Engineering, Graduate School of Science and Technology, Niigata University, Niigata, 950-2181, Japan b Center for Education and Research on Environmental Technology, Materials Engineering, Nanochemistry, Niigata University, Niigata, 950-2181, Japan c Center for Transdisciplinary Research, Niigata University, Niigata, 950-2181, Japan d Venture Business Laboratory, Niigata University, Niigata, 950-2181, Japan article info Article history: Received 16 February 2010 Received in revised form 12 April 2010 Accepted 14 April 2010 Available online 21 April 2010 Keywords: Helix-sense-selective polymerization Oligosiloxane chain Enantioselective permeation abstract To develop a new phenylacetylene monomer suitable for helix-sense-selective polymerization (HSSP) we reported previously and to improve the efficiency of the HSSP and membrane performance of the resulting polymer, a novel phenylacetylene having a trisiloxanyl group (S3BDHPA) was synthesized and polymerized by using a chiral catalytic system and enantioselectivity in permeation of its membrane was examined. S3BDHPA was suitable for the HSSP and the CD absorption of poly(S3BDHPA) was stronger and more stable than that of the corresponding polymer having no siloxanyl groups. In addition, enantioselectivity in permeation of poly(S3BDHPA) was much higher than that of a polymer membrane having no siloxanyl groups. They are thought to be caused by the flexibility and hydrophobicity of the trisiloxane groups. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Polydimethylsiloxane (PDMS) has many good properties such as high permeability for many gasses and low surface energy. However, since it has no self-membrane-forming property because of its low glass transition temperature based on the high flexibility of SiO bonds, many kinds of rigid structures as a second component were introduced to PDMS [1e 10]. For example we selected poly (substituted phenylacetylenes) as a second rigid component and synthesized and polymerized siloxane-containing substituted acetylenes and reported selectivity in permeation through the resulting polymeric membranes [11]. We found that introduction of short oligosiloxane chains such as disiloxanyl and trisiloxanyl groups was effective to afford advantage of PDMS to the new polymer material containing the rigid second component [12,13]. We have been studying optical resolution membranes using poly(chiral substituted acetylene)s as self-membrane-forming materials [14e18]. Since they had two kinds of chiral structures, i.e., one-handed helical conformation of the main chain and asym- metric carbons in the pendant groups, it had been difficult to confirm the effect of the main-chain chirality on enantioselectivity [19]. However, we obtained one-handed helical poly(substituted phenylacetylenes)(poly(DoDHPA) in Fig. 1) without the coexistence of any other chiral moieties by a helix-sense-selective polymeri- zation (HSSP) [20e24] and found enantioselectivity in permeation of the one-handed helical polymers [25,26]. Therefore, we proved directly the effect of the main-chain chirality on enantioselectivity. However, the selectivity was pretty low because the poly(DoDHPA) membrane was rigid and therefore tended to make defects. In the present communication, to develop a new phenyl- acetylene monomer which is more suitable for our HSSP and to improve membrane performance of the resulting polymer, a novel achiral phenylacetylene (S3BDHPA) having a trisiloxanyl group and two hydroxyl groups was synthesized and chiral poly(S3BDHPA) was synthesized by our HSSP of achiral S3BDHPA (Fig. 1) by using a chiral catalytic system and enantioselective permeation of the resulting polymer membrane was examined. To be compared with S3BDHPA, DoBDHPA which has an alkyl group instead of the oli- gosiloxanyl group in S3BDHPA was synthesized and polymerized. * Corresponding author. Department of Chemistry and Chemical Engineering, Graduate School of Science and Technology, Niigata University, Ikarashi 2-8050, Niigata 950-2181, Japan. Tel.:/fax: þ81 25 262 7280. E-mail address: toshaoki@eng.niigata-u.ac.jp (T. Aoki). Contents lists available at ScienceDirect Polymer journal homepage: www.elsevier.com/locate/polymer 0032-3861/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymer.2010.04.030 Polymer 51 (2010) 2460e2464