Synthesis of biodegradable thermoplastic elastomers from ε‐caprolactone and lactide

This article reports the synthesis and the properties of novel thermoplastic elastomers of A‐B‐A type triblock copolymer structure, where the hard segment A is poly(l ‐lactide) (PLLA) and the soft segment B is poly(ε‐caprolactone‐stat‐d ,l ‐lactide) (P(CL‐stat‐DLLA)). The P(CL‐stat‐DLLA) block with DLLA content of 30 mol % was applied because of its amorphous nature and low glass transition temperature (T_g = approximately ?40 °C). Successive polymerization of l ‐lactide afforded PLLA‐block‐P(CL‐stat‐DLLA)‐block‐PLLAs, which exhibited melting temperature (T_m = approximately 150 °C) for the crystalline PLLA segments and still low T_g (approximately ?30 °C) of the soft segments. The triblock copolymers showed very high elongation at break up to approximately 2800% and elastic properties. The corresponding d ‐triblock copolymers, PDLA‐block‐P(CL‐stat‐DLLA)‐block‐PDLAs (PDLA = poly(d ‐lactide)) were also prepared with the same procedure using d ‐lactide in place of l ‐lactide. When the PLLA‐block‐P(CL‐stat‐DLLA)‐block‐PLLA was blended with PDLA‐block‐P(CL‐stat‐DLLA)‐block‐PDLA, stereocomplex crystals were formed to enhance their T_m as well as tensile properties. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 489–495     

Use of tetramethylammonium fluoride (TMAF) and alkali metal alkoxides as an activator for catalytic deprotonative functionalization of heteroaromatic C(sp)–H bonds

Tetramethylammonium fluoride (TMAF) and some alkali metal alkoxides were found to be effective activators for deprotonative functionalization of heteroarenes. Onium amide bases, generated in situ from the combination of aminosilanes and a catalytic amount of TMAF or alkali metal alkoxides efficiently deprotonated C–H bonds of a series of heteroarenes in the presence of an electrophile such as ketones and aldehydes under mild conditions (room temperature). Addition products were obtained generally in good yields, thus providing a highly practical and efficient deprotonation method.     

Control of the stereochemical structure of silicon‐containing polymers

Various optically pure organosilicon compounds were synthesized or separated on HPLC. Stereoregular silicon‐containing polymers, poly(carbosilane)s, poly(carbosiloxane)s and poly(siloxane)s were synthesized from these compounds as monomer. Stereochemistry of the elementary reactions to give stereoregular polymers was elucidated.     

Preparation of asymmetric hollow‐fiber membrane with ultrathin dense skin layer on the outer surface using dry/wet phase inversion process

The authors have developed an asymmetric hollow‐fiber membrane with a skin layer on the outer surface using a dry/wet phase inversion process with a newly synthesized aromatic fluorinated polyamide. Because the skin layer is ultrathin and has no defects, the membrane has gas selectivity in addition to higher gas flux. The membrane has excellent hemocompatibility, which is probably related to packing density of the skin layer. Authors are now clarifying the mechanism of the microstructure formation of the membrane relating to spinning conditions by the standing point of polymer physics. Generally, the microstructure of a polymeric membrane prepared by a phase inversion process is discussed using the phase diagram of the system. However, the process is so dynamic that conventional discussion based on the start and end points is not sufficient, but which path is to be chosen on the phase diagram is more important.     

Novel biomaterials derived from deoxyribozyme and NAPzyme

We report the potential of a small Ca²⁺-dependent deoxyribozyme as a novel biomaterial to distinguish RNA foldings. It is found that an immobilized deoxyribozyme using avidin-biotin interaction cleaves the target site within only single-stranded RNAs. The RNA cleavage reaction is also detected using the deoxyribozyme SPR sensor chip. Furthermore, we develop a novel NAPzyme (nucleic acid peptide deoxyribozyme) with its RNA cleavage function in the absence of divalent metal ions.     

Molecular design and synthesis of novel side-chain liquid crystalline polymers

Novel side-chain liquid crystalline polymers were synthesized based on the molecular design of the chemical structures of main-chain, spacer, and mesogenic groups. The main-chain structures are polyether, by the cationic ring-opening polymerization of oxetane derivatives, and polydiene, by the radical polymerization of diene derivatives. Some of the polymers from oxetanes with various mesogen and spacer groups show smectic liquid crystalline phase. Both cyano- and fluorine-substituted biphenyls are good mesogenic groups in these liquid crystalline polymers. Polydiene also acts as a novel main-chain to give smectic liquid crystalline state with cyanobiphenyl or fluorobiphenyl as a mesogen. Not only oligomethylene groups but also siloxane and oligo(oxyethylene) groups act as a component of the spacer groups to give liquid crystalline state.