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Polypropylene with low isotacticity and high molecular weight is synthesized using specific C2-symmetric doubly bridged metallocene complexes. This polymer possesses some isotactic sequences in random order. Though it is the homopolymer of propylene, it is a characteristic polymer having low melting point, transparency and elasticity. This soft polypropylene does not have the drop in the glass transition temperature, and the drop in the compatibility to polypropylene in comparison with propylene copolymer, which is a kind of the conventional soft polypropylene.
Half-metallocene complexes of the type CpM(L^L)X2 (L^L=chelating ligands) offer the advantage of catalyst modification: by changing one cyclopentadienyl ligand of metallocene complexes to other ligands such as three-, four-, five-, six- and seven-membered chelates, bidentate and tridentate coordination, and monoanionic, dianionic and trianionic system, steric and/or electronic modification of the coordination environment is much flexible. The structural uniqueness of the metal complexes and the effects of the chelate ring sizes on their productivity and activation processes of the metal complexes with cocatalysts are highlighted.
Die-bonding film is widely applied for semiconductor package of electronic equipments. The die-bonding film based on epoxy resin/acrylic polymer system shows the higher flexibility to thermal stress during the heat cycle test compared with epoxy–matrix systems. In addition, properties of the film vary widely depending on the ratio of epoxy resin and acrylic polymer contents. To satisfy the target properties, novel material design method named weak conditioned combinatorial linear programming was developed.
Self-assembled organic nanotubes (S-ONTs) from rationally designed synthetic amphiphiles provide a variety of inner and outer surfaces as well as homogeneous hollow cylinders with precisely controlled inner diameters. Focusing on distinctive characteristics of the nanospace or nanochannel, we review the recent progress in the research on encapsulation, transportation, stabilization and release behavior of biomacromolecules in the S-ONT nanochannels in terms of application to a bioengineering field.
This review introduces recent attempts in the photoalignment processes of liquid crystalline polymers focusing on the two aspects. First, the strategies to ensure effective in-plane alignment of the photoresponsive mesogens are summarized. Despite many investigations reported so far, the film systems have not been optimized for efficient photoreaction. Second, new photoalignable systems involving block copolymer frameworks such as surface-grafted polymers and block copolymer thin films are introduced. The photoalignment processes in such mesoscopic systems involve strong cooperative motions among different hierarchical size features. Based on these approaches, a new strategic platform, photoalignment via a command surface at the free surface, is further proposed.
Polyglycolic acid (PGA) is a novel biodegradable resin. To mass-produce high-molecular-weight PGA on an industrial scale, Kureha Corporation has developed a new process for obtaining high yields of the intermediate glycolide (GL) with high levels of purity. Using the obtained GL, we developed a method to polymerize high-molecular-weight PGA continuously. A commercial production plant is now in operation. We have also developed various new applications that utilize its characteristics. The use of PGA in shale gas and oil exploration is of interest because PGA can supply ultra-strong and biodegradable materials.
