Nanocomposites derived from in situ grafting of linear and hyperbranched poly(ether‐ketone)s containing flexible oxyethylene spacers onto the surface of multiwalled carbon nanotubes

Linear and hyperbranched poly(ether‐ketone)s (PEKs) containing flexible oxyethylene spacers grafted multiwalled carbon nanotube (PEK‐g‐MWNT) nanocomposites were prepared by direct Friedel‐Crafts acylation as the polymer forming and grafting reaction. To achieve the composites, in situ polycondensations of AB monomers 3‐(2‐phenoxyethoxy)benzoic acid (3‐PEBA) and 4‐(2‐phenoxyethoxy)benzoic acid (4‐PEBA), and AB₂ monomer 3,5‐bis(2‐phenoxyethoxy)benzoic acid (3,5‐BPEBA) were carried out in the presence of multiwalled carbon nanotubes (MWNTs). The reaction conditions, polyphosphoric acid (PPA) with additional phosphorous phentoxide (P₂O₅) in the temperature range of 110–120 °C, were previously optimized. The conditions were used as the polymerization and grafting medium that were indeed benign not to damage MWNTs but strong enough to promote the covalent attachment of PEKs onto the surface of the electron‐deficient MWNTs. From scanning electron microscopy (SEM) and transmission electron microscopy studies, the polymers were uniformly grafted onto the MWNTs. The resultant nanocomposites are soluble in most strong acids such as trifluoroacetic acid, methanesulfonic acid, and sulfuric acid. Both isothermal and dynamic TGA studies in air showed that nanocomposites displayed improved thermo‐oxidative stability when compared with those of corresponding PEK homopolymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3471–3481, 2008     

Wide band laser heat treatment using pyramid polygon mirror

A wide laser beam optical system for laser heat treatment processing has been designed with a pyramid polygon mirror, which is able to adjust the amplitude and frequency. It consists of a rotating pyramid polygon mirror made of copper and a cooling part that protects the surface of the mirror from damage by heat. The system provides a linear laser heat source with the wide scanning width. This can increase the efficiency of production and quality of products. The CO₂ laser heat treatment has been processed on SNCM220 and SCM440 steels using the developed optical system. The width of specimens between 13 and 17 mm can be hardened for a single pass scanning.     

Chemiluminescent Probe for the In Vitro and In Vivo Imaging of Cancers Over‐Expressing NQO1

Activatable (turn‐on) probes that permit the rapid, sensitive, selective, and accurate identification of cancer‐associated biomarkers can help drive advances in cancer research. Herein, a NAD(P)H:quinone oxidoreductase‐1 (NQO1)‐specific chemiluminescent probe 1 is reported that allows the differentiation between cancer subtypes. Probe 1 incorporates an NQO1‐specific trimethyl‐locked quinone trigger moiety covalently tethered to a phenoxy‐dioxetane moiety through a para‐aminobenzyl alcohol linker. Bio‐reduction of the quinone to the corresponding hydroquinone results in a chemiluminescent signal. As inferred from a combination of in vitro cell culture analyses and in vivo mice studies, the probe is safe, cell permeable, and capable of producing a “turn‐on” luminescence response in an NQO1‐positive A549 lung cancer model. On this basis, probe 1 can be used to identify cancerous cells and tissues characterized by elevated NQO1 levels.     

Application and New Developments in Polymer‐Dispersed Liquid Crystal Simulation Studies

Polymer‐dispersed liquid crystals (PDLCs) represent an important new class of materials with electro‐optic applications such as flexible displays, large‐area devices projection displays, electrically switchable windows, etc. On considering such applications of these materials, many studies have been performed on the experimental side. Similarly, research on the simulation side for the PDLCs is of the fundamental interest too. The present article contains a short review on the present and past simulation studies of PDLCs. Various molecular simulation approaches applied to PDLC systems by different groups are reviewed here. In addition some new findings of the bulk phases are also extensively described.

     

Surface Structure and Stereocomplex Formation of Enantiomeric Polylactide Blends Using Poly(dimethyl siloxane) as a Probe Polymer

In the stereocomplex between enantiomeric poly(l-lactide) (l-PLA) and poly(d-lactide), crystallites formed as a result of stereocomplexation, equimolar l- and d-lactide unit sequences are packed side by side. The stereocomplex exhibits a melting temperature higher by about 50 °C than that of each homopolymer. In this study, we attempt to obtain further insight into the stereocomplex-induced surface structure of enantiomeric PLA blend films. The design of the blend systems is based on principles of surface segregation of multicomponent polymeric systems with a low surface energy, triblock copolymer (l-PLA-b-PDMS-b-l-PLA) of l-PLA and poly-(dimethyl siloxane). (l-PLA-b-PDMS-b-l-PLA/l-PLA) blend films showed the surface segregation of PDMS, regardless of blend composition while the surface composition of PDMS in the (l-PLA-b-PDMS-b-l-PLA/d-PLA) blend films was strongly depended on blend composition or a degree of complexation. These results are likely due to strong interaction between d- and l-lactide unit sequences, which prevents the surface segregation of PDMS.     

A new approach to an N/G/1 queue

We propose a new approach that gives a one-step computational algorithm to directly obtain the queue length distribution of an N/G/1 queueing system. The new approach is based on the supplementary variable method and the matrix–analytic method. We shall show that this approach enables us to derive the joint distribution of the queue length and the elapsed service time. This revised version was published online in June 2006 with corrections to the Cover Date.     

Direct, stereospecific generation of (Z)-disubstituted allylic alcohols

A one-pot method to prepare highly functionalized (Z)-disubstituted allylic alcohols is introduced. Hydroboration of a variety of 1-bromo-1-acetylenes with dicyclohexyl borane, reaction with t-BuLi, and transmetalation to zinc generates a (Z)-disubstituted vinylzinc reagent. In situ reaction of this reagent with aldehydes generates (Z)-disubstituted allylic alcohols in high yields (81-97%). Addition to chiral protected alpha- or beta-oxygenated aldehydes proceeds with diastereoselectivities between 6:1 and 18:1. The anti-Felkin product is obtained in most cases.