Effective grafting of polymers onto ultrafine silica surface: Photopolymerization of vinyl monomers initiated by the system consisting of trichloroacetyl groups on the surface and Mn2(CO)10

The effective grafting of vinyl polymers onto an ultrafine silica surface was successfully achieved by the photopolymerization of vinyl monomers initiated by the system consisting of trichloroacetyl groups on the surface with Mn₂(CO)₁₀ under UV irradiation at 25 °C. The introduction of trichloroacetyl groups onto the surface of silica was achieved by the reaction of trichloroacetyl isocyanate with surface amino groups, which were introduced by the treatment of silica with 3‐aminopropyltriethoxysilane. During the polymerization, the corresponding polymers were effectively grafted onto the surface, based on the propagation of polymer from surface radicals formed by the interaction of trichloroacetyl groups and Mn₂(CO)₁₀. The percentage of poly(methyl methacrylate) grafting onto the silica reached 714.6% after 90 min. The grafting efficiency (proportion of grafted polymer to total polymer formed) in the polymerization of methyl methacrylate was very high, about 80%, indicating the depression of formation of ungrafted polymer. Polymer‐grafted silica gave a stable colloidal dispersion in good solvents for grafted polymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2157–2163, 2001     

Synthesis of networked polystyrene endowed with nucleophilic reaction sites by the living anionic polymerization technique

The living anionic copolymerization of styrene with 1,2‐bis(4′‐ethenylphenyl)ethane (1) or p‐divinylbenzene (PDVB) with sec‐butyllithium in benzene was carried out. The copolymerizations of styrene with more than 20 mol % of 1 gave insoluble polymers in quantitative yields, whereas the yield showed the maximum (97%) for PDVB at 15 mol %. The content of unreacted double bonds of the network polymer formed by the copolymerization with PDVB was four times as large as that formed with 1. Gas chromatographic analyses of the copolymerization suggested close reactivities of the double bonds between styrene and 1, whereas a rapid consumption of PDVB compared with styrene was observed in their copolymerization. The r₁, r₂,and r₁r₂ values for the copolymerization of styrene with 1 were determined to be 1.00, 1.09, and 1.09, respectively, which suggests that a more homogeneous network structure can be attained with 1. The living chain end of the produced living gel initiated the polymerization of tert‐butyl methacrylate to give an insoluble block copolymer in a good yield. The hydrolysis of the ester group of the block copolymer led to an amphiphilic copolymer that exhibited a characteristic property of a hydrogel. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2543–2547, 2000     

Microstructure and mechanical properties of hot‐air drawn poly(ethylene terephthalate) fibers

Hot‐air drawing method has been applied to poly(ethylene terephthalate) (PET) fibers in order to investigate the effect of strain rate on their microstructure and mechanical properties and produce high‐performance PET fibers. The hot‐air drawing was carried out by blowing hot air controlled at a constant temperature against an as‐spun PET fiber connected to a weight. As the hot air blew against the fibers weighted variously at a flow rate of about 90 ℓ/min, the fibers elongated instantaneously at a strain rate in the range of 2.3–18.7 s⁻¹. The strain rate in the hot‐air drawing increased with increasing drawing temperature and applied tension. When the hot‐air drawing was carried out at a drawing temperature of 220°C under an applied tension of 27.6 MPa, the strain rate was the highest value of 18.7 s⁻¹. A draw ratio, birefringence, crystallite orientation factor, and mechanical properties increased as the strain rate increased. The fiber drawn at the highest stain rate had a birefringence of 0.231, degree of crystallinity of 44%, tensile modulus of 18 GPa, and dynamic storage modulus of 19 GPa at 25°C. The mechanical properties of fiber obtained had almost the same values as those of the zone‐annealed PET fiber reported previously. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1703–1713, 1999     

Water-soluble silicon containing polymer resist

Poly(divinylsiloxyethylene glycol), which consists of alternating oligo(ethylene glycol)s (MW = 300) and divinylsiloxanes were prepared by a polycondensation reaction (M_n = 6500–9300, M_w/M_n = 2.01–2.27). The obtained polymer (PVSE300) showed a lower critical solution temperature (LCST) at 10.5°C, meaning that the polymer was soluble in water below the LCST. The glass transition temperature (T_g) and onset temperature of degradation (T_d) of the PVSE300 were −72.5 and +317.5°C, respectively. The hydrolytic stability of the PVSE300 in aqueous media was also examined and it was found that PVSE300 was fairly stable in cold water. The lithographic characteristics of PVSE300 were examined against UV and electron-beam (EB) exposure and it was found that the PVSE300 film showed a negative character when developed by cold water. The photosensitivity parameter, Dg⁵⁰, which denotes the dose at half remaining film thickness after development, against EB exposure was extremely high (1.0 μC/cm²) when a probe current and an accelerating voltage was 100 pA and 20 kV, respectively. A high durability for O₂ reactive ion etching (O₂ RIE) was also observed. The characteristics of PVSE300 against photoirradiation were also examined. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2827–2833, 1997     

Retusone A,a Guaiane-Type Sesquiterpene Dimer from Wikstroemia retusa and Its Inhibitory Effects on Histone Acetyltransferase HBO1 Expression

Retusone A (1), a new sesquiterpene dimer consisting of two guaiane-type sesquiterpenoids, and oleodaphnal (2) were isolated from heartwood of Wikstroemia retusa (Thymelaeaceae). The planar structure of 1 was elucidated on the basis of HRESIMS and NMR spectroscopic data, and the relative stereochemistry was established by X-ray diffraction analysis. The absolute configuration of 1 was determined by electronic circular dichroism. Compound 1 suppressed luciferase reporter gene expression driven by the HBO1 (histone acetyltransferase binding to ORC1) gene promoter in human breast cancer MCF7 cells. Compound 1 also decreased the expression of endogenous HBO1 mRNA and protein, and inhibited proliferation of the cells. These results suggest that retusone A (1), which has a unique dimeric sesquiterpenoid structure with inhibitory activity against HBO1 expression, may contribute to the development of a novel therapeutic candidate for the treatment of breast cancer.     

Simultaneous analysis of 260 pesticide residues in agricultural products by gas chromatography/triple quadrupole mass spectrometry

A method for simultaneous analysis of about 260 pesticides by gas chromatography coupled to tandem mass spectrometry (GC/MS/MS) with a triple quadrupole analyzer (QqQ) has been studied. The pesticides were extracted with acetonitrile and cleaned up by a bilayer cartridge. A single injection method was developed for the monitoring of all of the targeted pesticides. Two MS/MS transitions were selected for each analyte using the intensity ratio obtained from them as a confirmatory parameter. By using matrix-matched standards, 260 pesticides could be determined in most matrixes with recoveries of 70-120% and a standard deviation of < or = 20 at 2 different fortification levels of 0.02 and 0.1 microg/g. The developed method was applied to the monitoring of 173 agricultural product samples from the local market. The sensitivities of this method were lower than with most of the selective GC detectors, such as flame photometric or single MS. The selectivity of QqQ gives a very clean chromatogram, making compound identification and confirmation easy. The quick and reliable monitoring was achieved by combination with rapid extraction and cleanup.