The coordination polymerization of silyl‐protected ω‐alkenols such as ω‐alken‐α‐oxytriisopropylsilanes 1 provides poly(ω‐alkenyl‐α‐oxytriisopropylsilalne)s with a highly isospecific microstructure ([mmmm] > 95%) when a combination of [OSSO]‐type bis(phenolato) dichloro zirconium(IV) complex 2 and dried methylaluminoxane is used as the precatalyst and activator, respectively. The resulting siloxy‐substituted polymers could be efficiently transformed into the corresponding functionalized polyolefins, which contained up to 90% acetyl groups and ≈7% hydroxy groups in the terminal side chains.
Cellulose is a major biopolymer on the earth that is produced by cellulose synthase in the cell membrane of living organisms. Cellulose synthase is a hetero-subunit complex composed of several different protein subunits, and is visualized as a supermolecular complex called a “terminal complex” by electron microscopy. Such supermolecular organization of an enzyme complex is believed to be important for the fiber formation or crystallization of cellulose microfibrils in cellulose biosynthesis. In the case of the cellulose-producing bacterium Acetobacter, it is hypothesized that the enzyme complex includes at least six subunits given its genetic constitution. However, to date, only three of these molecules have been experimentally confirmed as the subunits included in the terminal complex: CesB, CesD, and ccp2. In this study, we used fluorescence immuno-microscopy to show that CesA protein, the catalytic subunit, is included in the terminal complex of Acetobacter. Furthermore we discuss the obtained microscopic data for improving our understanding of the molecular organization of the bacterial cellulose synthase complex. 相似文献
Various N,N-dimethyl amides, N-methoxy-N-methyl amides, and isopropyl esters were smoothly transformed into the corresponding nitriles in good to moderate yields by the treatment with diisobutylaluminium hydride, followed by treatment with molecular iodine in aq ammonia. The present reactions are novel one-pot and practical methods for the transformation of N,N-disubstituted amides and isopropyl esters into nitriles, through the formation of hemiaminal O-AlBu2 and hemiacetal O-AlBu2, respectively. 相似文献
Various esters were efficiently converted into the corresponding nitriles in good yields by the treatment with sodium diisobutyl-tert-butoxyaluminium hydride (SDBBA-H), followed by treatment with molecular iodine in aq ammonia. The present one-pot method is very efficient and practical for the conversion of various aromatic and aliphatic esters into the corresponding nitriles. 相似文献
A mixture of ω-(4-cyanobiphenyl-4′-yloxy)alkyl methacrylate and 1,3,5-tris-(ω-methacryloyloxyalkyloxy)benzene was heated to
200 °C at 5–10 °C/min. A large, broad exothermic transition peak was observed by differential scanning calorimetry during
the first heating process. The transition indicated the formation of a networked polymer, which was then immersed for 24 h
in various nematic liquid crystals, such as 4-cyano-4′-pentylbiphenyl, to give liquid crystal gels. The networked polymers
and their corresponding liquid crystal gels exhibited different liquid crystal-isotropic transitions. The swelling behaviors
of the liquid crystal gels were compared with those of gels cross-linked with 1,6-hexanediol dimethacrylate, trimethylpropane
trimethacrylate, and pentaerythritol tetraacetate. The characteristics of liquid crystal gels cross-linked with 1,3,5-tris-(ω-methacryloyloxyalkyloxy)benzenes
were studied. 相似文献
This paper describes the preparation of iron oxide nanoparticles, surface of which was coated with extremely high immobilization stability and relatively higher density of poly(ethylene glycol) (PEG), which are referred to as PEG protected iron oxide nanoparticles (PEG-PIONs). The PEG-PIONs were obtained through alkali coprecipitation of iron salts in the presence of the PEG-poly(4-vinylbenzylphosphonate) block copolymer (PEG-b-PVBP). In this system, PEG-b-PVBP served as a surface coating that was bound to the iron oxide surface via multipoint anchoring of the phosphonate groups in the PVBP segment of PEG-b-PVBP. The binding of PEG-b-PVBP onto the iron oxide nanoparticle surface and the subsequent formation of a PEG brush layer were proved by FT-IR, zeta potential, and thermogravimetric measurements. The surface PEG-chain density of the PEG-PIONs varied depending on the [PEG-b-PVBP]/[iron salts] feed-weight ratio in the coprecipitation reaction. PEG-PIONs prepared at an optimal feed-weight ratio in this study showed a high surface PEG-chain surface density (≈0.8 chainsnm(-2)) and small hydrodynamic diameter (<50 nm). Furthermore, these PEG-PIONs could be dispersed in phosphate-buffered saline (PBS) that contains 10% serum without any change in their hydrodynamic diameters over a period of one week, indicating that PEG-PIONs would provide high dispersion stability under in vivo physiological conditions as well as excellent anti-biofouling properties. In fact we have confirmed the prolong blood circulation time and facilitate tumor accumulation (more than 15% IDg(-1) tumor) of PEG-PIONs without the aid of any target ligand in mouse tumor models. The majority of the PEG-PIONs accumulated in the tumor by 96 h after administration, whereas those in normal tissues were smoothly eliminated by 96 h, proving the enhancement of tumor selectivity in the PEG-PION localization. The results obtained here strongly suggest that originally synthesized PEG-b-PVBP, having multipoint anchoring character by the phosphonate groups, is rational design for improvement in nanoparticle as in vivo application. Two major points, viz., extremely stable anchoring character and dense PEG chains tethered on the nanoparticle surface, worked simultaneously to become PEG-PIONs as an ideal biomedical devices intact for prolonged periods in harsh biological environments. 相似文献
Phenyltriethoxysilane (PhTES) and tetraethoxysilane (TEOS) coatings [xPhTES·(100 − x)TEOS (mol%)] (x = 0 − 80) were prepared on polycarbonate (PC) substrate, and adhesion, surface hardness and distribution of phenyl groups
were studied. The coatings with more than 60 mol% of PhTES showed good adhesion (≈ 100%), and the pencil hardness of PC substrate
(4B) improved to 2B or B after the coatings. Bulk gels with the same compositions were also prepared, and distribution of
phenyl groups were estimated using fourier transform infrared (FT-IR) spectroscopy (KBr method for bulk gels and attenuated
total reflection (ATR) method for coatings). A significant difference for the distribution of phenyl groups was clearly observed
between bulk gels and coatings, suggesting PC substrate affects the distribution of phenyl groups in coatings. The adhesion
and FTIR results revealed that there is an interaction caused by π-electrons between benzene rings on PC substrate and phenyl
groups of PhTES-TEOS coatings. It was found that the adhesion was strongly correlated with the phenylsilsesquioxane networks
formed around PC substrate side. 相似文献