Electro‐conductive double‐network hydrogels

Novel electro‐conductive and mechanically‐tough double network polymer hydrogels (E‐DN gels) were synthesized by polymerization of 3, 4‐ethylenedioxythiophene in the presence of a double network hydrogel (DN gel) matrix. The E‐DN gels showed not only excellent mechanical performance, having a fracture stress of 1.4–2.1 MPa, but also electrical conductivity as high as 10^?3 S cm^?1, both under dry and water‐swollen states. The fracture stress and fracture energy of the E‐DN gel was increased by 1.7 and 3.4 times, respectively, as compared with the DN gel. From scanning electron microscope and AFM observations, it was found that electro‐conductive poly(3,4‐ethylenedioxythiophene) (PEDOT) was incorporated into DN gel matrix, apparently due to the formation of a poly‐ion complex with sulfonic acid group of the DN gel network. Thus, PEDOT incorporated into the DN gel matrix greatly improves not only electronic conductivity, but also mechanical properties, reinforcing the double network gel matrix. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Asymmetric total synthesis of (-)-azaspirene,a novel angiogenesis inhibitor

The asymmetric total synthesis of (-)-azaspirene, an angiogenesis inhibitor, has been accomplished, establishing its absolute stereochemistry. The key steps are a MgBr2.OEt2-mediated, diastereoselective Mukaiyama aldol reaction, a NaH-promoted, intramolecular cyclization of an alkynylamide, and the aldol reaction of a ketone containing functionalized gamma-lactam moiety without protection of tert-alcohol and amide functionalities.     

Structural effects of electrochemical oxidation of formic acid on single crystal electrodes of palladium

Structural effects on the rates of formic acid oxidation have been studied on Pd(111), Pd(100), Pd(110), and Pd(S)-[n(100) x (111)] (n = 2-9) electrodes in 0.1 M HClO4 containing 0.1 M formic acid with use of voltammetry. On the low index planes of Pd, the maximum current density of formic acid oxidation (jP) increases in the positive scan as follows: Pd(110) < Pd(111) < Pd(100). This order differs from that on the low index planes of Pt: Pt(111) < Pt(100) < Pt(110). Pd(S)-[n(100) x (111)] electrodes with terrace atomic rows n > or = 3 have almost the same jP as Pd(100), except Pd(911) n = 5. The value of jP on Pd(911) n = 5 is 20% higher than those of the other surfaces. Pd(311) n = 2, of which the first layer is composed of only step atoms, has the lowest jP in the Pd(S)-[n(100) x (111)] series. The adsorption geometry of the reaction intermediate (formate ion) is optimized by using density functional theory.     

Computational study on the reaction mechanism of the key thermal [4 + 4] cycloaddition reaction in the biosynthesis of epoxytwinol A

[reaction: see text] The key [4 + 4] cycloaddition in the biosynthesis of epoxytwinol A has been established by theoretical calculations to comprise of three processes. The first step is formation of the C8-C8' bond generating a biradical intermediate. Next, rotation about the C8-C8' bond occurs, and finally the C1-C1' bond is formed. Biradicals stabilized by conjugation and two hydrogen bonds are essential for realization of this rare thermal [4 + 4] cycloaddition.     

Oxygen ion implantation at 20 to 2000 keV into polysulfone for improvement of endothelial cell adhesion

The irradiation effects of oxygen on polysulfone have been investigated at energies of 20 keV, 150 keV and 2 MeV. The strong improvement of endothelial cell adhesion and proliferation is found on ion irradiated polysulfone at 20 keV. Such improvement is declined with increasing ion energy. The changes of surface color and free energy are strongly dependent on ion energy and dose. The formation of amorphous carbon phase is demonstrated by Raman spectroscopy and its degree is correspondent to the color changes observed. The formations of hydroxyl and carboxyl groups are confirmed by the attenuated total reflectance (ATR) FTIR spectroscopy. The depletions of heteroatoms are conjectured by detail analysis of X-ray photoelectron spectroscopy (XPS). Since no single one of these changes can be related directly to the improved adhesion and proliferation of endothelial cells on irradiated surface, we argue that the distribution of functional groups is crucial in promoting the adhesion of endothelial cells. Although the distribution cannot directly be detected at present, the irradiation effects were related to the results of TRIM simulation. The surface changes can be controlled by adjusting the size energy and dose of irradiating ion for the optimum morphology to cell adhesion.     

Hydrogels with Crystalline or Liquid Crystalline Structure

The formation of ordered structure in hydrogels derived from copolymers of hydrophilic and hydrophobic monomers with crystalline or liquid‐crystalline moieties is reviewed. The role of water in the formation of ordered structure and its influence on the thermal and mechanical properties of hydrogels are clarified. For example, by inducing a certain amount of water, an amorphous to crystalline transition occurs in gels of acrylic acid/alkyl acrylate copolymers. On the other hand, water induces a liquid‐crystalline (SmA) to liquid‐crystalline (SmI) transition in copolymers consisting of acrylic acid and 11‐(4′‐cyanobiphenyloxy)undecyl acrylate. These specific features regarding the formation of ordered structures in hydrogels might shed some light on the formation of ordered structure in biological tissues.     

Substrate effect on the formation of hydrogels with heterogeneous network structure

It was found that when an aqueous solution of vinyl monomers is polymerized on a hydrophobic substrate, obvious heterogeneity occurs in the region of the interface. This substrate effect was observed on polytetrafluroethylene (Teflon), polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyvinylchloride (PVC), but not on hydrophilic substrates. Compared with synthesis on hydrophilic surfaces, the surfaces of hydrogels synthesized on a hydrophobic substrate exhibit a larger degree of swelling, a lower surface coefficient of friction and elastic modulus, weaker interfacial adhesion, and reduced interaction with biological cells. This substrate effect has been observed for many types of aqueous monomer solutions. It was found that the above properties are related to the loosely cross-linked architecture, containing some graft-like polymer chains, that is formed on the gel surface when the gel is prepared on a hydrophobic substrate. To understand the mechanism of the substrate effect, two novel optical methods, electric speckle pattern interferometry (ESPI) and real-time laser sheet refraction (RT-LSR), were developed. It was found that oxygen trapped in the composite interface between the monomer solution and rough hydrophobic substrates played an important role in the substrate effect.     

Water-soluble porphyrins appending platinum(II) complexes as binders for synthetic nucleic acid polymers

Water-soluble porphyrins containing four platinum(II) complexes per molecule, [5alpha,10beta,15alpha,20beta-tetrakis(2-trans-(alpha,beta,alpha,beta-trans-Pt) and cis-(alpha,beta,alpha,beta-cis-Pt) [PtCl(NH(3))(2)]N-2-aminophenylporphyrin)], were synthesized and characterized. The binding of synthetic nucleotide polymers (poly(dG)-poly(dC), poly(dA)-poly(dT)) to the porphyrins was examined spectrophotometrically in aqueous solution. UV-vis spectral data suggested that these porphyrins bind to the nucleic acids by coordinative and Coulomb interactions.