Synthesis of Bioactive and Porous Organic-Inorganic Hybrids for Biomedical Applications

Bioactivity has been exhibited by a limited range of ceramics since the invention of Bioglass®. Recently, some bioactive polymeric organic-inorganic hybrids were introduced, including not only organically modified silicates (Ormosils) synthesized from polydimethylsiloxane (PDMS) and tetraethoxysilane but also those with gelatin and 3-glycidoxypropyl-tremethoxysilane. Preparation of the bulk and porous hybrids and their polymeric structures analyzed by Si NMR spectroscopy were presented. In vitro bioactivity or apatite deposition in a simulated body fluid of the Kokubo recipe were also described for those hybrids. Freeze-drying techniques introduced porosity (up to 90%) and pores extending in a preferred direction.     

Singlet and triplet photocycloaddition reactions of 2-pyridones with propenoate and 2,4-pentadienotes,and the frontier molecular orbital analysis

Regioselective photocycloadditions of 2-pyridones ( 1 ) with 2,4-pentadienoates ( 3 ) were analysed and compared with the reactions with propenoate ( 2 ), and origins of the different regioselectivities were inferred from frontier molecular orbital properties by the use of PM3-CI method. Direct photoreactions of 1 with 3 being α,β,γ,δ-unsaturated carboxylates gave four types of regio-selective [2+2]cycloadducts, 3-β:4-α-4, 5, 3-δ:4-γ-6,7,5-δ: 6-γ-8, 9 and 5-δ:6-γ-[2+2]cycloadducts 10,11. Sensitized photoreactions of 1 with 3 did not occur, and fluorescence of 1 was weakly quenched by 3. Otherwise, main cycloadducts in the sensitized reactions of 1 with 2 have been obtained as 5-α:6-β-[2+2]cycloadducts, which were different from main 3-β:4-α-[2+2]cycloadducts of the direct reactions, and these site-and regio-selectivities were inferred from the different frontier molecular orbital coefficients at the. 3-and 6-positions of 1 for the triplet and singlet states. Formations of 4–7 were also interpreted by both effects of frontier orbital HSOMO-LUMO interactions and of the electrostatic interaction between 1 and 3. The other site-and regioselective adducts 8–11 were inferred to be formed by the electrostatic interactions similar to 2-pyridone photodimerization.     

Syntheses,Structures, and Reactivities of Two Chalcogen‐Stabilized Carbones

Electronic effects on the central carbon atom of carbone, generated by the replacement of the S^IV ligand of carbodisulfane (CDS) with other chalcogen ligands (Ph₂E, E=S or Se), were investigated. The carbones Ph₂E→C←SPh₂(NMe) [E=S( 1 ) or Se( 2 )] were synthesized from the corresponding salts, and their molecular structures and electronic properties were characterized. The carbone 2 is the first carbone containing selenium as the coordinated atom. DFT calculations revealed the electronic structures of 1 and 2 , which have two lone pairs of electrons at the carbon center. The trend in HOMO energy levels, estimated by cyclic voltammetry measurements, for the carbones and CDS follows the order of 2 > 1 >CDS. Analysis of a doubly protonated dication and trication complex revealed that the central carbon atom of 2 behaves as a four‐electron donor.     

Synthesis of Bioactive Organic-Inorganic Hybrids with γ-Methacryloxypropyltrimethoxysilane

Bioactive organic-inorganic hybrids were synthesized through sol-gel processing starting from -methacryloxypropyltrimethoxysilane. NMR-spectroscopic studies showed the presence of silanol groups (Si–OH) and Si–O–Si bonds. In vitro tests of the hybrids for bioactivity with a simulated body fluid (Kokubo solution) indicated that only calcium-containing hybrids could form apatite on their surfaces. Thus the presence of calcium ions was no less important to deposit apatite than the formation of silanol groups or Si–O–Si bonds.     

Direct patterning of poly(amic acid) and low‐temperature imidization using a crosslinker,a photoacid generator,and a thermobase generator

A positive‐type photosensitive polyimide (PSPI) based on poly(amic acid) (PAA), a crosslinker 1,1,1‐tris{4‐[2‐(vinyloxy)ethoxy]phenyl}ethane (TVPE), a photoacid generator (PAG) (5‐propylsulfonyloxyimino‐5H‐thiophen‐2‐ylidene)‐2‐(methylphenyl)acetonitrile (PTMA), and a thermobase generator (TBG) t‐butyl 2,6‐dimethylpiperidine‐1‐carboxylate (BDPC) has been developed as a promising material in microelectronics. The PAA was prepared from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA) and 4,4′‐oxydianiline (ODA) in dimethyl sulfoxide (DMSO). The PSPI, consisting of PAA (69 wt %), TPVE (21 wt %), PTMA (3 wt %), and BDPC (7 wt %), showed high sensitivity of 21 mJ/cm² and a high contrast of 6.8 when it was exposed to a 436‐nm line (g‐line), postbaked at 90 °C for 5 min, and developed with 1.69 wt % TMAHaq. A clear positive image of 8 μm line and space pattern was printed on film, which was exposed to 50 mJ/cm² of g‐line by a contact printing mode and fully converted to the corresponding polyimide (PI) pattern on heating at 200 °C, confirmed by FTIR spectroscopy. Thus, this system will be a good candidate for next generation PSPIs. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3362–3369, 2009     

Kinetic and equilibrium studies of urea adsorption onto activated carbon: Adsorption mechanism

We found that activated carbon effectively removed urea from solution and that urea adsorption onto activated carbon followed a pseudo-second-order kinetic model. We classified the urea adsorption on activated carbon as physical adsorption and found that it was best described by the Halsey adsorption isotherm, suggesting that the multilayer adsorption of urea molecules on the adsorption sites of activated carbon best characterized the adsorption system. The mechanism of adsorption of urea by activated carbon involved two steps. First, an amino (–NH₂) group of urea interacted with a carbonyl (–C?O) group and a hydroxyl (?OH) group on the surface of activated carbon via dipole–dipole interactions. Next, the –C?O group of the urea molecule adsorbed to the activated carbon interacted with another –NH₂ group from a second urea molecule, leading to multilayer adsorption.     

Pattern formation of polyimide by using photosensitive polybenzoxazole as a top layer

A versatile method for positive-type patterning of polyimide (PI) based on a two-layer photosensitive poly(benzoxazole) (PSPBO) and poly(amic acid) (PAA) film has been developed to provide a promising material in the field of microelectronics. This patterning system consisted of a pristine PAA thick bottom-layer and a poly(o-hydroxy amide) (PHA) thin top layer with 9,9-bis[4-(tert-butoxycarbonyl-methyloxy)phenyl]fluorene (TBMPF) as a dissolution inhibitor, and (5-propylsulfonyloxyimino-5H-thiophene-2-ylidene)-(2-methylphenyl)-acetonitrile (PTMA) as a photoacid generator (PAG). The PHA and PAA were prepared from 4,4′-(hexafluoroisopropylidene)-bis(o-aminophenol) and 4,4′-oxybis(benzoic acid) derivatives, and 3,3′,4,4′-biphenyltetracarboxylic dianhydride and 4,4′-oxydianiline, respectively, in N,N-dimethylacetamide. This two-layer system based on PHA (150-nm thickness) and PAA (1.5-μm thickness) showed high sensitivity of 35 mJ/cm² and high contrast of 10.3 when exposed to a 365 nm line (i-line), post-baked at 100 °C for 2 min, and developed in a 2.38 wt.% tetramethylammonium hydroxide aqueous solution/5 wt.% iso-propanol at 25 °C. A clear positive image of a 4-μm line-and-space pattern was printed on a film which was exposed to 100 mJ/cm² of i-line by a contact-printing mode and fully converted to the corresponding PBO/PI pattern upon heating at 350 °C, confirmed by FT-IR spectroscopy. This two-layer system could be applied to the patterning of various PAAs.     

A molecular dynamics simulation of a homogeneous organic-inorganic hybrid silica membrane

A new molecular dynamics simulation method was successfully applied to construct a homogeneous organic-inorganic hybrid silica membrane using the hybrid-pcff (h-pcff) potential function. Analysis suggested that the hybrid BTESE silica membrane provided a looser network and larger cavity size for the enhancement of gas permeability and selectivity.