A novel UV-sensitive photopolymerization system with microgel matrix

A series of crosslinked microgels with quaternary ammonium ions on the surface was prepared by quaternization with N,N-dimethylbenzylamine in the presence of microgel particles prepared by emulsion copolymerization of styrene (St), chloromethylstyrene (CMS) and divinylbenzene (DVB). Microgels with diameters in the range of 15–100 nm were successfully dispersed in organic solvents such as 2-methoxyethanol and 2-ethoxyethanol without an emulsifier. A photosensitive layer was formed by coating a photosensitive solution on a grained aluminum plate. The solution was comprised of the microgels, the multifunctional monomer and standard ultraviolet (UV) photoinitiators, such as 2,4-diethyl thioxanthone (DETX)/ethyl p-di-ethylaminobenzoate (EPA). This gave a heterogeneous photosensitive layer which produced good polymer patterns after exposure to UV light followed by development in tap water. A typical polymer layer, consisting of the microgels (poly(styrene-co-N,N-dimethylbenzylvinyl-benzylammonium chloride-co-divinylbenzene)), DETX/EPA, and the multifunctional acrylate monomers, exhibited photosensitivity of 0.06 mJ/cm² for UV light. This sensitivity is much higher than the homogeneous photopolymerization system with an analogous composition.     

Gel formation and photopolymerization during supramolecular self-assemblies of α-CDs with LA-PEG-LA copolymer end-capped with methacryloyl groups

A novel gelation occurs in water during supramolecular self-assemblies of α-cyclodextrins being threaded onto amphiphilic LA-PEG-LA copolymer end-capped with methacryloyl groups. The rheologic studies show that the gels are thixotropic and reversible. While exposed to UV irradiation with a photoinitiator added in advance, they can be photopolymerized in situ to give rise to chemically cross-linked biodegradable hydrogels with the markedly improved mechanical strength. The gels formed prior to and after UV irradiation are characterized using FTIR, ¹H NMR, WAXD and TGA techniques. The swelling ratio and in vitro degradation of the photocured hydrogels are also investigated. It appears that both physical and chemical gels have the potential to be used as injectable biomaterials.     

Theoretical study on reaction mechanism of the vinyl radical with nitrogen atom

The complex triplet potential energy surface of the C₂H₃N system is investigated at the UB3LYP and CCSD(T) (single-point) levels in order to explore the possible reaction mechanism of C₂H₃ radical with N(⁴S). Eleven minimum isomers and 18 transition states are located. Possible energetically allowed reaction pathways leading to various low-lying dissociation products are obtained. Starting from the energy-rich reactant C₂H₃+N(⁴S), the first step is the attack of the N atom on the C atom having one H atom attached in C₂H₃ radical and form the intermediate C₂H₃N(1). The associated intermediate 1 can lead to product P₁ CH₂CN+H and P₂ ³CH₂+³HCN by the cleavage of C–H bond and C–C bond, respectively. The most favorable pathway for the C₂H₃+N(⁴S) reaction is the channel leading to P₁, which is preferred to that of P₂ due to the comparative lower energy barrier. The formation of P₃ ³C₂H₂+³NH through hydrogen-abstraction mechanism is also feasible, especially at high temperature. The other pathways are less competitive comparatively.     

Influence of functional groups on the self-assembly of liquid crystals

Functional groups in the molecule play an important role in the molecular o rganization process.To reveal the influence of functional groups on the self-assembly at interface,herein,the self-assembly structures of three liquid crystal molecules,which only differ in the functional groups,are explicitly characterized by using scanning tunneling microscopy(STM).The high-resolution STM images demonstrate the difference between the supramolecular assembly structures of three liquid crystal molecules,which attribute to the hydrogen bonding interaction and π-π stacking interaction between different functional groups.The density functional theory(DFT) results also confirm the influence of these functional groups on the self-assemblies.The effort on the self-assembly of liquid crystal molecules at interface could enhance the understanding of the supramolecular assembly mechanism and benefit the further application of liquid crystals.     

Regioselective synthesis of highly-substituted biaryls by reaction of vinyl malononitriles with acetylenic esters

The one-pot procedure for synthesis of highly-substituted biaryl derivatives has been described via cyclocondensation reaction between vinyl malononitriles and acetylenic esters. A series of complex biaryls containing one-donor and three-acceptor moieties was obtained with good yields.     

Application of photopolymer to core‐hair type microgels with various hair length

The new microgels, called “core‐hair” type microgels, were synthesized. They have a hair moiety consisting of the oxyhexano‐1,7‐diyl (? O? (CH₂)₅? C(O)? ) group as a spacer and the acryloyl group for polymerization. The hair length depends on the number of spacer units, and affects the viscosity and the thixotropy index of the microgel. These core‐hair microgels show the pseudo‐plastic flow of a non‐Newtonian fluid with moderate to high dispersibility in water or alcoholic solvents. Due ­to their viscosities and dispersibilities, these core‐hair microgels are useful for photopolymer, e.g. for screen printing. Therefore, these microgels were actually applied to screen printing and confirmed pattern forming on a screen printing plate through water development. We now discuss the relation between the viscosity, the dispersibility, the photosensitivity, and the rate of photopolymerization to the hair length of the microgel. Copyright © 2001 John Wiley & Sons, Ltd.     

Efficient synthesis of enynes by tetraphosphine-palladium-catalysed reaction of vinyl bromides with terminal alkynes

Through the use of [PdCl(C₃H₅)]₂/cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane as catalyst, a range of vinyl bromides undergoes Sonogashira cross-coupling reaction with a variety of alkynes, leading to the corresponding 1,3-enynes in good yields. The reaction tolerates several alkynes such as phenylacetylene, dec-1-yne, 2-methylbut-1-en-3-yne a range of alk-1-ynols, 3,3-diethoxyprop-1-yne and a propargyl amine. Higher reactions rates were observed in the presence of phenylacetylene, dec-1-yne, but-3-yn-1-ol, pent-4-yn-1-ol, 3,3-diethoxyprop-1-yne or 1,1-dipropyl-2-propynylamine than with propargyl alcohol, 3-methoxy-prop-1-yne or 2-methylbut-1-en-3-yne. This catalyst can be used at low loading even for reactions of sterically hindered vinyl bromides such as bromotriphenylethylene or 2-bromo-3-methyl-but-2-ene.     

New synthesis of allylidenecyclobutanes by the reaction of cyclobutylmagnesium carbenoids with vinyl sulfones

The reaction of cyclobutylmagnesium carbenoids, which were generated from 1-chlorocyclobutyl p-tolyl sulfoxides with EtMgCl via the sulfoxide-magnesium exchange reaction at low temperature, with carbanions derived from vinyl sulfones with n-BuLi or LDA resulted in the formation of allylidenecyclobutanes in moderate to good yields. The actual reactive species of the sulfones in this reaction were proved to be the lithium α-sulfonyl carbanion of allyl sulfones derived from the vinyl sulfones by double bond migration with the bases used. Mono- and di-substituted allylidenecyclobutanes can be obtained by using a variety of vinyl sulfones.     

Novel analytical method for determination of contents of backbone and terminal/branch vinyl acetate groups of poly(ethylene-co-vinyl acetate) using deacetylation reaction

Vinyl acetate (VA) groups in poly(ethylene-co-vinyl acetate) (EVA) exist in backbone, terminal, and branch positions. The VA moieties were converted to carbon-carbon double bonds (∼CH=CH∼) by deacetylation reaction. By deacetylation, the backbone VA group was converted to 1,4-unit (∼CH₂CH=CHCH₂∼) while the terminal and branch ones were converted to 1,2-unit (∼CH=CH₂). A novel analytical method for determination of ratio of backbone and terminal/branch VA contents was developed using off-line pyrolysis and transmission-Fourier transform infrared spectroscopy (FTIR). The analytical method included sample preparation of deacetylated EVA coated on NaCl window for transmission-FTIR analysis and calculation of backbone and terminal/branch VA contents using quantitative analysis of 1,4- and 1,2-units of the deacetylated EVA. Influence of deacetylation conditions (pyrolysis temperatures and times) on degree of deacetylation and other side reactions was also investigated, and proper deacetylation condition was suggested. From the experimental results, proper off-line pyrolysis condition of EVA coated on NaCl window was 300 °C for 60–80 min. The novel analytical method was reliable with the experimental error of below 5%.     

Convenient synthesis of α,β-unsaturated sulfones via a Mizoroki-Heck reaction of arylboronic acids with phenyl vinyl sulfones

Palladium acetate catalyzed Mizoroki-Heck reaction of arylboronic acids with phenyl vinyl sulfones afford α,β-unsaturated sulfones in good yields.     

Synthesis of polyfunctional imidazoles from vinyl azides and amidine along with NHBoc as a leaving group

An efficient method for the synthesis of polyfunctional imidazoles from vinyl azides and amidine has been developed. Starting from vinyl azide and amidine, this transformation proceeds without any additives and the obtained imidazoles can be decorated with ester functional group that is a promising site for further modification.     

Structural and electrostatic properties of atoms and functional groups using AIM theory: Saturated organics with one electronegative atom

Atoms in molecules (AIM) theory is used to determine the properties of functional groups within 73 saturated linear and branched molecules with at most one electronegative atom. The group properties found rigorously in AIM theory and computed in this study are energy, volume, exposed surface area, extent of electron density, charge, dipole moment and polarizability of the group. Properties of atoms and groups within small molecules are presented. Averaged values for group definitions subdivided by their first-bonded neighbors are also presented. Small variability in properties is seen for hydrogen, fluorine, oxygen, nitrogen and larger groups containing the latter three atoms. Greater variability exists within the database of alkyl group values, and the range of these quantities is discussed. Exposed surface area calculations using AIM theory are explained and related to van der Waals (vdW) radii methods.     

Non-catalyzed addition of heterocyclic thiols and 5-substituted-1H-tetrazoles to vinyl ethers

The alkylation of 1-substituted 1H-tetrazole-5-thiols and 4-substituted 4 H-1,2,4-triazole-3-thiols with alkyl halides or sulfonates lead to the formation of S-alkylated products regardless of the substituent on the heterocycle. In this work, we found that substituted 1H-tetrazole-5-thiols and 4 H-1,2,4-triazole-3-thiols readily reacted with vinyl ethers in the absence of a catalyst to exclusively form N-substituted 1H-tetrazole-5(4H)-thiones and 1H-1,2,4-triazole-5(4H)-thiones, respectively. Furthermore, the reactions of 5-substituted-1H-tetrazoles with vinyl ethers under the same conditions selectively yielded 2,5-disubstitued tetrazoles.     

Surface-grafting onto aramid powder: reaction of acyl chloride groups on the surface with functional polymers having terminal hydroxyl or amino groups

The surface-grafting of polymers onto aramid, poly(p-phenylene terephthalamide), powder surface by the reaction of acyl chloride groups on the surface with functional polymers having terminal hydroxyl and amino groups was investigated. The introduction of acyl chloride groups onto the aramid powder surface was achieved by the reaction of the aramid powder with adipoyl dichloride: the acyl chloride group content of the surface was estimated to be 1.14 mmol/g (0.17 mmol/m²) by elemental analysis. It was found that by the reaction of acyl chloride groups on the surface with functional polymers, such as terminal diol-type poly(propylene oxide) (PPG) and terminal diamine-type poly(dimethylsiloxane) (SDA), these polymers were grafted onto the aramid powder surface; the percentage of surface grafting of PPG and SDA onto the aramid powder was 16.7 and 22.4%, respectively. The thermogravimetric curve of PPG surface-grafted aramid powder exhibited an initial weight loss at about 250°C and a second weight loss at about 500°C. This indicated that the grafting of PPG is limited to the powder surface. The wettability of the aramid powder surface turned from hydrophobic to hydrophilic by the surface-grafting of PPG onto the surface.     

Effect of functional groups on the solubilities of coumarin derivatives in supercritical carbon dioxide

Summary Solubilities in supercritical CO₂ of coumarin, four monosubstituted coumarin derivatives (4-hydroxycoumarin, 7-hydroxycoumarin, 7-methoxycoumarin, and 7-methylcoumarin) and four disubstituted derivatives, (6,7-dihydroxycoumarin, 7-hydroxycoumarin-4-acetic acid, 7-methoxycoumarin-4-acetic acid, and 7-hydroxy-4-methylcoumarin) were measured in the temperature range 35–50 °C and the pressure range 8.5–25 MPa. In general, the substituted coumarin derivatives were less soluble than simple coumarin. It was also found that substitution at the C-4 position of coumarin tended to reduce the solubility more than substitution at the C-7 position. These solubility data are essential for the systematic application of SFE and SFC of coumarin derivatives from plant sources.     

Base-mediated reaction of vinyl bromides with aryl azides: one-pot synthesis of 1,5-disubstituted 1,2,3-triazoles

A one-pot base-mediated reaction of azides and β- or α-vinyl bromides has been reported. The effects of bases and solvents have been investigated in the process. A variety of 1,5-disubstituted triazoles were prepared in low to good yields. Further studies reveal that the corresponding alkynes were produced as intermediates via elimination reaction. Under the same reaction conditions, the reactions of alkyl alkynes with phenyl azide would give 1,5-disubstituted 1,2,3-triazoles.     

Synthesis of monodisperse hollow polymer microspheres with functional groups by distillation precipitation polymerization

<正>Monodisperse hollow polymer microspheres having various functional groups on the shell-layer,such as carboxylic acid,pyridyl and amide,were prepared by two-stage distillation precipitation polymerization in neat acetonitrile in the absence of any stabilizer or additive,during which monodisperse poly(methacrylic acid)(PMAA) afforded from the first-stage polymerization was utilized as the seeds for the second-stage polymerization.The shell layer with different functional groups was formed during the second-stage copolymerization of either divinylbenzene(DVB) or ethyleneglycol dimethacrylate(EGDMA) as crosslinker and the functional comonomers,in which the hydrogen-bonding interaction between the carboxylic acid group of PMAA core and the functional groups of the corresponding comonomers,including carboxylic acid,amide and pyridyl,played an essential role for the formation of monodisperse core-shell functional microspheres.The hollow polymer microspheres were then developed after the subsequent removal of PMAA cores by dissolution in ethanol under basic condition.Transmission electron microscopy(TEM) and scanning electron microscopy (SEM) were used to determine the morphology of the resultant PMAA core,functional core-shell microspheres and the corresponding hollow polymer microspheres with different functional groups.FT-IR spectra confirmed the successful incorporation of the various functional groups on the shell layer of the hollow polymer microspheres.     

Photochemical addition reaction of a polymer-bearing pendant vinyl ether with various thiol compounds

Photochemical addition reaction of the pendant vinyl ether group in the polymer ( P-1 ), which was synthesized by the alternate ring-opening copolymerization of glycidyl vinyl ether with phthalic anhydride, with various thiol compounds such as benzenethiol, phenylmethanethiol, 2-mercaptoacetic acid, ethyl 2-mercaptoacetate, N-acetyl-L -cysteine (AcCys), and 1,4-phenylenedi(methylthiol) was carried out using benzophenone (BP) as the photosensitizer in the THF solution. Each reaction proceeded very smoothly to give the corresponding polymers with high conversion, although the degree of reaction of the pendant vinyl ether group in P-1 was affected by the molar ratio between the thiol compounds and the vinyl ether group, and the amounts of photosensitizer BP added. Furthermore, it was also found that optically active polymer containing pendant N-acetyl-L -cysteine residue was synthesized by the photochemical addition reaction of P-1 with AcCys. The reactions of P-1 with dithiol or bisazide compounds occurred effectively to give gel products in the film state, and it was found that the polymer film containing P-1 and those compounds can be applied as negative-type photoresists with high practical photosensitivity. © 1993 John Wiley & Sons, Inc.     

Characterization of carbonyl chloride-terminated aromatic polyamide nanoparticles with carboxyl groups and their reaction

Aromatic polyamide nanoparticles with carbonyl chloride (COCl) and carboxyl (COOH) groups were obtained using a precipitation polymerization method. The morphology, number of COCl groups incorporated, and degree of polymerization of the resulting particles depended on the reaction system. The COOH group of diamine used decreased the reactivity of NH₂ groups and chemically stabilized the COCl groups existing at the ends of the molecular chains. Also, the COCl groups were retained in particles by the rapid formation of particles. Thus, the chemical structures and formation mechanism were found to play an important role in the formation of particles with COCl groups.     

Characterization and electrochemical applications of a carbon with high density of surface functional groups produced from beer yeast

Carbon materials enriched with nitrogen and oxygen surface functional groups were obtained by pyrolyzing strained beer yeast at 750 °C under an inert atmosphere. Physical and surface properties of the carbon obtained were characterized by X-ray powder diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, Raman spectrometry, and X-ray photoelectron spectroscopy. Results show that the carbon possesses an amorphous structure, a spherical morphology, and a high density of surface functional groups. Electrochemical properties were evaluated by cyclic voltammetry, a galvanostatic charge–discharge technique, and electrochemical impedance spectroscopy. The carbon has 989.65 mAh·g⁻¹ of initial discharge capacity and a stable cycle performance for a Li–C cell. A specific capacitance of 120 F·g⁻¹ was obtained for a single carbon electrode and good cycle performance was achieved for a symmetrical supercapacitor fabricated using this carbon. These carbons derived from strained beer yeast have promising applications in energy storage and conversion systems.