Dioxane Solution Research Articles

Polymerization of white phosphorus induced by internal β−-3H radiation

Available experimental and theoretical data demon-strate the ability of white phosphorus to form nanosizedassemblies in solutions [1]. Radiation-induced poly-merization of these assemblies leads to the formation ofan inorganic polymer (red phosphorus modified withsolvent fragments). The size distribution of the product,which determines to a great extent the useful propertiesof polymeric phosphorus, can be varied by changingthe conditions of this process (temperature, radiation,dose, solvent, additives) [2].We pioneered the polymerization of white phospho-rus in benzene and dioxane solutions containing tritiumwater (H

Nanosized starlike molecules. Synthesis and optical properties of tris- and tetrakis[oligo(disilanylenebithienylene)dimethylsilyl]benzene

The syntheses of two types of starlike molecules with the arms that extend to three and four directions have been reported. The molecules with the arms consisting of a regular alternating arrangement of a silicon–silicon bond and bithienylene unit that extend to three directions were synthesized by the reactions of 1,3,5-tris(chlorodimethylsilyl)benzene, which was chosen as a core, with the lithio[oligo(disilanylenebithienylene)] derivatives. The starlike molecules with extended arms to four directions were prepared by the reaction of 1,2,4,5-tetrakis(fluorodimethylsilyl)benzene used as a core, with lithio[oligo(disilanylenebithienylene)]s. UV–Vis absorption and fluorescence properties of these starlike molecules have been investigated in a dioxane solution. The present molecules showed absorption maxima in a range of 321–337 nm, and revealed higher fluorescence quantum yields than that of the corresponding linear polymer, poly[(tetraethyldisilanylene)bithiophene].

Electroless copper plating on acrylonitrile butadiene styrene material surfaces without chromic acid etching and a palladium catalyst

AbstractHydrolysis modification of nitrile groups on acrylonitrile butadiene styrene (ABS) plate surfaces into carboxylic acid groups was investigated to find a new recipe for electroless copper plating of ABS plate surfaces without etching reactions using chromic acid and also without a palladium catalyst. Hydrolysis modification of nitrile groups was successfully conducted in an aqueous sodium hydroxide (NaOH) solution (70 wt %) at 80°C for more than 72 h, and nitrile groups were modified into carboxylic acid groups. The hydrolysis modification was accelerated by the addition of dioxane as a supplement to the aqueous NaOH solution. The modification, when an aqueous mixture solution of NaOH (35 wt %) and dioxane (10 wt %) was used as a reagent, was accomplished at 65°C in 30 min. The hydrolyzed ABS plate surfaces were successfully metalized by electroless copper plating. A silver catalyst, instead of a palladium catalyst, was usable in the electroless copper‐plating process. Adhesion between the deposited copper metal and ABS plate surface was perfect for the Scotch tape test. Consequently, we propose a new recipe for an electroless copper‐plating process without an etching process using chromic acid and without a palladium catalyst. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Synthesis and Characterization of a New Methacrylate Polymer with Side Chain Benzofurane and Cyclobutane Ring: Thermal Properties and Antimicrobial Activity

The synthesis of a new methacrylate monomer (Benzofuran-2-yl)(3-mesityl-3-methylcyclobutyl)- O-methacrylketoxime is described. The monomer was polymerized in 1,4 dioxane solution at 65 °C using azobisisobutyronitrile as an initiator. The monomer and its polymers were characterized by infrared, and 1H-NMR spectroscopy. The glass transition temperature of the polymer was investigated by differential scanning calorimetry and the apparent thermal decomposition activation energies ( Ed) were calculated by the Ozawa method using a Shimadzu thermogravimetric analysis thermobalance. The Ed were values were determined to be 231 kJ mol-1. The antibacterial and antifungal effects of the momomer and its homopolymer were also investigated on various bacteria and fungi.

Effect of an Acid Protecting Group on the “Livingness” of Poly(acrylic acid-ran-styrene) Random Copolymer Macroinitiators for Nitroxide-Mediated Polymerization of Styrene

Poly(acrylic acid-ran-styrene) (P(AA-r-S)) and poly(tert-butyl acrylate-ran-styrene) (P(tBuA-r-S)) random copolymers previously made with different molar ratios (0, 4.5, and 9 mol %) of additional free nitroxide mediator, N-tert-butyl-N-[1-(diethylphosphono)-2,2-dimethylpropyl]nitroxide (SG1), relative to 2-[[N-tert-butyl-N-[1-(diethylphosphono)-2,2-dimethylpropyl]amino]oxy]-2-methylpropionic acid (BlocBuilder) alkoxyamine unimolecular initiator were used as macroinitiators for styrene chain extension. The reinitiating experiments were performed in the bulk at 115 °C when using P(tBuA-r-S) macroinitiators or 30−50 wt % dioxane solution at 120 °C when using P(AA-r-S) macroinitiators. The P(tBuA-r-S)-containing macroinitiators (number-average molecular weight Mn = 13.4−25.8 kg·mol−1) with polydispersities Mw/Mn = 1.13−1.57 were capable of initiating chains extended with styrene as indicated by monomodal and narrow molecular weight distributions with Mn = 34.6−66.3 kg·mol−1 and Mw/Mn ranging from 1.24 ...

Deformation behavior and mechanism of porous PLLA under compression

scaffolds. The PLLA dioxane solutions in test tubes were cooled from the bottom surfaces at a constant rate by using liquid nitrogen to induce solid–liquid phase separation. The phase-separated samples were then dried under vacuum at -5 C for about 6 days to remove the solvent completely. Cylindrical samples were obtained and then trimmed to be a cylinder with 8-mm diameter and 12-mm length. Porosity (volume fraction of pores) of a scaffold was estimated from the densities of PLLA solid and the scaffold. Compression tests were then performed using a conventional mechanical testing machine at a loading rate of 1 mm/min. A fieldemission scanning electron microscope (FE-SEM) was also used to observe the microstructures of the porous samples and the deformation behavior of the porous samples at the critical point. FE-SEM micrographs of the cross-sections in the transverse direction are shown in Fig. 1. Homogeneous distribution of pores is observed, and the size of the pores tends to decrease with increase in the concentration of the solution. The porosities of these porous samples were estimated as 94.7, 90.0, and 88.5% for the concentrations of 3, 5, and 7 wt.%, respectively. FE-SEM micrograph of a crosssection in the vertical direction is shown in Fig. 2. For all the samples, this kind of porous structure was observed. These structures shown in Figs. 1 and 2 suggest that the crystals of the solvent grow in the vertical and transverse directions at a constant speed by the freezing process. Typical stress–strain curves under compression are shown in Fig. 3. The stress– strain relation of this porous structure of PLLA can be characterized by four different regions as shown in Fig. 4. The region A is the initial linear portion corresponding to linear elastic deformation of the porous structure. The end of the region A and the transition point to the region B is recognized as a critical point where localized failures of the wall structures of the pores take place. In the region B, stress

Fabrication of collagen hybridized elastic PLCL for tissue engineering

Biodegradable elastic poly(L-lactide-co-epsilon-caprolactone) (PLCL) (50:50) copolymer was blended with collagen (0.05, 0.1 and 0.2% w/w) in an acidic dioxane solution to form a collagen/PLCL hybrid material suitable for tissue engineering applications. Stability and dispersivity of collagen on collagen/PLCL hybrid films and collagen coated PLCL films under mechanical stress were determined by a collagen release test and water contact angle measurement. Hybrid films had a higher stability than collagen-coated PLCL films. Elastic recovery as well as high interconnectivity and uniform pore morphology of the hybrid scaffolds were not affected by the collagen concentration. Fibroblasts (NIH-3T3) cell culture test was performed for cell growth and viability evaluation. Collagen concentration had little affect on the initial cell adhesion after 4 h cell culture; but after 48 h cell culture, increased cell proliferation on the hybrid films was observed. The hybrid material can be applied as a scaffold for vessel and cartilage regeneration for mechano-active tissue engineering.

Fabrication of Poly(L-Latic Acid) Scaffolds with Wool Keratin for Osteoblast Cultivation

As a natural protein, wool keratin was used to improve the cell affinity of poly(L-lactic acid) (PLLA). Small keratin particles were prepared from keratin solution by the spray-drying process. Keratin particles were blended with PLLA/1,4 dioxane solution and paraffin micro-spheres which were used as progens. After the mixture was molded and dried, the paraffin micro-spheres were removed by cyclohexane. PLLA/keratin scaffolds with controlled pore size and well interconnectivity were fabricated. Keratin releasing rate was detected by Fourier transform infrared (FTIR) after the scaffold was immersed into PBS up to 4 weeks. The surface chemical structure was examined by X-ray photoelectron spectroscope (XPS). The results suggested that the keratin could be held into the scaffold which was expected to improve the interactions between osteoblasts and the polymeric scaffolds.

PLLA biodegradable scaffolds for angiogenesis via Diffusion Induced Phase Separation (DIPS)

A critical obstacle in tissue engineering is the inability to maintain large masses of living cells upon transfer from the in vitro culture conditions into the host in vivo. Capillaries, and the vascular system, are required to supply essential nutrients, including oxygen, remove waste products and provide a biochemical communication “highway”. For this reason it is mandatory to manufacture an implantable structure where the process of vessel formation – the angiogenesis – can take place. In this work PLLA scaffolds for vascular tissue engineering were produced by dip-coating via Diffusion Induced Phase Separation (DIPS) technique. The scaffolds, with a vessel-like shape, were obtained by performing a DIPS process around a nylon fibre whose diameter was 700 μm. The fibre was first immersed into a 4% PLLA dioxane solution and subsequently immersed into a second bath containing distilled water. The covered fibre was then rinsed in order to remove the excess of dioxane and dried; finally the internal nylon fibre was pulled out so as to obtain a hollow biodegradable PLLA fiber. SEM analysis revealed that the scaffolds have a lumen of ca. 700 μm. The internal surface is homogeneous with micropores 1–2 μm large. Moreover, a cross section analysis showed an open structure across the thickness of the scaffold walls. A cell culture of endothelial cells was carried out into the as-prepared scaffolds. The result showed that cells are able to grow within the scaffolds and after 3 weeks they begin to form a “primordial” vessel-like structure.

Nonlinear optical properties of pyridinium-betaines of squaric acid: Experimental and theoretical study

The linear and nonlinear optical properties of six pyridinium-betaines of squaric acid were characterized by means of electro-optical absorption measurements (EOAM) in dioxane solution. All chromophores studied exhibit intense absorption bands in the visible region within 372–441 nm, accompanied with decrease in dipole moment upon excitation. The static hyperpolarizabilities of the NLO-phores studied depend strongly on the substituent in the pyridinium ring and increase significantly going from donor to acceptor substituent. Specifically, the noncentrosymmetrically crystallizing 4-benzoyl compound showed the highest static hyperpolarizability. These empirical trends were supported and verified by quantum-chemical calculations (DFT and ab initio RHF). Bulk crystal properties such as decomposition points within the high temperature range 480–665 K and improved thermal stability in melt demonstrate the advantage of these materials for nonlinear optical applications.

Nitric Oxide Reacts with Methoxide

Despite over a century of reports to the contrary, sodium methoxide has been found to react with nitric oxide (NO). The reaction, whose final organic product is sodium formate, is postulated to occur via an intermediate O-bound diazeniumdiolate [CH3O-N(O)=NO-] that decomposes to formaldehyde and nitrous oxide. Sodium formate forms from the aldehyde via a Cannizzaro reaction. Carboxylate salts have similarly been obtained by exposing sodium benzylate and sodium neopentoxide to NO in dioxane solution. Accordingly, sodium trimethylsilanoate should be considered as a substitute for sodium methoxide as the base used to accomplish the replacement of active hydrogens by the diazeniumdiolate functional group via the Traube reaction.

Pd/TEMPO Double-mediatory Electrooxidative Wacker-type Cyclizations

Palladium/2,2,6,6-tetramethylpiperidine-1-oxyl (Pd/TEMPO) double-mediatory electrooxidative Wacker-type cyclization of 1 was developed. In a mixture solution of dioxane and water, the reaction efficiently proceeded at room temperature to give benzofuran derivative 2.

Eplerenone 1,4-dioxane solvate

Eplerenone is an aldosterone receptor antagonist. Single crystals of the title compound [systematic name: 9α,11-ep­oxy-7α-(methoxy­carbon­yl)-3-oxo-17α-pregn-4-ene-21,17-carbolactone dioxane solvate], C24H30O6·C4H8O2, were obtained from a dioxane solution. Within the eplerenone mol­ecule, both five-membered rings display an envelope conformation. The three six-membered rings exhibit different conformations: chair, half-chair and envelope. In the crystal structure, adjacent eplerenone mol­ecules are linked together via weak inter­molecular C—H⋯O hydrogen bonding, forming a cavity of about 310 A3, and the dioxane solvent mol­ecules occupy the cavity. The solvent molecule is disordered equally over two positions.

Stereochemistry of dihydroxylation of N-arylbicyclo[2.2.1]-hept-5-ene-endo- and -exo-2,3-dicarboximides

Stereochemistry of the oxidation of N-arylbicyclo[2.2.1]hept-5-ene-endo-and-exo-2,3-dicarboximides at the double bond with peroxyacetic acid generated in situ in the presence of sulfuric acid and with an anhydrous dioxane solution of peroxyacetic acid was studied. In both cases, the reaction was stereospecific, regardless of the substituent in the N-aryl group and configuration of the imide ring, but the reaction direction depended on the presence of water in the system. In the first case, the corresponding trans-5,6-dihydroxy derivatives were formed, while in the second, exo-5,6-epoxy derivatives. The oxidation of N-arylbicyclo[2.2.1]-hept-5-ene-endo-and-exo-2,3-dicarboximides with a solution of potassium permanganate in aqueous acetone gave the corresponding N-aryl-cis-5,6-dihydroxybicyclo[2.2.1]heptane-endo-and-exo-2,3-dicarboximides. The exo,cis,exo and exo,cis,endo configurations of the synthesized compounds were determined by 1H NMR spectroscopy.

Enthalpy of solution of tigogenin saponin in dioxane and the temperature dependence of its heat capacity

The heats of solution of tigogenin C27H44O3 in dioxane at dilutions equal to 1: 9000, 1: 18 000, and 1: 36 000 (mol solute/mol solvent) have been studied by isothermal calorimetry. The standard enthalpy of C27H44O3 solution in dioxane at infinite dilution was derived by the mathematical processing of the calorimetric data. Dynamic calorimetry over the range 173–423 K has been used to study the heat capacity of tigogenin. The C p o ∼ f(T) plot has a jump at 298.15. K. The standard enthalpies of formation and combustion and the heat of melting of tigogenin have been indirectly calculated.

Photodegradation of poly(amidoamine) dendrimers peripherally modified with 1,8-naphthalimide units

This paper presents the photophysical and photochemical characteristics of four new poly(amidoamine) dendrimers of zero and second generation whose periphery has been modified with 1,8-naphthalimide units. Nitro- and allylamino groups have been used as substitutents at the C-4 position of the 1,8-naphthalimide fluorophores. The discussion is focused on the photodegradation of the dendrimers in N, N-dimethylformamide and dioxan solutions. Investigations have shown that the photodegradation of the dendrimers with 4-nitro substituted 1,8-naphthalimide proceed with yellow colour development in the solvent while no colour changes followed the same process in dendrimers with allylamino group substituent. The results also show that the photostability of the dendrimers depends on their generation.

Thiocarbonyl Photochemistry: The Photoreactions of Pyrimidine-2-thione Derivative with Alkynes and Alkenes

The photocycloaddition of pyrimidine-2-thione derivative 1 to alkynes 2a–c and alkenes 7 and 11 are studied. Irradiation of a dioxane solution of 1 in the presence of alkynes 2a–c produced the thiol derivatives 3a–c through ring cleavage of thietene 5. Irradiation of 1 in the presence of alkenes 7 and 11 under the same conditions produced the corresponding photoproducts 10 and 13, respectively. The structure of all products was confirmed by analytical and spectral data.

Quenching of poly(vinyl phenyl ketone) photolysis by energy transfer in solution

The Stern-Volmer constant of 40 quenchers was determined at 366 nm for poly(vinyl phenyl ketone) photolysis in benzene and dioxane solution at room temperature. Aromatic hydrocarbons, dienes and olefins were used as quenchers. A procedure for quantitative separation of the screening effect of quenchers absorbing at irradiation wavelength was elaborated. The correctness of this procedure was checked using 2-hydroxy-5-methyl benzophenone over the concentration range 0-10−3 mole/1. The values of the Stern-Volmer constants lay within the range 0-250 1./mole, expressing changes of the rate constant of quenching. Stern-Volmer constants were found to be constant for naphthalene, its alkyl, halogen derivatives and esters at about 70 1./mole, that of 1-naphtyl amine 1- and 2-naphtol being, however, substantially higher. Electron-deficient olefins were equally effective as dienes. There has not so far been found a parameter to characterize unambiguously the quenching efficiency of the compounds investigated.

Preparation and characterization of nanoscale aromatic polyamide particles

Aromatic polyamide particles were prepared by reacting m-phthalyl chloride and 4,4′-diaminodiphenyl ether in a dioxane solution with high water content using a precipitation polymerization method. These nanoscale particles were spherical with a narrow size distribution. The morphologies and characteristic features of the polyamide products obtained depended strongly on the water content of this polymerization system. The characteristic features of the polyamide products were correlated with the amount of HCl (generated during polycondensation) complexed with polyamide products. Water was essential for the formation of spherical particles and played an important role in determining the polarity of the reaction solution. Further, water removed HCl from this condensation reaction system and played an important role as a reaction accelerator.

Crystallization of poly( N-methyldodecano-12-lactam) in blends with poly(styrene- stat-acrylic acid)

Crystallization behaviour of blends of poly( N-methyldodecano-12-lactam) (PMDL) with statistical copolymer poly(styrene- stat-acrylic acid) (PSAA) has been studied by the DSC and WAXD methods. The blend films prepared from dioxane solutions were crystallized at laboratory temperature for five days. Approximate crystallinities of as-prepared neat lower- PMDL 5 and higher-molecular weight PMDL 45 were 28% and 19%, respectively. With increasing PSAA content in the blends the crystallinities decreased sharply. The melting point of the primary crystalline structure of PMDL showed a decreasing dependence on PSAA content in the blends, confirming miscibility of the PMDL–PSAA pair. Recrystallization was strongly suppressed in the blends. The lower-melting endotherm appearing at about 10–15 °C above the crystallization temperature was attributed to melting to less perfect structures formed during secondary crystallization. In neat PMDL, the extent of secondary crystallization was approximately 5–10%. In the blends containing 20% PSAA approximate relative proportion of secondary crystallites on total crystallinity was 40% and 60% for the blends with PMDL 5 and PMDL 45, respectively. WAXD measurements did not reveal any change in crystal modification on blending. Increased T g in blends of flexible PMDL cannot play a significant role in suppression of primary in favour of secondary crystallization. This was attributed to low mobility of PMDL chains due to dilution effect and specific interactions with the amorphous copolymer component, and, in case of the higher-molecular-weight PMDL, a greater involvement of entanglements. Higher T g of blends was involved in retardation of non-isothermal crystallization on cooling and subsequent cold crystallization.