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The morphological evolution of Cu pillars capped with Sn-1.8 wt pct Ag solder during high-temperature annealing was investigated. Two intermetallic compounds (Cu6Sn5 + Cu3Sn) formed at the Cu/solder interface which changed the pillar’s morphology. Surface diffusion enhanced the growth of Cu6Sn5 + Cu3Sn around the pillar brim and transformed the pillar top from a plane into a truncated cone. Bulk diffusion dominated after long-term annealing and the pillar top became hemispherical shaped. A mechanism was proposed to explain the unusual morphological evolution.

A diallyl-containing bisphenol, 1,1-bis(3-allyl-4-hydroxyphenyl)-1-(6-oxido-6H -dibenzo [c,e][1,2] oxaphosphorin-6-yl) ethane (1), was prepared by a two-step procedure. Then, a diallyl-containing diamine, 1,1-bis(3-allyl-4-(4-aminophenoxy)-phenyl)-1-(6-oxido-6H-dibenzo [c,e][1,2] oxaphosphorin-6-yl)ethane (3), was prepared from the nucleophilic substitution of (1) with 4-fluoronitrobenzene, followed by the reduction by Fe/HCl. A flexible polyimide (4) with curable diallyl linkages was prepared from the condensation of (3) and 4,4′-oxydiphthalic anhydride in m-cresol in the presence of isoquinoline. Curing polyimide (4) at 300 °C leads to thermosetting polyimide (5). We discussed the amounts of allyl group on Tg, coefficient of thermal expansion, and thermal stability of thermosetting polyimides, and found that thermal properties and dimensional stability of thermosetting polyimides increase with the amounts of cured allyl moieties. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 513–520

A pyridinyl-containing benzoxazine ( 6 ) was synthesized from the Mannich condensation of 4-phenyl-2,6-bis(4-aminophenyl) pyridine ( 2 ), phenol, and paraformaldehyde. For the purpose of properties comparison, a benzoxazine ( 7 ), which is structurally similar to ( 6 ) except for the pyridinyl group, was prepared. The solvent effect on the synthesis of ( 6 ) was discussed, and toluene/ethanol was found to provide ( 6 ) with the best purity and yield. The pyridinyl group provides solubility and acts as a catalyst for the ring opening of benzoxazine, as supported by the forward curing in the DSC thermograms. When curing with epoxy resins, a carbonyl absorption at 1670 cm −1 and 192 ppm was observed in the IR and 13 C NMR spectra. It is proposed that the formation a cyclic amide structure is responsible for the absorption. A reaction mechanism including nucleophilic addition, Diels–Alder reaction, and rearrangement was proposed. The pyridinyl group acts as a crosslinking site, and results in thermosets with good thermal properties.

A propargyl ether-containing benzoxazine (4) was prepared from a potassium carbonate-catalyzed nucleophilic substitution of propargyl bromide and a phenolic OH-containing benzoxazine (3), which was prepared from 1-(4-hydroxyphenyl)-1-(4-aminophenyl)-1-(6-oxido-6H -dibenz oxaphosphorin-6-yl)ethane (1) by a three-step procedure. The curing reactions of (4) were monitored by IR and DSC. A reaction mechanism was proposed based on the observation. Benzoxazines (3) and (4) were applied as epoxy curing agents. The microstructure and the structure-property relationship of the resulting thermosets are discussed. The double-strand structure in (4)-cured epoxy thermosets afforded higher crosslinking density, and led to higher thermal properties. In addition, the (4)-cured epoxy thermosets possess half the amount of highly polar hydroxyl groups than those of the (3)-cured epoxy thermosets, resulting in a lower dielectric constant, dissipation factor, and water absorption. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1359–1367

Phosphinated poly(2,6-dimethyl-1,4-phenylene oxide) ( 5–7 ) with various phosphorus contents were prepared through the bromination of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), followed by a catalyst-free nucleophilic substitution of 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) on the resulting benzyl bromide of brominated PPO ( 2–4 ). Phosphinated PPOs showed improved solubility when compared with neat PPO. A phosphinated PPO with a T g at 227 °C (DMA data), T d 5% at 452 °C (N 2 ) and 473 °C (air), low moisture absorption (0.7 wt% in boiling water, 48 h), a dielectric constant of 2.82 (1 GHz), and a UL-94 VTM-0 grade can be achieved with a phosphorus content as low as 1.0 wt%. Via this approach, the solubility and flame retardancy of PPO were enhanced while the thermal and dielectric properties were kept.

We prepared a side-chain phenol-functionalized poly(ether sulfone) ( P1 ) from a one-pot reaction of a 4,4′-dihydroxybenzophenone (DHBP)-based poly(ether sulfone), poly(oxy-1,4-phenylenecarbonyl-1,4-phenyleneoxy-1,4-phenylene-sulfonyl-1,4-phenylene (DHBP-PES)), with 9,10-dihydro-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and phenol in the presence of sulphuric acid. The phenol linkages of P1 act as reacting sites for epoxy resins. Subsequently, flexible and light-yellow transparent films of epoxy thermosets can be achieved from the curing of P1 with cresol novolac epoxy (CNE) and diglycidyl ether of bisphenol A (DGEBA). The thermoset based on P1 and CNE ( P1 /CNE) shows a high T g value (241 °C), a low coefficient of thermal expansion (44 ppm/°C), and flame retardancy (VTM-0). The moderate-to-high molecular weight of P1 is responsible for the characteristics high T g and flexibility, which are rarely seen in epoxy thermosets based on a low-molecular weight curing agent.

High-performance and flexible poly(pyrrolone imide)s (PPyIs) were firstly prepared by the reaction of dianhydrides with an unsymmetric phosphinated triamine, 1-(3,4-diaminophenyl)-1-(4-aminophenyl)-1-(6-oxido-6H -dibenz oxaphosphorin-6-yl)ethane (1), which was prepared by a facile, one-pot procedure from the reaction DOPO, 4-aminoacetophenone in excess o-phenylenediamine in the presence of p-toluenesulfonic acid. Thermal properties of the resulting PPyIs were evaluated and compared with those of phosphinated polyimides with a similar structure. All of the prepared PPyIs films are tough and creasable. They display higher Tg (374–412 °C), lower coefficient of thermal expansion (34–46 ppm/°C), and better thermal stability (Td 5 wt %: 456–477 °C, 800 °C char yield: 59–63%) than analogous phosphinated polyimides. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2709–2715

A phenolic OH-containing benzoxazine (F-ap), which cannot be directly synthesized from the condensation of bisphenol F, aminophenol, and formaldehyde by traditional procedures, has been successfully prepared in our alternative synthetic approach. F-ap was prepared by three steps including (a) condensation of 4-aminophenol and 5,5'-methylenebis(2-hydroxybenzaldehyde) (1), (b) reduction of the resulting imine linkage by sodium borohydride, and (c) ring closure condensation by formaldehyde. The key starting material, (1), was prepared from 2-hydroxybenzaldehyde and s-trioxane in the presence of sulfuric acid. F-ap is structurally similar to bis(3,4-dihydro-2H-3-phenyl-1,3-benzoxazinyl)methane (F-a, a commercial benzoxazine based on bisphenol F/aniline/formaldehyde) except for two phenolic OHs. The phenolic OHs can provide reaction sites with epoxy and 1,1'-(methylenedi-p-phenylene)bismaleimide (BMI). The structure–property relationships between the thermosets of F-ap/epoxy, F-a/epoxy, F-ap/BMI, and F-a/BMI were discussed. Experimental data showed that thermosets based on F-ap/epoxy and F-ap/BMI provided much better thermal properties than those based on F-a/epoxy and F-a/BMI. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2686–2694

This study focuses on developing advanced epoxy resins with characteristic of low water absorption for halogen-free copper clad laminates (CCL). To achieve this goal, we prepared a bisphenol (1) with two phosphinate pendants via the nucleophilic addition of 9, 10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) with the 1,4-phenylene diamine-based benzoxazines (P-pd) . A series of advanced epoxy resins (2) were prepared based on the advancement reaction of (1) and diglycidyl ether of bisphenol A (DGEBA). After curing of (2) , the properties of the resulting thermosets such as glass transition temperature, coefficient of thermal expansion, thermal decomposition temperature, water absorption, and flame retardancy were evaluated. The structure–property relationship was also discussed. Experimental data show that the resulting epoxy thermosets display moderate-to-high T g , good flame retardancy, high modulus, and very low water absorption.

Two phosphinated diamines, 1-(4-aminophenyl)-1-(3-t-butyl-4-aminophenyl) -1- (6-oxido-6H -dibenz oxaphosphorin-6-yl)ethane (1) and 1-(4-aminophenyl) -1-(3-methxoy-4-aminophenyl)-1-(6-oxido-6H -dibenz oxaphosphorin-6-yl)ethane (2) , were prepared via a facile, one-pot reaction of DOPO, 4-aminoacetophenone and 2-tertbutylaniline or 2-anisidine in the presence of p-toluenesulfonic acid. Based on diamines (1–2) , a series of unsymmetric polyimides (3–4) were prepared in NMP/xylene by high-temperature solution polymerization. Transparency polyimides 3 – 4 with flexibility, organo-solubility, high-T g values (310–384 °C), and moderate thermal properties (T d 5 wt%, nitrogen: 461–477 °C; air, 456–474 °C) can be achieved. We found that the transparency of polyimide films is related with the orientation of the biphenylene phosphinate pendant, and the orientation is influenced by the bulkiness of the ortho-substituted substituent.

Generally, protection and deprotection procedures of amino groups are required in preparing propargyl ether-containing benzoxazines. In this study, we report a facile, deprotection-free preparation of a propargyl ether-containing phosphinated benzoxazine (2) from the nucleophilic substitution of a phenolic OH-containing phosphinated benzoxazine (1) and propargyl bromide in the catalysis of potassium carbonate. The structure of (2) was characterized and confirmed by a high-resolution mass spectrum, 1H, 13C, 1H-1H, 1H-13C nuclear magnetic resonance (NMR) spectra, and X-ray single crystal diffractogram. infrared (IR) and differential scanning calorimetry were used to monitor the ring-opening of benzoxazine and crosslinking of propargyl ether. The microstructure and the structure–property relationship of the resulting homopolymers and copolymers are discussed. The Tg of homopolymer of (2) is 208 °C by dynamic mechanical analysis, the coefficient of thermal expansion is 43 ppm/°C, and Td 5% (N2) is 393 °C, respectively, which are higher than those of the homopolymer of (1). Similar trends were observed in the copolymerization system. The results demonstrate the beneficial effect of crosslinking afforded by the propargyl ether group is higher than that by the phenolic OH group. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

In this study, d -hydantoinase (DHTase) was purified using an immobilized metal ion affinity membrane (IMAM), on which the interactions between amino acid residues placed on the protein surface and the chelated metal ions located on the IMAM surface facilitate DHTase purification. Batch DHTase adsorption experiments showed that the adsorption capacity varied remarkably for IMAM with different metal ions. The maximum adsorption of DHTase (1.513 ± 0.12 mg) was reached when using Cu 2+ as the chelated ion, whereas the Co 2+ showed the highest activity with only small amounts of protein adsorption. The Mn 2+ , Co 2+ , Ni 2+ , Fe 2+ and Fe 3+ additions showed a positive effect on DHTase activity. The addition of Cu 2+ showed a varied effect from the inhibition on original DHTase to the promotion on Ni-purified DHTase. The purification folds using IMAM chelated with Co 2+ , Ni 2+ , and Zn 2+ were in the range of six to seven. SDS–PAGE analysis showed that all of the IMAM-purified DHTase exhibited the same molecular weight, meaning DHTase adsorbed on IMAM was highly specific. The DHTase purified by different metal ions showed various levels of increased activity when adding the corresponding metal ions. The addition of Mn 2+ or Co 2+ displayed a dramatic increase (9- to 10-fold) in activity of DHTase purified by IMAM chelated with the same ion.

Transdermal drug delivery system (TDDS) finds a variety of applications in drug delivery nowadays and is viewed as a potential method in controlled release of drug. Commonly known as a chemical enhancer in TDDS, urea alters the structure and composition of corneocyte and intracellular lipids, thus makes it easier for molecules to penetrate through stratum corneum, the major and outmost barrier layer of skin. In this research, however, urea itself is employed as a tracer diffusing through whole porcine skin in vitro . The diffusion process is recorded as the specific conductivity variation in time course. Concentration of urea is easily converted from its specific conductivity with aid of standard curves predetermined. Experimental results show the accumulation of tracer quantity diffusing through the skin sample as time proceeds. In parallel, a simple diffusion model is developed, attempting to describe this mass transport process in mathematical point of view. Output of the comparison between model data and experimental results generates the effective permeability of the whole skin, and quantifies the molecular mobility of the diffusing tracer. Permeability determined in this work is validated against literature data and discussed from molecular viewpoint theoretically. This study describes a combination of experiments and theory aiming at quantifying the transdermal permeation. Good agreement between model and experiment supports the efficacy of the approach and thus builds up a quantitative base for the upcoming researches seeking improvement of TDDS.

This work studied concentration enhancement of omega-3 fatty acids extracted from soft-shelled turtle fish ( Pelodiscus sinensis ) oil bags by using supercritical carbon dioxide (SC-CO 2 ). Crude oil was obtained by using top-down pressurized carbon dioxide extraction at 60 bar and 328 K. Crude oil was then ethylated and concentrated using a counter-current SC-CO 2 extractive distillation at 200 bar and 353 K. 81 wt% of unsaturated fatty acids (i.e. C 20–24 ) of this ethylated oil was successfully obtained in the raffinate of the distillation. The reflux flow rate, the carbon dioxide-to-oil ratio and the extraction temperature were found to be important in affecting this concentration of the C 20–24 . The column-height versus concentration of C 20–24 was examined using the Riccati equation. Furthermore, the catalase activity of rat macrophage RAW 264.7 treated with the SC-CO 2 raffinate was investigated.

Transport of biomolecules within cells plays a critical role in the maintenance of the cellular functions. Compared to diffusion in aqueous phase, cytoplasmic diffusion is partly retarded by the elevated viscosity of cytosol. In addition, intracellular diffusion is affected by cytoplasmic physical properties such as tortuosity, binding, and molecule crowding. This work develops a two dimensional mathematical model describing the intracellular diffusion and yielding probe concentration distribution within the cell in time course. Initially, cytoplasmic mobility is quantified as apparent diffusion coefficient (ADC), with which all the diffusion resistances encountered are accounted for. Binding, however, as an important diffusion resistance, is then isolated from all others included in ADC. Using the theoretical analysis from the literature, furthermore we quantify the contribution of steric hindrance in retarded cytoplasmic mobility. In all, three major diffusion resistances including molecular binding to cytoarchitecture, molecule detouring caused by cytoskeleton obstacles, and elevated cytosol viscosity are elucidated and quantified in this work. All of these factors play significant roles in mobility retardness in intracellular transport.

Three fluorinated benzoxazines (14–16), which cannot be synthesized by the traditional one-step approaches, were synthesized by a three-step procedure using fluorinated aromatic diamines (2–4) as starting materials. The structures of the monomers were confirmed by 1H NMR, IR, and high-resolution mass spectra. The low dielectric thermosets, P(14–16), were prepared by ring-opening of (14–16). IR analysis was utilized to monitor the ring-opening reaction of (14–16) and to propose the structures of P(14–16). The thermal and dielectric properties of P(14–16) were studied and compared with a nonfluorinated polybenzoxazine P(13), which is derived form the ring-opening of 2,2-bis(4-aminophenoxy)phenyl)propane (1). Besides, the structure–property relationship of the P(13–16) is discussed. According to Tg measurement, the ortho-positioned CF3 substituents impart greater steric hindrance for ring-opening of benzoxazines than CF3 substituents of hexafluoropropane. Incorporating a biphenol F-based benzoxazine, (F-a), into fluorinated benzoxazines (15–16) can dilute the effect of ortho-positioned CF3 substituents on steric hindrance, leading to a higher crosslinking density and consequently a higher Tg. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4970–4983, 2008

Urea release from a scoop of coated beads in a given volume of a well stirred liquid has been investigated analytically and experimentally. A method for determining the fractional cumulative release and fractional release rate curves for the scoop without knowing particle number and radii is presented. The representative D/Kb for a scoop of urea beads spray coated with ethyl cellulose is near 3.5 × 10−8 cm2 / s, and that with cellulose acetate phthalate is near 7 × 10−8 cm2 / s.

Although gap junction channels are still widely viewed as large, non-specific pores connecting cells, the diversity in the connexin family has led more attention to be focused on their permeability characteristics. We summarize here the current status of these investigations, both published and on-going, that reveal both charge and size selectivity between gap junction channels composed of different connexins. In particular, this review will focus on quantitative approaches that monitor the expression level of the connexins, so that it is clear that differences that are seen can be attributed to channel properties. The degree of selectivity that is observed is modest compared to other channels, but is likely to be significant for biological molecules that are labile within the cell. Of particular relevance to the in vivo function of gap junctions, recent studies are summarized that demonstrate that the connexin phenotype can control the nature of the endogenous traffic between cells, with consequent effects on biological effects of gap junctions such as tumor suppression.

Two novel antioxidants, obtusilactone A (1) and (-)-sesamin (2) have been identified in Cinnamomum kotoense Kanehira. Both showed effective 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity compared with vitamin C, and reducing power compared with BHA. These results suggest that these constituents of C. kotoense act as natural antioxidants and play a potential role in cancer prevention.

Tyrosinase is the first and rate limiting enzyme in the synthesis of melanin pigments for coloring hair, skin, and eyes. As reported in this study, a natural product, (-)-N-formylanonaine isolated from the leaves of Michelia alba D.C. (Magnolianceae), was found to inhibit mushroom tyrosinase with an IC50 of 74.3 microM and to have tyrosinase and melanin reducing activities in human epidermal melanocytes without apparent cytotoxicity to human cells, superior to the known tyrosinase inhibitors, such as kojic acid and 1-phenyl-2-thiourea (PTU). Based on homology modeling, the compound binds the active site by coordinating with two Cu2+ ions. In addition, the compound had antioxidation activities in tests for scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH), reducing power, and chelating metal ions. To our knowledge, this is the first study to reveal the bioactivities of (-)-N-formylanonaine from this plant species.

This work reveals a facile, one-pot synthesis of phosphinated bisphenols (1–2) from a nucleophilic addition of 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) to diaminophenylmethane- and diaminophenylether-based benzoxazines (P-ddm and P-oda). A reaction mechanism including active hydrogen abstraction, ring-opening, and nucleophilic addition was proposed for the synthesis. Phosphinated dicyanate esters (3–4) were prepared based on bisphenols (1–2), and were copolymerized with a commercially available dicyanate ester of bisphenol A (BACY). The properties such as glass transition temperature, coefficient of thermal expansion, thermal decomposition temperature, water absorption, and flame retardancy of the resulting thermosets were evaluated. Experimental data show that incorporating (3–4) into BACY enhances the flame retardancy, dimensional stability and dielectric properties with small penalty to the thermal properties. A thermoset with Tg 241 °C, CTE 50 ppm per °C, Dk 3.01 (1 GHz), Td (5%), N2: 407 °C, and UL-94 V-0 rating can be achieved via this approach.

Two novel antioxidants, obtusilactone A (1) and (-)-sesamin (2) have been identified in Cinnamomum kotoense Kanehira. Both showed effective 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity compared with vitamin C, and reducing power compared with BHA. These results suggest that these constituents of C. kotoense act as natural antioxidants and play a potential role in cancer prevention.

Gap junctions have traditionally been characterized as nonspecific pores between cells passing molecules up to 1kDa in molecular mass. Nonetheless, it has become increasingly evident that different members of the connexin (Cx) family mediate quite distinct physiological processes and are often not interchangeable. Consistent with this observation, differences in permeability to natural metabolites have been reported for different connexins, although the physical basis for selectivity has not been established. Comparative studies of different members of the connexin family have provided evidence for ionic charge selectivity, but surprisingly little is known about how connexin composition affects the size of the pore. We have employed a series of Alexa dyes, which share similar structural characteristics but range in size from molecular weight 350 to 760, to probe the permeabilities and size limits of different connexin channels expressed in Xenopus oocytes. Correlated dye transfer and electrical measurements on each cell pair, in conjunction with a three-dimensional mathematical model of dye diffusion in the oocyte system, allowed us to obtain single channel permeabilities for all three dyes in six homotypic and four heterotypic channels. Cx43 and Cx32 channels passed all three dyes with similar efficiency, whereas Cx26, Cx40, and Cx45 channels showed a significant drop-off in permeability with the largest dye. Cx37 channels only showed significant permeability for the smaller two dyes, but at two- to sixfold lower levels than other connexins tested. In the heterotypic cases studied (Cx26/Cx32 and Cx43/Cx37), permeability characteristics were found to resemble the more restrictive parental homotypic channel. The most surprising finding of the study was that the absolute permeabilities calculated for all gap junctional channels in this study are, with one exception, at least 2 orders of magnitude greater than predicted purely on the basis of hindered pore diffusion. Consequently, affinity between the probes and the pore creating an energetically favorable in-pore environment, which would elevate permeant concentration within the pore and hence the flux, is strongly implicated.

As ubiquitous conduits for intercellular transport and communication, gap junctional pores have been the subject of numerous investigations aimed at elucidating the molecular mechanisms underlying permeability and selectivity. Dye transfer studies provide a broadly useful means of detecting coupling and assessing these properties. However, given evidence for selective permeability of gap junctions and some anomalous correlations between junctional electrical conductance and dye permeability by passive diffusion, the need exists to give such studies a more quantitative basis. This article develops a detailed diffusion model describing experiments (reported separately) involving transport of fluorescent dye from a “donor” region to an “acceptor” region within a pair of Xenopus oocytes coupled by gap junctions. Analysis of transport within a single oocyte is used to determine the diffusion and binding characteristics of the cellular cytoplasm. Subsequent double-cell calculations then yield the intercellular junction permeability, which is translated into a single-channel permeability using concomitant measurements of intercellular conductance, and known single-channel conductances of gap junctions made up of specific connexins, to count channels. The preceding strategy, combined with use of a graded size series of Alexa dyes, permits a determination of absolute values of gap junctional permeability as a function of dye size and connexin type. Interpretation of the results in terms of pore theory suggests significant levels of dye-pore affinity consistent with the expected order of magnitude of typical (e.g., van der Waals) intermolecular attractions.