Miscibility and adhesive properties of ethylene vinyl acetate copolymer (EVA)‐based hot‐melt adhesives. I. Adhesive tensile strength

A series of ethylene vinyl acetate copolymers (EVA) were blended with some tackifier resins that are made from wood extracts, and possible relations between their miscibility and properties as hot‐melt adhesives (HMA) were investigated. From our previous report on miscibility of various EVA‐based HMAs, we chose some blends that represent some of typical miscibility types and measured their adhesive tensile strengths. When the blends were miscible at testing temperatures, the temperature at which the maximum value of adhesive tensile strength was recorded tended to move toward higher temperature as tackifier content of blends increased. This result corresponds to the glass transition temperature (T_g) of the blends that became higher as tackifier content of blends increased when blend components were miscible. In terms of HMA performances, we suggest that factors other than miscibility affect absolute values of adhesive tensile strength more directly than miscibility; this idea has to be investigated further in a future study. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 719–725, 2002     

Electrochemical and AFM studies of mussel adhesive protein (Mefp-1) as corrosion inhibitor for carbon steel

Adsorption of mussel adhesive protein (Mefp-1) derived from the marine mussel Mytilus edulis and its corrosion inhibition for carbon steel were studied by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements in NaCl solutions at pH 4.6. The results indicate that the Mefp-1 confers significant corrosion inhibition of carbon steel, and the chloride concentration of the solution has an influence on the inhibition efficiency. Within a short exposure time, the inhibition efficiency is higher in the solution with a higher chloride concentration, whereas, for longer exposure time, up to one week, higher inhibition efficiency was obtained in the solution with a lower chloride concentration. AFM imaging was used both ex situ and in situ to investigate Mefp-1 adsorption. The in situ AFM measurements enable the protein adsorption on carbon steel to be visualized in real time in the solution. The AFM images illustrate how the Mefp-1 layer is formed on carbon steel. Measurements using bovine serum albumin (BSA) were also performed for comparison. The results showed that BSA also confers significant corrosion inhibition of carbon steel even though the BSA film formation process is slightly different from that of Mefp-1.     

Metal adhesive properties of polyamides having the 2,3‐bis(1,4‐phenylene)quinoxalinediyl structure

Polyamides were synthesized by interfacial polycondensation of 2,3‐bis(4‐chloroformylphenyl)quinoxaline (BCFPQ) and several aliphatic diamines using a phase transfer catalyst, and their adhesive property for stainless steel was investigated. The inherent viscosity of the obtained polyamides ranged from 0.37 to 1.24 dL g⁻¹. The glass transition temperatures of the polyamides ranged between 154 and 201°C, and their thermal decomposition temperatures were above 450°C. The polyamides were soluble in several organic solvents, including m‐cresol, N‐methyl‐2‐pyrrolidone (NMP), and formic acid. The adhesive property for stainless steel was examined by a standard tensile test. One member of the series, polyamide P8, derived from BCFPQ and 1,8‐octanediamine, displayed high tensile strength with values of 232 kgf cm⁻² at 20°C, 173 kgf cm⁻² at 120°C, and 137 kgf cm⁻² at 180°C. Thus, the tensile strength of P8 decreased at 180°C, but the decrease was much smaller than that of an epoxy resin in wide use as a metal adhesive. Heat distortion temperature, measured by thermal mechanical analysis, of P8 was 191°C. This suggested that P8 possessed high thermal resistance in metal adhesives. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1366–1370, 1999     

Synthesis of novel thermo‐ and redox‐sensitive polypeptide hydrogels

Multi‐responsive hydrogels have recently received considerable attention for bioapplications. Here, novel temperature‐ and redox‐responsive polypetide hydrogels have been developed. Thermo‐sensitive hydrogels based on poly(ethyleneglycol)‐block ‐poly(γ‐propargyl‐l ‐glutamate) (PEG‐PPLG ) were first synthesized by the ring opening polymerization of γ‐propargyl‐l ‐glutamate N ‐carboxyanhydride (PLG‐NCA ) with amino group terminated PEG monomethyl ether (mPEG‐NH₂ ) as macroinitiator and were then functionalized via the ‘thiol‐yne’ click reaction between the propargyl pendents and the thiol‐containing 1‐propanethiol. The sol ? gel phase transition of the obtained copolymer aqueous solution in response to temperature change was studied. The mass loss of the hydrogel in vitro was accelerated in the presence of H₂O₂ , exhibiting a redox‐responsive property. Further, the methyl thiazolyl tetrazolium viability results revealed that this polypetide hydrogel has excellent biocompatibility, presenting potential applications in the biomedical field. © 2016 Society of Chemical Industry     

Synthesis and adhesive property study of polyoxetanes grafted with catechols via Cu(I)-catalyzed click chemistry

Mussel-inspired catechol-containing polymers have drawn great attention due to their outstanding adhesive properties. Catechol-containing polyethylene glycol (cPEG) is a well-studied catechol-containing polymer used for tissue repair. Nevertheless, catechols can only be attached to the chain ends of polyethylene glycols thus the bonding strength of the resulting polymers is limited. Aiming at solving the problem, a series of clickable polyoxetane copolymers with grafted catechol moieties were synthesized in an efficient manner. Upon addition of FeCl₃ as the cross-linker, strong bonding strength of the adhesive was achieved. Polymer containing 15.5 molar percent of catechol showed the strongest bonding strength up to 5.59 MPa on sanded stainless steel. It was found that the triazole groups also contributed to the overall adhesive performance. This polyoxetane-based adhesive also displayed strong bonding ability to a variety of other substrates including porcine skin.     

Surface characteristics of poly(γ‐alkyl α l‐glutamate)s with different alkyl groups

A series of poly(γ‐alkyl α L ‐glutamate)s with different alkyl groups were synthesized by the ring opening polymerization of corresponding α‐amino acid N‐carboxyanhydrides. The characteristics of these polyglutamate surfaces were evaluated by attenuated total reflectance Fourier transform infrared spectroscopy spectra, water contact angle, water absorption, protein adsorption, and platelet adhesion measurements. Changing the length of the alkyl side chain provides a unique opportunity to study the influence of carbon number in the alkyl group on the surface properties of the polyglutamates. Water contact angle and water absorption data show that the hydrophilicity of these polyglutamate surfaces decreases with the increasing of methylene in the alkyl group. Protein adsorption on these polyglutamate surfaces increases with the enhancing of surface hydrophobicity. However, the changes in platelets adhesion could be attributed to the hydrophilicity/hydrophobicity of the polyglutamates and the specific effect of alkyl group. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Copper(I) Oxide‐Mediated Cyclization of o‐Haloaryl N‐Tosylhydrazones: Efficient Synthesis of Indazoles

An efficient synthesis of indazoles from readily accessible E/Z mixtures of o‐haloaryl N‐tosylhydrazones has been developed. The thermo‐induced isomerization of N‐tosylhydrazones is discussed. A series of valuable indazole derivatives are prepared in good yields, and the method has been successfully applied to the synthesis of the bioactive compounds, lonidamine, AF‐2785, axitinib, YC‐1 and YD‐3.

     

Epoxy–imide resins from N‐(4‐ and 3‐carboxyphenyl)trimellitimides. I. Adhesive and thermal properties

Epoxy–imide resins were obtained by curing Araldite GY 250 (diglycidyl ether of bisphenol‐A and epichlorohydrin; difunctional) and Araldite EPN 1138 (Novolac–epoxy resin; polyfunctional) with N‐(4‐ and 3‐carboxyphenyl)trimellitimides derived from 4‐ and 3‐aminobenzoic acids and trimellitic anhydride. The adhesive lap shear strength of epoxy–imide systems at room temperature and at 100, 125, and 150°C was determined on stainless‐steel substrates. Araldite GY 250‐based systems give a room‐temperature adhesive lap shear strength of about 23 MPa and 49–56% of the room‐temperature adhesive strength is retained at 150°C. Araldite EPN 1138‐based systems give a room‐temperature adhesive lap shear strength of 16–19 MPa and 100% retention of room‐temperature adhesive strength is observed at 150°C. Glass transition temperatures of the Araldite GY 250‐based systems are in the range of 132–139°C and those of the Araldite EPN 1138‐based systems are in the range of 158–170°C. All these systems are thermally stable up to 360°C. The char residues of Araldite GY 250‐ and Araldite EPN 1138‐based systems are in the range of 22–26% and 41–42% at 900°C, respectively. Araldite EPN 1138‐based systems show a higher retention of adhesive strength at 150°C and have higher thermal stability and T_g when compared to Araldite GY 250‐based systems. This has been attributed to the high crosslinking possible with Araldite EPN 1138‐based systems arising due to the polyfunctional nature of Araldite EPN 1138. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1729–1736, 2000     

Thermoplastic polymers as modifiers for urea‐formaldehyde (UF) wood adhesives. I. Procedures for the preparation and characterization of thermoplastic‐modified UF suspensions

Acrylic thermoplastic copolymers with different degrees of hydrophilicity were prepared and introduced into a commercial aqueous urea‐formaldehyde (UF) suspension at 5–10% w/v. The most hydrophilic acrylic thermoplastic was introduced into the UF suspension as an aqueous solution, whereas the most hydrophobic acrylic was introduced as a surfactant‐stabilized suspension. Acrylics with intermediate hydrophilicity were introduced into the UF suspension as a self‐dispersed aqueous suspension. The thermoplastic‐modified UF suspensions with 5% thermoplastic (58% solids) had a viscosity at 30°C of ～ 114 cP, compared with a viscosity of ～112 cP for the original UF suspension (60% UF solids). At 10% thermoplastic (63% solids), all the thermoplastic‐modified UF suspensions exceeded 200 cP. The viscosity of the UF suspension modified with self‐dispersed thermoplastic was reduced by ～ 50% by reducing the thermoplastic molecular weight. SEM micrographs of cured thermoplastic‐modified UF showed phase‐separated thermoplastic domains in a continuous UF phase for the UF modified with self‐dispersed and surfactant‐stabilized thermoplastic, but UF modified with the water‐soluble thermoplastic showed a single phase. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 890–897, 2003     

Enantioselective Synthesis of Cyclopentadienes by Gold(I)‐ Catalyzed Cyclization of 1,3‐Dien‐5‐ynes

An asymmetric synthesis of elusive chiral cyclopentadienes has been developed by gold(I)‐catalyzed alkoxycyclization of 1,3‐dien‐5‐ynes. The application of these substrates in completely diastereoselective Diels–Alder cycloaddition reactions, which can be carried out in one pot from achiral 1,3‐dien‐5‐ynes, allows the preparation of highly functionalized products bearing five stereogenic centers with high enantiomeric excesses.     

Chemoselective Cascade Synthesis of N‐Fused Heterocycles via Silver(I) Triflate‐Catalyzed Friedel–Crafts/N‐C Bond Formation Sequence

An efficient cascade methodology toward chemoselective synthesis of N‐fused heterocycles including 9H‐pyrrolo[1,2‐a]indole, 3H‐pyrrolo[1,2‐a]indole and 1H‐pyrrolo[1,2‐a]indole derivatives has been developed. This transformation proceeds via a silver(I) triflate‐catalyzed consecutive Friedel–Crafts reaction/N C bond formation sequence between readily available propargyl alcohols and 3‐substituted 1H‐indoles. Not only is excellent chemoselectivity observed according to the substitution patterns of propargyl alcohols, but also the Lewis acid‐catalyzed N C bond formation process can be carried out under base‐ and ligand‐free conditions.     

Synthesis of water‐soluble polyphenol‐graft‐poly(ethylene oxide) copolymers via enzymatic polymerization and anionic polymerization

Water‐soluble polyphenol‐graft‐poly(ethylene oxide) (PPH‐g‐PEO) copolymers were prepared using grafting‐through methodology. Polyphenol chains were synthesized via enzymatic polymerization of phenols, and the graft chains were synthesized via living anionic polymerization of ethylene oxides. The polymers were characterized using gel permeation chromatography, static light scattering and ¹H NMR, infrared and ultraviolet spectroscopies. The PPH‐g‐PEO graft copolymers are soluble in several common solvents, such as water, ethanol, N,N‐dimethylformamide, tetrahydrofuran and methylene dichloride. The solubility of the PPH‐g‐PEO graft copolymers is improved significantly compared with that of polyphenol. Copyright © 2009 Society of Chemical Industry     

Ruthenium(II)‐Catalyzed Regioselective Synthesis of Allyl Ketones from Alkynes and their Silver(I)‐Catalyzed Hydroarylation into γ‐Functionalized Ketones

The regioselective synthesis of β,γ‐unsaturated ketones from terminal alkynes is achieved by cooperative action of tris(acetonitrile)pentamethylcyclopentadieneruthenium hexafluorophosphate [Cp*Ru(NCMe)₃⁺ PF₆⁻] and para‐toluenesulfonic acid catalysts. These allyl ketones undergo direct regioselective hydroarylation/Friedel–Crafts reaction to introduce an electron‐rich aryl group at the γ‐position in the presence of ligand‐free silver triflate (AgOTf) catalyst. Both catalytic reactions take place with atom economy and provide an alternative to the synthesis of a variety of allyl ketones and γ‐arylated ketones.     

Gold(I)/Copper(II)‐Cocatalyzed Tandem Cyclization/Semipinacol Reaction: Construction of 6‐Aza/Oxa‐Spiro[4.5]decane Skeletons and Formal Synthesis of (±)‐Halichlorine

A simple and efficient strategy for the construction of 6‐aza/oxa‐spiro[4.5]decane skeletons under the cocatalysis of gold(I)/copper(II) was developed, and its potential utility was demonstrated by a formal synthesis of the biologically active marine alkaloid (±)‐halichlorine.

     

Thermo‐responsive injectable hydrogel system based on poly(N‐isopropylacrylamide‐co‐vinylphosphonic acid). I. Biomineralization and protein delivery

To achieve the injectable hydrogel system in order to improve bone regeneration by locally delivering a protein drug including bone morphogenetic proteins, thermo‐responsive injectable hydrogels composed of N‐isopropylacrylamide (NIPAAm) and vinyl phosphonic acid (VPAc) were prepared. The P(NIPAAm‐co‐VPAc) hydrogels were also biomineralized by urea‐mediation method to create functional polymer hydrogels that deliver the protein drug and mimic the bone extracellular matrix. The loosely cross‐linked P(NIPAAm‐co‐VPAc) hydrogels were pliable and fluid‐like at room temperature and could be injected through a small‐diameter aperture. The lower critical solution temperature (LCST) of P(NIPAAm‐co‐VPAc) hydrogel was influenced by the monomer ratio of NIPAAm/VPAc and the hydrogel with a 96/4 molar ratio of NIPAAm/VPAc exhibited an LCST of ～34.5°C. Water content was influenced by temperature, NIPAAm/VPAc monomer ratio, and biomineralization; however, all hydrogels maintained more than about 77% of the water content even at 37°C. In a cytotoxicity study, the P(NIPAAm‐co‐VPAc) and biomineralized P(NIPAAm‐co‐VPAc) hydrogels did not significantly affect cell viability. The loading content of bovine serum albumin in hydrogel, which was used as a model drug, gradually increased with the amount of VPAc in the hydrogel owing to the ionic interaction between VPAc groups and BSA molecules. In addition, the release behavior of BSA from the P(NIPAAm‐co‐VPAc) hydrogels was mainly influenced by the drug loading content, water content, and biomineralization of the hydrogels. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of monodisperse poly(butyl acrylate) initiated by SmMe(C5Me5)2(THF) and its adhesive properties after crosslinking by electron‐beam irradiation

Polymerization reactions of butyl acrylate (BuA) were carried out using an organosamarium complex, SmMe(C₅Me₅)₂(THF), as an initiator. Polymerization proceeds quantitatively to give high number‐average molecular mass polymers (M_n > 200,000) and narrow molecular weight distributions (M_w/M_n < 1.07). Irradiation of the resulting poly(BuA) with an electron beam (EB) gave crosslinked poly(BuA). Improved viscoelastic and adhesive properties of these polymers were useful for high‐temperature applications. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 432–437, 2001     

Silver(I)‐Catalyzed Conia‐Ene Reaction: Synthesis of 3‐Pyrrolines via a 5‐endo‐dig Cyclization

A novel method has been developed for the synthesis of 3‐pyrrolines from β‐ketopropargylamines via a 5‐endo‐dig carbocyclization. This transformation involves a silver‐catalyzed Conia‐ene type reaction tolerating broad substrate scope with good to excellent yields. Furthermore, this methodology has been extended for the construction of 2‐substituted pyrroles under base‐mediated conditions.

     

Regio‐ and Enantioselective Monoborylation of Alkenylsilanes Catalyzed by an Electron‐Donating Chiral Phosphine–Copper(I) Complex

An asymmetric monoborylation of alkenylsilanes catalyzed by a copper(I) complex with the chiral bisphosphine ligand BenzP* is reported. The reaction proceeded with excellent regioselectivity and high enantioselectivity to afford the corresponding optically active organoboronate esters with a stereogenic C B bond containing a vicinal silyl group. The synthetic utility of the product is demonstrated through stepwise transformations to multifunctional optically active compounds in a stereospecific manner.

     

Synthesis and characterization of an amphiphilic hyperbranched poly(amine‐ester)‐co‐D,L‐lactide (HPAE‐co‐PLA) copolymers and their nanoparticles for protein drug delivery

A series of hyperbranched poly(amine‐ester)‐co‐D ,L ‐lactide (HPAE‐co‐PLA) copolymer were synthesized by ring‐opening polymerization of D ,L ‐lactide with Sn(Oct)₂ as catalyst to a fourth generation branched poly(amine‐ester) (HPAE‐OHs4). The chemical structures of copolymers were determined by FTIR, ¹H‐NMR, ¹³C‐NMR, and TGA. Double emulsion (DE) and nanoprecipitation (NP) method were used to fabricate the nanoparticles of these copolymers encapsulating bovine serum albumin (BSA) as a model. DSC thermo‐grams indicated that the nanoparticles with BSA kept stable below 40°C. Different factors which influence on particular size and encapsulation efficiency (EE) were investigated. Their EE to BSA could reach 97.8% at an available condition. In vitro release behavior of NPs showed a continuous release after a burst release. The stability maintenance of BSA in the nanoparticle release in vitro was also measured via circular dichroism and fluorescence spectrometry. The results showed that the copolymer nanoparticles have a promising potential in protein delivery system. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010