Epoxy Units Research Articles

Cinnamigones A–C, three highly oxidized guaiane-type sesquiterpenes with neuroprotective activity from Cinnamomum migao

Cinnamigones A–C, three undescribed highly oxidized guaiane-type sesquiterpenes were isolated from the fruits of Cinnamomum migao. Cinnamigone A (1), structurally artemisinin-like, is a natural 1,2,4-trioxane caged endoperoxide with an unprecedented tetracyclic 6/6/7/5 ring system. Compounds 2–3 are classic guaiane sesquiterpene featuring different epoxy units. Guaiol (4) is considered to be the precursor of 1–3 in the biosynthesis pathway hypothesis. The planar structures and configurations of cinnamigones A–C were elucidated by spectral analysis, HRESIMS, X-ray crystallography and ECD calculations. Evaluation of the neuroprotective activity of 1–3 on N-methyl-ᴅaspartate (NMDA) toxicity was demonstrated that compounds 1–2 exhibited moderate neuroprotective activity against NMDA-induced neurotoxicity.

High Thermal Resistance of Epoxy/Cyanate Ester Hybrids Incorporating an Inorganic Double-Decker-Shaped Polyhedral Silsesquioxane Nanomaterial.

In this study, we prepared a difunctionalized cyanate ester double-decker silsesquioxane (DDSQ-OCN) cage with a char yield and thermal decomposition temperature (Td) which were both much higher than those of a typical bisphenol A dicyanate ester (BADCy, without the DDSQ cage) after thermal polymerization. Here, the inorganic DDSQ nanomaterial improved the thermal behavior through a nano-reinforcement effect. Blending the inorganic DDSQ-OCN cage into the epoxy resin improved its thermal and mechanical stabilities after the ring-opening polymerization of the epoxy units during thermal polymerization. The enhancement in the physical properties arose from the copolymerization of the epoxy and OCN units to form the organic/inorganic covalently bonded network structure, as well as the hydrogen bonding of the OH groups of the epoxy with the SiOSi moieties of the DDSQ units. For example, the epoxy/DDSQ-OCN = 1/1 hybrid, prepared without Cu(II)-acac as a catalyst, exhibited a glass transition temperature, thermal decomposition temperature (Td), and char yield (166 °C, 427 °C, and 51.0 wt%, respectively) that were significantly higher than those obtained when applying typical organic curing agents in the epoxy resin. The addition of Cu(II)-acac into the epoxy/BADCy and epoxy/DDSQ-OCN hybrids decreased the thermal stability (as characterized by the values of Td and the char yields) because the crosslinking density and post-hardening also decreased during thermal polymerization; nevertheless, it accelerated the thermal polymerization to a lower curing peak temperature, which is potentially useful for real applications as epoxy molding compounds.

Development of PSQ-RO membranes with high water permeability by copolymerization of bis[3-(triethoxysilyl)propyl]amine and triethoxy(3-glycidyloxypropyl)silane

Epoxy-based reverse osmosis (RO) membranes with an organically bridged polysilsesquioxane (PSQ) skeleton were prepared by a sol-gel process that involved the copolymerization of bis[3-(triethoxysilyl)propyl]amine (BTESPA) and triethoxy(3-glycidyloxypropyl)silane (TEGPS). RO experiments using 2000 ppm NaCl aqueous solution indicated that the use of epoxy-containing monomer TEGPS significantly improved performance, yielding water permeability of 1 × 10 −12 m 3 /m 2 sPa and salt rejection of 98%, approximately. This is likely because of the ring opening of the epoxy units, which leads to the formation of hydroxy (C–OH) groups during sol formation. Some C–OH groups underwent condensation with silanol to generate C–O–Si bonds in the gelation process. Immersion of the resultant membrane in water resulted in the hydrolysis of C–O–Si bonds to re-generate C–OH units. This increased membrane hydrophilicity and further improved permeability, although salt rejection slightly decreased. It was also found that membranes derived from TEGPS showed high resistance to chlorine and thermal stability. • New polysilsesquioxane (PSQ)-based RO membranes were prepared. • The use of epoxy-containing monomer significantly improved performance. • Water permeance of 9.6 × 10 −13 m 3 /m 2 sPa and salt rejection of 97.5% were obtained. • The present membranes showed high chlorine resistance and thermal stability.

Photocurable selenophene/maleimide-based high-refractive-index copolymers obtained via radical copolymerization

Selenophene-containing copolymers with either alternating or random sequences and high refractive indices were synthesized via conventional free-radical copolymerization of 2-vinylselenophene (2VS). Copolymers with a moderate alternating tendency were obtained via radical copolymerization of electron-donating 2VS and electron-accepting maleimide derivatives, such as N-methyl maleimide (MMI), N-phenyl maleimide (PMI), and N-vinyl maleimide (VMI). Copolymerization of 2VS with glycidyl methacrylate (GMA) also afforded copolymers containing selenophene and reactive epoxy units in the side chains. The selenophene-containing poly(2VS) showed a high refractive index (1.6420 @ 589 nm) and a reasonable Abbe number (30.7). High refractive indices of 1.6138–1.5959 with corresponding Abbe numbers of ~30 were similarly achieved for the selenophene/maleimide copolymers. The introduction of the maleimide moiety into the polymer side chain improved its thermal stability (Td5 > 320 °C) and enhanced the glass transition temperature (Tg = 158–160 °C). Selenophene-containing copolymers with pendant N-vinyl units were obtained via copolymerization of 2VS and VMI, which was successfully employed as a precursor for obtaining a photoinduced crosslinked film via a thiol-ene reaction with 1,6-hexanedithiol in the presence of a photo-radical initiator under ultraviolet irradiation. Thus, for the first time, photocurable and high-refractive-index selenophene-based copolymers were developed through the combination of a selenophene-containing vinyl monomer and a maleimide derivative with a pendant N-vinyl group.

Interfacial Properties of ZnO Nanowire-Enhanced Carbon Fiber Composites: A Molecular Dynamics Simulation Study

The interfacial properties of ZnO nanowire (NW)/carbon fiber-reinforced epoxy composites are investigated using molecular dynamics (MD) simulations. An atomistic representative volume element (RVE) is developed in which a single ZnO NW is aligned on carbon fiber and embedded in the cross-linked epoxy. Effects of ZnO NWs on the fiber-matrix adhesion are studied by evaluating the fiber and the enhanced matrix interaction. The traction-separation behavior in both sliding mode (shear separation) and opening mode (normal separation) is evaluated. The cohesive parameters, including the peak traction and adhesion energy, are calculated in each mode. Different numbers of cross-linked epoxy units in the system are studied and validated. The interfacial properties of the hybrid system are compared with the simulated bare RVE containing fiber and epoxy. MD results showed that the interfacial strength is increased from 485 MPa to 1066 MPa with the ZnO NWs. The adhesion energy in both opening and sliding modes is significantly improved by growing ZnO NWs on the carbon fibers. In addition, the hybrid system shows more rate-independent behavior compared with the bare system in the opening mode.

Poly(amidoamine) dendrimer-grafted carbon nanotubes as a hybrid multifunctional curing agent for epoxy-modified polyurethane

Carbon nanotube (CNT) grafted with hyperbranched poly(amidoamine) (PAMAM) dendrimer (CNTD) were used as a multifunctional curing and composite agent of polyurethane (PU) terminated with epoxy units. Amino-functionalized CNT was used as the core for grafting the first generation of PAMAM dendrimer by sequential addition of methyl acrylate and ethylenediamine. Two different epoxy-terminated PUs (PUB and PU-PMDA) were prepared from the reaction of poly(ethylene glycol), excess amounts of hexamethylene diisocyanate, and different chain extenders (1,4-butanediol for PUB and pyromellitic dianhydride (PMDA) for PU-PMDA), and subsequent end group transformation of the isocyanate groups to epoxy functionalities using glycidol. Fourier transform infrared spectra and thermogravimetric analysis (TGA) results showed that CNTD was successfully prepared. TGA thermograms revealed that thermal decomposition of composites were carried out in two main steps related to the soft and hard segments. In addition, char content and thermal stability of the composites were increased with increasing the CNTD content. Most importantly, the PMDA chain extender resulted in high thermal stability of the epoxy-terminated PU composites. X-ray diffraction and scanning and transmission electron microscopies presented morphological and structural properties of nanotubes and hybrid composites.

Ladder-Structured Polysilsesquioxane/Al2O3 Nanocomposites for Transparent Wear-Resistant Windows

As a protective layer for deformable displays, we synthesized ladder-type polysilsesquioxanes (LPSQs) containing cyclic epoxy as a curable unit. The mechanical properties after photo- and thermal-curing of LPSQs with a small amount of added Al2O3 nanoparticles were compared with those of the pure LPSQs. The prepared LPSQ-Al2O3 nanocomposites and the pure LPSQs exhibited comparable optical transparencies and thermal stabilities. In addition, the degree of conversion of the applied epoxy units in LPSQs and the resulting mechanical properties, as monitored by Fourier transform infrared spectroscopy and nanoindentation tests, indicated that the addition of nanoparticles to LPSQs moderately enhanced the epoxy conversion rate and remarkably improved the wear resistance, including hardness, after photo-/thermal-curing processes. The LPSQ-Al2O3 nanocomposites achieved higher wear resistance than epoxy-silica nanocomposites containing similar curable functional groups and reinforcing fillers (silica). The excellent mechanical properties of the LPSQ-Al2O3 nanocomposites could be attributed to three-dimensionally interconnected networks of organic-inorganic hybrid-type chemical structures in the LPSQ as well as additional reinforcement from amine-functionalized Al2O3 nanoparticles covalently interconnected with the LPSQ. We believe that the devised LPSQ-Al2O3 nanocomposites could serve effectively as a wear-resistant platform for deformable display windows.

From atomistic structure to thermodynamics and mechanical properties of epoxy/clay nanocomposites: Investigation by molecular dynamics simulations

Polymer/clay nanocomposites (PCNs) are multi-functional materials that have superior mechanical and thermal properties than polymer-based materials while maintaining their characteristic properties of lightweight and optical clarity. These materials are obtained by adding small amounts of clay nanofillers to a polymer matrix. In this work, we proposed a molecular model to investigate the morphology and thermomechanical properties of thermosetting clay nanocomposites. The epoxy matrix was composed of several representative cross-linked epoxy units, and different structures of PCNs, which correspond to intercalated or exfoliated status, were considered by varying the amount of polymer phase in the interlayer space. Molecular dynamics simulations of different nanocomposite structures were used to provide atomistic insights into the arrangement of the constitutive components of PCNs, the molecular interactions occurring in the interphase zone, and the influence of silicate layer on the thermodynamic and elastic properties of these multi-functional materials.

Thermal degradation of polystyrene composites. Part II. The effect of nanoclay

In this work, thermal degradation behavior polystyrene/organoclay nanocomposites containing tribromophenol end-capped brominated epoxy oligomer, (BE) with or without Sb2O3 were investigated systematically via direct pyrolysis mass spectrometry. Incorporation of organically modified montmorillonite into polystyrene, (PS) matrix not only increased thermal stability but also the probability of radical recombination, disproportionation and carbonization reactions causing increase in the char yield. Exfoliation of organoclay in BE phase of PS-BE matrix affected the extent of radical coupling and disproportionation reactions between the thermal degradation products of PS and organic modifier. In addition, the evolution of BE based products was hindered partly and the attacks of HBr to epoxy units generating H2O became more efficient. During the pyrolysis of polystyrene/organoclay nanocomposite involving both BE and Sb2O3, the relative yields diagnostic products of both oxybromides and bromides of antimony were increased significantly in the temperature region where PS decomposition took place which in turn increased the efficiency of radical scavenging and reduced peak heat release rate while increasing limiting oxygen index.

Carbonyldiimidazole‐accelerated efficient cure of epoxidized soybean oil with dicyandiamide

ABSTRACTThis study investigates the curing of epoxidized soybean oil (ESO) using dicyandiamide (DICY) and combinations of DICY with several accelerators as curing agents. The differential scanning calorimetry (DSC) results indicated that carbonyldiimidazole (CDI) is a highly efficient accelerator for the ESO‐DICY curing system. CDI accelerated ESO‐DICY curing system can gel within a short period of 13 min at 190 °C. The activation energies of the ESO‐DICY curing systems with and without CDI are 95 and 121 kJ mol−1, respectively. Similar acceleration effect was observed in the ESO‐diglycidyl ether of biphenyl A (DGEBA) blending formulations. When the molar part of the glycidyl epoxy groups of DGEBA was equal to the internal epoxy groups of ESO in the mixture, gelation of the DICY curing system accelerated by CDI was achieved in 3 min at 160 °C. Furthermore, the DSC results with FTIR analysis suggest that the stoichiometric curing molar ratio was 3 ESO epoxy units per 1 DICY molecule. Two epoxy units reacted with DICY to give secondary alcohols, while the other one linked to the nitrile group. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 375–382

Novel aliphatic polyesters from an oleic acid based monomer. Synthesis, epoxidation, cross-linking and biodegradation

The synthesis of polymeric materials based on monomers from renewable feedstocks is a steadily growing field. New aliphatic polyesters derived from the 1,18-(Z)-octadec-9-enedioic acid (D18:1), a high oleic sunflower oil fatty acid derivative, and aliphatic diols of different molecular weight (from 1,3-propanediol to 1,12-dodecanediol) have been synthesized and characterized. The polymerization was undertaken by direct bulk polycondensation of a diacid with a diol, with or without a metal catalyst, leading to viscous liquid to solid semi-crystalline polyesters at room temperature, depending on the diol type. The molecular weights of polyesters ranged between 7000 and 20,000gmol−1. The main attractive aspects of these polyesters are the renewable biomass origin of the diacid and the presence of double bonds on the polymer backbone (oleic acid derivative) allowing subsequent chemical modifications. The epoxidation of these double bonds was undertaken on the macromolecular chains to induce the photochemical cross-linking of the epoxide functions. Transparent and homogeneous cross-linked films were made by photo-polymerization of the epoxy units with less than 5% of extractible products. Enzymatic degradation of these polyesters (cross-linked) was poor over 8weeks.

Preparation and characterization of epoxy/polyhedral oligomeric silsesquioxane hybrid nanocomposites

AbstractWe have prepared epoxy/polyhedral oligomeric silsesquioxane (POSS) nanocomposites by photopolymerization from octakis(glycidylsiloxy)octasilsesquioxane (OG) and diglycidyl ether of bisphenol A. We used nuclear magnetic resonance, Raman, and Fourier transform infrared spectroscopies to characterize the chemical structure of the synthetic OG. Differential scanning calorimetry and dynamic mechanical analysis (DMA) revealed that the nanocomposites possessed higher glass transition temperatures than that of the pristine epoxy resin. Furthermore, DMA indicated that all of the nanocomposites exhibited enhanced storage moduli in the rubbery state, a phenomenon that we ascribe to both the nano‐reinforcement effect of the POSS cages and the additional degree of crosslinking that resulted from the reactions between the epoxy and OG units. Thermogravimetric analysis revealed that the thermal stability of the nanocomposites was better than that of the pristine epoxy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1927–1934, 2009

Reworkable UV curing materials

Novel UV curing materials which became soluble in solvents by photo/thermal degradation were studied. Three types of systems were designed and prepared, i.e. (a) base polymer/crosslinker blended system, (b) functionalized polymer system, and (c) multifunctional acrylate monomer system. In the base polymer/crosslinker blended system, as a crosslinker, multifunctional epoxy compounds containing tertiary esters of carboxylic acid or sulfonate ester units were synthesized and used in combination with polyvinylphenol. Functionalized polymers bearing epoxy units and thermally degradable linkages in the side chain were prepared. Furthermore, multifunctional methacrylate or acrylate monomers bearing acetal linkages in a molecule were prepared. Photocrosslinking and thermal decrosslinking of those materials were studied.

Photocrosslinking System Using Highly-Functionalized Epoxy Crosslinkers Having Degradable Property

Multifunctional crosslinkers having two, three, four and six functionalities were synthesized using a convergent method and were applied to a photocrosslinking system having thermally degradable properties. The multifunctional crosslinkers contained epoxy units and tertiary ester linkages. When the blended films of epoxides/poly(p-vinylphenol) with a photoacid generator were irradiated and followed by baking at relatively lower temperatures ( 120 °C). The reaction pathway of the blended system was studied by in situ FT-IR measurements.

Epoxy-containing ArF resists with narrow molecular weight distribution

Terpolymers consisting of γ-butyrolactone-2-yl methacrylate, 2-methyl-2-adamantyl methacrylate, and 1-methyl-1-(6-methyl-7-oxabicyclo[4,1,0]hept-3-yl)ethyl methacrylate were prepared by the reversible addition-fragmentation chain transfer polymerization technique. The molecular weight distribution of the polymers was 1.29–1.39. Although the polymers have epoxy units and cross-linking of the polymer occurred during prebake treatment, they worked as a highly sensitive positive-tone resist. The cross-linking efficiency of the resist was dependent on the type of amines used as a quencher. The line edge roughness values were dependent on the prebake temperature.

Photocrosslinking and Thermal Degradation of Epoxy-containing Polymers Using Photobase Generators

Abstract A new system consisting of a photobase generator and an oligomer bearing both epoxy and tertiary ester units was prepared as a photocrosslinkable and thermally de-crosslinkable polymer system. The sample film became insoluble on UV-irradiation and followed by baking at 100–160 °C. The crosslinked film became soluble in methanol when baked at 180–200 °C.

Equilibrium Swelling of an Epoxy‐Resin in Contact with Water – A Molecular Dynamics Simulation Study

AbstractFull Paper: We have studied the equilibrium swelling of an idealized model network based on a realistic epoxy‐resin in contact with water using the molecular dynamics simulation method. We use a novel method to measure the water chemical potential inside the network as function of water concentration. The equality of the water chemical potential computed in this fashion with the bulk water chemical potential under the same thermodynamic conditions determines the equilibrium water content and the swelling ratio. We study the dependence of the water content as function of temperature and as function of the size of the atomic partial charges.Schematic representation of the simulation volume. Spheres represent epoxy units with n = 0. The dashed lines represent curing agent units with m = 5.imageSchematic representation of the simulation volume. Spheres represent epoxy units with n = 0. The dashed lines represent curing agent units with m = 5.

A selective reaction of polyhydroxy fullerene with cycloaliphatic epoxy resin in designing ether connected epoxy star utilizing fullerene as a molecular core

A novel ether connected epoxy star like polymer was synthesized by selective reaction of water soluble polyhydroxy fullerene (fullerenol) with a commercial grade cycloaliphatic epoxy resin (CY-230, Ciba Geigy) in heterogeneous medium at ambient alkaline condition using tetrabutylammonium hydroxide as phase transfer catalyst. The reaction went well in such conditions and the hydroxy groups of fullerenol underwent selective nucleophilic addition reaction with polar carbonyl groups of the epoxy resin with the formation of a hemiketal. The progress of the reaction was monitored by FTIR analysis of the product formed. The disappearance of characteristic FTIR bands of fullerenol (at 1593.2, 1381.2, and 1068 cm −1) and the typical carbonyl peak (at 1725 cm −1) of parent epoxy resin and also changes of broad hydroxy peak (at 3431 cm −1) of fullerenol into a sharp peak (at 3396.6 cm −1, indicating reduced hydrophilicity) in the reaction product clearly demonstrated the chemical attachment of the epoxy units to the fullerene core. Multiple epoxy units (about 8–10) were attached to fullerene core. Non-reactivity of fullerenol towards DGEBA epoxy resin (LY 556 Ciba Geigy) in similar conditions further supports our result. The thermal properties of the product were influenced by the presence of fullerenol and exhibits higher thermal stability compared to parent epoxy. A probable reaction mechanism for the reaction has also been discussed.

New phosphazene-based chain extenders containing allyl and epoxide groups

In this paper we present the synthesis and the characterization of cyclophosphazenes substituted with allyl groups, their transformation in epoxide-containing cyclophosphazenes and the final utilization of these compounds as chain extenders in combination with polyamides. The reaction at high temperature of Nylon-6 with epoxy-functionalized cyclophosphazenes leads to the opening of the epoxy units by the action of both amino (—NH2) and carboxylic (—COOH) end-groups of the polymer to enhance the final molecular weight of this material. The consequences of this fact on the thermal, mechanical and visco-elastic properties of treated Nylon-6 have been also evaluated and compared to those of the pristine material. Possible utilization of these cyclophosphazenes in recycling processes for degraded polyamides could be envisaged.

Polysiloxane formation at the irradiated surface of polymers containing both photoacid generating units and epoxy units

Polymers bearing both epoxy units and photoacid generating units which can generate sulfonic acid upon irradiation with 254 nm light were prepared and the effect of crosslinking of polymer films on the formation of polysiloxanes at the irradiated surface by the chemical vapor deposition (CVD) method was investigated. When the surface of the irradiated film was exposed to the vapor of alkoxysilanes, polysiloxanes were formed at the surface. The thickness of the surface layer composed of polysiloxanes and base polymer was largely reduced by the crosslinking of the film surface. The surface modified with polysiloxanes showed a good resistance to the etching using an oxygen plasma.