Synthesis of thermally stable aromatic poly(spiroorthocarbonate)s having a Cardo or bent structure

Novel poly(spiroorthocarbonate)s [poly(SOC)]s having a Cardo or bent structure were synthesized by polycondensation of several bis‐catechols having fluorene (BCFL), spirobisindane (BCSPI), or spirobischromane (BCSPC) in the structure with 2,2,6,6‐tetrachlorobenzo[1,2‐d:4,5‐d’]bis[1,3]dioxole (4ClBD). Synthesis of poly(SOC)s was confirmed by NMR and IR spectrometry. The poly(SOC)s obtained from BCFL or BCSPC were soluble in common organic solvents. The glass transition temperature of the poly(SOC)s was not detected by differential scanning calorimetry (DSC) in the range of 50–300 °C. The 10 wt % decomposition temperature of the poly(SOC)s was found to be above 400 °C. These results indicated the high thermal stability of the poly(SOC)s. Soluble poly(SOC)s could be possessed to form a film on a glass plate by the spin coat method. The obtained polymer films were 0.2 μm in thickness with 95% light transmission in the optical wavelength range. These results suggested that the Cardo or bent structure may block the packing of the main‐chain of the structure, which improves the solubility of the polymers, increases transparency, and enhances the thermal stability of SOCs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1409‐1416     

Infrared thermographic analysis on copolymerization of spiroorthoester with oxetane

Infrared (IR) thermography was employed to monitor temperature changes during the copolymerization of a spiroorthoester monomer with an oxetane monomer initiated with a benzyl sulfonium salt. The temperature changes in the polymerizations decreased with the increase of the initial feed ratios of the spiroorthocarbonate monomer. For instance, the temperature in the copolymerization of the equimolar mixture of both of the monomers increased only ～1 °C, whereas that in the homopolymerization of the oxetane monomer increased more than 20 °C. This result indicates that the copolymerization employing spiroorthocarbonate monomers effectively suppress temperature increase, which are responsible to shrinkage during cooling. The suppression of polymerization shrinkage by spiroorthocarbonate was also confirmed by density measurement of the polymers using a gas pycnometer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1388–1393, 2007.     

Nanocomposites based on vapor-grown carbon nanofibers and an epoxy: Functionalization, preparation and characterization

Vapor-grown carbon nanofibers (VGCNF) were functionalized with amine-containing pendants via a Friedel-Crafts acylation reaction with 4-(3-aminophenoxy)benzoic acid. The resulting H₂N-VGCNF was treated with epichlorohydrin, followed by sodium hydroxide solution to afford N,N-diglycidyl-modified VGCNF that is designated as epoxy-VGCNF. Subsequently, epoxy-VGCNF was dispersed in an epoxy resin (Epon 862) with the aid of acetone and sonication. After acetone had been removed under vacuum from the mixture, curing agent “W” was added to epoxy-VGCNF/Epon 862 mixture, which was then poured into molds and cured at 250 °F (121 °C) for 2 h and 350 °F (177 °C) for 2 h to form a series of epoxy/fVGCNF samples; fVGCNF designated for “functionalized VGCNF” was used to denote our belief that all epoxy functions have reacted in the resulting nanocomposites. The VGCNF content was increased from 0.10 to 10.0 wt%. For comparison purposes, the pristine VGCNF or pVGCNF (0.1-5.0 wt%) was also used in the in situ polymerization of Epon 862 and curing agent “W” to afford another series of epoxy/pVGCNF samples. The epoxy-VGCNF showed a better dispersion in the epoxy resin than pVGCNF according to SEM results. Both the tensile moduli and strengths of epoxy/fVGCNF nanocomposites are higher than those of epoxy/pVGCNF. The additive effect of VGCNF on glass-transition (T_g) was discussed in terms of thermal analysis results. The thermal stability of the nanocomposites was investigated by thermogravimetric analysis (TGA).     

Effects of graphene and carbon nanotube fillers on the shear properties of epoxy

The effects of quantity of graphene and carbon nanotube‐based fillers and their pendant functional groups on the shear properties of a thermoset epoxy were investigated. Two novel functionalized graphenes, one with epoxy functionality and the other with an amine, are synthesized for this purpose. Nanocomposites are prepared at concentrations of 0.5, 1, 2, 3, 5, and 10 wt % and the effects of functionalization on the homogeneity of dispersion and the shear mechanical properties are investigated. The properties of the epoxy nanocomposites containing epoxy‐ and amine‐functionalized graphene are compared with those containing graphene oxide, Claisen‐functionalized graphene, neat multiwalled carbon nanotubes (MWNTs), three types of epoxy‐functionalized MWNT (EpCNT), and the unfilled epoxy. One of the EpCNT ( EpCNT3 ) was found to increase the plateau shear storage modulus by 136% (1.67–3.94 MPa) and the corresponding loss modulus by almost 400% at a concentration of 10 wt %. Several other fillers were also found to increase shear properties at certain concentrations. A hybrid system of EpCNT3 and graphite was also studied, which improved the storage modulus by up to 51%. SEM images reveal a correlation between thorough dispersion of the additive and enhancement of shear modulus. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 997–1006     

含螺环原碳酸酯的预聚物对环氧树脂的改性研究

Bailey发现螺环原酸酯和螺环原碳酸酯等单体在阳离子引发剂作用下进行双开环聚合反应时，伴随着体积膨胀［‘j．这一现象引起了高分子材料学家的极大兴趣，因为树脂固化时产生体积收缩，会使树脂材料内部产生收缩应力，是导致材料力学性能下降，使用寿命降低的主要原因之一．例如，用不饱和螺环原碳酸酯改性的某种补牙材料与牙的粘接力比不含螺环原碳酸酯的大一倍，并且改善了冲击强度而不改变模量．更为重要的是，由于体积稍微膨胀，补牙材料与牙齿间无缝隙，从而消除了在缝隙中繁殖细菌的可能性，达到既结实又卫生的目的【‘］．利用螺环…     

Polyether-functionalized disiloxanes as new film-forming electrolyte additive for Li-ion cells with graphitic anodes

New type of film-forming electrolyte additive (functional co-solvent) for rechargeable lithium batteries has been demonstrated. The additive prevents solvent co-intercalation and graphite exfoliation in propylene carbonate based electrolytes. The additive performs best at 15% w/w ratio and is a mixture of homologous disiloxanes functionalized with polyether side chains of variable length. Galvanostatic and potentiodynamic charge/discharge characteristics are presented. SEM/EDX analysis has been carried out to evidence the suppression of PC co-intercalation.     

Effect of oligo(spiroorthocarbonate)s on the volume shrinkage of epoxides during crosslinking by sulfonium salt‐initiated cationic polymerization of epoxides

Oligo(spiroorthocarbonate)s 1 , which were synthesized by the polycondensation of pentaerythritol derivatives with tetraethylorthocarbonate, were employed as comonomers in the cationic polymerization of epoxide initiated by sulfonium salt. In the copolymerization, the spiroorthocarbonate moiety of 1 underwent double ring‐opening reaction, leading to the efficient diminution of the volume shrinkage upon the copolymerization. Thermal properties of the resulting networked polymers were evaluated by TGA. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1564–1568     

Modification of epoxy polymers with small additives of multiwall carbon nanotubes

The effect of small additives of functionalized multiwall carbon nanotubes used as a modifier on the formation and properties of epoxy polymers cured with diaminodiphenyl sulfone is investigated. In the range of additive concentrations 0.01–0.50 wt %, there are extreme dependences of dynamic storage modulus and the glass-transition temperature on modifier concentration. As shown by electron microscopy and X-ray scattering, regions with increased packing densities of macromolecules are formed in the polymers in the presence of the modifier. The effect of the specific surface on the kinetics of curing of epoxy resins is observed. A mechanism controlling the formation of the epoxy matrix that is responsible for the inhomogeneous polymer structuring that defines the final properties of the polymers is suggested.     

AM1 semiempirical computational analysis of the homopolymerization of spiroorthocarbonate

Spiroorthocarbonates (SOCs) are monomers that have been shown to expand when homopolymerized. SOCs are potential monomer systems that can be combined with other monomers such as epoxy resin to produce a non-shrinking dental matrix for dental composites. The purpose of this study was to use a computer model (AM1) to study possible homopolymerization pathways for several SOC monomers. The gas phase transition states of three feasible reaction mechanisms for the homopolymerization of four spiroorthocarbonate 1,5,7,11-tetraoxaspiro[5,5]undecane (TOSU) systems have been examined using the AM1 semiempirical quantum mechanical model. In addition to the base TOSU noted above, the 2,8-dimethyl, 2,4,8,10-tetramethyl, and the 3,3,9,9-tetramethyl analogs were used in this study. The results of these calculations produced the heats of reaction, activation enthalpies and transition state structures. Our calculations indicate stabilization of the transition states by electron-donating and resonance-stabilizing substituent groups. The energies of activation of all of these systems were between 24 and 38 kcal/mol and all reactions were endothermic. Further, we found that there was a significant intermolecular attraction between TOSU monomers (≈3.5 kcal/mol). When compared with experimental studies of methylated TOSU by Sakai and co-workers, our calculations agree with the preferred site of nucleophilic attack, but not with the experimental rate results. It was concluded that the homopolymerization of the unsubstituted TOSU and its derivatives studied was endothermic and that the rate of homopolymerization of TOSU depends on an intermolecular pre-association of TOSU monomer in the condensed phase.     

Investigation of the synergistic effect with chiral D-penicillamine functionalized gold nanoparticle as an additive for enantiomeric separation in capillary electrophoresis

The authors describe a synergistic system for nanoparticle based chiral separation. It is based on the use of a conventional chiral selector hydroxyproyl-β-cyclodextrin and a kind of gold nanoparticle functionalized with D-penicillamine as an additive. This nanomaterial displays a synergistic effect on the efficiency of the enantioseparation of the chiral drugs amlodipine, tropicamide, and ofloxacin. A comparative study on the enantioseparation capability of three separation systems, viz. (a) single hydroxyproyl-β-cyclodextrin system, (b) achiral citrate capped gold nanoparticle/ hydroxyproyl-β-cyclodextrin system, and (c) chiral D-penicillamine functionalized gold nanoparticle/ hydroxyproyl-β-cyclodextrin system was performed. The results show that the D-penicillamine functionalized gold nanoparticle/hydroxyproyl-β-cyclodextrin synergistic system has remarkable superiority. The effects of concentrations of D-penicillamine functionalized gold nanoparticle and hydroxyproyl-β-cyclodextrin, of buffer pH value and concentration, and of applied voltage on the performance of enantioseparation were investigated.     

Functional dye as a comonomer in a water‐soluble polymer

In many applications, a functional additive is blended into a polymer matrix to enhance its properties. However, when the polymer and functional additive are applied to a surface, the functional molecule may be easily lost. In favorable cases, it may be possible to incorporate the additive directly into the polymer as a comonomer. In this study, a functionalized polymer has been obtained through the combination of linking a photodynamic, antimicrobial dye, Rose Bengal, to vinyl benzyl chloride via etherification and then polymerizing this into a water‐soluble polymer using chain growth copolymerization. Characterization of the efficiency of synthesis, solubility of the final product, and singlet oxygen production rate has been performed. Dialysis was used to determine the extent of incorporation of the dye into the polymer. The chemical structure of the intermediate produced through etherification has been verified. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1594–1599     

Effects of directed architecture in epoxy functionalized prepolymers for photocurable thin films

Cationic photopolymerization has become increasingly important in thin‐film applications for advantages including no oxygen inhibition and rapid polymerization rates. Photocurable cationic thin film properties are often modulated by incorporation of oligomeric and prepolymer materials, but little work has directly examined the effect of prepolymer structure and reactive group placement on the thermomechanical properties of the final material. To explore the role of molecular architecture, epoxy functionalized butyl acrylate gradient copolymers were synthesized with reactive groups in end segments or randomly distributed along the prepolymer chain. Polymerized end functionalized formulations exhibit moduli almost double that of random functionalized oligomer formulations. In addition, inclusion of end functionalized prepolymers decreases creep of resulting thin films by a factor of 10. Furthermore, decreasing the concentration of the cross‐linking diluent in end functionalized prepolymer systems results in amorphous networks with significantly lower mechanical strength. Increasing reactive groups at the ends of prepolymers produces stronger materials without affecting tensile elongation at break. These properties indicate that the structured oligomers facilitate the formation of continuous hard domains with high cross‐link density with inclusions of soft, flexible domains of low cross‐link density. This study demonstrates that the prepolymer architecture governs network formation and ultimate properties. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 144–154     

New insight into relaxation dynamics of an epoxy/hydroxy functionalized polybutadiene from dielectric and mechanical spectroscopy studies

Dielectric and mechanical spectroscopy methods have been employed to describe the temperature dependencies of the segmental and macromolecular relaxation rates in epoxy/hydroxy functionalized polybutadiene. Dielectric studies on the dynamics of segments of the polymer as well as the mobility of small ions trapped in the system have been carried out both as a function of temperature and pressure under isobaric and isothermal conditions, respectively.     

Alum as an efficient catalyst for the multicomponent synthesis of functionalized piperidines

An effective approach to the synthesis of functionalized piperidines via a one-pot multicomponent reaction of aniline, β-ketoester and aldehyde in the presence of alum as an efficient catalyst has been reported. The present procedure offers advantages such as simple workup, short reaction time and offers rapid access to a variety of functionalized piperidines.     

The acid free asymmetric intermolecular α-alkylation of aldehydes in fluorinated alcohols

The acid free asymmetric intermolecular α-alkylation of aldehydes with alcohols has been discovered using trifluoroethanol as solvent. This unprecedented system affords the enantioenriched functionalized primary alcohols (after NaBH(4) reduction) in high yields and good to excellent enantioselectivities with wide substrate scope in the absence of any acid additive.     

A direct route to angularly substituted hydrindanes. Formal synthesis of bakkenolide-A and synthesis of an advanced intermediate to umbellactal

A direct route for the synthesis of highly functionalized angularly substituted hydrindanes has been developed. The key step involves RO-RCM of an appropriately functionalized norbornene derivative. The hydrindane derivative obtained in this way has been used to accomplish a formal synthesis of bakkenolide-A. This protocol has also been extended for the synthesis of an advanced intermediate to the synthesis of the diterpene umbellactal.     

Reinforcing epoxy resin through covalent integration of functionalized graphene nanosheets

A chemically converted graphene/epoxy (EP) resin nanocomposite has been developed through the use of the functionalized graphene nanosheets (FGNs). The FGNs were prepared via the reaction of amines with alkylcarboxyl groups attached to the graphite oxides in the course of a dicarboxylic acid acyl peroxide treatment. FGNs/EP composites were prepared by dissolving the FGNs in organic solvent followed by mixing with EP and curing agent. In this composite, the FGNs were able to create molecular entanglement with EP matrix by taking advantage of the reactions between amine groups of FGNs and EP groups of EP, thus the FGNs could be covalently integrated into the EP matrix and became part of the cross‐linked network structure rather than just a separated component. Great enhancement in the mechanical properties of the epoxy composite, such as the ultimate tensile strength and toughness, had been achieved with small loading (0.1 wt%) of FGNs by 17.0% and 262.2%, respectively. However, the FGNs reinforced EP composites showed a slight decrease in glass transition temperature (Tg). Copyright © 2014 John Wiley & Sons, Ltd.     

Grignard Reagent/CuI/LiCl‐Mediated Stereoselective Cascade Addition/Cyclization of Diynes: A Novel Pathway for the Construction of 1‐Methyleneindene Derivatives

Diynes containing a cyclopropane group smoothly undergo a novel intramolecular and stereoselective cascade addition/cyclization reaction to produce the corresponding 1‐methyleneindene derivatives in moderate to good yields. This interesting transformation is mediated by Grignard reagent/CuI with LiCl as an additive under mild conditions. The obtained product can easily be further functionalized through cyclopropyl ring opening. A plausible reaction mechanism has also been presented on the basis of deuterium labeling and control experiments.     

Surface functionalized boehmite sheets filled epoxy composites with enhanced mechanical and thermal properties

Boehmite (AlOOH) sheets were synthesized via a hydrothermal method and then successfully functionalized with a bi‐functional coupling agent, γ‐aminopropyl‐ triethoxysilane (APTES), through a facile neutral solvent method. Scanning electron microscope and transmission electron microscopy images showed a uniform morphology of AlOOH sheets. APTES was found to be covalently bound with AlOOH sheets. The linked APTES can be combined with an epoxy oligomer through a ring opening addition reaction. The modified AlOOH was used as reinforcing agent to reinforce the epoxy resin cured by 4,4‐diaminodiphenylsulfone. The results of tensile and differential scanning calorimetric test revealed the tensile strength and glass transition temperature (Tg) firstly increase and then decrease with the increase of functionalized AlOOH sheets loading. When the loading of functionalized AlOOH sheets increased to 5 parts per hundred resin, the highest tensile strength and Tg were obtained. They are 100.8 MPa and 174.5 °C. Microscopic examinations revealed the presence of large plastic deformations at the micronscale in the formed composites in agreement with the observed strengthening effect of functionalized AlOOH sheets. Copyright © 2014 John Wiley & Sons, Ltd.     

New palladium catalyst immobilized on epoxy resin: synthesis,characterization and catalytic activity

A new thiol‐functionalized epoxy resin as a support for palladium(II) complexes has been synthesized in good yields. A palladium catalyst was ‘heterogenized’ by anchoring [PdCl₂(PhCN)₂] complexes to these thiol‐functionalized polymers via ligand exchange reaction. These new palladium catalysts were tested in Mizoroki–Heck coupling and hydrogenation reactions. The activity of the complexes in terms of yield is comparable to that of homogeneous PdCl₂(PhCN)₂. The stability and a good recycling efficiency of these catalysts make them useful for prolonged use. The constant and good selectivity of the supported catalysts during recycling experiments indicate that they could be useful for practical application in many organic reactions. To characterize the heterogeneous complexes before and after use, X‐ray photoelectron spectroscopy, infrared spectroscopy, scanning electron microscopy, energy dispersive X‐ray microscopy, atomic absorption spectroscopy and time‐of‐flight secondary ion mass spectrometry were applied. Density functional theory calculations were also used to better understand the structures of the obtained palladium complexes. Polythiourethanes contain three atoms, oxygen, nitrogen and sulfur, capable of coordinating to transition metals. We examined the possibility of intra‐ and intermolecular binding for both cis and trans palladium complexes. Copyright © 2015 John Wiley & Sons, Ltd.