Synthesis,characterization, and properties of amphiphilic chitosan copolymers with mixed side chains by click chemistry

Novel amphiphilic chitosan copolymers with mixed side chains of poly(ε‐caprolactone) and poly(ethylene oxide) (CS‐g‐PCL/PEO) were successfully synthesized by “graft to” approach via click chemistry. The melting and crystallization behaviors and crystalline morphology of CS‐g‐PCL/PEO copolymers can be adjusted by the alteration of the feed ratio of PCL and PEO segments. CS‐g‐PCL/PEO copolymers revealed crystalline morphology different from that of linear alkynyl PCL and alkynyl PEO due to the influence of brush structure of copolymers and the mutual influence of PCL and PEO segments. The hydrophilicity of the CS copolymers can be improved and adjusted by the alteration of the composition of PCL and PEO segments. Moreover, the CS copolymers can self‐assemble into spherical micelles in aqueous solution. Investigation shows that the size of the CS copolymer micelles increased with the increase of the content of hydrophobic PCL segments in copolymers, which indicated that the micellar behavior of the copolymers can be controlled by the adjustment of the ratio of PCL and PEO segments in copolymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3476–3486, 2010     

Properties of methyltetrahydrophthalic anhydride‐cured epoxy resin modified with MITU

Methylimidazole‐terminated chain‐extended urea (MITU) containing polypropylene oxide spacer was synthesized and employed to modify epoxies composed of a diglycidyl ether of bisphenol‐A (E‐51) and methyltetrahydrophthalic anhydride (MTHPA). The curing behavior, viscoelastic property, impact response, and fracture surface morphology of the curing systems were systematically investigated. Differential scanning calorimeter (DSC) analysis reveals that the curing reactivity of the epoxy system is greatly enhanced with the addition of MITU. From the dynamic mechanical analysis, besides the low‐temperature β relaxation, shoulder at higher temperature side appears for the MITU‐modified systems. Meanwhile, the addition of MITU leads to the increase of loss factor (tan δ) over the temperature range of 0–75°C. Impact tests show that the modifier can be effective in toughening the epoxy resin at relatively low loading, and the scanning electron microscope (SEM) images of the fracture surface for the modified systems display signs of ductility. Copyright © 2008 John Wiley & Sons, Ltd.     

Study on curing reaction of epoxy resin modified with prepolymers containing spiro orthocarbonate

Prepolymers were prepared by the reaction of 3,9-dihydroxyethyl-3′9′-dibenzyl-1,5,7,11-tetraoxaspiro(5,5)undecane with 4,4′-diphenylmethane diisocyanate (MDI) and 1,6-hexa-methylene diisocyanate (HDI). The number-average molecular weights of the prepolymers can be controlled by changing the mole ratios of spiro compound and diisocyanates. Kinetic studies of the cure reaction for the epoxy resin system modified with or without prepolymers were followed by a HLX-1 dynamic torsional vibration apparatus. The results indicated that gel time (t_g) and activation energy (E_a) increased as the content of prepolymers in the epoxy resin system increased. A difference with the cure reaction of the pure epoxy resin, the second-order reaction for the epoxy resin modified with the prepolymers, was obtained. Rate constants (k) of the cure reaction are 0.231 min^?1 for the epoxy resin, and 0.312 min^?1 for the modified epoxy resin. The mechanism of the cure reaction was discussed. © 1995 John Wiley & Sons, Inc.     

Preparation and properties of waterborne epoxy resin modified by poly(meth)acrylates containing long fluorinated side chains

Abstract

Two waterborne poly(meth)acrylates containing fluorinated side chains (PALF and PASF) were synthesized by conventional radical copolymerization. Then waterborne epoxy composites with hydrophobic surface were obtained through a phase-inversion emulsion technique, using the PALF and PASF acrylates as reactive surface additives. Contact angle measurements and X-ray photoelectron spectroscope were employed to characterize the surface properties and the results confirmed that the fluorine atoms in the longer fluorinated side chains migrated to the outmost layer more efficiently. The effect of the fluorinated content and the length of the fluorine side chain on thermal and bulk properties of the waterborne epoxy resin was investigated. With increasing the fluorinated content or the length of the fluorine side chain, the contact angles and thermal properties improved while the mechanical properties showed no deterioration.     

Preparation and properties of aniline chain-extended thermoplastic epoxy resin using triphenylphosphine as catalyst

Thermoplastic resins have been widely used in fiber reinforced polymer composites because of its recyclability and short cycle times. However, the high viscosity after heating and melting restricts its infiltration on the surface of fiber. In this study, a series of thermoplastic epoxy resins were prepared via the chain extension reaction of epoxy groups with liquid aniline using triphenylphosphine (TPP) as catalyst. The relationship between polymer network structure and performance was comprehensively investigated. The solubility tests indicated that excessive aniline or TPP facilitated the crosslinking of resins. Besides, on the premise of thermoplasticity, appropriate TPP could increase the degree of chain extension, molecular weight, and glass transition temperature of resins. Furthermore, the in-situ polymerization process facilitated infiltration between epoxy resin and the fibers before chain extension reaction. The bending test showed that the flexural performance of the sample with 2 phr of TPP was improved by 38.8%. Therefore, this work provides a feasible method to prepare the thermoplastic epoxy resins and its fiber-reinforced composites with good mechanical properties.     

Microencapsulation of hydrophilic solid powder as a flame retardant with epoxy resin by using interfacial reaction method

Microencapsulation of Bistetrazol · diammonium (BHT · 2NH₃) as a hydrophilic powdery flame retardant was tried by the interfacial reaction method in reverse emulsion. In this microencapsulation method, water droplets containing BHT · 2NH₃ and hydrazine as gelation agent for epoxy resin were dispersed in the continuous phase of corn oil. When epoxy resin was added to the continuous phase, BHT · 2NH₃ as a core material was microencapsulated by the reaction of epoxy resin with hydrazine on the interface between the surface of water droplet and the continuous phase. The content of the core material from 70 to 85%, and the microencapsulation efficiency from 89 to ca 100% were able to be attained under the experimental conditions adopted here. Copyright © 2009 John Wiley & Sons, Ltd.     

基于巯基-烯点击反应制备有机-无机杂化硼酸亲和整体柱用于糖蛋白的选择性富集

发展了以巯基-烯点击反应制备有机-无机杂化硼酸亲和整体柱的新方法。首先以四甲氧基硅烷(TMOS)和巯丙基三甲氧基硅烷(MPTMS)作为反应单体,采用溶胶-凝胶反应制备表面含巯基的硅胶整体柱。然后利用巯基-烯(thiol-ene)的点击反应在整体柱上修饰硼酸配基3-丙烯酰胺基苯硼酸(AAPBA),制成AAPBA-硅胶杂化亲和整体柱。对影响硼酸亲和整体柱性能的条件如TMOS与MPTMS的比例、聚乙二醇和甲醇的用量等进行了优化。并采用扫描电镜、红外光谱等分析仪器对整体柱形貌和机械稳定性能进行了表征。研究了AAPBA-硅胶杂化亲和整体柱的分离性能,结果表明,其在中性条件下对含有顺式二醇的生物小分子核苷具有良好的特异亲和能力,并已成功地应用于卵清蛋白、辣根过氧化物酶等糖蛋白的分离。基于巯基-烯反应的制备方法新颖、可靠,可用于制备多种不同类型的硼酸亲和整体柱,具有较大的应用前景。     

Synthesis of an amphiphilic spiro-multiblock copolymer via thiol-ene click chemistry

A multiblock [poly(ethylene oxide)-b-spiro-polystyrene] ([(PEO-b-spiro-PS)]) copolymer with a topologically novel architecture was synthesized using thiol-ene step-growth polymerization reaction. Spiro-PS with dimercapto groups as the hard segment was synthesized in three main steps: (a) preparation of tetra-arm PS by atom transfer radical polymerization and the conversion of the chain-end group to azide functionality, (b) alkyne-azide click coupling reaction to synthesize a tricyclic PS, and (c) tactical ring opening of the tricyclic PS through disulfide/thiol redox reaction. The PEO soft segment was obtained as chain-ends modified with norbornene groups. Finally, the hydrothiolation of the highly reactive norbornene chain-ends of polyethylene glycol with the dimercapto groups of spiro-PS produced the multiblock ([(PEO-b-spiro-PS)]) copolymer in quantitative yield. The multiblock copolymer was characterized using size-exclusion chromatography, proton nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 132–138     

Transparent and toughening epoxy thermosets modified by linear telechelic polymer containing rigid spiroacetal moieties: Uncovering the relationship between the heterogeneous crosslinked network and thermoset performances

Spiroacetal moieties containing linear telechelic polymers (LTPs) with two terminal epoxy groups were facilely synthesized via the successive thiol-ene and thiol-epoxy click additions. The LTPs were incorporated into epoxy matrix to fabricate the transparent and toughening thermosets. In term of the miscibility of epoxy with the adduct of ethanedithiol and 3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane (BTU), it is proposed that the size of the formed nanostructures was small enough to allow light penetrate. Therefore, the modified thermosets were transparent, which was further confirmed by small-angle X-ray scattering (SAXS) measurements. The LTPs with an alternating structure of rigid spiroacetal moiety and soft thioether could formed heterogeneous crosslinked networks (HCNs) and obviously toughen epoxy thermosets. Flexural strength increased from 1.06 GPa for neat epoxy to 2.09 GPa for toughening thermosets modified with 15 wt% LTPs. The stress field intensity (K_IC) value reached up to 3.93 by more than 125% compared with that of the control sample (1.75). This work uncovered the role of HCNs on performance and paved a way for technological advances toward transparent and toughening materials in epoxy thermosets.     

Thermal stability and toughening of epoxy resin with polysulfone resin

The cure behavior, thermal stability, and mechanical properties of diglycidylether of bisphenol A (DGEBA)/polysulfone (PSF) blends initiated by 1 wt % N‐benzylpyrazinium hexafluoroantimonate as a cationic latent catalyst were investigated. The DGEBA/PSF content was varied within 100/0–100/40 wt %. Latent properties were studied through the measurement of the conversion as a function of the curing temperature, and the cure activation energy (E_a) was studied by the Kissinger method with a dynamic differential scanning calorimetry analysis. The thermal stabilities, largely based on the integral procedural decomposition temperature (IPDT) and decomposed activation energy (E_t), were investigated by the measurement of thermogravimetric analysis. For the mechanical properties of the casting specimens, the critical stress intensity factor (K_IC) test was performed, and their fractured surfaces were examined with scanning electron microscopy. E_a, IPDT, E_t, and K_IC increased with PSF increasing in the neat epoxy resin up to 30 wt %. However, there was a marginal decrease in the blend system in both the thermal and mechanical properties due to the phase separation between DGEBA and PSF. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 121–128, 2001     

Surface modification of carbon black by thiol-ene click reaction for improving dispersibility in aqueous phase

Carbon black (CB) particles were firstly encapsulated by γ-Methacryloxypropyltrimethoxysilane (MEMO) using a sol-gel method and then grafted with sodium 3-Mercapto-1-propanesulfonate (MPS) via thiol-ene click reaction. Morphology characterization reveals that modified CB particles have a core-shell structure. Element composition and chemical status derived from X-ray photoelectron spectroscopy (XPS) results prove the grafting of MPS molecules. Moreover, the crystal structure and thermal behavior of modified CB particles were characterized by Raman spectra and Thermogravimetric analysis (TGA) curves, respectively. The modified CB particles exhibit excellent self-dispersing ability in aqueous media and the dispersion has high thermal and centrifugal stability. This research provides a new insight into the preparation of inkjet printing ink with excellent stability.     

Synthesis and curing of new aromatic azomethine epoxies with alkoxy side groups

Four new aromatic epoxies containing azomethine unit as a backbone linkage and alkoxy group as a flexible side chain were synthesized and characterized by means of IR and NMR spectrometry, and differential scanning calorimetry (DSC). The carbon number (n) of the alkoxy group was varied from hexyloxy (6) to nonyloxy (9). The cure kinetics for an epoxy/diamine-system was investigated by a DSC technique. From a multi-temperature scan method, developed by Ozawa and Kissinger, the activation energy (E) and the frequency factor (A) were determined and compared for the epoxies with different lengths of alkoxy group. The E and A value from Kissinger method are higher than those from Ozawa method for all side chain lengths. Each method shows that E increases slightly but A increases greatly when the length of the side chain increases. The large increase in A overriding the small increase in E may lead to the acceleration of the cure reaction as the side chain becomes longer.     

Using click reaction to covalently link heterogeneous gold nanorods into head-to-head one-dimensional chains with an alternating sequence as plasmonic Fano resonators

We present the deterministic linkage of short and long gold nanorods into one-dimensional (1D) alternating nanorod chains in a head-to-head manner using click reactions. By precisely controlling the surface chemistry, we achieve orientation-specific and robust covalent linkage between nanorods with high-product yield. The optical response of the alternating nanorod chains exhibits Fano-like resonances. This method enables the high-throughput production of covalently linked plasmonic particle networks consisting of heterogeneous nanoparticles with specifically chosen spectral responses.     

液晶环氧p-PEPB的合成及改性双酚-A环氧树脂的研究

本文以对羟基苯甲酸乙酯、丙烯溴、对苯二酚等为原料合成了双4-环氧丙基醚苯甲酸对苯二酚酯液晶环氧树脂(p-PEPB).用IR、1HNMR、DSC、POM和XRD的对其进行了表征,结果表明该化合物为向列型液晶,其熔点为180℃,清晰点为250 ℃.研究了 p-PEPB/双酚-A环氧(BPAER)/4,4,-二氨基二苯醚(DDE)体系的非等温固化过程,得到了固化温度参数、表观活化能Ea及p-PEPB含量对Tg的影响,结果表明p-PEPB为5%可使BPAER的Tg提高14 ℃,固化过程服从Ozawa模型.     

Synthesis and characterization of a novel cycloaliphatic epoxy resin starting from dicyclopentadiene

A novel tri-functional cycloaliphatic epoxy resin was synthesized starting from dicyclopentadiene. The chemical structures of the resultant epoxy resin and its precursor were characterized with FTIR spectroscopy, EEW, ¹H NMR and Mass spectrographic analyses. The thermal and mechanical properties of the resulting polymer were evaluated with differential scanning calorimeter (DSC), thermo-gravimetric and thermal mechanical analysis. Compared to that of the common cycloaliphatic epoxy resin ERL-4221, the cured polymer of the novel epoxy resin exhibited lower thermal degradation temperature with much higher char yield and similar thermal expansion coefficient. These excellent overall performances make it a promising packaging material.     

Synthesis and curing of liquid crystalline epoxy resin based on naphthalene mesogen

Aromatic liquid crystalline epoxy resin (LCE) based on naphthalene mesogen was synthesized and cured with aromatic diamines to prepare heat‐resistant LCE networks. Diaminodiphenylester (DDE) and diaminodiphenylsulfone (DDS) were used as curing agents. The curing reaction and liquid crystalline phase of LCE were monitored, and mechanical and thermal properties of cured LCE network were also investigated. Curing and postcuring peaks were observed in dynamic DSC thermogram. LCE network cured with DDE displayed liquid crystalline phase in the curing temperature range between 183 and 260°C, while that cured with DDS formed one between 182 and 230°C. Glass transition temperature of cured LCE network was above 240°C, and crosslinked network was thermally stable up to 330°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 419–425, 1999     

Rigid-rod polymers with polysiloxane side chains. I. Synthesis and characterization of rigid-rod polyimides with polysiloxane side chains and their compatibility with linear polysiloxanes

Rigid-rod aromatic polyimdies having polydimethylsiloxane side chains were prepared for the purpose of dispersing rigid-rod molecules in silicone matrices for molecular reinforcement. The polyimides were obtained by imidizing the polyamide-acids bearing the side chains either thermally or chemically, which were synthesized by reacting 4,4′-diaminobiphenyl-terminated polysiloxane macromonomers with pyromellitic dianhydride in THF. The polyamide-acid films obtained by removing the solvent were soluble in THF, but the polyimides were insoluble in any common solvent. The polyimides showed no melting transition below 350°C on DSC analysis, at which temperature the side chain started decomposing. Although all the polyimides were anisotropic as observed by a polarizing microscope, x-ray diffraction analysis suggested the presence of only limited chain organization. Blends with linear polydimethylsiloxanes were prepared by casting the THF solution containing the polyamide-acid and the polydimethylsiloxane, followed by solvent evaporation and thermal imidization. With relatively longer side chains, the polyimides were proved to be compatibilized with polydimethylsiloxanes. © 1994 John Wiley & Sons, Inc.     

Rigid-rod polymers with polysiloxane side chains. 2. Synthesis and characterization of aromatic polybenzobisoxazoles with polysiloxane side chains and composite formation with polysiloxane matrices

Aromatic polybenzobisoxazoles, having polydimethylsiloxane side chains (SCPBOs), were prepared using terephthaloyl chloride-terminated polydimethylsiloxane macromonomers and 3,3′-bis(trimethylsiloxy)-4,4′-bis(trimethylsilylamino)biphenyl for the purpose of dispersing rigid-rod molecules in silicone matrices for molecular reinforcement. The degree of polymerization of the side chain was varied from 7.8 to 45.4, and a small amount of (3-butenyloxy)terephthaloyl chloride was copolymerized to give the polymers a functionality that can be linked to the matrices. For all the SCPBOs, the WAXD pattern showed only diffuse reflections, suggesting limited structural regularity, although the polymers were optically anisotropic. No melting transition was observed below the side chain decomposition temperature, 350°C. A polydimethylsiloxane/polybenzobisoxazole composite elastomer was obtained first curing the polysiloxane matrix containing the prepolymer of the SCPBO, followed by in situ thermal ring closure of the prepolymer. Some reinforcement was observed, but the presence of plasticizing effect by the unbound SCPBO was suggested at the same time. © 1995 John Wiley & Sons, Inc.     

Effects of thiol-ene click reaction on morphology and electro-optical properties of polyhedral oligomeric silsesquioxane nanostructure-based polymer dispersed liquid crystal film

Polymer dispersed liquid crystals (PDLCs) have lit a flash of interest due to the distinctive property of electrically controlled switching. However, too high-driving voltage associated with porous polymer networks always limit their wider range of applications. Herein, we reported a PDLC system containing LCs, 2,2′-(Ethylenedioxy)diethanethiol (DET) with thiol groups, cage-like nanostructure acrylic polyhedral oligomeric silsesquioxane (KH570-POSS) and KH570-SiO₂ nanoparticle modified by acrylic groups. The cage-like KH570-POSS microstructure was injected to the polymer matrix when KH570-POSS reacted with DET via thiol-ene click reaction. The morphological results demonstrated that the droplet size increased with the higher content of DET due to the decrease of the crosslink between the acrylic groups in KH570-POSS, which results in a less dense of polymer network and thus make the LC droplets easier to be driven in the electric filed. Then, a silica-based nanoparticle KH570-SiO₂ modified by acrylic groups was introduced into the system. The results indicated that KH570-SiO₂ could replace partial KH570-POSS to form the polymer network via thiol-ene click reaction, which increased the compatible ability of SiO₂ nanoparticles in the as-made film. The contrast ratio was increased to 165 when there was nearly 5 wt% content of KH570-SiO₂. Besides, the driving voltage was reduced by almost 60% and the sample could be fully driven by 30 V which is lower than the safe voltage (36 V). This study opens a route for the preparation of commercial PDLC films by thiol-ene click reaction, enabling the creation of low-voltage-driven smart windows.