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Chirality is one of the most common and significant phenomenon in nature, and epoxy resin is one of the most widely used and researched thermosetting resins, however the influences of chiral carbon in epoxy group on the performances of the cured epoxy resins have ever been hardly studied, therefore it is crucial and meaningful to explore the structure–function relationship of chirality and performance of epoxy resins. Herein, from the analysis of synthesis mechanism, the different chiral configuration with high percent enantiomeric excess (>99%) and racemic bisphenol A epoxy resins were simply prepared by controlling the chirality of epichlorohydrin. The apparent activation energy of the curing process with D230 was calculated by Kissinger method and Flynn–Wall–Ozawa method, respectively, and both results indicate that chirality have no effect on the curing reaction. We found that the secondary structure of epoxy monomer is untouched by its chirality, and they are all right helix structure. For this reason, the thermal stability, glass transition temperature, and thermomechanical properties of diverse chiral epoxy resins cured by D230 have no significant difference. Nevertheless, it was found that the optical rotation activity of chiral epoxy resins can be partially maintained after curing reaction, it manifests the cured products of chiral epoxy resins possesses the possibility of application in the field of polarized materials. [ABSTRACT FROM AUTHOR]

Bio‐based epoxy resins with low‐dielectric constant, low viscosity and excellent mechanical properties have great significance for the future of advanced electronic and microelectronic industries. Cyclosiloxane segment possesses low polarity, high‐dissociation energy, and elevated molecular volume, thereby making it useful for the synthesis of materials with low dielectric constant and viscosity. Herein, a tetrafunctional eugenol‐based epoxy resin (DEP) based on a cyclosiloxane structure was designed and prepared through a hydrosilylation reaction. Allyl glycidyl ether (AGE) was selected as a reference compound and generated a silylation epoxy resin (AGDEP). The viscosity of these silicone‐containing tetrafunctional epoxy monomers (< 0.315 Pa·s) was significantly lower than that of the conventional oil‐based epoxy resin (14.320 Pa·s). After curing with methyl hexahydrophthalic anhydride (MHHPA), the dielectric constant of DEP‐MHHPA was as low as 2.8 (10 MHz), which was superior to that of EP‐MHHPA. Notably, the glass transition temperature (Tg) of DEP‐MHHPA was as high as 100.3°C. The tensile strength and elongation at break of DEP‐MHHPA were estimated to be 66.1 MPa and 6.0%, respectively. Multifunctional eugenol‐based epoxy monomers with low‐dielectric constant and viscosity provide an efficient guideline for building epoxy‐based materials to better design future‐oriented engineering materials. [ABSTRACT FROM AUTHOR]

A novel high purity dual-functional epoxy monomer, diglycidyl ether of 4,4′-diallyl-bisphenol-A, is deliberately designed for the construction of a fishbone-shaped heterochain polymer by polymerizing it with the methyl phenyl polysiloxane. Their curing reactions with Jeffamine D230 are investigated. The cured fishbone-shaped heterochain polymer presents a wide transition range spanning over 120 °C with a peak half-width of 62 °C. In contrast to the traditional epoxy/polysiloxane materials, the cured fishbone-shaped heterochain polymer takes full advantage of the cooperative effect of epoxy and polysiloxane exhibiting excellent damping properties (tan δ > 0.3) at temperatures near the Tg of the polysiloxane. This outstanding low-temperature damping performance can be ascribed to the fishbone-shaped structure of the heterochain polymer. These results provide new approach to explore high damping materials used at extremely low temperature (−125 °C). [ABSTRACT FROM AUTHOR]

A series of regular and tunable rigid-flexible crosslinking networks have been prepared to investigate shape memory effects. The tunable rigid-flexible epoxy resins (TRFEPs) were synthesized by ultraviolet light thiol-ene click chemistry. The FTIR and H NMR measurements indicated that TRFEPs were successfully synthesized. The thermal, thermomechanical, mechanical, and shape memory properties of all regular crosslinking networks were systematically investigated by DSC, DMA, tensile test, and quantitative shape memory evaluation method, respectively. It was found that with the flexibility of the crosslinking networks increasing, T , T , E′ (25 °C), shape recovery rate, and tensile stress decreased and elongation at break increased. Besides, DMA measurements showed that the regular network had relatively narrow glass transition zone. The tunable rigid-flexible crosslinking networks exhibited a ductile plastic fracture feature with the occurrence of yielding phenomenon and had relatively high tensile strength (20-44 MPa). Quantitative shape memory evaluation disclosed that the regular crosslinking networks exhibited excellent shape memory performance with high shape memory fixity (>97 %) and shape memory recovery (>99 %). Especially, it was discovered that the regularity of network was the primary effect factor and the flexibility was the subordinate effect factor on the shape recovery rate. Excellent shape memory properties and great mechanical properties make the materials good candidates for space deployable structure materials and wide applications in other important fields. [ABSTRACT FROM AUTHOR]

Supported polymer film models based on epoxy resin networks with four different cross-linking densities and silica substrates have been established using molecular dynamics simulations. Van der Waals forces in the form of Lennard-Jones 9-6 are applied in calculating the interfacial interactions between the polymer and substrate. The existence of the interphase adjacent to the substrate surface was confirmed by carrying out density profile. Detailed analyses including mean square displacement and radial distribution functions of the structural properties of interphases for the four models were performed and compared. It was found that, with increasing the cross-linking density, the polymer sticks to the substrate more tightly, accompanied by stronger interactions arising from more hydrogen bonds formed between them. Furthermore, the mechanical properties of the interphase were found to be enhanced with the conversion by carrying out tensile deformation. This research regarding the interphase region within supported ultrathin epoxy films will be helpful in understanding the effect mechanism of nanofillers in the epoxy nanocomposites. [ABSTRACT FROM AUTHOR]

Allyl-based epoxy resin/Sulfur (S) system is a facile and novel dual-curing system which conducts a unique curing mechanism. In this paper, Bisphenol-A diglycidyl ether (BADGE) and 2-Allylphenol (OAP) cured by S were comparatively investigated to clarify the dual-curing mechanism of Epoxy (EP)/Allyl Compound (AC)/S system. When the temperature was above 170 °C, DSC and FTIR data showed that S could cleave to form thiyl radicals, and FTIR, NIR, and H NMR measurements proved the disappearance of allyl groups and the generation of thiol groups by the thiyl radicals abstracting α-H atoms of allyl groups in the OAP/S reaction system. Real-time infrared spectroscopy (RT-FTIR) results showed that the reaction of the generation of thiol groups is the dominant reaction in the two possible pathways of the OAP/S system; allyl groups and epoxy groups disappeared sequentially in the OAP/S/BADGE system. DSC curve also revealed the one-stage reaction for OAP/S system and two-stage reaction for OAP/S/BADGE system. These data were used to develop a detailed, experimentally validated pathway for the dual-curing of EP/AC/S system, in which thiol groups are important intermediate, and the dual-curing process included the crosslinking of double bonds that initiated by thiyl radicals and the ring-opening reaction of epoxy groups with thiol groups. Besides, the dual-curing mechanism of EP/AC/S system shares a close resemblance to the classical rubber vulcanization mechanism and the recent thiol-ene radical addition mechanism. [ABSTRACT FROM AUTHOR]

In this study, bi-, tri-, and tetra-functional epoxy systems were chosen to design network structures using hexahydrophthalic anhydride as curing agent and tris-(dimethylaminomethyl) phenol as accelerant with bifunctional 1,4-butanediol diglycidyl ether as the flexible reactive diluents to further adjust the network structure. The cross-link density and activation energy (Ea) of glass transition were calculated by dynamic mechanical thermal analysis (DMTA) data. The packing of molecular chain and average distance between molecular chains were analyzed by DMTA and X-ray diffraction measurements, respectively. As a result, the loss modulus, glass transition temperature (Tg), cross-link density, average distance between molecular chains and Ea were found to be positively correlated with the degree of functionality. Meanwhile, the storage modulus of cured epoxy products at glass state was found to vary as follows: diglycidyl ether of bisphenol F (DGEBF) > tetraglycidyl diaminodiphenylmethane > triglycidyl-p-aminophenol (TGPAP). The loading of diluents decreased Tg and Ea and increased the storage modulus at glass state of DGEBF and TGPAP systems. [ABSTRACT FROM AUTHOR]

The curing kinetics of the hexahydro-4-methylphthalic anhydride (MHHPA)/diglycidyl 1,2-cyclohexane dicarboxylate (CY184) epoxy resin system and MHHPA/CY184 epoxy/episulfide resin system (containing 2 mass% DMP-30 as an accelerator) was comparatively investigated by non-isothermal differential scanning calorimetry with a model-fitting Málek method and a model-free advanced isoconversional method of Vyazovkin, and the curing behavior was discussed based on the proposed curing mechanism. The results indicated that both of the MHHPA/CY184 epoxy resin system and MHHPA/CY184 epoxy/episulfide resin system fitted Šesták-Berggren model. The activation energy of MHHPA/CY184 epoxy/episulfide resin system was lower than that of MHHPA/CY184 epoxy resin system, suggesting that the episulfide resin has higher reactivity and can accelerate the reaction. The value of m in the kinetic model equation in MHHPA/CY184 epoxy/episulfide resin system is much smaller than that in MHHPA/CY184 epoxy resin system, indicating, unlike the MHHPA/CY184 epoxy resin system, MHHPA/CY184 epoxy/episulfide resin system has much less autocatalytic effect. [ABSTRACT FROM AUTHOR]

A diglycidylether of propoxylated bisphenol-A with two oxypropylene units (DGEBAPO-2) was prepared, and the structure was characterized by FTIR, H NMR, and ESI-MS, and a flexible curing agent 2-methyl-1,5-pentanediamine (MPDA) was used to obtain an intrinsically toughened network for potential shape-memory application. The curing kinetics of DGEBAPO-2/MPDA was systematically investigated by using both non-isothermal and isothermal DSC methods; in addition, the dynamic mechanical property, mechanical property, and shape-memory property were investigated by DMA, tensile experiment, and quantitative shape-memory evaluation method. The results showed that Šesták-Berggren model and Kamal model were able to well describe the non-isothermal curing reaction rate and isothermal curing reaction rate, respectively. Tensile test at 49 °C indicated that the cured DGEBAPO-2/MPDA combined a relatively large elongation at break of 95.53 ± 2.27 % with a relatively large tensile stress of 6.33 ± 0.11 MPa. Quantitative shape-memory evaluation revealed good shape-memory properties of cured DGEBAPO-2/MPDA with shape fixity of 98.88 ± 0.04 % and shape recovery of 96.67 ± 6.91 %. [ABSTRACT FROM AUTHOR]

A series of intrinsically toughened shape memory epoxy resins (SMEPs) were prepared by curing two bisphenol-A type epoxy resins containing two and six oxyethylene units (DGEBAEO-2 and DGEBAEO-6) with hexahydrophthalic anhydride in the presence of tris-(dimethylaminomethyl) phenol. The thermal, thermomechanical, mechanical and shape-memory properties of these SMEPs were systematically investigated by DSC, DMTA, tensile test and fold-deploy shape memory test, respectively. DSC and DMTA experiments showed that as the concentration of the DGEBAEO-6 increased, the glass transition temperature and storage modulus in the rubbery plateau of the SMEPs decreased gradually. The tensile stress at yield also decreased with increase in the relative content of DGEBAEO-6 and all the SMEPs exhibit a ductile fracture feature with the appearance of yielding, according to the uniaxial tensile test. The fold-deploy shape memory test showed that all the SMEPs showed a good shape memory effect with a combination of relatively high shape fixity and shape recovery. [ABSTRACT FROM AUTHOR]

A novel kind of bisphenol-type epoxy resin with a vinyl side-chain was developed and its miscibility behavior with liquid nitrile-butadiene rubber (NBR) was investigated. The diglycidyl ether of bisphenol propylene (DGEBP) was prepared by the condensation of phenol with acrolein in the presence of an acid catalyst and the subsequent epoxidization with epichlorohydrin (ECH). The structures of the bisphenol and corresponding epoxy resin were characterized by infrared (IR) and nuclear magnetic resonance (NMR) spectral analyses and the epoxy value was determined to be 0.34 mol/100 g by titration. The mixture of DGEBP with the liquid NBR containing diglycidyl ether of bisphenol acetone (DGEBA) was prepared and cured with diaminodiphenylmethane (DDM). The miscibility and morphology of the mixture system were studied by dynamic mechanical thermal analysis (DMTA) and transmission electron microscopy (TEM), respectively. The cured mixture of DGEBP/NBR/DDM exhibited good miscibility and, therefore, no separation, along with a transparent appearance at rubber contents of 10 wt% and 30 wt%. For cured DGEBP/DGEBA/NBR/DDM systems at 20 wt% rubber content, the dispersed rubber phase and rubber particles were not observed by DMTA or TEM at DGEBP content above 40 wt%. The DMTA plot showed a single peak related to the glass transition temperature (Tg) which decreased with increasing DGEBP content. The appearance of the system varied from transparent to opaque and the rubber separated from the epoxy matrix to form two phases when the DGEBP content decreased. The Tg values of the rubber- and epoxy-rich phases were strongly dependent on the DGEBP content in the mixed system. The miscibility of epoxy resin with liquid NBR can be altered by varying the ratio of DGEBP to DGEBA. [ABSTRACT FROM AUTHOR]

Since its first report in 2011, researches on vitrimer transesterification catalyst systems had been gradually focused on three aspects: low toxicity and low corrosion, good compatibility with resin matrix, and high catalytic performance for bond exchange reactions. However, it is difficult to obtain a catalytic system that can simultaneously meet the above three expectations. This research conducted the preparation of autocatalytic transesterification epoxy vitrimers by directly mixing small tertiary amine molecules with epoxy-anhydride systems and covalent incorporating tertiary amine structures into curing systems. And the influence of tertiary amine structures and covalent incorporation on the various properties of vitrimers was also discussed. A tertiary amine promoter composed of isofunctional group ratio reaction from di-n-hexamine and epoxy resin provided by this research overcame the problem of poor compatibility between tertiary amine and epoxy resin, introduced a highly active catalytic structure into vitrimer curing system. And the result indicated that the vitrimer prepared according to our new strategy had excellent comprehensive performance. In conclusion, a new idea of covalent incorporation was proposed to provide ideas and inspiration for the development of new tertiary amine-based autocatalytic transesterification epoxy vitrimers. [Display omitted] • We proposed a strategy for the preparation of transesterification vitrimers containing self-atalytic structures by using pre-reaction products of epoxy resins with secondary amines with equal functional group ratios. The effects of tertiary amine structure and covalent integration on the performance of vitrimers were obtained. • The test results of a series of vitrimer materials showed that the vitrimer prepared according to this new strategy, namely the 10DGEBA+(1DGEBA+2DnHA)+20 GA system, had excellent comprehensive performance. • The data and conclusions obtained in this paper will provide guidance and reference for the development of self-catalytic vitrimers and composites based on tertiary amine structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of cross-linking network on enthalpy value of polymeric FSPCMs was revealed. • Polarity effect and steric hindrance effect greatly affect phase change properties. • Optimized CNT modified epoxy/beeswax PCM exhibits multifunctionalization. High encapsulation rate resulting from the good compatibility between cross-linking network and encapsulated solid–liquid phase change materials (SLPCMs) cannot necessarily result in high enthalpy value for the polymeric PCMs. However, the inner mechanism considering the above fact is not clear due to the lack of suitable model compound systems. In this work, a type of epoxy resin with crystalline alkyl side chains (named D18) and four types of amine curing agents (with similar structure but different polarity and molecular size) were primarily used as the model compound to achieve the encapsulation of beeswax (Bw, a kind of bio-based wax), and then the influence of the cross-linking network structure (using different curing agents) on the phase change performances of the D18/Bw polymeric form-stable PCMs (FSPCMs) was systematically studied. The results suggest that polarity effect and steric hindrance effect are the two factors that affect the phase change performances of the polymeric FSPCMs. Though the encapsulation rate of Bw is the highest (near 70 wt%) in the EP H-Y systems (using 1,3-Cyclohexanebismethylamine as the curing agent), it is the EP M-60 sample (using M−Xylylenediamine as the curing agent and containing 60 wt% Bw) that exhibited the highest enthalpy value of 146.2 J/g. Subsequently, different amount of multi-walled carbon nanotubes (CNT) was introduced to improve the thermal conductivity (TC) and achieve multifunctionalization of the EP M-60 sample. The TC, electromagnetic interference (EMI) shielding performance, and contact angle of the 30 wt% CNT modified EP M-60 sample can reach 1.37 W/mK, 37.4 dB, and 137°, while the enthalpy value can remain 101.1 J/g. This work is very helpful in clarifying the relationship between cross-linking network structure and phase change performances of polymeric FSPCMs, so as to providing theoretical guidance for the cross-linking network structure optimization in preparing other reliable polymeric FSPCMs with high enthalpy value, high reliability, and multifunctionalization. [ABSTRACT FROM AUTHOR]

At present, the demand for green energy has reached a new height in history, and thermal energy storage technology has been widely used to reduce energy consumption. It is still a challenge to develop bio-based polymeric form-stable phase change materials (FSPCMs) with high enthalpy value and thermal conductivity (TC), short curing time, and multifunctional properties. This work not only exploited a series of adjustable and photo-curable comb/bottle brush bio-based epoxy resin/beeswax (bw) FSPCMs with the above superiorities, but also revealed the effects of cross-linking density on the energy storage capacity and encapsulation rate of the FSPCMs. As a result, the optimal system can encapsulate the maximum amount of bw (60 wt%) and obtain the highest enthalpy value (142.1 J/g) with only 0.5% enthalpy loss. Through further introducing the optimal curing system into the copper (Cu) foam, the electromagnetic interference shielding property, TC, tensile strength, and photo-thermal conversion efficiency of the final composite (modified by Cu of 95% porosity) can reach 110 dB, 2.387 W m−1K−1, 2.81 MPa, and 80%, respectively, and the enthalpy value (84.2 J/g) is still satisfactory. This study can provide theoretical guidance for the structural design of reliable fast photo-curable bio-based polymeric FSPCMs with excellent phase change performances and multifunctional properties. [Display omitted] [ABSTRACT FROM AUTHOR]

The silver migration limits the application of silver based conductive adhesives in wet environment. The existing methods for inhibiting silver migration in epoxy conductive silver adhesives involve one or more issues such as cost, complexity, and inhibition of conductivity. Moreover, there is currently a lack of strategies that can suppress the silver migration effect while ensuring good dispersion of silver fillers in the matrix and constructing a good filler matrix interface. Herein, a facile method was reported suppressing the silver migration in silver-epoxy conductive adhesive. Tetrafunctional thiopentaerythritol tetramercaptoacetate (PERTMA) was introduced into 1,4-cyclohexanedimethanol diglycidyl ether (CHDMGE) epoxy resin as the curing agent. This method utilized the strong interaction between silver and thiols, including coordination and covalent bonding, to achieve good compatibility between filler and matrix. By tightly combining silver with the resin system, the content of free silver atoms was reduced, capturing and inhibiting the hydrolysis of silver atoms and their migration with current, and the conductivity of the conductive silver adhesive was not greatly degraded due to the silver-thiol interaction. At the same time, the introducing of PERTMA was able to reduce the surface hydrophilicity of epoxy resin, which also helped suppressing the silver migration effect under humid circumstances. The interaction between silver and thiol was characterized, and the influence of silver content on the curing behavior, material mechanical performance, conductivity, resistivity on silver migration and flexibility was explored. The CHDMGE/PERTMA/Ag conductive adhesive based on strong thiol-silver interaction had excellent resistance to silver migration, which occurred after 3500s, which was 10.67 times longer than the control group. In addition, the silver filler enhanced the tensile strength of the matrix resin by this thiol-silver interaction. This study will provide new ideas for the design and development of silver migration resistant conductive adhesives based on matrix filler interaction. [Display omitted] • We applied tetrafunctional thiopentaerythritol tetramercaptoacetate (PERTMA) as the curing agent of 1,4-cyclohexanedimethanol diglycidyl ether (CHDMGE) epoxy resin to suppress the silver migration rate of silver-epoxy composite by forming strong filler-matrix interaction. • We characterized the interaction between silver and thiol by FTIR and XPS, and explored the influence of silver content on material mechanical performance, conductivity, silver migration and flexibility. • The strong interaction between thiol and silver enhanced the binding between silver powder and resin matrix, making it less prone to silver migration. • Our research provides new perspective for the constructing of silver-epoxy composites with suppressed silver migration rate. [ABSTRACT FROM AUTHOR]

It is a longstanding bottleneck for epoxies applied in high-tech fields to obtain integrated performances, including excellent thermal mechanical and stability properties, hydrophobicity, low permittivity and curing activation energy. A novel epoxy monomer with stiff tetrafluorophenyl backbone and robust intramolecular/intermolecular forces is expected to fundamentally break through this challenge. Herein, three model epoxy monomers with different symmetrical para-hexatomic ring blocks were synthesized, including tetrafluorophenyl-based (FEP), phenyl-based (TEREP) and cyclohexyl-based (CEP), followed by curing with methylhexahydrophthalic anhydride (MeHHPA) and polyetheramine (D230), respectively. As expected, TEREP showed better thermal mechanical properties than CEP due to closer stacking density and electronic effect. Noticeably, FEP self-consistently showed the best comprehensive properties among three resins, which mainly benefited from the introduced C–F bonds and the unique electronic effect caused by tetrafluorophenyl. Moreover, the exhilarating results of tetrafluorophenyl para-hexatomic ring provide an efficient guideline for building epoxy-based material genomes to better design future-oriented engineering materials. Image 1 • A novel epoxy resin with tetrafluorophenyl para-hexatomic ring (FEP) was prepared firstly. • The effect of tetrafluorophenyl was systematically studied by comparing with para-hexatomic ring: phenyl and cyclohexyl. • FEP exhibits excellent thermal mechanical and stability properties, hydrophobicity as well as exceptional low permittivity. • FEP-MeHHPA possesses lower curing activation energy than model systems. [ABSTRACT FROM AUTHOR]

• Porous epoxy resin was fabricated via UV irradiated CFA. • Porous size was tunable from 1 mm to tens nm. • Curing extent was evaluated in the real time. The fabrication of submicro/nano porous thermosetting resin with defined cell size and distribution remains a challenge. Diazirine was induced into the epoxy resin matrix as the on-demand UV initiated chemical foaming agent (CFA) under room temperature. Cell dimension became tunable ranging from around 1 mm to tens nm by varying the matrix curing extent when the UV took effect. Curing extent of the matrix was monitored by measuring the rheological properties in the real time. UV foaming showed the potential to be used for the control of cell morphology in porous thermosetting materials. [ABSTRACT FROM AUTHOR]

• BPA, TCBPA, and TBBPA were used as latent hardeners in adhesives with bisphenol A epoxy resin as matrix. • Imidazole was selected as the accelerator which is stable and non-catalyzed at room temperature. • Curing temperature of EP-BPA, EP-TCBPA, and EP-TBBPA systems can reduced to 126 ℃, 94 ℃, and 106 ℃, respectively. • The as-prepared single component epoxy adhesives are stable and the shelf life for all three systems is five months at least. • Kinetic parameters of curing reaction of all three systems were obtained and their mechanisms were understood. As a representative single component epoxy resin, diglycidyl ether of bisphenol A resin (DGEBA) is the most widely used matrix in adhesives. However, challenges are still remained including high curing temperature and short shelf life. Herein, bisphenol A (BPA), Tetrachlorobisphenol A (TCBPA), and Tetrabromobisphenol A (TBBPA) as latent curing agents and imidazole as accelerator were used in adhesives. Curing kinetics was studied by non-isothermal DSC, using a model-fitting Málek approach and a model-free advanced isoconversional method of Vyazovkin. Results indicated that curing temperature of EP-BPA, EP-TCBPA, and EP-TBBPA was reduced to 126 ℃, 94 ℃, and 106 ℃, respectively. Storage stability evaluated by DSC indicated the shelf life was up to five months. After curing, molecular weights of the as-prepared linear polymers (EP-BPA, EP-TCBPA, and EP-TBBPA) were 33,822 g/mol, 14,913 g/mol, and 18,846 g/mol, and their tensile strength and shear strength were more than 40.06 MPa and 13.64 MPa, respectively. [ABSTRACT FROM AUTHOR]

In this study, molecular dynamic simulation and experiment study are combined to explore the main control factors of dielectric constant of Dicyandiamide cured epoxy resin. The density and glass transition temperature obtained by experiment and simulation were compared to verify the rationality of simulation models. Then dielectric constant was calculated by dipole fluctuation formula, here motion mobility, polarity, and free volume were employed to interpret the influence mechanism of conversion on dielectric constant. Results indicate that before gelation the dielectric constant is controlled by the content of unreacted monomers especially dicyandiamide, and after gelation it is dominated by the segmental mobility, hydroxyl group density and free volume, where the influence of segmental mobility is more significant than that of free volume and hydroxyl group density. [Display omitted] • Molecular dynamics simulation and experiment have good consistency in the changing trend. • The control factors of the dielectric properties change significantly before and after gel. • At high crosslinking degree, the influence of segment motion ability on dielectric constant is most significant. [ABSTRACT FROM AUTHOR]

The neat episulfide of benzyl thiirane ether (BTE) resin was synthesized by the reaction of benzyl glycidyl ether (BGE) epoxy resin and KSCN under the microwave atmosphere at low temperature. The ring opening kinetic behaviors of neat BGE and neat BTE with polyether amine (D230) as the hardener were comparatively investigated by non-isothermal differential scanning calorimetry(DSC), and analyzed by the model-fitting Málek method and the model free advanced iso-conversional method of Vyazovkin. The results indicated that both BGE/D230 and BTE/D230 systems fitted Šesták–Berggren model well. The activation energy of neat BTE/D230 system (43.2 kJ/mol) was much lower than that of neat BGE/D230 system (58.7 kJ/mol ). And, the m value in the Šesták–Berggren kinetic model equation for BTE/D230 system ( m = 0.1902) is much higher than that for BGE/D230 system ( m = 0.0512), indicating BTE/D230 system has much more autocatalytic effect and/or a secondary reaction initiated by the sulfhydryl groups, which generated from the ring-open reaction of thiirane groups. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bio-based solid–solid phase change polymer material was successfully prepared. • The reversible D-A reaction endowed the phase change material with ability to recycle. • The chemical structure and phase change latent heat of phase change material were all unchanged after reprocess. • The potential application of the phase change material was explored in the field of intelligent thermal management. Polymer-based form-stable phase change materials (FPCMs) have attracted much attention due to their excellent shape stability and facileness, low-energy-consumption preparation. However, bio-based recyclable phase change energy storage materials (PCMs), crucial for reducing pollution and sustainable energy storage, have not yet been prepared. Herein, we prepared a novel bio-based recyclable PCM (DGEM-18/FA/MA/xBW), in which a novel epoxy resin (DGEM) was synthesized by using bio-based magnolol and epichlorohydrin, bio-based 2-Furanmethanamine (FA) and C36-alkylenediamines bismaleimide (MA) were used to construct a reversible crosslinked network based on epoxy-amine ring opening and Diels-Alder (D-A) reactions as the supporting frame. And 1-Octadecanethiol (ODT) and bio-based beeswax (BW) with phase change property were introduced into this supporting frame by grafting on the C=C of Magnolol via "thiol-ene" click reaction and physical blending, respectively. The D-A and rD-A reactions proceed at the temperature below 80 ℃ and above 120 °C, respectively, which provides recyclability of the crosslinked network. The ODT and beeswax provide phase change latent heat up to 119.1 J/g for the sample DGEM-18/FA/MA/1.1BW. Furthermore, taking DGEM-18/FA/MA/0.4BW as an example, its shape memory performance has been explored, as well as its potential applications in recyclable thermal management coatings. To the best of our knowledge, this is the first report on the preparation of bio-based recyclable FPCMs. [ABSTRACT FROM AUTHOR]

A series of epoxy resins containing side aliphatic pendant chains (abbreviated as EP C-04 , EP C-08 , EP C-12 and EP C-18 ) were prepared by the reaction between the diglycidyl ether of bisphenol F (DGEBF) and the single-ended fatty amine with a chain length ranging from C4 to C18. Studies on the film morphology and the physical performance demonstrate that the cured EP C-04 , EP C-08 , EP C-12 and EP C-18 composites possess excellent mechanical and thermal properties, which are originated from the micro-, submicro- and nano-structured phases distributed in the epoxy matrix. In addition, by adjusting the lengths of the dangling aliphatic chains, the mechanical properties of the cured resins can be tuned in different scales. Consequently, by prolonging the pendant chain length to C18, the cured resin exhibits a striking tensile strength of 90.65 MPa, an elongation of 6.1% and a modulus of 2.55 GPa. [ABSTRACT FROM AUTHOR]

[Display omitted] • A modified epoxy (EGP) with POSS dangling chain is prepared by thiol-ene click reaction with ∼100% conversion of POSS-SH. • Covalent bond constrains the aggregation and phase separation of POSS, as well as increases the content of POSS up to 50%. • EGP-30-DDM shows the lowest dielectric constant by 3.52 and the lowest dielectric loss value by 0.015. • EGP-20-DDM shows the highest tensile strength by 70.32 MPa and the highest tensile modulus by 2.5 GPa. • The amount of POSS by 20–30% can effectively reduce the dielectric constant and improve mechanical property of epoxy resins. Polyhedral oligomeric silsesquioxane (POSS) is an ideal nano particle for epoxy polymer to reduce dielectric constant and enhance mechanical properties due to its hollow cage type organic silicon. However, the poor compatibility between POSS and epoxy resin has always been the key factor limiting the amount of addition and the improvement of performance. Herein, a modified epoxy (EGP) with POSS dangling chain is designed, that is, mercaptopropyl isobutyl POSS (POSS-SH) is grafted to diglycidyl ether of 4,4′-diallyl bisphenol-A (DADGEBA) backbone via 'thiol-ene' click reaction. Compared with the reported researches, thiol-ene click chemistry shows efficient and controllable, which makes the grafting efficiency of POSS-SH close to 100%. Covalent bond linking between POSS and DADGEBA constrains the aggregation and phase separation of POSS, and the content of used POSS is up to 50%. As expected, the obtained polymer (EGP-x-DDM) cured by 4,4′-diaminodiphenylmethane (DDM) presents low dielectric constant and dielectric loss, as well as tensile strength and tensile modulus are enhanced by 22.9% and 31.6%, respectively. The novel epoxy resin EGP has potential application in the electronic and electrical field. [ABSTRACT FROM AUTHOR]

Abstract: The curing kinetics of an extrinsic toughened epoxy (mixture of diglycidyl ether of bisphenol-A and 1,4-butanediol epoxy resin, DGEBA/DGEBD) and an intrinsic toughened epoxy (ethoxylated bisphenol-A epoxy resin with two oxyethylene units, DGEBAEO-2) using hexahydrophthalic anhydride (HHPA) as curing agent and tris-(dimethylaminomethyl) phenol (DMP-30) as accelerator were comparatively studied by non-isothermal DSC with a model-fitting Málek approach and a model-free advanced isoconversional method of Vyazovkin. The dynamic mechanical properties and thermal stabilities of the cured materials were investigated by DMTA and TGA, respectively. The results showed that Šesták–Berggren model can generally simulate well the reaction rates of these two systems. The activation energy of DGEBA/DGEBD/HHPA/DMP-30 at high fractional conversion changed much higher than that of DGEBAEO-2/HHPA/DMP-30, indicating the increased steric hindrance mainly affected the reaction kinetic scheme of DGEBA/DGEBD/HHPA/DMP-30. The T g and storage moduli of cured DGEBAEO-2/HHPA/DMP-30 were lower than those of cured DGEBA/DGEBD/HHPA/DMP-30 according to DMTA while TGA showed that the thermal stabilities of these two cured systems were similar. [Copyright &y& Elsevier]

Abstract: In this paper the curing kinetics of diglycidyl ether of 4,4′-diallyl-bisphenol-A (DADGEBA) using sulfur (S) as curing agent was studied by non-isothermal and isothermal differential scanning calorimetry (DSC). The kinetic mechanism equations were determined using autocatalytic models and nth-order reaction model. DSC measurement showed that the curing process of DADGEBA/S system contains two steps because of the double exothermic peaks in DSC curve. The model data simulation results indicated that the Šesták-Berggren (SB) model had a great distinction with the experimental data. Isothermal DSC analysis showed that the curing reactions followed Kamal''s autocatalytic model when the reaction temperature was below 210°C, and when the temperature was above 210°C the nth-order model can be used to describe the curing reaction process of the DADGEBA/S system perfectly. The two kinetic equations in the entire reaction process of DADGEBA/S system are consistent with the two-step reaction mechanisms of the same system. [Copyright &y& Elsevier]

It is a longstanding challenge for epoxy-based nanocomposites to optimize the dispersity of graphene so as to improve the mechanical properties and endow more functions. Non-covalent functionalization of graphene via dispersants is a crucial strategy to achieve well-dispersion, which can maintain the original physical/chemical properties. However, the reported dispersants significantly reduce mechanical properties of matrix and their stable graphene concentration is limited. Herein, 2,3,5,6-tetrafluorobenzyloxyglycidyl ether (TFGE) is synthesized and used as a dispersant to realize non-covalent functionalization of graphene, which can further improve the interface, dispersity and loading of graphene via π-π F interactions between tetrafluorophenyl and graphene, compared with π-π interactions. Moreover, TFGE can simultaneously reinforce and toughen the matrix via internal antiplasticization. The well-designed epoxy-based nanocomposite with ultralow graphene loading (less than 0.03 wt%) shows outstanding mechanical and thermomechanical properties, photo/thermochromic ability, light absorption, flame resistance as well as adhesive strength. This facile strategy provides an efficient guideline for better design and large-scale preparation of high-performance and multi-functional graphene/epoxy nanocomposites applied in adhesive, coating, anti-fake and structural materials. [Display omitted] • Graphene is well dispersed by π-π F interactions. • High-performance EP/7.5%TFGE-G 5 nanocomposite is obtained via well-dispersed graphene and internal antiplasticization. • EP/7.5%TFGE-G 5 shows fine photo/thermochromic ability, light absorption, flame resistance and adhesive properties. [ABSTRACT FROM AUTHOR]

The hydrogen bonds (H-bonds) are employed for the thermal and mechanical property enhancement of epoxy networks; however, the formation and evolution of H-bonds, especially in emerging bio-based furan epoxy, cannot be deeply understood at the atomic level in the traditional experimental method. Herein, molecular dynamic (MD) simulation is employed to clearly investigate the H-bonds, free volume and its distribution, mean square displacement, as well as their further influence on thermomechanical behaviors of selected model epoxy resins. The model epoxy resins composed of 2,5-bis [(2-oxiranylmethoxy)-methyl]-furan (BOF), 1,4-bis [(2-oxiranylmethoxy)-methyl]-benzene (pBOB) and 2.5-bis(2-oxiranylmethoxy)-methyl)-cyclopentadiene (BOC), which were cured by 4,4′-diamino diphenyl methane (DDM), respectively. These three epoxy molecules have very similar structure with the only difference in ring blocks of monomers from furan, benzene to cyclopentadiene. Wherein, BOC is artificially designed to further explore the influence of the oxygen atom of furan rings, with ensuring the consistency with the rotation and planarity of BOF. From contrastive simulation results, BOF-DDM has the highest Young's modulus among all these systems due to the least free volume leading by the maximum H-bonds. However, for DDM crosslinking networks, H-bonds seem to have limited influence on T g of BOF-DDM, and the effect of molecular weight and steric hindrance on T g is more decisive, which is different from the most relevant reports on furan-based epoxy. Our study gives the significant insight of H-bonds behavior of furan rings, and it is expected to effectively guide the design of epoxy resins. • Three epoxy models were constructed. • H-bonds was studied at the atomic level. • The effect of H-bonds on T g and Young's modulus. • H-bonds seem to have limited influence on Tg of BOF. • H-bonds could effectively increase the Young's modulus of BOF by reducing the free volume. [ABSTRACT FROM AUTHOR]

• Resveratrol-based epoxy resin (REEP) was synthesized from sustainable feedstocks. • REEP/HDDM exhibited an ultrahigh T g and good processability. • REEP/HDDM performed good mechanical property and excellent thermal stability. Preparing and designing an epoxy system with ultrahigh glass transition temperature (T g > 300 °C) is always a big challenge, which restrict its applications in some cutting-edge areas such as aerospace engineering and electrical electronics. Herein, a biomass-based epoxy resin (REEP) was prepared from resveratrol, and then curing behavior, thermal–mechanical properties, mechanical performance, thermal stability, dielectric properties and optical properties of REEP/HDDM, REEP/DGEBA/HDDM and DGEBA/HDDM were respectively studied systematically. Results suggested that the T g of REEP/HDDM was above 320 °C, higher than those of most reported epoxy systems, both derived from biomass-based and petroleum-based materials. Moreover, the tensile strength of REEP/HDDM, REEP/DGEBA/HDDM and DGEBA/HDDM were 77.8 MPa, 70.8 MPa and 63.6 MPa, respectively, and the T d5% of REEP/HDDM, REEP/DGEBA/HDDM and DGEBA/HDDM were 319.9 °C, 335.1 °C and 348.1 °C, respectively, indicating excellent mechanical performance and thermal stability of the cured epoxy system. Interestingly, the REEP/HDDM exhibited outstanding blocking properties in the range of 220–400 nm (UV-light) and low flammability with compact and continuous char residues. In short, REEP, with a well-defined chemical structure, has a stiffness conjugated stilbene structure to prevent the molecular from motioning in the crosslinked network structure and three epoxy groups, thereby increasing the crosslinked density dramatically, which endows REEP/HDDM network with outstanding comprehensive properties. [ABSTRACT FROM AUTHOR]

The special structure and excellent properties make graphene a great potential in developing advanced polymer nanocomposites; however, its dispersion in molecular-level as well as reinforcement in high efficiency in matrixes has been a challenge. Herein, we report a facile and effective strategy to disperse graphene in epoxy resin by using benzyl glycidyl ether (BGE) as a dispersant and surface modifier through π-π interaction between BGE and graphene. The measurements of UV–vis spectroscopy and Raman spectrum confirm π-π interaction of BGE and graphene, and the remarkably improvement in properties of graphene reinforced epoxy resin are achieved. For 5 mg/mL graphene dispersion, tensile strength increases by 15%, Young's modulus increases by 32.8%, storage modulus at 30 °C increases by 37%, and thermal conductivity increases by 95.7%. This method opens up a feasible approach to make high performance graphene nanocomposites for engineering and high-tech applications. Graphical Abstract. High-performance graphene reinforced epoxy nanocomposites has been fabricated via using benzyl glycidyl ether(BGE) as a dispersant and surface modifier. This work achieves graphene's dispersion in molecular-level and reinforcement in high efficiency in epoxy. The addition of a small amount of graphene has a significant enhancement to the strength and modulus of the host epoxy. Image 1 • BGE acts as both a dispersant and a surface modifier for graphene through π-π interaction between BGE and graphene. • BGE can not only enhance epoxy but also improve the dispersity and the interaction between graphene and matrix. • High-performance graphene reinforced epoxy nanocomposites were fabricated with a small amount of graphene. [ABSTRACT FROM AUTHOR]

• A renewable resveratrol-based epoxy resin was prepared. • REEP/MeHHPA exhibits high T g , high strength and high modulus. • REEP/MeHHPA possesses exceptional low permittivity. • REEP/MeHHPA shows low flammability and corresponding mechanisms are investigated. Preparing low-flammable biobased epoxy resins with a high glass transition temperature (T g) and excellent mechanical properties is significant for the rapid growing electronics and microelectronics industry. In this research, a resveratrol-based epoxy resin (REEP) with well-designed chemical structures possessing trifunctional epoxy groups and rigid conjugate structures was prepared through the one-pot method and was then cured by methyl hexahydrophthalic anhydride (MeHHPA). The conventional petroleum-based epoxy resin (DGEBA) was cured by the same kind of curing agent. Results showed that T g of REEP/MeHHPA was up to 210.8 °C, much higher than that of DGEBA/MeHHPA (only 146.5 °C). The tensile strength and modulus of REEP/MeHHPA were 73.5 MPa and 3.0 GPa, respectively. More importantly, REEP/MeHHPA exhibited exceptional low permittivity (about 3.5) and low flammability with high char yield of 19.0% (800 °C). Therefore, the resveratrol-based epoxy resin could be a promising candidate for DGEBA and has great potential application in electronics and microelectronics industry. [ABSTRACT FROM AUTHOR]

In this work, two types of rigid-flexible integrated epoxy resins, diglycidyl ether of eugenol-2-mercaptoethanol (DGEEM) and diglycidyl ether of vanillic alcohol (DGEVA), which possess similar rigid methoxy-substituted aromatic structures and different soft aliphatic chains in length, were prepared. Micro-morphology structures were tested by AFM, AFM nanomechanical mapping, and AFM-IR. Macro-properties were respectively characterized by tensile test and shape memory test. Results showed that a series of tunable micro-morphology structures including hard-phase-rich sea-island structure, bi-continuous structure, and soft-phase-rich sea-island structure were explored after cured with 4,4-methylenedianiline. Moreover, the shape memory mechanism for these SMEPs was concluded: phase separation structures are the base of these SMEPs, and soft phase acts as switching segments, which contributes to shape memory strain of the SMEPs. The optimal designed SMEPs with bi-continuous phase structure was prepared from this mechanism, which exhibit good mechanical properties and excellent shape memory performance. Image 1 • Two types of rigid-flexible integrated epoxy resins (DGEEM and DGEVA) were prepared by an effective one-pot method. • For the first time, a series of tunable micro-phase separation structures of epoxy resins were explored. • Optimized SMEPs with bi-continuous structure exhibits good mechanical properties and excellent shape memory performance. [ABSTRACT FROM AUTHOR]