Epoxy resin cured with diamine bearing azobenzene group

The epoxy resin: N,N-diglycidyl-4-glycidyloxyaniline (DGOA) is cured with the new diamine-chromophore: 2,4-diamino-4′-methylazobenzene (DMAB). The spectral characterization of infrared spectroscopy (FTIR), ¹H NMR spectroscopy and of elemental analysis (EA), confirm the chromophore structure. The curing kinetics of aminophenol epoxy resin/2,4-diamino-4′-methylazobenzene system is studied in isothermal experiments by means of differential scanning calorimetry (DSC). The structural changes occurring during the cure reaction are investigated by Fourier transform infrared spectroscopy (FTIR). Thermal stability characterized by the temperature of 5 and 10% weight loss and residue at 1000 °C of the cured product is studied by thermogravimetric analysis (TGA). Amorphous character of the cured material is determined using X-ray spectroscopy. The preliminary investigations of optical grating recording are carried out.     

Changes of properties of cured and uncured disiloxane bisbenzocyclobutene thin films under irradiation

The effects induced by α-particles and laser beam irradiation in air atmosphere in uncured and cured bisbenzocyclobutene (BCB) 2 μm thick films, spin-coated on glass/ITO surface have been investigated. α-Particle irradiation was done by means of a thin film ²⁴¹Am source (E_α = 5.486 MeV), up to the total fluence of about 5 × 10¹⁰ particles/cm². Laser irradiation was performed by a Nd³⁺:YAG (λ = 1.06 μm) laser in the free generation and the Q-switch regime, using both focused and unfocused beams. Irradiation induced changes were investigated using Light and Atomic Force Microscopy (AFM), infrared (IR), Ultraviolet/visible (UV/vis) and Raman spectroscopy by inspecting several uncured and cured BCB films before and after irradiation. It has been found that both types of irradiation under investigated conditions have produced a novel phase in the material, which is not present either in the uncured or the cured BCB films. Possible implications of the observed effects on curing and degradation of BCB films have been discussed.     

Soybean oil-based thermoset reinforced with rosin-based monomer

A full bio-based cured resin was synthesized by copolymerization of acrylated-epoxidized soybean oil (AESO) and 2-acrylamidoethyl dehydroabietic acid (DHA-HEMAA). The rigid rosin-based monomer 2-acrylamidoethyl dehydroabietic acid was first prepared from dehydroabietic acid and N-hydroxyethylacrylamide, which was characterized by nuclear magnetic resonance and Fourier transform infrared (FTIR) spectrometry techniques. The cured resin was then synthesized and characterized by FTIR spectroscopy, differential scanning calorimetry, dynamic thermomechanical analysis, and thermogravimetric analysis, as well as using a Kruss tensiometer and a universal testing machine. The results indicated that the resin cured with rosin-based monomer exhibited excellent thermomechanical properties. The crosslink density and thermal stability of cured samples containing DHA-HEMAA at molar ratio between 10 and 30% were higher than those of AESO/DHA-HEMAA0 sample. With increasing DHA-HEMAA content, the glass transition temperature (T_g), elongation-at-break, and tensile strength of samples increased, in the stated order, from 16 to 38 °C, from 24 to 45.8%, and from 1.7 to 6.5 MPa. Due to DHA-HEMAA with a hydrophenanthrene structure, the θ values increased with the increase of DHA-HEMAA molar ratios. The full bio-based rosin thermosetting resins may have great potentials in practical application fields, such as coating, adhesive, and packaging materials.     

Ethynyl aromatic siliconhybridized resin: Synthesis,characterizations, and thermal properties

A novel silicon‐containing resin (ESA resin) was successfully synthesized by the condensation reaction of lithium arylacetylide with chlorosilane in high yields. The resin was characterized by the techniques of FTIR, ¹H‐NMR, ²⁹Si‐NMR, and gel permeation chromatography. Thermal cure process was monitored by DSC and FTIR methods. This resin could melt at around 100°C and thermally cured at 200–250°C with low exothermal enthalpy. Owing to the high aryl groups containing and the complete crosslinking of ethynyl groups, the cured ESA resin exhibited excellent thermal stability and high char yield. The decomposition temperature $T_{d_5}$ of the cured resin was at 510°C, and the residue yield at 900°C was 82.9% in N₂. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Smart corrosion sensing phenanthroline modified alkyd coatings

Alkyd resin was chemically modified with 1,10-phenanthroline-5-amine and characterized by Fourier transform infrared (FTIR) and ¹³C Nuclear magnetic resonance (¹³C NMR) spectroscopy. The complex forming ability of phenanthroline modified alkyd resin with Fe²⁺ ions was studied by UV–Visible spectroscopy. Mixture of Fe²⁺ solution and modified alkyd resin showed new absorption bands in UV–Visible spectroscopy confirmed the formation of modified alkyd resin-Fe(II) complex. Corrosion sensing property of modified alkyd coating was evaluated by immersing the coated mild steel specimens in 3.5% NaCl solution. Color change was observed in the coating due to onset of corrosion at metal-coating interface. Electrochemical impedance spectroscopy (EIS) was used for correlating the polarization resistance (R_p) of coating with color change. Scanning electron microscopic (SEM) analysis on the surface of metal specimens indicated that the point of color change was the corrosion site. Results revealed that phenanthroline modified alkyd resin can be used in corrosion sensing coating formulations.     

Synthesis and characterization of UV‐curable acrylic resin containing fluorine groups

A novel fluorine‐containing acrylic resin, 4‐trifluoromethylphenyl glycerol dimethacrylate (TPGD), was synthesized and the structure was characterized by FTIR, ¹³C NMR, ¹H NMR, and ¹⁹F NMR spectroscopy. The conversion of cure reaction, thermal stability, glass transition temperature (T_g), and electrical properties of the TPGD acrylic resin cured with UV radiation were investigated. The thermal stability and T_g of the UV‐cured specimens show a maximum value at 1 wt% photoinitiator, due to the formation of advanced network structures. The cured specimens had a relatively low dielectric constant, attributed to the decreased deformation polarizability of segment motion in the fluorine‐containing resin. Copyright © 2004 Society of Chemical Industry     

Synthesis of UV‐curable difunctional silane monomer based on 3‐methacryloxy propyl trimethoxysilane (3‐MPTS) and its UV‐curing characteristics and thermal stability

In the present investigation, silicon containing UV‐curable difunctional monomer was synthesized by reacting 3‐methacryloxy propyl trimethoxysilane (3‐MPTS) with acrylic acid using anhydrous ether as a solvent under inert atmosphere. The synthesized acryloxymethacryloxy silane monomer was characterized by FTIR, ¹H‐NMR, and ¹³C‐NMR spectroscopy. The silane monomer along with 4 wt % photoinitiator (Darocure 1173) was cured under UV‐light for different exposure time. The curing characteristic of the monomer was investigated using FTIR spectroscopy. The conversion of the double bond due to curing has been evaluated from the peak intensity of the C?C double bond (at 1636 cm^?1) in the FTIR spectrum considering the peak intensity at 1720 cm^?1 due to C?O as internal standard. The maximum double bond conversion is observed to be 72%. The optimum cure time for the silane monomer has been estimated to be 7.8 sec. The UV‐cured sample decomposes at 440°C. The char residue is 35% at 700°C. The synthesized UV‐curable silane monomer may be useful for UV‐coating formulations, for fabrication of 3D‐objects by lithographic technique and as a precursor for organic–inorganic hybrid materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Materials containing benzocyclobutene units with low dielectric constant and good thermostability prepared from star-shaped molecules

With the development of ultralarge-scale integrated circuits, polymers with low dielectric constant and high thermal stability have aroused great interest. We prepared two novel bridged siloxane-based benzocyclobutene (BCB) star-shaped monomers, tetrakis[dimethyl siloxy-4-(1′,1′-dimethyl-1′-ethyl silicon)-benzocyclobutene] (TDSDES-BCB) and tetrakis(hexamethyl siloxane vinyl-benzocyclobutene) (THSV-BCB), and the corresponding resins were obtained by curing. The structures of TDSDES-BCB and THSV-BCB were confirmed by ¹H-NMR, ¹³C-NMR, and ²⁹Si-NMR spectra and time-of-flight mass spectrometry analysis. The curing behavior of these monomers was investigated by Fourier transform infrared spectroscopy and differential scanning calorimetry. The dielectric constant of cured TDSDES-BCB is only 2.43 at 10 MHz (that of THSV-BCB is 2.46). In addition, these resins display high thermal stability: the 5 wt % weight loss temperature of cured TDSDES-BCB is about 467 °C (454 °C for THSV-BCB resin). The excellent low dielectric property is attributable to the free volume created by the star-shaped structure and crosslinked network structure of BCB after curing. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47458.     

Synthesis, preparation and properties of novel high-performance allyl-maleimide resins

Three novel allyl-maleimide monomers (i.e., A₂B, AB and AB₂) were designed, synthesized and thermally cured to yield a series of high-performance allyl-maleimide resins. All the monomers obtained are readily soluble in common organic solvents enabling an easy solution processing. The thermal properties of the three monomers were studied by the differential scanning calorimetry (DSC). A₂B and AB showed fairly low melting temperature (T_m < 90 °C) and wide processing window ranging from 90 °C to 260 °C. The thermal stability of the cured allyl-maleimide resins (i.e., PA₂B, PAB and PAB₂) was studied by the thermogravimetric analysis (TGA). Dynamic mechanical analysis (DMA) was used to investigate the dynamic mechanical properties of the composites based on the cured allyl-maleimide resins. PA₂B and PAB₂ showed good glass transition temperatures (T_g > 270 °C) and their corresponding composites showed high bending modulus (E′ > 1900 MPa). Allyl-compound-modified BMI resins based on AB monomer were prepared. Rheometer revealed that the processability of the prepolymer (BR-AB-pre) was improved by the addition of AB monomer. The cured BMI resins (BR and BR-AB) showed good thermal stability (T_d > 400 °C, both in nitrogen and in the air), high glass transition temperature (T_g > 320 °C), and good mechanical properties and low water uptake (<2.6%, 120 h).     

Reversible isomerization and cure monitoring of epoxy azobenzene resins

The photoresponsive behavior of the glycidyloxyazobenzene (GOAB) monomer, synthesized using an improved method, is examined by UV/Vis spectroscopy. The monomer is cured with diethylenetriamine (DETA), forming a new epoxy resin. Proton NMR spectroscopy is used to monitor the completion of the curing reactions. Kinetics for reversible trans and cis isomerization in the cured system and also in the epoxy monomer are identified by UV/Vis spectroscopy during in situ irradiation with appropriate wavelengths (290–320 nm for UV and 400–500 nm for visible). The rates of recovery of the monomer from cis to trans forms are also obtained by heating and storing in the dark. Furthermore, the reactivity of the monofunctional GOAB monomer with a common amine, DETA, as a curing agent, is investigated using isothermal and dynamic heating scans in a DSC pan and by simultaneously monitoring the near‐FTIR spectra. The modified epoxy azobenzene proved to be reactive enough with DETA to form a network that can sustain temperatures of up to 200°C. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40770.     

Synthesis and properties of novel dicyanate with low dielectric and water absorption performance

The 1,4‐bis (3,5‐dimethyl‐4‐cyanatobenzyl) benzene (BBZCy) was synthesized successfully by the reaction of 1,4‐bis (3,5‐dimethyl‐4‐hydroxybenzyl)benzene(BBZ) with cyanogen chloride in the presence of triethylamine at −5–0°C. Its structure was confirmed by means of FTIR, elemental analysis, MS, and ¹H NMR spectra. The monomer of BBZCy was cured by itself or cured with catalysts to form sym‐triazine structure. Thermal properties of cured BBZCy were studied using DSC, DMA, TMA, and TGA. Compared with the commercial bisphenol A dicyanate resin (BADCy), the cured BBZCy resin exhibited a lower dielectric constant (2.66 at 1 GHz), a lower dissipation factor (0.0054 at 1 GHz), lower water absorption (0.8% at 100 h), less thermal stability, and lower glass transition temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and Characterization of Stimuli-Responsive Poly(N-isopropylacrylamide-co-N-vinyl-2-pyrrolidone)

Radical copolymerization of N-isopropylacrylamide (NIPA) with N-vinyl-2-pyrrolidone (VP) were carried out with 2,2′-azobisisobutyronitrile (AIBN) as an intiator in N,N′-dimethylformamide solution at 65°C under nitrogen atmosphere. Compositon of the copolymers synthesized in a wide range of monomer feed ratios were determined by FTIR and ¹H (¹³C) NMR-DEPT-135 spectroscopy. The monomer reactivity ratios were determined by Fineman-Ross, Kelen-Tüdös and non-linear regression methods. It was observed that the studied monomer pair has some tendency to alternation in the chosen monomer feed ratios due to formation of intermolecular interaction through H-bonding and N → O = C coordination. The synthesized poly(NIPA-co-VP)s show temperature sensitivity (T _s), higher glass-transiton temperature (T _g ), thermal stability, polyelectrolyte and stimuli-responsive (temperature- and pH-sensitive) behavior and can be attributed to the class of bioengineering functional copolymers useful for application in various gene- and bioengineering processes, drug delivery systems and biomacromolecule conjugations.     

Reactivity,chemical structure,and molecular mobility of urea–formaldehyde adhesives synthesized under different conditions using FTIR and solid‐state 13C CP/MAS NMR spectroscopy

This study was conducted to investigate the effects of reaction pH condition and hardener type on the reactivity, chemical structure, and molecular mobility of urea–formaldehyde (UF) resins. Three different reaction pH conditions, such as alkaline (7.5), weak acid (4.5), and strong acid (1.0), were used to synthesize UF resins, which were cured by adding four different hardeners (ammonium chloride, ammonium sulfate, ammonium citrate, and zinc nitrate) to measure gel time as the reactivity. FTIR and ¹³C‐NMR spectroscopies were used to study the chemical structure of the resin prepared under three different reaction pH conditions. The gel time of UF resins decreased with an increase in the amount of ammonium chloride, ammonium sulfate, and ammonium citrate added in the resins, whereas the gel time increased when zinc nitrate was added. Both FTIR and ¹³C‐NMR spectroscopies showed that the strong reaction pH condition produced uronic structures in UF resin, whereas both alkaline and weak‐acid conditions produced quite similar chemical species in the resins. The proton rotating‐frame spin–lattice relaxation time (T_1ρH) decreased with a decrease in the reaction pH of UF resin. This result indicates that the molecular mobility of UF resin increases with a decrease in the reaction pH used during its synthesis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2677–2687, 2003     

Complex-radical copolymerization of <Emphasis Type="Italic">N-</Emphasis>vinyl pyrrolidone with isostructural analogs of maleic anhydride

Radical copolymerizations of N-vinyl-2-pyrrolidone (VP) with isostructural analogs of maleic anhydride (MA), such as citraconic anhydride (CA) and N-substituted maleimides [maleimide (MI), N-ethylmaleimide (EMI) and N-phenylmaleimide (PhMI)] were studied. Compositions of copolymers synthesized in a wide range of monomer feed ratios were determined by alkali titration (for anhydride copolymers), FTIR and ¹H NMR spectroscopy using 1495 and 630 cm^-1 (for VP-MI), 1289 and 1225 cm^-1 (for VP-EMI) and 1050 and 3067 cm^-1 (for VP-PhMI) analytical bands and integral areas of CH₂ (pyrrolidone ring) and CH (MI), CH₃ (EMI) and CH= (benzene ring in PhMI) groups, respectively. Electron-donor VP monomer was found to have substantially different reactivities in the radical copolymerization with MA, CA and N-substituted (H, C₂H₅ and phenyl) malemides as electron-acceptor comonomers. Effects of H-bonding and N→O=C coordination on the monomer reactivity ratios were evaluated. Tendency to alternation of the monomer pairs increases in the order of VP–MA > VP–CA > VP-MI > VP-PhMI > VP-EMI. Structure-thermal property-relationship for the synthesized copolymers was also studied.     

The structural transformation during polymerization of benzoxazine/FeCl3 and the effect on the thermal stability

The mixture of bisphenol A/aniline-based benzoxazine (BA-a) and FeCl₃ was prepared at 40 °C and then was cured to get the polymer at elevated temperatures. The thermal stability of the modified polybenzoxazine was improved and its char yield at 800 °C increased by 11%. The reason for the improvement of the thermal stability and the structural transformation during polymerization was systematically investigated by Fourier transform infrared (FTIR) spectroscopy, ¹H nuclear magnetic resonance spectroscopy (¹H NMR), thermo-gravimetric analysis (TGA), pyrolysis-gas chromatography/mass spectrometry (Py/GC–MS), TGA-IR and element analysis (EA). The results show that BA-a can partially undergo the ring-opening polymerization at a low temperature in the presence of FeCl₃ and generate some oligomers containing N, O-acetal-type bridge structures. At a high temperature, this structure can be transformed into the arylamine Mannich bridge structure which can delay degradation of the aniline moiety. Besides, the volatilization of fragmented Schiff base structures can be found during cure and more thermostable crosslinked structures are formed in polybenzoxazine. The entire polymerization mechanism of BA-a with FeCl₃ was proposed.     

Preparation and film properties of tri(3,4-epoxycyclohexylmethyl) phosphate based cationically UV curing coatings

A facile synthesis of phosphorus-containing trifunctional cycloaliphatic epoxide resin, tri(3,4-epoxycyclohexylmethyl) phosphate (TECP), used for cationically UV curing coatings as a reactive-type flame retardant, was proposed. The molecular structure was confirmed by FTIR, ¹H NMR and ³¹P NMR spectroscopic analysis. A series of flame retardant formulations by incorporating into a commercial difunctional cycloaliphatic epoxide resin, CYRACURE™ UVR-6110, were prepared, and exposed to a medium pressure lamp to form the cured films under the presence of diaryliodonium hexafluorophosphate salt as a cationic photoinitiator. Their flame retardancy examined by the limiting oxygen index showed the improvement up to 27 for 50 wt% TECP addition compared with 21 for pure UVR-6110. The T_s and T_g decreased from 86 °C and 131 °C to 55 °C and 91 °C, respectively, by using dynamic mechanical thermal analysis, whereas the tensile strength showed a slight increase (11%) with 50 wt% TECP addition. The thermogravimetric analysis (TGA) and real-time Fourier transform infrared spectroscopy (RT-FTIR) measurement demonstrated the condensed-phase flame retardant mechanism.     

Synthesis and properties of methyl hexahydrophthalic anhydride‐cured fluorinated epoxy resin 2,2‐bisphenol hexafluoropropane diglycidyl ether

The fluorinated epoxy resin, 2,2‐bisphenol hexafluoropropane diglycidyl ether (DGEBHF) was synthesized through a two‐step procedure, and the chemical structure was confirmed by ¹H n uclear magnetic resonance (NMR), ¹³C NMR, and Fourier transform infrared (FTIR) spectra. Moreover, DGEBHF was thermally cured with methyl hexahydrophthalic anhydride (MHHPA). The results clearly indicated that the cured DGEBHF/MHHPA exhibited higher glass transition temperature (T_g 147°C) and thermal decomposition temperature at 5% weight loss (T₅ 372°C) than those (T_g 131.2°C; T₅ 362°C) of diglycidyl ether of bisphenol A (DGEBA)/MHHPA. In addition, the incorporation of bis‐trifluoromethyl groups led to enhanced dielectric properties with lower dielectric constant (D_k 2.93) of DGEBHF/MHHPA compared with cured DGEBA resins (D_k 3.25). The cured fluorinated epoxy resin also gave lower water absorption measured in two methods relative to its nonfluorinated counterparts. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2801–2808, 2013     

Microstructure evolution of ammonia‐catalyzed phenolic resin during thermooxidative aging

The thermooxidative aging of ammonia‐catalyzed phenolic resin for 30 days at 60–170°C was investigated in this article. The aging mechanism and thermal properties of the phenolic resin during thermooxidative aging were described by thermogravimetry (TG)–Fourier transform infrared (FTIR) spectroscopy, attenuated total reflectance (ATR)–FTIR spectroscopy, and dynamic mechanical thermal analysis. The results show that the C? N bond decomposed into ammonia and the dehydration condensation between the residual hydroxyl groups occurred during the thermooxidative aging. Because of the presence of oxygen, the methylene bridges were oxidized into carbonyl groups. After aging for 30 days, the mass loss ratio reached 4.50%. The results of weight change at high temperatures coincided with the results of TG–FTIR spectroscopy and ATR–FTIR spectroscopy. The glass‐transition temperature (T_g) increased from 240 to 312°C after thermooxidative aging for 30 days, which revealed the postcuring of phenolic resins. In addition, an empirical equation between the weight change ratio and T_g was obtained. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of copolymers of bromoacrylated methyl oleate

In this study, methyl oleate was bromoacrylated in the presence of N‐bromosuccinimide and acrylic acid in one step. Homopolymers and copolymers of bromoacrylated methyl oleate (BAMO) were synthesized by free radical bulk polymerization and photopolymerization techniques. Azobisisobutyronitrile (AIBN) and 2,2‐dimethoxy‐2‐phenyl‐acetophenone were used as initiators. The new monomer BAMO was characterized by FTIR, GC‐MS, ¹H, and ¹³C‐NMR spectroscopy. Styrene (STY), methylmethacrylate (MMA), and vinyl acetate (VA) were used for copolymerization. The polymers synthesized were characterized by FTIR, ¹H‐NMR, ¹³C‐NMR, and differential scanning calorimetry (DSC). Molecular weight and polydispersities of the copolymers were determined by GPC analysis. Ten different feed ratios of the monomers STY and BAMO were used for the calculation of reactivity ratios. The reactivity ratios were determined by the Fineman–Ross and Kelen–Tudos methods using ¹H‐NMR spectroscopic data. The reactivity ratios were found to be r_sty = 0.891 (Fineman–Ross method), 0.859 (Kelen–Tudos method); r_bamo = 0.671 (Fineman–Ross method), 0.524 (Kelen–Tudos method). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2475–2488, 2004