Molten state reactivity of difunctional cyanates: Thermal and spectroscopic studies by liquid and solid CP-MAS 13C-NMR

Using differential scanning calorimetry, we have investigated three difunctional cyanate monomers differing by their central group: bisphenol A dicyanate (BADCy), bisphenol E dicyanate (BEDCy), and hexafluorinated bisphenol A dicyanate (BAFDCy), to determine the effect of the central group on the molten state reactivity of heat-treated cyanates. To identify the different phenomena occurring during the heat cycle, which was followed by differential scanning calorimetry, ¹³C-NMR (liquid and solid) was undertaken. This technique was used to characterize the major products and side products formed. Using ¹³C-NMR and HPLC, we were able to detect the formation of compounds with a triazine ring at one chain end and a hydroxyl function at the other. The presence of the latter depended on the purity of the initial monomers. In light of the purity parameter, inherent in the synthesis of the products, we propose an order of reactivity, at molten state, of the polymerization of the three cyanate monomers in the temperature range of 180–300°C. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1245–1254 1997     

Synthesis and characterization of novel low‐dielectric cyanate esters

For the purpose of increasing the mobility of residual bisphenol A dicyanate ester (BADCY) during the final stage of curing and achieving a complete reaction of cyanate groups, a small quantity of monofunctional phenol was added to BADCY to form an imidocarbonate, or a small quantity of monofunctional cyanate esters was added to form cyanate ester copolymers. The proposed structures were confirmed with Fourier transform infrared, elemental analysis, mass spectrometry, and NMR spectroscopy. The thermal properties of the cured cyanate esters were measured with dynamic mechanical analysis, thermogravimetric analysis, and dielectric analysis. These data were compared with those for the cured BADCY resin. The cured modified cyanate esters exhibited a lower dielectric constant, a lower dissipation factor, and lower moisture absorption than the cured BADCY system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2589–2600, 2004     

Synthesis and characterization of new dicyanate monomers. A way to obtain fully aromatic crosslinked poly(ether ketone)s

Several aromatic mono- and dicyanate monomers bearing ether and ketone groups in the main chain have been synthesized through high-yield reactions widely used in organic chemistry. FT-IR and NMR were used to characterize these monomers and the intermediate products. The cyclotrimerization reaction was studied by DSC in monocyanate models, and the enthalpy of the reaction was determined. The value obtained was approximately 95 kJ/mol of cyanate irrespective of the substituent and symmetry of the substitution. For short dicyanates, cyclotrimerization did not reach completion, and for long dicyanates, the enthalpy of reaction could not be evaluated with accuracy. The resulting cured polycyanurates networks, due to the selectivity of the cyclotrimerization reaction, could be considered as true fully aromatic crosslinked poly(ether ketone)s with controlled structure. T_g values of the networks were above 180°C. The higher values were found for shorter dicyanates and for monomers with para substitution. The 1% and 5% weight loss values in nitrogen were above 310 and 380°C, respectively, with char yields in the range 50–60%. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3155–3168, 1999     

High performance toughened cyanate ester resin with low injection temperature for RTM process

A high‐performance modified cyanate resin system with low injection temperature for fabricating advanced composites via resin transfer molding (RTM) was developed, which was made of bisphenol A dicyanate ester (BADCy) and diallyl phthalate (DAP). The processing characteristics, mechanical, and thermal properties of the resin were studied, and the effect of the content of DAP on the processing and performance parameters was discussed. The results show that the processing properties of the modified cyanate system are dependent on the content of DAP. All the formulations studied in this paper have good processing characteristics; their injection temperatures are between 30 and 40°C and the pot life is about 20 hr at 50°C. The cured resins exhibited good thermal stability, excellent toughness, and good hot–wet resistance, suggesting that the toughened cyanate resin is a potential high‐performance RTM matrix for advanced composites. Copyright © 2008 John Wiley & Sons, Ltd.     

Flame retardant polycyanurate thermosets from the cyanate esters of triphenylphosphine oxide

Three cyanate esters containing phosphorus are synthesized in good overall yields starting from bromoanisoles. Di‐ and tricyanates with meta configuration are most stable while para is less so. The para dicyanate ester isomer is particularly affected by water from the atmosphere. The meta dicyanate ester 2 has good thermal properties with glass transition at 268 °C and char yield of 65% in air at 600 °C. All three phosphorus‐containing cyanate esters are low flammability in an open flame. They make highly combustible cyanate esters resins less flammable simply by blending. Mixing 10 wt% dicyanate ester 2 into bisphenol A or E dicyanate esters makes them rate V‐0. Published 2018.^† J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1100–1110     

Sucrose-based epoxy monomers and their reactions with diethylenetriamine

Two sets of sucrose-based epoxy monomers, namely, epoxy allyl sucroses (EAS), and epoxy crotyl sucroses (ECS), were prepared by epoxidation of octa-O-allyl and octa-O-crotyl sucroses (OAS and OCS, respectively). Synthetic and structural characterization studies showed that the new epoxy monomers were mixtures of structural isomers and diastereoisomers that contained varying numbers of epoxy groups per sucrose. EAS and ECS can be tailored to contain an average of one to eight epoxy groups per sucrose. Quantitative ¹³C-NMR spectrometry and titrimetry were used independently to confirm the average number of epoxy groups per sucrose. Sucrose-based epoxy monomers were cured with diethylenetriamine (DETA) in a differential scanning calorimeter (DSC), and their curing characteristics were compared with those of diglycidyl ether of bisphenol A (DGEBA) and diepoxycrotyl ether of bisphenol A (DECEBA). EAS and DGEBA cured at 100 to 125°C and exhibited a heat of cure of about 108.8 kJ per mol epoxy. ECS and DECEBA cured at 150 and 171°C, respectively, and exhibited a heat of cure of about 83.7 kJ per mol epoxy. Depending upon the degree of epoxidation (average number of epoxy groups per sucrose) and the concentration of DETA, glass transition temperatures (T_gs) of cured EAS varied from −17 to 72°C. DETA-cured ECS containing an average of 7.3 epoxy groups per sucrose (ECS-7.3) showed no DSC glass transition between −140 and 220°C when the ratio of amine (NH) to epoxy group was 1:1 and 1.5:1. Maximum T_gs obtained for DETA-cured DGEBA and DECEBA polymers were 134 and 106°C, respectively. DETA-cured bisphenol A-based epoxy polymers degraded at about 340°C, as observed by thermogravimetric analysis (TGA). DETA-cured sucrose-based epoxy polymers degraded at about 320°C. Sucrose-based epoxies cured with DETA were found to bind aluminum, glass, and steel. Comparative lap shear tests (ASTM D1002–94) showed that DETA-cured epoxy allyl sucroses with an average of 3.2 epoxy groups per sucrose (EAS-3.2) generated a flexible adhesive comparable in bond strength to DGEBA. However, DETA-cured ECS-7.3 outperformed the bonding characteristics of both DGEBA and EAS-3.2. All sucrose-based epoxy polymers were crosslinked and insoluble in water, N,N-dimethylformamide, tetrahydrofuran, acetone, and dichloromethane. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2397–2413, 1998     

Synthesis and properties of a cyanate ester containing dicyclopentadiene(II)

A 2,6‐dimethyl phenol‐dicyclopentadiene novolac (DCPDNO) was synthesized from dicyclopentadiene and 2,6‐dimethyl phenol, and the resultant DCPDNO was reacted with cyanogen bromide into 2,6‐dimethyl phenol‐dicyclopentadiene cyanate ester (DCPDCY). The structures of the novolac and cyanate ester were confirmed with Fourier transform infrared spectroscopy, elemental analysis, mass spectrometry (MS), and nuclear magnetic resonance. For the purpose of increasing the mobility of residual DCPDCY during the final stage of curing and achieving a complete reaction of cyanate groups, a small quantity of a monofunctional cyanate ester, 4‐tert‐butylphenol cyanate ester (4TPCY), was added to DCPDCY to form the cyanate ester copolymer. The synthesized DCPDCY was then cured with 4TPCY at various molar ratios. The thermal properties of the cured cyanate ester resins were studied with dynamic mechanical analysis, dielectric analysis, and thermogravimetric analysis. These data were compared with those of the commercial bisphenol A cyanate ester system. Compared with the bisphenol A cyanate ester system, the cured DCPDCY resins exhibited lower dielectric constants (2.52–2.67 at 1 GHz), dissipation factors (0.0054–0.0087 at 1 GHz), glass‐transition temperatures (261–273 °C), thermal stability (5% degradation temperature at 406–450 °C), thermal expansion coefficients (4.8–5.78 × 10^?5/°C before the glass‐transition temperature), and moisture absorption (0.8–1.1%). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 671–681, 2005     

Low dielectric thermoset. IV. Synthesis and properties of a dipentene‐containing cyanate ester and its copolymerization with bisphenol A dicyanate ester

A 2,6‐dimethylphenol‐dipentene dicyanate ester ( DPCY ) was synthesized from the reaction of 2,6‐dimethylphenol‐dipentene adduct and cyanogen bromide. The proposed structure was confirmed by Fourier transform infrared (FTIR), elemental analysis, mass, and nuclear magnetic resonance (NMR) spectra. DPCY was then cured by itself or cured with bisphenol A dicyanate ester ( BADCY ). Thermal properties of cured epoxy resins were studied using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), dielectric analysis (DEA), and thermogravimetric analysis (TGA). These data are compared with those of BADCY . The cured DPCY exhibits a lower dielectric constant (2.61 at 1 MHz), dissipation factor (29.3 mU at 1 MHz), thermal stability (5% degradation temperature and char yield are 429 °C and 17.64%, respectively), glass transition temperature (246 °C by TMA and 258 °C by DMA), coefficient of thermal expansion (33.6 ppm before Tg and 134.1 ppm after Tg), and moisture absorption (0.95% at 48 h) than those of BADCY , but higher moduli (5.12 GPa at 150 °C and 4.60 GPa at 150 °C) than those of the bisphenol A system. The properties of cured cocyanate esters lie between cured BADCY and DPCY , except for moduli. Moduli of some cocyanate esters are even higher than those of cured BADCY and DPCY . A positive deviation from the Fox equation was observed for cocyanate esters. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3986–3995, 2004     

Synthesis and characterization of self‐catalyzed imide‐containing pthalonitrile resins

Some new amino‐ and imide‐containing phthalonitrile compounds with 1:1 molar ratio of amino group to pthalonitrile unit were successfully synthesized. The molecular structures were characterized by spectroscopic techniques. They were thermally polymerized under nitrogen/air, even in the absence of curing additives. The thermal properties of the cured products were characterized by thermogravimetric analysis and differential scanning calorimetry. The 5% weight loss temperatures ranged from 525 to 528 °C and 513 to 520 °C under nitrogen and air, respectively. Char yields (900 °C) were in the range of 62–70%. Rheometric measurements showed that the rate of the cure reaction differs for all the three monomers. The glass transition temperature advances with increasing extent of cure and disappears on postcure at 375 °C. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of novel bismaleimide monomers based on fluorene cardo moiety and ester bond: Characterization and thermal properties

Two novel bismaleimide monomers based on fluorene cardo moiety and ester bonds, namely 9, 9-bis[4-(4-maleimidobenzoate) phenyl]fluorene (PEFBMI) and 9,9-bis[4-(4-maleimidobenzoate)-3-methylphenyl]fluorene (MEFBMI) were designed and synthesized. Their structures were confirmed by FTIR, ¹H-NMR, ¹³C-NMR spectroscopy and Elemental analysis. Both monomers obtained have excellent solubility in some organic solvents with low boiling point, including acetone, chloroform and dichloromethane. The curing process of the monomers were investigated by DSC, displaying that the melting point of the monomers were 157.1°C and 193.6°C respectively, and all processing windows exceed 30°C. DMA results showed the glass transition temperature of the cured PEFBMI/glass cloth composite was higher than 390°C while that of the cured PEFBMI composite was 349.2°C. TGA results indicated that the cured BMI resins have good thermal stability and their 5% weight loss temperatures were both higher than 410°C.     

Preparation and property comparison of ortho,meta, and para autocatalytic phthalonitrile compounds with amino group

Phthalonitrile resins with many striking properties have drawn much attention as potential candidates for use in composite matrices, adhesives, films, and electrical conductors for the last 30 years. However, it is common shortcomings for phthalonitrile monomers to have high‐temperature melting point and need extreme conditions to develop binary phthalonitrile/additives composition. Here, three kinds of self‐catalyzed phthalonitrile compounds with low melting point were synthesized, whose structures were characterized by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance. The different cure behaviors, owing to the different positions of catalyzed group on benzene ring, were investigated by differential scanning calorimetry, and cure kinetics parameters were also calculated. The results showed that the meta and para position monomers possessed better reactivity. Melt‐processability study by a rheometer indicated that the ortho one owned the largest processing window. Furthermore, the FTIR spectra demonstrated that the cured monomers contained the same structure with a conventional binary phthalonitrile system. All the cured monomers had excellent thermal stability according to thermogravimetric analysis. Mechanical property was determined by dynamic mechanical analysis, and the results showed that the glass transition temperature (represented by the peak temperature of tanδ) was high up to 550°C for all the three cured monomers. Consequently, these autocatalytic phthalonitrile monomers may be good candidates as matrix for high‐performance polymeric materials. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis,characterization, thermal,and flame retardant properties of phosphate-based epoxy resins

A new phosphorus-containing oxirane bis-glycidyl phenylphosphate (BGPP), and a diamine, bis(4-aminophenyl)phenylphosphate (BAPP), were synthesized. Both of these two phosphorus-containing compounds lead to phosphate-containing epoxy resin via curing reaction. The kinetics of the curing reaction of BGPP with various curing agents, including BAPP, were studied. The introduction of electron-withdrawing group into the compounds increases the BGPP and decreases the BAPP reactivity in the curing reaction. The thermal and the weight loss behavior of the cured epoxy resins were studied by TGA. High char yields (32–52%) as well as high limiting oxygen index (LOI) values (34–49) of these phosphorylated resins were found, confirming the usefulness of these phosphorus-containing epoxy resins as flame retardants. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 565–574, 1997.     

Synthesis and thermal properties of thermosetting bis-benzocyclobutene–terminated arylene ether monomers

A series of new bis-benzocyclobutene-endcapped arylene ether monomers was prepared and characterized. Whereas 2,6-bis(4-benzocyclobutenyloxy)benzonitrile (BCB-EBN) could be prepared in good yield using the standard procedure (K₂CO₃/NMP/toluene/Dean–Stark trap/120°C), other bis(benzocyclobutene) (BCB)-terminated monomers containing ether-benzophenone (BCB-EK), ether-phenylsulfone (BCB-ES), and ether-6F-benzoxazole (BCB-EBO) moieties were invariably contaminated by mono-endcapped products under similar reaction conditions. This can be attributed to a much greater activating effect of the nitrile group on the ortho-fluorides in the aromatic nucleophilic displacement reaction than the carbonyl, sulfonyl, and benzoxazolyl groups. However, the latter monomers could be synthesized (70–80%) from 4-trimethylsiloxybenzocyclobutene and respective aromatic fluorides in the presence of CsF at 140°C. Similar curing behaviors under N₂ (DSC: extrapolated onset and peak temperatures at 227–230° and 260–262°C, respectively) characterized all four monomers. BCB-EK, BCB-ES, and BCB-EBN showed melting transitions at 108, 119, and 146°C, in that order. As BCB-EBO contained more rigid benzoxazole segments, it only exhibited a glass transition (T_g) at 85°C prior to curing exotherm, after it had been previously heated to 125°C. The following T_gs were observed for the cured materials: BCB-EK (201°C), BCB-EBN (224°C), BCB-ES (264°C), and BCB-EBO (282°C). The relative thermal stability according to TGA (He) results is: BCB-ES < BCB-EBN < BCB-EK < BCB-EBO. Finally, the results from thermal analysis, infrared spectroscopic, and variable temperature microscopic studies indicated that the nitrile group plays an important role in the cure chemistry, thermal, and microstructural properties of BCB-EBN. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2637–2651, 1998     

Synthesis and characterization of polyimides endcapped with phenylethynylphthalic anhydride

The synthesis of high glass transition temperature (T_g > 300°C), amorphous, soluble, poly-imide oligomers of controlled molecular weight endcapped with 4-phenylethynylphthalic anhydride endcapping agent is described. The 4-phenylethynylphthalic anhydride was employed to afford a higher curing temperature (380–420°C) which widens the processing window compared to unsubstituted acetylene-endcapped polyimides. The polyimides were synthesized via solution imidization techniques, using the ester-acid of various dianhydrides and aromatic diamines. A “ one-pot” procedure utilizing NMP as the solvent and o-dichlo-robenzene as the azeotroping agent reproducibly produced fully imidized, but yet soluble wholly aromatic polyimides. Thermally cured samples were prepared with gel contents of up to 98% that displayed good solvent resistance. Glass transition temperatures comparable to high molecular weight linear analogs were produced. These polyimides also show excellent thermal stability as judged by thermogravimetric analysis (TGA). Model phenylethynyl imide compounds were synthesized and used to follow and elucidate the nature of the products formed from the phenylethynyl curing by using high temperature magic-angle ¹³C nuclear magnetic resonance (MAS NMR). Preliminary results indicate that the cure reaction can be followed by MAS NMR. However, the nature of the products being formed during the curing process is difficult to determine by the solid-state MAS NMR alone. Differential scanning calorimetry (DSC) data clearly show that the model system does indeed melt and displays a wide window before the strong cure exotherm is observed. © 1995 John Wiley & Sons, Inc.     

Propargyl silicon‐cyclopentadiene oligomeric resin with high temperature resistance

Multiple propargyl substituted cyclopentadiene was synthesized by phase transfer reaction between cyclopentadiene and propargyl bromide in an aqueous solution mediated by sodium hydroxide. It was found that propargylated cyclopentadiene (PCp) could be thermally cured with a mass loss of ca 28%, while the cured material showed a high char yield of ca 76% at 900°C. In order to overcome the processing problems of PCp, a condensation reaction between PCp di‐anion and dimethyldichlorosilane was performed to make a silicon‐PCp (SiPCp) oligomeric resin. SiPCp resin has an acceptable processability, attributed to its organosolubility, low viscosity, and broad processing window. SiPCp resin can readily undergo thermal cure via addition polymerization of ethynyl groups in the temperature range of 170–270°C with an exothermic maximum at ca 240°C, and the mass loss upon cure was less than 5%. Evidenced by the results of dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) in a nitrogen atmosphere, the cured SiPCp resin exhibited stable thermo‐mechanical properties up to 320°C, and possessed an anerobic char yield of ca 77% at 900°C. The results of TGA in air atmosphere revealed the higher oxidation resistance of SiPCp resin. Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of temperature on cure kinetics and mechanical properties of vinyl–ester resins

The relationships among cure temperature, chemical kinetics, microstructure, and mechanical performance have been investigated for vinyl–ester resins. Fourier transform infrared spectroscopy was used to follow the reactions of vinyl–ester and styrene during isothermal curing of Dow Derakane 411‐C‐50 at 30 and 90°C. Reactivity ratios of vinyl–ester and styrene vinyl groups were evaluated using the copolymer composition equation. The results indicate that the ratio of vinyl–ester to styrene double bonds incorporated into the network is greater for 30 than for 90°C cure. Mechanical properties were obtained for systems subjected to isothermal cures at 30 and 90°C and postcured above ultimate T_g. The results show that the initial cure temperature significantly affects the mechanical behavior of vinyl–ester resin systems. In particular, values of strength and fracture toughness for postcured samples initially cured isothermally at 30°C are significantly higher than those obtained for samples cured isothermally at 90°C. Examination of fracture surfaces using atomic force microscopy revealed the existence of a nodular microstructure possessing characteristic nodule dimensions that are affected by the temperature of cure. Such features suggest the existence of phase separation during cure. A binary interaction model in conjunction with chemical kinetic data and estimated solubility parameters was used to evaluate enthalpic interactions between the growing polymer network and monomers of the vinyl–ester system. The results indicate that the interaction energy becomes increasingly endothermic as cure progresses and that this energy is affected by the temperature of cure through differences in copolymerization behavior. Hence, in addition to entropic factors, the changes in enthalpic contribution to the Gibbs free energy suggest that the probability of phase separation increases with extent of cure and that its onset is potentially affected by cure temperature. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 725–744, 1999     

Influence of the stoichiometry of epoxy-cyanate systems (non-catalyzed and catalyzed) on molten state reactivity

Based on an FT-IR and ¹³C-NMR spectroscopic study using model compounds, we previously proposed an epoxy-cyanate coreaction path in the molten state, by identifying all chemical species and their role in the reaction mixture. These data were then applied to difunctional systems involving diglycidyl ether of bisphenol A (DGEBA) and bisphenol A dicyanate (BADCy), with mixtures prepared in different epoxy/cyanate ratios. Using FT-IR and solid state ¹³C-NMR spectroscopic analyses, we show the effect of epoxy group concentration on the final structure of the system. We were able to show that epoxy functions react on the triazine rings formed in the first step of homopolymerization of cyanates, and that the structure of the final system depends on their initial concentration. In addition, a study of difunctional systems for identical cyanate-epoxy stoichiometry was undertaken in the presence of anionic (imidazole) and metallic (AcAcCu and AcAcCr) catalysts in order to determine their effect on the reactivity of the two monomers and on the structure of the final system. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3101–3115, 1997     

Thermostable laminating resins based on aromatic diketone bis- and tetramaleimides

Twelve structurally different bis- and tetramaleimides were synthesized by Friedel–Crafts reaction between 4-maleimido-benzoylchloride or 3,5-bismaleimido-benzoylchloride and various aromatic reagents. They were characterized by infrared (IR) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy. Crosslinked resins were obtained by curing the monomers at 250°C/6 h. Thermal characterization of monomers and cured resins was accomplished by differential thermal analysis (DTA), dynamic thermogravimetric analysis (TGA), and isothermal gravimetric analysis (IGA). Tetramaleimides were polymerized at lower temperatures than did the respective bismaleimides. The cured resins were stable up to 317–385°C in N₂ atmosphere and formed an anaerobic char yield of 52–66% at 800°C.     

Preparation,characterization, and polymerization of maleimidobenzoxazine monomers as a novel class of thermosetting resins

New series of benzoxazine‐based monomers, namely maleimidobenzoxazines, were prepared with hydroxyphenylmaleimide, formalin, and various amines (e.g., aniline, allylamine, and aminophenyl propargyl ether). The structure of the novel monomers was confirmed by IR, ¹H NMR, and elemental analysis. The monomers were easily dissolved in many common organic solvents. Differential scanning calorimetry of the novel monomers showed exotherms at different temperature ranges that corresponded to the polymerization regime of benzoxazine and maleimide along with other functionalities such as allyl or propargyl, if any. IR was studied to follow the progress of the curing reaction of maleimidobenzoxazine after various thermal treatments. The thermal cure of the monomers at 250 °C afforded a novel network structure that combined polybenzoxazine and polymaleimide. The dynamic mechanical analyses showed that the storage moduli of the thermosets derived from maleimidobenzoxazine were kept constant up to high temperatures. The glass‐transition temperatures were as high as 241–335 °C. Moreover, thermogravimetric analyses revealed that the thermosets did not show any weight loss up to about 350 °C, with char yields ranging from 62 to 70% at 800 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1424–1435, 2006     

Functionalized monomers based on N-(4-hydroxy phenyl)maleimide

N-(4-Hydroxy phenyl)maleimide (HPMI) is functionalized with acryloyl, methacryloyl, allyl, propargyl and cyanate groups and the structures of the materials are characterized by FTIR, ¹H NMR and ¹³C NMR. Thermal curing behaviours of the monomers and thermal stabilities of the polymers are studied using thermal analysis. Introduction of polymerizable groups shifts the curing exotherm to low temperatures, and the curing behaviour is dictated by the polymerizable substituent present in the aromatic ring. Polymer from acryloyl-functionalized monomer shows the highest thermal stability (402 °C), whereas the highest char value (49 % at 700 °C) is noted for the polymer obtained from propargyl-functionalized monomer. Polymers derived from functionalization of HPMI with acryloyl and methacryloyl showed better thermal stabilities. Thermosets formed by the thermal polymerization of HPMI functionalized with propargyl and cyanate groups showed higher char values at 700 °C in nitrogen atmosphere.