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1.
Instead of the traditional isocyanate curing system as the binder of solid propellant, a triazole curing system has been developed by the reaction of azide group and alkynyl group due to a predominant advantage of avoiding to the interference of humidity. In this work, the propargyl‐terminated polybutadiene (PTPB) was blended with glycidyl azide polymers (GAPs) to produce new composites under the catalysis of cuprous chloride at ambient temperature. The triazole‐crosslinked network structure was regulated by changing the molar ratio of azide group in GAP versus alkynyl group in PTPB, and hence various crosslinked densities together with the composition changes of GAP versus PTPB cooperatively determined the mechanical properties of the resultant composites. Furthermore, the formed triazole‐crosslinked network derived from the azide group in GAP and alkynyl group in PTPB resulted in the slight increase of glass transition temperatures and a‐transition temperatures, and improved the miscibility between GAP and PTPB. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40007.  相似文献   

2.
Bis‐propargylhydroquinone (BPHQ) is an alkyne functionalized isocyanate‐free curing agent for hydroxyl terminated azido polymers. Conventionally, glycidyl azide polymer (GAP) is cured by isocyanate based curatives, which are toxic and hygroscopic in nature. The reaction between hydroxyl end group of GAP and isocyanate is highly sensitive to moisture causing voids in the propellant, leading to poor mechanical properties. Herein, an alternate approach was adapted to exploit 1,3‐dipolar cycloaddition reaction between azido group of GAP and the triple bond (–C≡CH) of BPHQ without catalyst at 50 °C forming triazole crosslinked polymer. The curing behavior of GAP‐BPHQ system was studied by rheological method and based on the results the gel time was determined. In addition, the reaction between GAP and BPHQ was carried out with various GAP/BPHQ ratios (0.9 to 2.5) and effects on mechanical properties of resulting triazole polymers were investigated. Post curing hardness of GAP‐BPHQ binder system was tested by surface Shore‐A hardness measurement. The compatibility of BPHQ with energetic oxidizers such as ammonium dinitramide (ADN) and hydrazinium nitroformate (HNF) were also studied by differential scanning calorimetery (DSC) technique and showed good compatibility. The activation energy (E a) of cured GAP‐BPHQ binder was evaluated by DSC using Ozawa and Kissinger methods and are found to be 33.55 and 33.16 kcal mol–1, respectively. The advantage of this curing system between GAP and BPHQ is unaffected by moisture as compared to isocyanate based urethane systems and also no need to control humidity during the processing of propellant. The experimental results reveal that triazole crosslinked polymer system could be a better choice to develop novel energetic binder systems for explosives as well as propellants composition with improved performance and eco‐friendly nature.  相似文献   

3.
Instead of using urethane curing systems, which have long been used as solid propellants, a triazole curing system has been introduced into a new binder recipe in which azide groups in the polymer react with triple bonds of a dipolarophile curing agent. Commercially available glycidyl azide polymers (GAP) were used and an aliphatic curing agent, bispropargyl succinate (BPS), as well as an aromatic curing agent, 1,4‐bis(1‐hydroxypropargyl)benzene (BHPB), were synthesized as dipolarophile curing agent. Together with networks prepared under the triazole curing system, the networks under dual curing systems, which consist of an isocyanate curing agent and a dipolarophile curing agent, were prepared. Through swelling experiments, solubility parameters and crosslinking densities of the triazole crosslinked networks were determined by using Gee’s theory and Flory–Rhener theory. The mechanical properties of the triazole crosslinked networks were also investigated with different contents of the dipolarophile curing agent, along with the type of dipolarophile curing agent. The networks prepared under the triazole curing system did not show good mechanical properties. However, GAP‐based networks prepared under a dual curing system showed excellent mechanical properties with only a small amount of dipolarophile curing agent used. The effects of BPS and BHPB on the mechanical properties of the networks were much more distinguishable in networks prepared under a dual curing system rather than a single curing system.  相似文献   

4.
Glycidyl azide polymer (GAP) was cured through “click chemistry” by reaction of the azide group with bispropargyl succinate (BPS) through a 1,3‐dipolar cycloaddition reaction to form 1,2,3‐triazole network. The properties of GAP‐based triazole networks are compared with the urethane cured GAP‐systems. The glass transition temperature (Tg), tensile strength, and modulus of the system increased with crosslink density, controlled by the azide to propargyl ratio. The triazole incorporation has a higher Tg in comparison to the GAP‐urethane system (Tg−20 °C) and the networks exhibit biphasic transitions at 61 and 88 °C. The triazole curing was studied using Differential Scanning Calorimetry (DSC) and the related kinetic parameters were helpful for predicting the cure profile at a given temperature. Density functional theory (DFT)‐based theoretical calculations implied marginal preference for 1,5‐addition over 1,4‐addition for the cycloaddition between azide and propargyl group. Thermogravimetic analysis (TG) showed better thermal stability for the GAP‐triazole and the mechanism of decomposition was elucidated using pyrolysis GC‐MS studies. The higher heat of exothermic decomposition of triazole adduct (418 kJ ⋅ mol−1) against that of azide (317 kJ ⋅ mol−1) and better mechanical properties of the GAP‐triazole renders it a better propellant binder than the GAP‐urethane system.  相似文献   

5.
Acrylic polymers bearing pendant azide and propargyl groups were synthesized by chemical transformation of epoxy‐ and carboxylic functional acrylic precursor polymers and were characterized. These copolymers were crosslinked by reacting them in the presence of Cu(I) catalyst via the azide–alkyne click reaction leading to triazole networks. Influence of catalyst concentration on the crosslinking cure kinetics was investigated, and the activation parameters were evaluated. The activation energy decreased from 90 kJ mol?1 to 25 kJ mol?1 on catalyzing the cure reaction as estimated by Ozawa method. Differential scanning calorimetric analysis indicated thermal decomposition of the residual azide groups at around 200–220°C, which was catalyzed by Cu(I) with associated activation energy of 130–94 kJ mol?1. Isothermal cure reaction and decomposition of the azide groups were predicted using these parameters. Estimation of crosslink density by solvent swelling and dynamic mechanical analyses showed a normal crosslinking behavior. While the solvent swelling rate and the equilibrium swelling decreased, the front factor and diffusion coefficient of swelling showed a transition from non‐Fickian to Fickian as the triazole concentration increased in the network. The click reaction offered an alternate means to crosslink acrylate polymers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1289‐1300, 2013  相似文献   

6.
Depending upon the advantages of high efficiency, insensitivity to humidity and so on, the reaction of azide groups in glycidyl azide polymers (GAP) with alkynyl compounds has been used as a substitute of the urethane curing strategy to develop GAP‐based binder for solid propellant. In this work, an alkynyl compound of dimethyl 2,2‐di(prop‐2‐ynyl)malonate (DDPM) reacted with GAP to produce new crosslinked materials under the catalysis of Cu(I)Cl at ambient temperature, and showed great potential as a binder in composite propellant. As the feeding molar ratio of DDPM vs. GAP increased from 1 : 1 to 5 : 1, the crosslinking densities of as‐prepared materials gradually increased, together with simultaneous enhancement of Young's modulus and tensile strength. The breaking elongation showed the maximum value of ca. 82% when the feeding molar ratio of DDPM vs. GAP was 3 : 1. In addition, with an increase of the crosslinking densities, the glass transition temperatures of as‐prepared materials significantly increased from ?43.9°C to ?5.1°C while the mechanical loss peaks also gradually broadened and shifted up to high temperature, and even presented two peaks at the feeding molar ratio of DDPM vs. GAP higher than 4 : 1. It indicated that the formation of triazole‐based network resulted in structural heterogeneity in the as‐prepared materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40636.  相似文献   

7.
The mechanical properties of crosslinked polymers depend on their structural features, one of which is the functionality of the crosslinks in a polymer network. To study the effect of crosslink functionality (?) on the mechanical properties of 1,2,3‐triazole polymers for potential application as rocket propellant binders, crosslinkers with different ?'s (3, 4, 6, 16, 32, and 64) were used in the polymerization. As the percentage of acetylenic groups provided by crosslinker was kept constant and the functionality of the crosslinker increased, the resulting polymer showed a higher modulus but a lower strain. Compared to traditional polyurethane binders, 1,2,3‐triazole polymers showed comparable mechanical properties, although the stress and modulus tended to be lower and the strain capability tended to be greater for the triazole‐linked rubbers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

8.
The thermokinetics of the curing reactions between poly‐(3‐azidomethyl‐3‐methyloxetane) (PAMMO) and bispropargyl succinate (BPS) were studied using a microcalorimeter. On the basis of experimental and calculated results, three thermodynamics parameters (the activation enthalpies, the activation entropies, the activation free energies), the rate constant, three thermokinetic parameters (the activation energies, the pre‐exponential constant, and the reaction order) and the enthalpies of the curing reactions between PAMMO and BPS in the temperature range of 50–65 °C were obtained, showing that the main reaction leading to a triazole structure easily took place in the studied temperature range. The linear relationship between lnk and the molar ratio of triple bonds to azide groups was found. Furthermore, the corresponding kinetic equation describing the curing reaction between PAMMO and BPS was dα/dt=10−4.48(1−α)0.962 at 333.15 K.  相似文献   

9.
New poly(phthalazinone ether ketone)s (PPEKs) with pendent terminal ethynyl groups were synthesized by the aromatic nucleophilic substitution (SNAr) polycondensation reaction of a new bisphenol monomer, 2‐(3‐ethynylphenyl)hydroquinone, with 4‐(4′‐hydroxyphenyl)phthalazin‐1(2H)‐one and 4,4′‐bis(4‐fluorophenyl) ketone, followed by click modification reaction with 1‐azidopyrene. Fourier transform infrared and NMR spectral data of the model compound indicated that the terminal ethynyl groups were stable in SNAr reaction conditions, thus allowing the synthesis of the desired polymers. The PPEKs obtained with glass transition temperature (Tg) in the range 152–245 °C were amorphous, characterized by wide‐angle X‐ray diffraction, and dissolved in organic solvent to cast into transparent and flexible films. Differential scanning calorimetry results indicated that the curing reaction of the terminal ethynyl groups of the copolymers took place upon heating to 250 °C. The Tg of cured PPEKs was increased to about 260 °C. They also exhibited excellent thermal stability with 5% weight loss temperatures ranging from 448 to 527 °C in various atmospheres. The PPEKs with pendent terminal ethynyl groups were subsequently functionalized with pyrene through click reaction. A dilute chloroform solution displayed a red‐shifted emission profile. © 2014 Society of Chemical Industry  相似文献   

10.
Lately, copper‐assisted azide–alkyne cycloaddition (CuAAC) has become a very interesting tool for synthesizing biocompatible polymer‐based materials such as hydrogels or microgels, which can be used as biomaterials for tissue engineering and drug delivery. Novel poly(2‐hydroxyethyl aspartamide)s (PHEAs) functionalized with pendent acetylene or azide groups were prepared from polysuccinimide, which is the thermal polycondensation product of aspartic acid, through successful ring‐opening reactions using propargylamine, 1‐azido‐2‐aminoethane and ethanolamine. The composition of the prepared copolymers was analyzed using 1H NMR spectroscopy. Clickable PHEA derivatives were crosslinked by mixing together in water with a catalyst system of Cu(I) and N, N, N′, N′, N″‐pentamethyldiethylenetriamine, a type of Huisgen's 1,3‐dipolar azide‐alkyne cycloaddition. The reaction of the polymers resulted in a chemoselective coupling between alkynyl and azido functional groups with multiple formation of triazole crosslinks to give hydrogels. The triazole linkages in the hydrogels are highly stable and may also play a role in swelling behavior. PHEA‐based hydrogels were also obtained by the crosslinking of azide‐ or alkyne‐modified PHEA with a small‐molecule crosslinker. The hydrogels prepared using these two methods were characterized by their degree of swelling and the morphology of the hydrogels was confirmed using scanning electron microscopy. The approach we describe here presents a promising alternative to common chemical hydrogel preparation techniques, and these hydrogels seem to possess structures having potential for a variety of industrial and biomedical applications. © 2012 Society of Chemical Industry  相似文献   

11.
N‐[2‐Methyl‐5‐(triazol‐1‐yl)phenyl]pyrimidin‐2‐amine derivatives were synthesized and evaluated in vitro for their potential use as inhibitors of Bcr‐Abl. The design is based on the bioisosterism between the 1,2,3‐triazole ring and the amide group. The synthesis involves a copper(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) as the key step, with the exclusive production of anti‐(1,4)‐triazole derivatives. One of the compounds obtained shows general activity similar to that of imatinib; in particular, it was observed to be more effective in decreasing the fundamental function of cdc25A phosphatases in the K‐562 cell line.  相似文献   

12.
A new approach to the modification of azidomethyl polyethersulfones using click reactions with acetylenic derivatives in the presence of CuBr as catalyst is presented. An azidomethyl polyethersulfone was prepared by the reaction of chloromethylated polysulfone with sodium azide in dimethylformamide. By the Cu(I)‐catalysed Huisgen 1,3‐dipolar cycloaddition reaction of the azidomethyl polyethersulfone to acetylenic derivatives, new polyethersulfones containing 1,2,3‐triazole rings were obtained. The structures of the polymers were confirmed using attenuated total reflectance Fourier transform infrared and NMR spectroscopy. The polymers were characterized using dynamic mechanical analysis, thermogravimetric analysis, stress‐strain and water contact angle measurements and solubility tests. The polymers bearing 1,2,3‐triazole rings having OH or COOH as substituents exhibited static contact angles smaller than that of the parent polyethersulfone. Copyright © 2010 Society of Chemical Industry  相似文献   

13.
Alkyne functional phenolic resin was cured by azide functional epoxy resins making use of alkyne‐azide click reaction. For this, propargylated novolac (PN) was reacted with bisphenol A bisazide (BABA) and azido hydroxy propyloxy novolac (AHPN) leading to triazole‐linked phenolic‐epoxy networks. The click cure reaction was initiated at 40–65°C in presence of Cu2I2. Glass transition temperature (Tg) of the cured networks varied from 70°C to 75°C in the case of BABA‐PN and 75°C to 80°C in the case of AHPN‐PN. DSC and rheological studies revealed a single stage curing pattern for both the systems. The cured BABA‐PN and AHPN‐PN blends showed mass loss above 300°C because of decomposition of the triazole rings and the novolac backbone. Silica fiber‐reinforced syntactic foam composites derived from these resins possessed comparable mechanical properties and superior impact resistance vis‐a‐vis their phenolic resin analogues. The mechanical properties could be tuned by regulating the reactant stoichiometry. These low temperature addition curable resins are suited for light weight polymer composite for related applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41254.  相似文献   

14.
To further understand the relationship between the polymer structure and nonlinear optical (NLO) property, in this article, three fluorene‐based triazole functional polymers with different linked chains were designed and controllably prepared by click chemistry method. The structures and properties of these polymers were characterized and evaluated with Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, ultraviolet spectroscopy, fluorescence spectra, dynamic state laser light scattering, thermogravimetric analysis, and NLO analyses. The results exhibited that the target polymers displayed good solubility, high thermal stability, and well NLO properties. The relationships between molecular structures and optical properties were investigated by both theoretical simulation and experimental results. It was found that the rigid conjugated linked chain between triazole and chromophore can effectively enhance the NLO properties of the resultant polymers. The suitable rigid and flexible groups in the triazole polymers will result in good thermal stabilities. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40878.  相似文献   

15.
A series of new polyphosphazene polymers were synthesized using three different pendant groups with the goal of probing structure–function relationships between pendant group substitution and polymer swelling/water flux through thin dense films. Formation of polymers with relative degrees of hydrophilicity was probed by varying the stoichiometry of the pendant groups attached to the phosphazene backbone: p‐methoxyphenol, 2‐(2‐methoxyethoxy)ethanol, and o‐allylphenol. The polymers in this study were characterized using NMR, thermal methods, and dilute solution light‐scattering techniques. These techniques revealed that the polymers were amorphous high polymers (Mw = 105–107) with varying ratios of pendant groups as determined by integration of the 1H‐ and 31P‐NMR spectra. Thin dense film membranes were solution‐cast with azo‐bis(cyclohexane)carbonitrile included in the matrix and crosslinked using thermal initiation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 422–431, 2001  相似文献   

16.
A maleimide‐functional phenolic resin was reactively blended with an allyl‐functional novolac in varying proportions. The two polymers were coreacted by an addition mechanism through Alder‐ene and Wagner–Jauregg reactions to form a crosslinked network system. The cure characterization was done by differential scanning calorimetry and dynamic mechanical analysis. The system underwent a multistep curing process over a temperature range of 110–270°C. Although the cure profiles were independent of the composition, the presence of maleimide led to a reduced isothermal gel time of the blend. Increasing the allylphenol content decreased the crosslinking in the cured matrix, leading to enhanced toughness and improved resin‐dominant mechanical properties of the resultant silica laminate composites. Changing the reinforcement from silica to glass resulted in further amelioration of the resin‐reinforcement interaction, but the resin‐dominant properties of the composite remained unaltered. Increasing the maleimide content resulted in enhanced thermal stability. Integrating both the reactive groups in a single polymer and its curing led to enhanced thermal stability and Tg, but to decreased mechanical properties of the laminate composites. This can be attributed to a brittle matrix resulting from enhanced crosslinking facilitated by interaction of the reactive groups located on the polymer of an identical backbone structure. The cured polymers showed a Tg in the range of 170–190°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 737–749, 2001  相似文献   

17.
BACKGROUND: ‘Click’ chemistry, or the 1,3‐dipolar cycloaddition of organic azides with alkynes, has been evaluated for many biomedical purposes; however, its utility in crosslinking hydrogels in situ is limited by the toxicity of the requisite copper(I) catalyst. We report the first use of catalyst‐free Huisgen cycloaddition to generate crosslinked hydrogels under physiological conditions using multivalent azide‐functionalized polymers and an electron‐deficient dialkyne crosslinker. RESULTS: Water‐soluble azide‐functionalized polymers were crosslinked with an electron‐deficient dialkyne crosslinker to form hydrogels at physiological temperature without the addition of copper(I) catalyst. Crosslinking was confirmed using scanning electron microscopy, Fourier transform infrared and 1H NMR analyses. Flow by vial inversion and dynamic rheological methodologies were implemented to evaluate gelation kinetics at 37 °C of variable polymer compositions, concentrations and stoichiometric ratios. Kinetic studies revealed gelation in as little as 12 h at 37 °C, although strong gels that withstand inversion were observed by 1–8 days. CONCLUSION: The ability to form hydrogel networks under mild conditions demonstrates the potential viability of the catalyst‐free ‘click’ crosslinking chemistry for in situ gelling and other biological applications. Further chemical modifications in the crosslinking moieties, as well as polymer and crosslinker conformations, are expected to enhance gelation kinetics to a more biomedically practical rate. Copyright © 2009 Society of Chemical Industry  相似文献   

18.
Crosslinking and de‐crosslinking reactions of an alternating copolymer of maleic anhydride (MAn) and 2,4‐dimethyl‐1,3‐pentadiene (DMPD) by thermal curing with polyfunctional alcohols as the crosslinkers and subsequent ozone degradation are reported in this article. The ring‐opening reaction of an anhydride group by polyfunctional alcohols produces network polymers with an ester linkage. The rate of crosslinking reaction depends on the curing conditions, i.e. the structure of the used alcohols and the curing temperature and time. The crosslinking density of the alcohol‐cured copolymers is low due to a slow reaction between the anhydride and hydroxy groups, being different from the corresponding epoxy‐cured copolymer with a dense network structure reported in a previous article. The insoluble resins are readily de‐crosslinked and solubilized by ozone degradation. The polymer surface modification by ozone is also investigated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42763.  相似文献   

19.
A new, asymmetrical zinc phthalocyanine (aZnPc)‐functional photocurable copolymer was prepared by the combination of atom transfer radical polymerization and copper (I)‐catalyzed azide‐alkyne cyclo‐addition (CuAAC) click reaction and used as polymer matrix of polymer dispersed liquid crystal (PDLC) film. For this purpose, aZnPc was prepared through statistical condensation of 4‐tert‐butylphthalonitrile and 4‐pent‐4‐ynyloxyphthalonitrile. Double CuAAC click reaction between azido‐functional poly(methyl methacrylate‐co‐2‐(2‐bromoisobutyryloxy)‐ethyl methacrylate), terminal alkynyl‐substituted aZnPc, and 4‐ethynyl‐N,N‐dimethyl aniline yielded photocurable aZnPc‐functional copolymer. Thereby, synthesized copolymer was crosslinked in the presence of liquid crystalline mesogen 4′‐(octyloxy)‐4‐biphenylcarbonitrile by ultraviolet irradiation using benzophenone as initiator and ethylene glycol dimethacrylate as difunctional crosslinker. Thermal and optical properties of PDLC film were investigated by using differential scanning calorimetry and polarized optical microscopy. Smectic A liquid crystal mesophases were observed in both PDLC film and its mesogenic component 4′‐(octyloxy)‐4‐biphenylcarbonitrile. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41574.  相似文献   

20.
Novel hyperbranched poly([1,2,3]‐triazole‐[1,3,5]‐triazine)s (HBP TT) were synthesized by a 1,3‐dipolar cycloaddition reaction from AB2 monomer – 2‐azido‐4,6‐bis‐prop‐2‐yn‐1‐yloxy‐ [1,3,5]‐triazine (ABPOT). The monomer contains one azide group A and two terminal alkyne units B. Thermal polymerization of ABPOT in bulk or in DMF solution leads to hyperbranched polymers containing both 1,4‐ and 1,5‐disubstituted [1,2,3]‐triazoles. The monomer was also polymerized catalytically in the presence of Cu(I) salts under mild reaction conditions in DMSO solution and in bulk affording hyperbranched poly‐[1,2,3]‐triazoles 1,4‐disubstituted only. The reactions lead to the products soluble in aprotic polar solvents like DMSO or DMF. Side reactions can proceed in a few cases, particularly: (i) homocoupling of alkyne groups, leading to the formation of insoluble products as a result of cross‐linking, (ii) isomerization of propynyloxytriazine fragments to propynyl‐ or propadienyltriazinone ones, and (iii) hydrolysis of triple bonds without the loss of solubility. Heats of formation of monomer and synthesized polymers were calculated from their combustion heats. All products were characterized by NMR‐, IR‐spectroscopy, and size exclusion chromatography (SEC) data. The obtained results open the prospect for the use of HBP TT as the high‐enthalpy modifiers for energetic and non‐energetic binders.  相似文献   

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