Synthesis of novel polyimides containing side‐chain azo‐2‐naphthol moieties

An amine‐ester derivative of isoeugenol was prepared in three steps. This amine‐ester was converted to diazonium salt and subsequently was reacted with 2‐naphthol and a novel isoeugenol ester‐azo derivative as a new monomer was obtained in quantitative yield. This monomer was characterized by high‐field ¹H‐NMR, IR, and elemental analysis and then was used for the preparation of model compound and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione was allowed to react with this new monomer. The reaction was very fast and gave only one double adduct by Diels–Alder and ene pathways in excellent yield. The polymerization reactions of novel monomer with bistriazolinediones [bis(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane and 1,6‐bis(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane] were carried out in N,N‐dimethylacetamide at room temperature. The reactions were exothermic, fast, and gave novel heterocyclic polyimides by repetitive Diels–Alder‐ene polyaddition reactions. Some structural characterization and physical properties of these novel heterocyclic polyimides are reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1942–1951, 2003     

Synthesis of novel photoactive heterocyclic polyimides containing naphthalene moieties via cycloaddition reactions

1‐Naphthylacetic acid (1) was reacted with thionyl chloride and 1‐naphthyl‐ acetyl chloride (2) was obtained in a quantitative yield. The reaction of this acid chloride (2) with isoeugenol (3) was performed in chloroform and a novel isoeugenol ester derivative (4) as a monomer was obtained in a high yield. The compound (4) was characterized by ¹H‐NMR, IR, mass, and elemental analyses and then was used for the preparation of a model compound (6) and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione (PhTD) (5) was allowed to react with compound (4). The reaction is very fast and gives only one double adduct (6) via Diels–Alder and ene pathways in an excellent yield. The polymerization reactions of the novel monomer (4) with bistriazolinediones [bis‐(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane (7) and 1,6‐bis‐(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane] (8) were carried out in N,N‐dimethylacetamide (DMAc) at room temperature. The reactions are exothermic and fast and gave novel heterocyclic polyimides containing a naphthalenic pendant group (9) and (10) via repetitive Diels–Alder‐ene polyaddition reactions. Stereochemical analysis of the model compound and fluorimetric studies of the model compound as well as polymers were done conclusively. Excimer formation of the polymers and its effect on fluorescence emission were investigated and some structural characterization and physical properties of these novel heterocyclic polyimides are reported. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 527–536, 2000     

Highly diastereoselective synthesis of novel polymers via tandem Diels–Alder–ene reactions

Cis -9,10-dihydro-9,10-ethanoanthracene-11-12-dicarboxylic acid anhydride (1) was converted into its amic acid derivative by reaction with L -leucine. The cyclization reaction was carried out in situ using triethylamine to give the succinic imide-acid derivative (2). Compound (2) was converted to the acid chloride (3) by reaction with thionyl chloride. The reaction of acid chloride (3) with isoeugenol (4) was carried out in chloroform and a novel optically active isoeugenol ester derivative (5) was obtained in high yield. 4-Phenyl-1,2,4-triazoline-3,5-dione (PhTD) (6) was allowed to react with compound (5). The reaction is very fast and gives only one diastereoisomer of (7) via Diels–Alder and ene pathways in quantitative yield. Compound (7) was characterized by ¹H NMR, IR, specific rotation and elemental analysis, and was used as a model for the polymerization reactions. The polymerization reactions of compound (5) with bis-triazolinediones (8), (9) were performed in N,N-dimethylacetamide (DMAc) at room temperature. The reactions are exothermic and fast, and give novel optically active polymers. Some physical properties and structural characterizations of these new polymers have been studied, and are reported. © 1999 Society of Chemical Industry     

Synthesis and characterization of novel optically active and flame‐retardant heterocyclic polyimides

Tetrachlorophthalic anhydride (1) was reacted with L ‐leucine (2) in toluene solution at refluxing temperature in the presence of triethylamine and the resulting imide‐acid (4) was obtained in quantitative yield. The compound (4) was converted to the N‐(tetrachlorophthaloyl)‐L ‐leucine acid chloride (5) by reaction with thionyl chloride. The reaction of this acid chloride (5) with isoeugenol (6) was carried out in chloroform and novel optically active isoeugenol ester derivative (7) as a chiral monomer was obtained in high yield. The compound (7) was characterized by ¹H‐NMR, IR, Mass and elemental analysis, and then was used for the preparation of model compound (10) and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione, PhTD (8) was allowed to react with compound (7). The reaction is very fast, and gives only one diastereomer of (10) via Diels–Alder and ene pathways in excellent yield. The polymerization reactions of novel monomer (7) with bistriazolinediones [bis‐(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane (11) and 1,6‐bis‐(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane] (12) were carried out in N,N‐dimethylacetamide (DMAc) at room temperature. The reactions are exothermic, fast, and give novel optically active polymers (13) and (14) via repetitive Diels–Alder‐ene polyaddition reactions. The resulting polymers are optically active, thermally stable, and flame resistant. All of the above compounds were fully characterized by IR, ¹H‐NMR, elemental analysis, and specific rotation. Some structural characterization and physical properties of these novel heterocyclic polyimides are reported. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 240–248, 2000     

Synthesis of novel heterocyclic polyimides containing trimellitimide acid moieties

4‐Nitrobezoyl chloride (2) was reacted with isoeugenol in chloroform in the presence of triethyl amine and ester (4) was obtained in high yield. Ester (4) was reacted with SnCl₂·2H₂O to give amine‐ester (5), and subsequently was reacted with trimellitic anhydride (6) and novel isoeugenol ester‐imide derivative (7), as a new monomer was obtained in quantitative yield. Compound (7) was characterized by high‐field ¹H–NMR, IR, and elemental analysis and then was used for the preparation of model compound (9) and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione (PhTD) (8) was allowed to react with compound (7). The reaction is very fast and gives only one double adduct (9) via Diels–Alder and ene pathways in excellent yield. The polymerization reactions of novel monomer (7) with bistriazolinediones [bis(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane (10) and 1,6‐bis(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane (11)] were carried out in N,N‐dimethylacetamide (DMAc) at room temperature. The reactions are exothermic, fast, and gave novel heterocyclic polyimides (12) and (13) via repetitive Diels–Alder‐ene polyaddition reactions. Some structural characterization and physical properties of these novel heterocyclic polyimides are reported. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1716–1725, 2001     

Copolymerization of a bisanthracene compound with bismaleimides by Diels–Alder cycloaddition

Four new polymers have been synthesized via succesive Diels–Alder cycloadditions of a bisdiene compound bearing two anthracene groups and four bisdienophiles, all containing bismaleimide functions. The polycondensation reaction was performed in N,N‐dimethylacetamide at 120 °C leading to polymers soluble in polar solvents having molecular weights lower than 6000 g mol^?1. © 2001 Society of Chemical Industry     

Diels–Alder‐based crosslinked self‐healing polyurethane/urea from polymeric methylene diphenyl diisocyanate

Crosslinked self‐healing polyurethane/urea based on a Diels–Alder reaction (C‐PMPU–DA) was synthesized from a multiple‐furan monomer and a commercial bismaleimide. The multiple‐furan monomer (PMPU–furan) was obtained from a functionalized prepolymer (polymeric MDI: PBA‐2000 = 2:1) by furfuryl amine. The structures of both the PMPU–furan and C‐PMPU–DA were characterized by attenuated total reflectance (ATR)–Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and ¹H‐NMR. The Diels–Alder bonds enabled C‐PMPU–DA thermal reversibility, which was investigated by ATR–FTIR spectroscopy, ¹H‐NMR, gel–solution–gel experiments, and viscosity tests. Meanwhile, the self‐healing properties of C‐PMPU–DA were also investigated by the recovery of the mechanical properties. The results showed that C‐PMPU–DA exhibited good thermal reversibility and self‐healing properties. C‐PMPU–DA exhibited thermosetting properties at room temperature, although it exhibited thermoplastic properties at higher temperatures and may find applications in self‐healing materials, recyclable materials, or removable materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40234.     

Polymerization of 1-methyl-2,5-bis[1-(4-phenylurazolyl)] pyrrole dianion with alkyldihalides

1-Methyl-2,5-bis[1-(4-phenylurazolyl)] pyrrole was prepared from the reaction of 4-phenyl-1,2,4-triazoline-3,5-dione with N-methylpyrrole in methylene chloride solution. This compound was converted to its potassium dianion salt upon reaction with potassium hydroxide in absolute ethanol. The reaction of this dianion salt with excess methyl iodide in dimethyl sulphoxide gave the methylated adduct in high yield. Polymerizations of this dianion salt with 1,2-dibromoethane, 1,2-diiodoethane and 1,4-diiodobuthane were performed in dimethyl sulphoxide and led to the formation of new polymers. Some structural characterization and physical properties of these novel polymers are reported. © 1998 SCI.     

Synthesis and thermal behavior of some anthracene‐based copolymers obtained by Diels–Alder cycloaddition reactions

New polymer structures have been synthesized via Diels–Alder cycloaddition of bisdiene compounds bearing two anthracene groups and different bisdienophiles, all containing bismaleimide or biscitraconimide functions. The monomers and polymers were characterized by FTIR, UV, and ¹H NMR techniques and compared with two models having a cycloadduct structure. The polymers were studied by thermogravimetric analyses. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Networks of partially hydrogenated cis-1,4-polybutadiene and ‘rigid rods’

Networks of ‘flexible’ and ‘rigid’ chains were synthesized. As ‘flexible’ component we have used different partially hydrogenated cis-1,4-polybutadiene. The ‘rigid’ component was synthesized from bis(1,2,4-triazoline-3,5-dione)s and biscyclohexadienes via repetitive Diels-Alder reaction. A slight excess of bis(1,2,4-triazoline-3,5-dione)s leads to polymers with 1,2,4-triazoline-3,5-dione end groups, which can easily react with the partially hydrogenated cis-1,4-polybutadiene. The influence of the extent of hydrogenation and the amount of crosslinker on the mechanical and thermal behaviour is described.     

Retro‐Diels–Alder Reactions of Masked Cyclopentadienones Catalyzed by Heterogeneous Brønsted Acids

The zeolite H‐Beta catalyzes the retro‐Diels–Alder reaction of a range of cyclopentadiene cyclo‐adducts at moderate temperatures and ambient pressure, in the presence of an active dienophile. The active catalyst was identified and optimum reaction conditions established after screening a range of zeolites in the retro‐Diels–Alder reaction of the cyclopentadiene adduct of cyclopentenone. Our results suggest that retro‐Diels–Alder reactions of tricyclodecadienones are catalyzed by Brønsted acids and the high catalytic performance of H‐Beta catalysts can be ascribed to the optimal balance between the number of acid sites and their strength as well as to the accessibility of these sites. The methodology was then applied to a series of alkyl derivatives of cyclopentadienylcyclopentenones to provide a viable alternative synthetic route to 4‐alkylcyclopentenones and the versatility of the approach was demonstrated by the successful cycloreversion of N‐cyclohexyl‐2‐azanorborn‐5‐ene.     

Polymerization of acrylated epoxidized soybean oil with phenol furfural resins via repeated forward and retro diels–alder reactions

In this work, the Diels–Alder reaction between the acrylate groups of acrylated epoxidized soybean oil and the furan rings of p‐tertiary butyl phenol furfural resin (TBPF) is described. The reaction was carried out at 110°C in presence of FeCl₃ catalyst, and tough polymers were obtained in 1 h. Surprisingly, samples that were heated and cooled 5, 10, and 20 times to 140°C and room temperature had better mechanical properties than samples that were kept at 140°C for the same total duration. This unexpected behavior is attributed to a series of forward and retro Diels–Alder reactions between the functional groups. To prove this hypothesis, a model reaction between TBPF and n‐butyl acrylate was studied. At 100°C, ¹H‐nuclear magnetic resonance signals of the furan ring protons disappeared, only to reappear at 140°C. Thermogravimetric analysis of the adduct showed a weight loss at 140–150°C, which was in quantitative agreement with the amount of butyl acrylate. Infrared analysis showed that furan rings were not completely consumed by extended heating at 110°C. After five heating and cooling cycles of much shorter duration at 140°C, the furan absorption in the infrared disappeared. The storage modulus of acrylated epoxidized soybean oil‐TBPF samples after 20 heating cycles was 1.15 GPa. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of novel azo‐containing polyureas derived from 4‐[4′‐(2‐hydroxy‐1‐naphthylazo)phenyl]‐1,2,4‐triazolidine‐3,5‐dione

4‐[4′‐(2‐Hydroxy‐1‐naphthylazo)phenyl]‐1,2,4‐triazolidine‐3,5‐dione ( HNAPTD ) ( 1 ) has been reacted with excess amount of n‐propylisocyanate in DMF (N,N‐dimethylformamide) solution at room temperature. The reaction proceeded with high yield, and involved reaction of both N? H of the urazole group. The resulting bis‐urea derivative 2 was characterized by IR, ¹H‐NMR, elemental analysis, UV‐Vis spectra, and it was finally used as a model compound for the polymerization reaction. Solution polycondensation reactions of monomer 1 with Hexamethylene diisocyanate ( HMDI ) and isophorone diisocyanate ( IPDI ) were performed in DMF in the presence of pyridine as a catalyst and lead to the formation of novel aliphatic azo‐containing polyurea dyes, which are soluble in polar solvents. The polymerization reaction with tolylene‐2,4‐diisocyanate ( TDI ) gave novel aromatic polyurea dye, which is insoluble in most organic solvents. These novel polyureas have inherent viscosities in a range of 0.15–0.22 g dL^?1 in DMF at 25°C. Some structural characterization and physical properties of these novel polymers are reported. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3177–3183, 2001     

Polyimides containing s‐triazine rings

A series of new polyimides containing s‐triazine rings have been synthesized via Diels–Alder intermolecular polymerization of 2,6‐bis(2‐furanylmethylimino)‐4‐isopropoxy‐1,3,5‐triazine with various bis(maleimide)s. All the poly(imino‐s‐triazine imide)s were characterized by elemental analyses, FTIR spectral studies, number average molecular weight ( M _n) by non‐aqueous conductometric titration and thermogravimetry. Glass‐fibre reinforced composites were prepared via an in situ Diels–Alder intermolecular reaction between 2,6‐bis(2‐furanylmethylimino)‐4‐isopropoxy‐1,3,5‐triazine and various bis(maleimide)s. The composites were characterized for chemical resistivity and mechanical properties. © 2003 Society of Chemical Industry     

No Evidence Found for Diels–Alder Reaction Products in Soybean Oil Oxidized at the Frying Temperature by NMR Study

It has been generally accepted that the Diels–Alder reaction mechanism is one of the major reaction mechanisms to produce dimers and polymers during heating process of vegetable oil. Soybean oil oxidized at 180 °C for 24 h with 1.45 surface area-to-volume ratio showed 36 % polymer peak area in gel permeation chromatogram. However, the NMR DEPT (Distortionless Enhancement by Polarization Transfer) 135 spectrum did not show any signals of possible Diels–Alder products. A fraction separated from the oxidized soybean oil by column chromatography contained 98 % polymers, but again, showed no signals of proposed Diels–Alder products in the DEPT 135 spectrum. Methyl oleate and triolein without a diene required for the Diels–Alder reaction produced 27 and 63 % of total polymers, respectively, under the same condition. This indicates that the polymers must be produced by reactions other than the Diels–Alder reaction for these oils. This study shows that the Diels–Alder reaction is not the major reaction to produce polymers during oxidation of soybean oil, within the DEPT 135 spectroscopy sensitivity level, about 5 mol %.     

Asymmetric Carbon‐Carbon Bond Forming Reactions Catalysed by Metal(II) Bis(oxazoline) Complexes Immobilized using Supported Ionic Liquids

A series of bis(oxazoline) metal(II) complexes has been supported on silica and carbon supports by non‐covalent immobilisation using an ionic liquid. The catalytic performance of these solids was compared for the enantioselective Diels–Alder reaction between N‐acryloyloxazolidinone and cyclopentadiene and the Mukaiyama‐aldol reaction between methyl pyruvate and 1‐methoxy‐1‐trimethylsilyloxypropene. In both reactions the enantioselectivity was strongly influenced by the choice of support displaying enantioselectivies (ee values) up to 40% higher than those conducted under homogeneous reaction conditions.     

A new method for producing optically active polybutadiene

The anionic polymerization of butadiene monomer in cyclohexane at 20°C gave polybutadiene (PB50) with a narrow molecular weight distribution. This polymer was allowed to react with 4-phenyl-1,2,4-triazoline-3,5-dione via the ‘ene’ reaction to the extent of 5, 10 and 15%. These functionalized polymers were reacted with N-phthaloyl-L -leucine acid chloride in the presence of pyridine at room temperature. These reactions lead to the replacement of N-H by an optically active group, and the resulting polymers became optically active. Some structural characterization and physical properties of these optically active polybutadienes are reported. © 1998 Society of Chemical Industry     

Chromophoric poly(urea‐urethane)s with pendent 3‐hydroxynaphthalene group: Synthesis and characterization

The reaction of 4‐(3‐hydroxynaphthalene)‐1,2,4‐triazolidine‐3,5‐dione ( 3HNTD ) with n‐propylisocyanate was performed at different molar ratios. The resulting monosubstituted urea and disubstituted urea‐urethane derivatives were obtained in high yields and were used as model compounds for polymerization reactions. 3HNTD as a monomer was used in the preparation of heterocyclic poly(urea‐urethane)s to produce photoactive polymers, by polycondensation with different diisocyanates in N,N‐dimethylacetamide (DMAc) solution. Chromophoric heterocyclic polymers containing naphthalene group, obtained in quantitative yields, possessed inherent viscosities in the range of 0.14–0.38 dL/g. The resulting poly(urea‐urethane)s is insoluble in most organic solvents, but easily soluble in polar solvents such as dimethyl sulfoxide (DMSO), DMAc, and N‐methylpyrrolidone (NMP). The polymers were characterized by IR, ¹H‐NMR, elemental analysis, and TGA. Fluorimetric and UV–vis studies of the monomer as well as polymers were performed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Epoxy‐amine based thermoresponsive networks designed by Diels–Alder reactions

The synthesis of Diels–Alder (DA) adducts from stoichiometric quantities of a new multi‐maleimide dienophile and epoxy‐amine type oligomers bearing furan group units on their side chains was investigated. Precursors of the DA reaction were first synthesized and their functionalities were determined by ¹H NMR and gel permeation chromatography/SEC analysis. TGA and DSC were used to characterize their thermal properties. In this study, the effect of the multi‐furan diene functionality on the network density was analyzed. Rheological analysis was used to highlight the thermal reversibility of the DA reaction and to calculate the average molar weight between crosslinks. The results showed that network density could be regulated or modulated by varying the functionality of the diene. Copyright © 2012 Society of Chemical Industry     

Synthesis and characterization of poly(ester-urethane-imide)s by Diels–Alder polyaddition

Poly(ester-urethane-imide)s were prepared by Diels–Alder polyaddition of 1,6-hexamethylene-bis(2-furanylmethylcarbamate) with various bismaleimides containing ester groups in the backbone. The Diels–Alder reaction was carried out in m-cresol, at 110°C, followed by thermal and chemical aromatization of tetrahydrophthalimide intermediates. The monomers and polymers were characterized by IR, ¹H-NMR spectroscopy and elemental analysis. Thermal properties of the polymers were investigated by differential scanning calorimetry and dynamic thermogravimetric analysis.