Laminating resins obtained from 2,2′-(1,4-phenylenedivinylene)bispyridine bismaleimides and maleimide-terminated styrylpyridine prepolymers

A new bismaleimide (2a) , biscitraconimide (2b) , and bisnadimide (4) were synthesized by reacting 2-amino-6-methylpyridine with an equimolar amount of maleic, citraconic, or nadic anhydride, respectively, and then with a half molar amount of 1,4-benzenedicarbaldehyde in the presence of acetic anhydride. They, as well as the intermediate amic acids ( 1a, 1b, and 3 ) were characterized by IR and ¹H-NMR spectroscopy. The DTA thermograms showed that crosslinking of polymer precursors started at 180–212°C. The crosslinked resins obtained from 2a and 2b were stable up to 300–313°C and afforded anaerobic char yield of 53–60% at 800°C. The cured resin of 4 was less thermostable. In addition, end-capping of styrylpyridine prepolymers was accomplished by reacting 2,6-dimethylpyridine (n mol) with 1,4-benzenedicarbaldehyde (n + 1 mol) in acetic anhydride to yield a formyl-terminated styrylopyridine prepolymer. The latter reacted with the maleamic acid 1a (2 mol) to afford a series of maleimide-terminated styrylpyridine prepolymers MTSOs. They showed lower curing temperatures than did the ordinary poly(styrylpyridine). Their cured resins did not lose weight up to 310–344°C both in N₂ or air and afforded anaerobic char yield of 66-72% at 800°C.     

Synthesis and radical polymerization behavior of bifunctional vinyl monomer derived from N‐vinylacetamide and p‐chloromethylstyrene

The radical polymerization of N‐(p‐vinylbenzyl)‐N‐vinylacetamide ( 1 ) prepared by the reaction of N‐vinylacetamide with p‐chloromethylstyrene was carried out by using radical initiators such as AIBN or BPO in benzene, chlorobenzene, or bulk. As a result, poly 1 was successfully isolated by dialysis (yield, 10–36%). The crosslinking reaction of poly 1 was carried out at 60–100 °C for 8 h. By using a radical initiator such as AIBN or BPO (3 mol %), the crosslinking reaction proceeded (yield, 63–79%). Moreover, the crosslinking reaction of poly 1 proceeded at 100 °C without a radical initiator in 50% yield. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2714–2723, 2006     

Studies on metathetical and thermal polymerization of 5-norbornene 2,3-dicarboximide end-capped resins Pt-II

The article deals with synthesis, characterization, and polymerization of 5-norbornene-2,3-dicarboximide end-capped resins (bisnadimides) based on 4,4′-diaminodiphenylether, 1,4/1,3-bis(4′-aminophenoxy) benzene, 2,2′-bis[4-(4′-aminophenoxy)phenyl]propane, and bis[4-(4′-aminophenoxy)phenyl]sulphone. Both exo and endo bisnadimides were prepared by reacting the aromatic diamines with exo or endo nadic anhydride in glacial acetic acid at 120°C. The exo or endo bisnadimides could be distinguished on the basis of differences observed in IR or ¹H-NMR spectra. Both thermal (in solid state) and metathetical polymerization (using WCl₆/tetramethyltin catalyst and chlorobenzene solvent) of bisnadimides was carried out. Only exo bisnadimides could be polymerized using metathesis reaction whereas thermal polymerization of both endo and exo bisnadimide could be successfully carried out at 300°C in static air atmosphere. The polymers were highly crosslinked and insoluble in common organic solvents. The polymers obtained by metathesis polymerization were light brown in color whereas those obtained by thermal polymerization were dark brown in color. Thermal stability of the thermally polymerized exo or endo bisnadimides was comparable. These polymers were stable up to 400°C and decomposed in a single step above this temperature. The char yield at 800°C depended on the structure of the polymer and was in the 39–56% range. The polymers formed by metathesis polymerization showed a 1–3% weight loss in the temperature range 226–371°C and decomposed in a single step above 440°C. The char yields were higher in these polymers (53–71%) compared to those obtained by thermal polymerization. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2323–2331, 1997     

Poly(Ether sulfone)s made from 4,4′-dihydroxystilbene and 4,4′-difluorodiphenylsulfone: Synthesis,crosslinking, and epoxidation with hydrogen peroxide

High molecular weight polymers from trans-4,4′-dihydroxystilbene, bisphenols, and 4,4′-difluorodiphenylsulfone were synthesized by a nucleophilic displacement reaction using DMAc as solvent in the presence of potassium carbonate. Characterization and crosslinking studies of these polymers were carried out by DSC, TGA, TMA, x-ray diffraction, and solution and solid NMR. It was found that all polymers can be crosslinked to some extent on heating to 350°C. We also studied the epoxidation of these polymers with hydrogen peroxide in the presence of methyltrioctylammonium tetrakis (diperoxotungsto) phosphate (3—) as the catalyst in a biphasic system. The epoxidized polymers are thermally cross-linkable. Very efficient crosslinking was obtained by heating the epoxidized polymers at 350°C under nitrogen. © 1995 John Wiley & Sons, Inc.     

Thermally crosslinkable polyimides containing the 1,2-diphenylcyclopropane or diphenylacetylene moiety

Poly(ether imide)s containing the 1,2-diphenylcyclopropane or diphenylacetylene moiety have been synthesized from two new dianhydrides by solution condensation. Characterization of and crosslinking studies on these polymers were carried out utilizing DSC, TGA, and NMR. The polymers can be thermally crosslinked when heated above 350°C and the glass transition temperatures (T_g) of the polymers increase after crosslinking. The resulting crosslinked networks are insoluble in all solvents tried. Thermogravimetric analysis shows that no significant weight loss accompanies the cross-linking reaction. © 1996 John Wiley & Sons, Inc.     

Crosslinking of porcine aortic leaflets with butane‐1,4‐diol diglycidyl ether

Currently, efforts are being made to reduce xenograft calcification and to optimize biomechanical properties by applying different crosslinking methods and techniques. Porcine aortic leaflets could be stabilized with a bisepoxy compound, butane‐1,4‐diol diglycidyl ether (BDDGE), under acidic (pH 4.5) or alkaline conditions (pH > 8.5). Maximum values of the shrinkage temperature (83°C), which are comparable to glutaraldehyde‐crosslinked materials, are achieved at pH 9.0 and 10.0 within 48 h with a BDDGE concentration of 4 wt6percnt;. The crosslinking efficacy decreased at higher pH values or at prolonged reaction times due to a higher proportion of one‐side or masking reactions. Crosslinking of aortic leaflets at pH 4.5, which consisted in a reaction between the epoxide groups of BDDGE and the carboxylic acid groups of the tissue, afforded crosslinked material with a shrinkage temperature of 76°C after 7 days of reaction.     

Heat-Resistant thermosetting polyamide and polymides with styrlpyridine segments derived from 2,2′-(1,4-phenylenedivinylene) bisaminoquinoline

The nitration of quinaldine by fuming nitric and sulfuric acid afforded nitroquinaldine. It was condensed with a half molar amount of 1,4-benzenedicarbaldehyde in the presence of acetic anhydride to yield 2,2′-(1,4-phenylenedivinylene) bisnitroquinoline. The latter was catalytically hydrogenated to the corresponding diamine, PBAQ. The new polyamide and polymides bearing styrylpyridine segments were prepared utilizing PBAQ as starting material. In addition, a model diamide and diimide were synthesized and characterized IR and ¹H-NMR spectroscopy. Inherent viscosities of polymers ranged from 0.31 to 0.60 dl/g. Certain polymer precursors such as a bismaleimide and bisnadimide were synthesized from the reactions of PBAQ with maleic and nadic anhydride, respectively. Their curing behavior was investigated by DTA. Curing of polyamide, polyimides, and polymer precursors at 240°C for 15 h yielded crosslinked polymers. They were stable up to 329–310°C in N₂ or air and afforded a char yield of 67–62% in N₂ at 800°C. © 1994 John Wiley & Sons, Inc.     

Polyaromatic ether-ketones containing various biphenylene units as crosslinking sites

Polyaromatic ether-ketones were prepared from diphenyl ether, isophthaloyl dichloride, and small amounts of 2,6-, 2,7-, 1,5-, and 1,8-dicarboxylic acid chloride of biphenylene, respectively, by Friedel–Crafts reaction. Biphenylene units were incorporated as crosslinking sites. Crosslinking is achieved by curing the polymers at 310–350°C for several hours. While the uncured resins are soluble in concentrated sulfuric acid, the fully crosslinked polymers are completely insoluble.     

Modification of poly(vinyl chloride). X. Crosslinking of poly(vinyl chloride) with a soft segment of an elastomer containing thiol groups

To obtain poly(vinyl chloride) (PVC) of excellent toughness, a new method of crosslinking PVC is proposed in which PVC is crosslinked with the soft segment in an elastomer such as liquid Thiokol. The reaction can be accomplished by immersing PVC–Thiokol blends in liquid ammonia at 20–30°C. A similar reaction occurs in aqueous ammonia when hexamethylphosphoramide is used as an activator. Characteristics of the crosslinked PVC thus obtained and of the controls of a similar uncrosslinked composition (PVC–Thiokol LP-8, 100:5 by weight) were as follows: tensile strength, 7.3 and 4.8 kg/mm²; elongation at break, 30 and 2.5%; Young's modulus, 3.5 × 10⁴ and 2.9 × 10⁴ kg/cm²; tensile impact, 88 and 15 kg-cm/cm³, respectively. The crosslinked PVC as plasticized with dioctyl phthalate (DOP) and the control blend (PVC–Thiokol LP-8–DOP, 100:10:10 by weight), respectively, showed tensile strengths of 5.9 and 4.8 kg/mm², elongations at break of 44 and 24%, Young's moduli of 2.5 × 10⁴ and 1.6 × 10⁴ kg/cm², and tensile impact strengths of 62 and 120 kg-cm/cm³. As the crosslinkage through the soft segments increases up to about 5%, the elongation at break, Young's modulus, and tensile impact, in addition to the tensile strength, are improved. This is different from the results so far observed with the crosslinked amorphous polymers and is characteristic of the products of crosslinking through the soft segment. The experimental results are discussed in this paper.     

Acid‐promoted double ring‐opening reaction of bicyclobis (γ‐butyrolactone) with alcohol and its application to polyester synthesis

Bicyclobis(γ‐butyrolactone) (BBL) bearing methyl group 1a reacted with benzyl alcohol (BnOH) in the presence of p‐toluenesulfonic acid (p‐TsOH) through the double ring‐opening of the bislactone structure to afford the corresponding adduct 2a bearing carboxyl group. The resulting carboxyl group underwent condensation with BnOH to afford the corresponding diester 3a . The second step was quite slow at ambient temperature; however, it was efficiently accelerated by elevating temperature to 120 °C or performing under reduced pressure at 80 °C to afford 3a in an excellent yield. Based on these results, the reaction of 1a with xylene‐α,α‐diol (XyD) was carried out in chlorobenzene at 120 °C to obtain the corresponding polyester bearing ketone group in the side chain. The condensation reaction in the second step was effectively promoted by simultaneous removal of water under reduced pressure. BBLs 1b and 1c bearing reactive groups, isopropenyl and chloromethyl, respectively, were also employed as monomers efficiently. Their reactions with XyD gave the corresponding reactive polyesters bearing methacryloyl and chloroacetyl moieties, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Polyimides derived from diels-alder polymerization of furfuryl-substituted maleamic acids or from the reaction of bismaleamic with bisfurfurylpyromellitamic acids

Certain AB or AA and BB Diels-Alder polymer precursors bearing maleimide and furan segments were synthesized, characterized, and polymerized. Particularly, the monomaleamic acid derived from 4,4'-diaminodiphenylmethane, reacted with the monofurfurylpyromellitamic acid to yield a triamic acid which was cyclodehydrated to the corresponding triimide. A polyimide was obtained upon heat-curing of triimide or the intermediate triamic acid. In addition, equimolar amounts of N,N'-bismaleimido-4,4'-diphenylmethane (BMDM) and bisfurfurylpyromellitimide or their intermediate diamic acids were cured to afford a polyimide. The polymer precursors were characterized by IR and ¹H-NMR spectroscopy and their curing behavior was investigated by DTA. It was shown that the Diels-Alder polymerization of monomers took place at lower temperature than that required for crosslinking of BMDM. The thermal stabilities of polymers were ascertained by TGA and isothermal gravimetric analysis (IGA). The synthesized Diels-Alder polymers were remarkably more heat-resistant than the crosslinked polymer obtained from BMDM or its intermediate bismaleamic acid. They were stable up to about 360°C in N₂ or air and afforded anaerobic char yield of 58% at 800°C. © 1992 John Wiley & Sons, Inc.     

Synthesis and crosslinking of cyano-substituted polyamides and polyimides prepared from 1-(2,2-dicyano-1-hydroxyviyl)-3,5-diaminobenzene,sodium salt

3,5-Dinitrobenzoyl chloide was condensed with malononitrile in the presence of sodium hydroxide under phase-transfer conditions to afford 1-(2,2-dicyano-1-hydroxyvinyl)-3,5-dinitrobenzene, sodium salt, which was catalytically hydrogenated to the corresponding diamine. The latter was used as starting material for the preparation of unsaturated cyanosubstituted polyamides and polyimides. The polymers were soluble in polar aprotic solvents, dilute sodium hydroxide, and certain strong inorganic and organic acids. Upon curing at 300°C for 65 h, crosslinked polymers were obtained that were stable up to 392–404°C in N₂ or air and afforded an anaerobic char yield of 60–71% at 800°C. Their glass transition temperatures as determined by thermal mechanical analysis (TMA) were 221–275°C. © 1995 John Wiley & Sons, Inc.     

Living cationic polymerization of a coumarin‐substituted vinyl ether and reversible photoinduced crosslinking of the resulting homopolymers and amphiphilic block copolymers

Living cationic polymerization of 4‐methyl‐7‐(2‐vinyloxyethoxy)coumarin (CMVE) was achieved using SnCl₄ in the presence of nBu₄NBr as an added salt at 0 °C. The number‐average molecular weight of the resulting polymers increased in direct proportion to the monomer conversion while retaining relatively low polydispersity. Structural analysis revealed that the resulting polymers carried pendant coumarinyl moieties. These coumarinyl moieties were crosslinked by irradiation with UV light at λ_max = 366 nm, and the crosslinked sites were then cleaved by irradiation with UV light at λ_max = 254 nm. The crosslinking behaviors of the polymers were studied by UV and FTIR spectroscopic measurement. PolyCMVE was soluble in dichloromethane but was found to be insoluble upon UV light irradiation. We also synthesized amphiphilic block polymers bearing coumarinyl moieties by living cationic copolymerization with an amphiphilic vinyl ether. The resulting block polymers were soluble in an aqueous medium and also formed micelle‐like aggregates. Upon UV irradiation of aqueous solutions above the critical micelle concentration, an efficient crosslinking reaction occurred. Photoinduced structural changes of these polymer aggregates in the solution state were further investigated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A novel polyaddition of bis(epoxide)s with triazine diaryl ether for the synthesis of poly(ether)s containing triazine group in the main chain

Poly(ether)s (P‐1–P‐4) containing triazine groups in the main chain and pendant phenoxy groups in the side chain were synthesized by the polyaddition of bis(epoxide)s with 2,4‐di‐(p‐chlorophenoxy)‐6‐(diphenylamino)‐s‐triazine (DCTA) with quaternary onium salts or crown ether complexes as catalysts. The polyaddition of diglycidyl ether of bisphenol A with DCTA proceeded smoothly in chlorobenzene at 120 °C for 24 h to give P‐1 with a number‐average molecular weight of 24,800 in a 95% yield when tetraphenylphosphonium chloride (TPPC) was used as a catalyst; however, no reaction occurred without a catalyst under the same reaction conditions. Polyadditions of other bis(epoxide)s with DCTA also proceeded smoothly with 5 mol % TPPC as a catalyst in chlorobenzene to produce the corresponding polymers (P‐2–P‐4) in high yields under similar reaction conditions. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3604–3611, 2000     

Lignin,a biomass crosslinker,in a shape memory polycaprolactone network

This work reports a new direction of natural lignin valorization, which utilizes lignin to produce crosslinked polycaprolactone (PCL) via a straightforward synthesis. Lignin's hydroxyl groups of its multibranched phenolic structure allow lignin to serve as crosslinkers, whereas the aromatic groups serve as hard segments. The modified natural lignin containing alkene terminals is crosslinked with a thiol‐terminal PCL via Ru‐catalyzed photoredox thiol‐ene reaction. The high rate of gel contents measured for all crosslinked polymers, with the least being 84% of gel content, indicates efficient crosslinking. The prepared flat rectangular shape lignin‐crosslinked PCL sample demonstrates rapid thermal responsive shape memory behavior at 10 °C and 80 °C showing interconversion between a permanent and temporary shape. The melting temperature of the lignin‐crosslinked PCL is tunable by varying the percent weight of lignin. The 11, 21, and 30 wt % lignin demonstrated T_m of 42 °C, 35 °C, and 26 °C, respectively. The role of lignin as a crosslinker presented in this work suggests that lignin can serve as an efficient biomass‐based functional additive to polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2121–2130     

Crosslinkable aromatic polyimides containing 2,3-dicyanopyrazine rings

New crosslinkable aromatic polyimides were synthesized from 2,3-dicyano-5,6-di(aminophenyl)pyrazine ( 1b ) and 2,3-dicyanopyrazino [5,6–9,10] diaminophenanthrene ( 2b ). They were characterized by viscosimetry, IR, NMR, x-ray, DTA, TMA, TGA, and isothermal gravimetric analysis. The polyimides derived from 1b were amorphous whereas those prepared from 2b showed microcrystalline or crystalline character. The polymers were soluble in polar aprotic solvents (DMF, NMP, DMSO) at ambient temperature or upon heating. They dissolved also completely or partially in certain hot inorganic and organic acids (H₂SO₄, CCl₃COOH). Their glass transition temperatures were in the range of 257–370°C. The crosslinked polymers obtained after an appropriate thermal treatment, were stable up to 397–426°C in N₂ or air and afforded anaerobic char yields of 62–75% at 800°C. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1303–1311, 1997     

Free‐radical crosslinking copolymerization of 2,2′‐azobis[N‐(2‐propenyl)‐2‐methylpropionamide] with vinyl benzoate resulting in polymeric azo initiators

2,2′‐Azobis[N‐(2‐propenyl)‐2‐methylpropionamide] (APMPA) with two carbon–carbon double bonds and an azo group was copolymerized with vinyl benzoate (VBz) at 60 °C, resulting in azo groups containing VBz/APMPA prepolymers and crosslinked polymers as soluble and insoluble polymeric azo initiators, respectively. The polymerization characteristics of APMPA as a novel diallyl monomer were clarified with the rate and degree of polymerization and the monomer reactivity ratios. The gelation behaviors in VBz/APMPA crosslinking copolymerizations were examined in detail with a comparison of the actual gel point and the theoretical gel point calculated according to Stockmayer's equation with the tentative assumption of equal reactivity for both vinyl groups belonging to VBz and APMPA. The effectiveness of the resulting branched or crosslinked poly(VBz‐co‐APMPA)s as soluble or insoluble polymeric azo initiators, respectively, at providing graft polymers through the cleavage of azo groups at an elevated temperature was examined by the polymerization of allyl benzoate at 120 °C. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 317–325, 2002     

Synthesis and characterization of fluorinated poly(aryl ether ketone)s containing 1,4-naphthalene moieties

The new monomer 2,2-bis[4-(4-{4-fluorobenzoyl}-1-naphthoxy)phenyl]hexafluoropropane ( 2 ) was synthesized in a two-step reaction sequence. 2,2-his[4-(1-naphthoxy)phenyl]-hexafluoropropane ( 1 ) was prepared using the Ullmann ether synthesis reaction of 4,4-(hex-afluoroisopropylidiene)diphenol with 1-bromonaphthalene. Friedel-Crafts acylation of 1 with 4-fluorobenzoyl chloride in methylene chloride containing dimethylsulfone selectively afforded 2 in 82% yield. The polycondensation of 2 with various bisphenols in DMAc in the presence of an excess of potassium carbonate as a condensation reagent was carried out at 165°C to quantitatively afford the corresponding fluorinated poly(aryl ether ketone)s containing 1,4-naphthalene moieties. Thermal analysis of the polymers showed them to have T_gs ranging from 194 to 230°C and to be thermally stable in air up with initial weight losses at about 500°C. In addition, these novel polymers exhibited excellent solubility in organic solvents including NMP, DMAc, and chloroform. © 1997 John Wiley & Sons, Inc.     

Cyclic Acetal-Photosensitized Polymerization. XI. Photoirradiations onto Polycyclic Acetals

Photoirradiations onto polycyclic acetals, i. e., polymers containing cyclic acetal groups in the molecule, were carried out at 30 or 40°C. The terpolymer of vinyl formal/vinyl acetate/vinyl alcohol (PVFAcA) was decomposed by means of irradiation, while poly-2-vinyl-1,3-dioxolane (PVDO) and poly-2-vinyl-4-hydroxy-methyl-1,3-dioxolane (PVHDO) were crosslinked. These results indicate the possibility of control of the decomposition or the crosslinking of polymer.     

Thermally reversible linking of halide-containing polymers by potassium dicyclopentadienedicarboxylate

A novel crosslinker for thermally reversible covalent (TRC) linking of halide-containing polymers is suggested. Chlorine-containing polymers such as chloromethylstyrene copolymers, chlorinated polypropylene, polyvinylchloride, chlorinated polyisoprene, and polyepichlorohydrin were crosslinked with potassium dicyclopentadienedicarboxylate (KDCPDCA). The crosslinker was prepared by reacting potassium ethoxide with dicyclopentadienedicarboxylic acid. Because of the low solubility of KDCPDCA in organic solvents, a phase transfer catalyst, benzyltrimethyl-ammonium bromide, was employed for the crosslinking reaction. The crosslinking reaction occurred at a higher rate in a polar solvent, such as dimethylformamide, than in a nonpolar one, such as toluene, and was affected by the nature of the chlorine-containing polymer. Some of the polymers crosslinked even at room temperature. The chain-extending reaction between KDCPDCA and a α,ω-dihalide compound such as α,α′-dichloro-p-xylene, 1,4-dichlorobutane, or 1,4-dibromobutane also was carried out to obtain linear oligomers. The IR spectra indicated that the crosslinking and chain-extending reactions were based on the esterification between the halide carbon bonds of the polymer and the COOK groups of KDCPDCA. The flowability at 195 °C and solubility on heating in a dichlorobenzen-maleic compound mixture of the crosslinked polymers indicated that the TRC crosslinking occurred via the reversible Diels–Alder cyclopentadiene/dicyclopentadiene conversion as long as the polymer was thermally stable and did not contain olefinic CC bonds. The TRC linking also was confirmed by the rapid decrease of the specific viscosity of the obtained linear oligomers on heating. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4390–4401, 1999