Synthesis of polyimides by photoaddition of bismaleimides to alkylbenzenes

Bismaleimides undergo successive 2 + 2 and 2 + 4 cycloadditions to alkylbenzenes to form polyimides. For the series toluene, ethylbenzene, cumene, tert-butylbenzene, highest yields of polymer are obtained with toluene and tert-butylbenzene with three different bismaleimides. This is explained in terms of inductive and steric effects of the alkyl substituents.     

Addition polyimides. III. Thermal behavior of bismaleimides

This article describes the synthesis of N,N′-bis(3,3′-maleimidophenyl) sulfone (S) and its Michael addition products with (4,4′-diaminodiphenyl) methane (S-M), 4,4′-diaminodiphenyl ether (S-E), (3,3′-diaminodiphenyl) sulfone (S-DDS_m), (4,4′-diaminodiphenyl) sulfone (S-DDS_p), (3,3′,3″-tris aminophenyl) phosphine oxide (S-TAP), and 9,9-bis(p-aminophenyl) fluorene (S-B). Curing behavior of these bisimides was investigated by differential scanning calorimetry. Activation energy of curing reaction was determined by using isothermal and multiple heating rate method. Thermal stability of bisimides was evaluated by thermogravimetric analysis. Better char yields were obtained in S-TAP resins.     

Synthesis of new polyimides by Diels–Alder reaction of bis(2-pyrone)s with bismaleimides

The reaction of various substituted bis(2-pyrone)s with bismaleimides in dilute solution was carried out to produce linear soluble polymers with coronand structure. The number-average molecular weights of the polymers ranged from 7000 to 18,000 (vapor pressure osmometry). Polymer structures were identified by NMR spectroscopy and model reactions. The stereochemistry and the mechanism are discussed. © 1995 John Wiley & Sons, Inc.     

Synthesis of oxetanes by photoaddition of carbonyl compounds to pyrrole derivatives

Several electron attracting groups have been substituted on the nitrogen atom to decrease the electron density of the pyrrole ring in order to make it more suitable for photoaddition reactions. Once it was found that N-benzoylpyrrole is the only compound of the series studied, capable of undergoing oxetane formation, other carbonyl compounds in addition to benzophenone were tested as possible addends to the ring. Successful additions were observed when 3- and 4-benzoyl-pyridine were used.     

Synthesis of oxetanes by photoaddition of carbonyl compounds to thiophene derivatives

2,3-Dimethyl, 3,4-dimethyl and 2,3,5-trimethylthiophene were synthesized and subjected to interaction with excited benzophenone. 2,3-Dimethylthiophene affords an oxetane in good yield. These experiments were carried out in order to generalize this reaction which thus far has only been successful with 2,5-dimethylthiophene.     

Synthesis of cyclodextrin-based carbohydrate clusters by photoaddition reactions.

The syntheses of homogeneous cyclodextrin-based carbohydrate clusters, persubstituted with beta-D-thioglucosyl or D-thiolactosyl residues on either (a) the primary face, (b) the secondary face, or (c) both the primary and the secondary faces of their cyclodextrin tori, are described. The key step in the synthetic methodology, namely the attachment of the carbohydrate residues to the cyclodextrin torus, proceeds in moderate-good yields (42-70%) by the photoaddition of thiol groups, positioned at the anomeric centers of the carbohydrate residues, to allyl ether functions on the cyclodextrins. Facile removal of protecting groups then affords the free cluster compounds. Extensive 1-D and 2-D NMR spectroscopic investigations were performed on these compounds to determine their structures and establish their homogeneities, and a brief computer molecular modeling study allowed estimates of the dimensions of the clusters to be determined.     

Synthesis and characterization of organosoluble polyimides with trifluoromethyl‐substituted benzene in the side chain

New aromatic diamines substituted with a trifluoromethyl group in the side chain, 2,4‐diamino‐3′‐trifluoromethylazobenzene, 2,4‐diamino‐1‐[(4′‐trifluoromethylphenoxy) phenyl] aniline, and 3,5‐diamino‐1‐[(4′‐trifluoromethyl phenoxy) phenyl] benzamide were synthesized and characterized and used to prepare polyimides by a one‐step high‐temperature polycondensation method. Experimental results indicated that the prepared polyimides possess good solubility in strong organic solvents such as N‐methyl‐2‐pyrrolidinone, N,N′‐dimethylformamide, and N,N′‐dimethylacetamide. Homogeneous solutions with solid contents as high as 15–20% can be prepared, which are stable for storing longer than 2 weeks at room temperature. The polyimides exhibited glass‐transition temperatures of 249–292 °C and good thermal stability. The PI‐I_c and PI‐III_c films prepared by casting the fully imidized polymer solutions showed good transparency with cutoff wavelengths at 320–330 nm. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1572–1582, 2002     

Synthesis and characterization of bismaleimides from epoxy resins

Novel bismaleimides (BMIs) were prepared from functional monomaleimides and diglycidyl ether of bisphenol A (DGEBA) and some of them were shown to have good processibility and improved water resistance while retaining characteristic thermal stability of polyimide. Functional monomaleimides were synthesized via the condensation reaction of maleic anhydride with either aminobenzoic acid or aminophenol. Crosslinking reaction of thus obtained BMIs was carried out with or without catalyst at the temperature range of 100–250°C. The type of the functional group species and their position in monomaleimides significantly affected the crosslinking behavior of the resulting BMIs and the thermal property of their crosslinked products. BMIs with meta linkage, obtained from meta monomaleimides, exhibited much faster thermal crosslinking behavior than corresponding para BMIs. When the molecular weight of BMI was larger, the crosslinking density became smaller and T_g was lower as expected, while the viscosity started to increase at a higher temperature. Glass transition temperatures of the crosslinked resins were in the range of 160–250°C and these resins showed excellent thermal stability up to 370°C.     

Synthesis and characterization of bismaleimides derived from polyurethanes

A series of novel bismaleimides (BMIs) were prepared from maleic anhydride and polyurethane prepolymers based on MDI (4,4′-diphenylmethane diisocyanate) and polyether and polyester diols with various chain lengths. All the BMIs were characterized by IR, ¹H-NMR, and elemental analysis. DSC studies indicated that the thermal polymerization of the BMIs could be carried out in the temperature range of 102–245°C, and that curing behavior was significantly affected by the molecular weight of the BMIs. The crosslinked BMI elastomers showed good mechanical properties and much better thermal stability than that of the traditional polyurethane elastomers. The glass transition temperatures, mechanical, and dynamic mechanical properties were dependent on the types of polyols used and the resultant crosslink densities due to various chain lengths of the BMIs. © 1994 John Wiley & Sons, Inc.     

Synthesis of stereospecific hinged ladder polyimides by Diels-Alder reaction

A one-stage synthesis of hinge-ladder polyimides by Diels-Alder poly-condensation of polychlorinated cyclic bisimidodienes with bismaleimides containing aromatic and aliphatic groups was studied.

     

Synthesis of polyimides and segmented block copolyimides by transimidization

The transimidization reaction has been successfully utilized to prepare a series of segmented block copolyimides. The synthesis and polymerization of an AX‐type amino imide monomer containing the tetrahydro[5]helicene unit were accomplished. The AX‐type amino imide monomer is stable during isolation and purification, owing to its inert X (e.g., N‐pyridyl) group, but yet readily underwent a self‐transimidization reaction and produced polyimide. Because of the presence of two reactive ends, such an AX‐type polyimide could be incorporated into a series of block copolyimides by reaction with commercially available dianhydrides and diamines. All the copolymers showed two distinct glass‐transition temperatures, typically around 250 and 430 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3991–3996, 2000     

Synthesis and characterization of photosensitive polyimides

All aromatic polyimides bearing diarylsulfide linkages in the main chain were prepared either by condensation of a sulfur containing dianhydride with an aromatic diamine or the condensation of a sulfur containing aromatic diamine with a dianhydride. Phenylation with diphenyl iodonium salts was then used to convert the diarylsulfide groups to triarylsulfonium salts. The resulting photosensitive polyimides were shown to undergo main chain cleavage during photolysis using UV irradiation. These new polyimides are candidates for positive working, high temperature photoresist materials.     

Synthesis and properties of chloro-containing polyimides

A number of soluble chloro-containing (co)polyimides are synthesized by the one-step high-temperature polycondensation in m-cresol. The obtained (co)polymers are characterized by high heat resistance and thermal stability: 285–350 and 515–565°C, respectively. It is shown that these (co)polymers containing chlorine atoms in benzene rings and hexafluoropropylidene and cardo groups are soluble in a number of common organic solvents and form with light wavelength up to 440 nm transparent films with high stress–strain characteristics.     

Synthesis and optical properties of polyimides

Polyimides are important industrial materials because of their excellent properties. They are extensively used in the electronics industry and have great potential in the field of optical communications. In this article, we discuss the effect of the polyimide structure and the processing conditions on the optical properties. Both commercially available fluorinated polyimides and polyimides synthesized in our laboratory were used in this study. The relationship between the extent of fluorination and the refractive index was studied, and it was found that fluorination reduced the refractive index as expected. Studies conducted on the structure–property relationship revealed that with the use of more rigid monomers for the polyimides, the polyimides could be modified to show a large birefringence. The extent of birefringence depended on the composition of the polymer. In addition, the processing conditions directly controlled the residual stress in the polymer films. The residual stress was an important factor in inducing light scattering, which resulted in higher optical loss. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4832–4838, 2000     

Synthesis and properties of urethane-modified polyimides

The synthesis and properties of thermoplastic urethane-modified polyimides, based on different isocyanates, with different concentrations of hard segments and different ratios of imide and urethane groups, were studied. The effect of catalysts, isocyanates, and temperature was investigated on model reactions leading to formation of monoimides, bisimides, and polyimides. A polymer based on 2,4-TDI, poly(oxytetramethylene) glycol of 1000 molecular weight and pyromellitic dianhydride, with 75% of imide in the hard segments, retained about 50% of the original tensile strength at 120°C and about 30% at 150°C. Increasing the temperature up to 150°C had very little effect on the elongation of this copolymer. In general, increasing the imide concentration in the polymer structure provided better retention of stress-strain properties at elevated temperatures.