Synthesis and characterization of highly soluble aromatic polyimides

Two highly soluble aromatic polyimides were synthesized successfully from a diamine with two tert-butyl groups （MBTBA）and dianhydrides with a thioether or sulfone moiety（DTDA and DSDA）.Both of them showed excellent solubility in common solvents such as chloroform,tetrahydrofuran and dioxane at the room temperature.The number-average molecular weight was 6.0×10⁴ and 8.3×10⁴ according to gel permeation chromatography relative to a polystyrene standard,and the polydispersity index was 1.80 and 1.82 respectively.The glass-transition temperatures of them were 286℃and 314℃（or 315℃and 358℃）respectively,as measured by differential scanning calorimetry（or dynamic mechanical analysis）.The 5%weight loss temperature of both was near 490℃in N₂ by thermogravimetric analysis.These results indicated that the tert-butyl pendent groups reduced the interactions among polymer chains and the thioether or sulfone moiety was flexible which may improve their solubility in conventional organic solvents without the loss of thermal stability. Transparent and flexible films of the two polyimides were obtained via solution casting.The MBTBA-DTDA membrane had higher storage moduli than those of the MBTBA-DSDA membrane.     

Synthesis and characterization of some novel aromatic polyimides

Three new diamines 1,2-di(p-aminophenyloxy)ethylene, 2-(4-aminophenoxy)methyl-5-aminobenzimidazole and 4,4-(aminopheyloxy) phenyl-4-aminobenzamide were synthesized and polymerized with 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BP), 4,4′-(hexafluoroisopropyledene)diphthalic anhydride (HF) and 3,4,9,10-perylene tetracarboxylic acid dianhydride (PD) either by one step solution polymerization reaction or by two step procedure. The later includes ring opening poly-addition to give poly(amic acid), followed by cyclodehydration to polyimides with the inherent viscosities 0.62-0.97 dl/g. Majority of polymers are found to be soluble in most of the organic solvents such as DMSO, DMF, DMAc, m-cresol even at room temperature and few becomes soluble on heating. The degradation temperature of the resultant polymers falls in the ranges from 240 °C to 550 °C in nitrogen (with only 10% weight loss). Specific heat capacity at 300 °C ranges from 1.1899 to 5.2541 J g⁻¹ k⁻¹. The maximum degradation temperature ranges from 250 to 620 °C. T_g values of the polyimides ranged from 168 to 254 °C.     

Synthesis and characterization of organosoluble ditrifluoromethylated aromatic polyimides

Two novel diamine monomers, 1,4‐bis (4‐aminophenoxy)‐2‐[(3′,5′‐ditrifluoromethyl)phenyl]benzene and 1,4‐bis [2′‐cyano‐3′(4″‐amino phenoxy)phenoxy]‐2‐[(3′,5′‐ditrifluoromethyl)phenyl] benzene, were synthesized from (3,5‐ditrifluoromethyl)phenylhydroquinone. A series of ditrifluoromethylated aromatic polyimides derived from the diamines were prepared through a typical two‐step polymerization method. These polyimides had a high thermal stability, and the temperatures at 10% weight loss were above 507 °C in nitrogen. Most of the polymers showed good solubility in anhydrated 1‐methyl‐2‐pyrrolidone, N,N‐dimethylacetamide, N,N‐dimethylformamide, chloroform, and tetrahydrofuran at room temperature. All the polymers formed transparent, strong, and flexible films with tensile strengths of 63.6–95.8 MPa, elongations at break of 5–10%, and Young's moduli of 2.38–2.96 GPa. The dielectric constants estimated from the average refractive indices are 2.69–2.89. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3018–3029, 2005     

Synthesis and characterization of aromatic polyimides containing tetraphenylfuran-thiazole moiety

Journal of Thermal Analysis and Calorimetry - 2,5-Bis(4-(2-aminothiazole) phenyl)-3,4-diphenyl furan (BATPDF), well prepared in four steps. Novel aromatic polyimides containing...     

Synthesis and characterization of new soluble aromatic polyimides from diaminotetraphenylimidazolinone and aromatic tetracarboxylic dianhydrides

A series of new soluble aromatic polyimides with inherent viscosities of 0.65–1.12 dL/g were synthesized from 1,3-bis(4-aminophenyl)-4,5-diphenylimidazolin-2-one and various aromatic tetracarboxylic dianhydrides by the conventional two-step procedure that included ring-opening polyaddition and subsequent thermal cyclodehydration. These polyimides could also be prepared by the one-pot procedure in homogeneous m-cresol solution. Most of the tetraphenyl-pendant polyimides were soluble in organic solvents such as N,N-dimethylacetamide, 1,3-dimethyl-2-imidazolidone, and m-cresol. Some polyimides gave transparent, flexible, and tough films with good tensile properties. The glass transition temperatures and 10% weight loss temperatures under nitrogen of the polyimides were in the range of 287–326 and 520–580°C, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1767–1772, 1998     

Synthesis and properties of alkylene-linked aromatic polyimides

Alkylene-linked aromatic polyimides were prepared from a family of new dianhydride monomers and aromatic diamines. The dianhydrides were synthesized by Friedel-Crafts catalysis of the condensation of ditertiary alcohols with o-xylene, subsequent oxidation of the aryl methyl groups to carboxy, and finally, dehydration of the ortho-carboxy substituents to anhydride groups. Alkylene-linked aromatic polyimides, with up to 8 methylene groups in the polymer chain, are stable to 400°C in air and can be extruded or compression-molded at 300°C. In addition, these polymers are soluble in solvents within the solubility parameter range of 10.4 ± 1.2.     

Synthesis and characterization of processable polyborate precursors

Polyborates have been formed by disproportionation and polycondensation of trimethoxyboroxine and also of trimethoxyboroxine and boric acid. The crtiical role of stoichiometry in the formation of polyborates without requiring incorporation of a metal counter ion is revealed. The emphasis is on integration of this chemistry with fabrication processes. Incorporation of an appropriate linear organic polymer is shown to yield the required rheological and thermal characteristics in this regard. These polyborates are inferred to be suitable as precursors for boron nitride in geometrical forms that can be processed as supported structures. However, they are also determined to be unsuitable as precursors for boron nitride fibers, oriented or isotropic, primarily due to their low glass transition temperature.     

Novel processable aromatic thermoplastic polyimides: Films,adhesives, moldings,and graphite composites

Novel hot-melt type flexible, tough, thermally stable, processable, thermoplastic, aromatic polyimides have been synthesized involving reaction of a keto-ether containing diamine with hinged aromatic dianhydrides followed by thermal and chemical cyclodehydration. Inherent viscosity in DMAC at 35°C of the synthesized polymers ranged 1.02 to 1.4 dl/g (0.5% solution). The polymers showed a glass transition temperature (T_g) of 250°C to 180°C as determined by differential scanning calorimetry (DSC) and thermomechanical analysis (TMA). Thermogravimetric analysis showed polymer stability up to 510°C, in both air and nitrogen atmospheres. All the polymers have shown good melt-flow. Films of 1.5–2.8 ml thickness were made and tested for mechanical properties at room temperature, 177°C and 210°C. The developed films are suitable for adhesion of Ti/Ti specimens and showed a lap shear strength of 5575 psi. Melt-fusion of the polymers gave tough moldings. Graphite cloth composites have been made and tested for mechanical properties.     

Synthesis and characterization of chemically modified polystyrene as processable carbon fiber precursors

In this study, the chemically modified polystyrene was studied for improvement of polystyrene which had low carbon yield, as a carbon fiber precursor. The polystyrene was synthesized with divinylbenzene which was used as a cross-linking agent by the solution polymerization method. Then the synthesized polystyrene was nitrated with sulfuric and nitric acids solution (H₂SO₄/HNO₃) followed by reduction to form nitrogen-functional groups. The surface properties of the modified polystyrene were investigated by Fourier transfer infrared spectroscopy to confirm the introduction of functional groups on the modified polystyrene surfaces. The thermal properties of the modified polystyrene were measured by thermogravimetric analysis and differential scanning calorimetry. The morphologies of the electrospun polystyrene fibers by a chemical modification were observed by scanning electron microscopy. From the results, the nitrogen-functional groups were introduced on the modified polystyrene surfaces which affected the quantity of functional groups. Also, the chemical treatment affected the carbon yield of the polystyrene owing to the introduction of nitrogen-functional groups on polystyrene surfaces. Consequently, it was concluded that the chemical treatment of polystyrene fibers enables it to be used as a possible carbon fiber precursor.     

Synthesis and characterization of novel polyimides derived from pyridine-bridged aromatic dianhydride and various diamines

A new kind of pyridine-bridged aromatic dianhydride monomer, 4-phenyl-2,6-bis[4-(3,4-dicarboxyphenoxy)phenyl]-pyridine dianhydride (PPDA), was successfully synthesized by modified Chichibabin reaction of benzaldehyde and substituted acetophenone, 4-(3,4-dicyanophenoxy)-acetophenone (DCAP), followed by acidic hydrolysis of the intermediate tetranitrile and cyclodehydration of the resulting tetraacid. The pyridine-bridged aromatic dianhydride was employed to synthesized a series of new pyridine-containing polyimides by polycondensation with various aromatic diamines in N-methyl-2-pyrrolidone (NMP) via the conventional two-step method, i.e. ring-opening polycondensation forming the poly(amic acid)s and further thermal or chemical imidization forming polyimides. The inherent viscosities of the resulting polyimides were in the range of 0.49-0.63 dL/g, and most of them were soluble in aprotic amide solvents and cresols, such as N,N-dimethylacetamide (DMAc), NMP, and m-cresol, etc. Meanwhile, strong and flexible polyimide films were obtained, which have good thermal stability with the glass transition temperatures (T_g) of 223-256 °C, the temperature at 5% weight loss of 523-569 °C, and the residue at 700 °C of 52.1-62.7% in nitrogen, as well as have outstanding mechanical properties with the tensile strengths of 70.7-97.6 MPa and elongations at breakage of 7.9-9.7%. Wide-angle X-ray diffraction measurements revealed that these polyimides were predominantly amorphous.     

Synthesis and characterization of soluble polyimides based on trifluoromethylated aromatic dianhydride and substitutional diaminetriphenylmethanes

A series of novel and soluble polyimides containing fluorine were synthesized by the polycondensation of fluorine-containing aromatic dianhydride TFDA with substitutional diaminetriphenylmethanes TDPT, FTDPT and 3FTDPT. The composition, structure and properties of the resulting polyimides were studied by means of FT-IR, DSC, TGA and elemental analysis methods, as well as general characterization methods that test solubility or viscosity. The results show that all the novel polyimides were obtained in quantitative yields with inherent viscosities of 0.70-0.76 dL/g, and showed excellent solubility in common organic solvents, such as NMP, DMAc, DMF, DMSO, THF, m-cresol, chloroform and 4-butyrolactone. Meanwhile, their T_g values from DSC are in the range of 265-293 °C, the temperature of 5 and 10% weight loss from TGA are in the range of 460-465 and 513-524 °C in N₂, respectively.     

Advancement of chitin and chitosan as promising biomaterials

Biopolymers like cellulose, polysaccharides, chitosan, starch, chitin, and alginates have sparked an increasing curiosity in creating natural replacements for synthetic polymers during the last several decades. Chitin is a major part of fungi’s cell walls, the crustaceans’ exoskeletons, like lobsters, crabs, and shrimps, cephalopod beaks, the radulae of mollusks, and fish and lissamphibians scales. Since the late 1970 s, biopolymer chitosan has gathered interest in basic science and applied research due to its incredible macromolecular framework, physicochemical properties, and biological activities, which differ from those of synthetic polymers. Chitin and derivatives thereof have practical usages in chemistry, the agriculture sector, medicine, cosmetics, as well as textile and paper industries. Chitosan has also received a lot of recent interest in the fields of dentistry, ophthalmology, veterinary science, biomedicine, the drink industry, hygiene and personal care, catalysis, chromatography, sewage treatment, and biotechnology. Numerous fundamental investigations have been conducted on chitin and chitosan. This article presents a short compact summary of research over the last two decades in an attempt to highlight the works on chitin and chitosan applications.     

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 characterization of crosslinkable polyimides

A series of copolyimides were prepared from benzophenone-3,3′,4,4′-tetracarboxylic dianhydride (BTDA) and various aromatic diamines which contain a fluorenyl group and/or alkyl substituents in ortho position to the amine groups. The effect of the chemical composition on the glass transition temperature (T_g), thermal stability as well as on the dielectric constant of these polymers was studied. High T_g polymers (T_g ranging from 260 °C to 370 °C), withstanding temperatures as high as 400 °C for 10 h and having a low dielectric constant (from 2.6 to 3.1) were successfully synthesized. All these polymers were able to crosslink under UV or thermal treatments.     

Hydroxyapatite/polyurethane composites as promising biomaterials

The biomaterials are intended to augment or replace the function of tissues or organs in human body. Every year millions of people require soft- or hard-tissue regeneration worldwide. Polymers and their composites are a large class of biomaterials appreciated for tissue regeneration. Polyurethane (PUR) is an organic synthetic multifunctional polymer with established biomedical applications. The hydroxyapatite (HA) is one of the biocompatible ceramic materials similar to natural bone material. The amalgamation of hydroxyapatite with polyurethane enhances the bioactivity of final product along with the combination of individual properties. Here, we review the synthesis, characterization, and applications studies of HA/PUR-based biomaterials. We initiate this review with a brief and representative compilation of the chemical composition and methods of preparation for HA/PUR biomaterials. Then, moving ahead, first, we review the simple HA/PUR biomaterials and use of PUR templates. Second, we review the significance of modified HA and PUR in these biomaterials. Third, we discuss the potential of bio-based PUR and inclusion of third constituent in the HA/PUR biomaterials. Then, we appraise the involvement of trace nutrient in deposition of HA on PUR scaffolds. Finally, we consider the other expedient applications of HA/PUR composites such as drug delivery system and sorbent of pollutants.     

Synthesis and characterization of soluble polyimides containing trifluoromethyl groups in their backbone

A series of polyimides were synthesized from 2,2‐Bis(3,4‐dicarboxyphenyl)hexafluoropropane, 2,2‐bis(3‐amino‐4‐hydroxyphenyl)‐hexafluoropropane, and 4,4′‐oxydianiline by chemical imidization. The effects of the diamine ratios on the properties of the films were evaluated through the study of their thermal, electrical, and morphological properties. All the polymers exhibited better solubility in most of the organic solvents and hence were easily processable. Polyimides with more 2,2‐bis(3‐amino‐4‐hydroxyphenyl)‐hexafluoropropane exhibited better solubility and a low refractive index, which is highly desired for microelectronic applications. The dielectric constant and birefringence were strongly dependent on the fluorine content. With an increase in the fluorine substitution, both the dielectric constant and birefringence decreased. All the polymers exhibited high thermal stability (>400 °C). The absence of crystalline melting in differential scanning calorimetry and broad wide‐angle X‐ray diffraction patterns revealed the amorphous nature of the polymers, which was due to the presence of bulky CF₃ groups and hinged ether linkages of the diamine component. The residual stress values decreased with an increase in the 4,4′‐oxydianiline content, and the results were in agreement with the dielectric constant. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4303–4312, 2004     

Synthesis,characterization of naphthalene‐based polyimides,and their use as immobilized enzyme membrane

A new monomer, 1,5‐bis(p‐dimethylaminophenylimino)naphthalene, was prepared through Schiff‐base condensation reaction of 1,5‐diaminonaphthalene and 4‐(dimethylamino)benzaldehyde in the presence of ethanol. A series of aromatic polyimides bearing naphthalene and ? CH?N? groups were synthesized from the diamine with five kinds of commercial dianhydrides via a conventional one‐stage process. The resulting naphthalene based polyimides (NBPs) showed good solubilities in N‐methyl‐2‐pyrrolidone and m‐cresol. NBPs had glass‐transition temperatures at 139–174°C and 10% weightloss temperatures above 430 °C in nitrogen atmospheres. Excellent properties of NBPs are attributed to the incorporation of the naphthalene and ? CH?N? group in 1,5‐bis(p‐dimethylaminophenylimino)naphthalene. Moreover, chemically prepared polyimides were used for immobilization of glucose oxidase (GOx). The amperometric responses of the NBPs‐GOx‐Pt electrodes toward glucose were examined at a potential of 0.7 V in PBS solution by means of time‐base (TB) technique. Results show that NBPs bearing ? O? group membrane (PI‐3) has many advantages in the immobilization of glucose oxidase because of its strong adherence to electrode surface and chemical stability and selectivity. Copyright © 2010 John Wiley & Sons, Ltd.