Synthesis and characterization of hyperbranched aromatic poly(ester-imide)s

The synthesis and characterization of hyperbranched aromatic poly(ester-imide)s are described. A variety of AB(2) monomers, N-[3- or 4-bis(4-acetoxyphenyl)toluoyl]-4-carboxyl-phthalimide and N-{3- or 4-[1,1-bis(4-acetooxyphenyl)]ethylphenyl}-4-carboxy phthalimides were prepared starting from condensation of nitrobenzaldehydes or nitroacetophenones with phenol and used for synthesis of hyperbranched poly(ester-imide)s containing terminal acetyl groups by transesterification reaction. These hyperbranched poly(ester-imide)s were produced with weight-average molecular weight of up to 6.87 g/mol. Analysis of H-1 NMR and C-13 NMR spectroscopy revealed the structure of the four hyperbranched poly(ester-imide)s. These hyperbranched poly(ester-imide)s exhibited excellent solubility in a variety of solvents such as N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran and showed glass-transition temperatures between 217 and 255 degreesC. The thermogravimetric analytic measurement revealed the decomposition temperature at 10% weight-loss temperature (T-d(10)) ranging from 365 to 416 degreesC in nitrogen.

Preparation and characterization of nanocrystalline CeO2 by precipitation method

CeO2 nanocrystalline particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD spectra show that the synthesized CeO2 has cubic crystalline structure of space group O-H(5)-F-M3M, when calcination temperature is in the range of 250 similar to 800 degreesC. TEM images reveal that CeO2 particles are spherical in shape. The average size of the particles increases with the increase of calcination temperature. Thermogravimetric analysis indicates that the weight loss of precursor mainly depends on the calcination temperature, and little depends on the calcination time. Measurements of CeO2 relative density show that the relative density of CeO2 nanocrystalline powders increases with increasing CeO2 particle size.

Syntheses of biphenyl polyimides via nickel-catalyzed coupling polymerization of bis(chlorophthalimide)s

A facile method for the synthesis of biphenyl polyimides, which involves the nickel-catalyzed coupling of aromatic dichlorides containing imide structure in the presence of zinc and triphenylphosphine, has been developed. The polymerizations proceeded smoothly under mild conditions and produced biphenyl polyimides with inherent viscosities of 0.13-0.98 dL/g. The polymerizations of bis(4-chlorophthalimide)s with bulky side substituents gave high molecular weight polymers. Low molecular weight polymers from bis(4-chlorophthalimide)s containing rigid diamine moieties and bis(3-chlorophthalimide)s were obtained because of the formations of polymer precipitate and cyclic oligoimides, respectively. The effects of various factors, such as amount of catalyst, solvent volume, ligand, reaction temperature, and time, on the polymerization were studied. The random copolymerization of two bis(chlorophthalimide)s in varying proportions produced medium molecular weight material. The TgS of prepared polyimides were observed at 245-311 degreesC, and the thermogravimetry of polymers showed 10% weight loss in nitrogen at 470-530 degreesC.

Thermal degradation kinetics of poly(propylene carbonate) obtained from the copolymerization of carbon dioxide and propylene oxide

The kinetics of the thermal degradation of poly(propylene carbonate) (PPC) were investigated with different kinetic methods with data from thermogravimetric analysis under dynamic conditions. The apparent activation energies obtained with different integral methods (Ozawa-Flynn-Wall and Coats-Redfern) were consistent with the values obtained with the Kinssinger method (99.93 kJ/mol). The solid-state decomposition process was a sigmoidal A(3) type in terms of the Coats-Redfern and Phadnis-Deshpande results. The influence of the heating rate on the thermal decomposition temperature was also studied. The derivative thermogravimetry curves of PPC confirmed only one weight-loss step.

Photochromic behavior and luminescent properties of novel hybrid organic-inorganic film doped with Preyssler's heteropoly acid H-12[EuP5W30O110] and polyvinylpyrrolidone

A novel hybrid photochromic composite film composed of Preyssler's heteropoly acid H-12[EuP5W30O110] (EuP5W30) and polyvinylpyrrolidone (PVP) was prepared by dip-coating method. Atomic force microscopy (AFM) was used to investigate the surface topography. The change of characteristic peak in the infrared spectra (IR) was investigated. The TG curve showed three steps of weight loss and approximately revealed the composition of the hybrid film. Ultraviolet-visible adsorption spectra (UV-VIS) and electron resonance spectrum (ESR) were used to investigate the photochromic behavior and mechanism of hybrid film. The photoluminescent behavior of the film at room temperature was investigated to show the characteristic Eu3+ emission pattern of D-5(o)-F-7(J). The occurrence of photoluminescent activity confirms the potential for creating luminescent thin film with polyoxometalates (POMs).

Polyimides from isomeric oxydiphthalic anhydrides

2,2',3,3'-Oxydiphthalic dianhydride (2,2',3,3'-ODPA) and 2,3,3',4'-ODPA were synthesized from 3-chlorophthalic anhydride with 2,3-xylenol and 3,4-xylenol, respectively. Their structures were determined via single-crystal X-ray diffraction. A series of polyimides derived from isomeric ODPAs with several diamines were prepared in dimethylacetamide (DMAc) with the conventional two-step method. Matrix-assisted laser desorption/ionization time-of-flight spectra showed that the polymerization of 2,2',3,3'-ODPA with 4,4'-oxydianiline (ODA) has a greater trend to form cyclic oligomers than that of 2,3,3',4'-ODPA. Both 2,2',3,3'-ODPA and 2,3,3',4'-ODPA based polyimides have good solubility in polar aprotic solvents such as DMAc, dimethylformamide, and N-methylpyrrolidone. The 5% weight-loss temperatures of all polyimides were obtained near 500 degreesC in air. Their glass-transition temperatures measured by dynamic mechanical thermal analysis or differential scanning calorimetry decreased according to the order of polyimides on the basis of 2,2',3,3'-ODPA, 2,3,3',4'-ODPA, and 3,3',4,4'-ODPA. The wide-angle X-ray diffraction of all polyimide films from isomeric ODPAs and ODA showed some certain extent of crystallization after stretching. Rheological properties revealed that polyimide (2,3,3',4'-ODPA/ODA) has a comparatively lower melt viscosity than its isomers, which indicated its better melt processability.

Synthesis and characterization of network liquid crystal elastomers and thermosets

A new series of network liquid crystal polymers were synthesized by graft copolymerization of the difunctional mesogenic monomer 4-allyloxy-benzoyloxy-4'-allyloxybiphenyl (M) upon polymethylhydrosiloxane (PMHS). Monomer M acted not only as a mesogenic unit but also as a crosslinker for the network polymers. The chemical structures of the polymers were confirmed by IR spectroscopy. DSC, TGA, and X-ray scattering were used to measure their thermal properties and mesogenic properties. The glass transition temperature (T-g) of these network liquid crystal polymers was increased when the monomer was increased, and T-d (temperature of 5% weight loss) at first went up and reached a maximum at P, then went down. The slightly crosslinked polymers (P, P,) show rubber-like elasticity, so it was called liquid-crystal elastomer. Network polymers will lose elasticity property with a highly crosslinked degree, and turn into thermosetting polymers (P-4, P-5). All polymers exhibited a smectic texture by X-ray scattering.

Polyimides from isomeric biphenyltetracarboxylic dianhydrides and the effects of chemical structure on solubility

A series of homopolyimides and copolyimides was synthesized by the solution condensation of biphenyltetracarboxylic dianhydride (BPDA) isomers and various diamines followed by chemical imidization. These polyimides had intermediate to high molecular weights with inherent viscosities of 0.34-1.01 dL/g for homopolyimides and 0.48-1.02 dL/g for copolyimides. Thermogravimetric analysis indicated that the aromatic polyimides were stable up to 500degreesC, and the 5% weight loss temperatures were recorded in the range of 506-597degreesC in an air atmosphere and in the range of 517-601degreesC in a nitrogen atmosphere, depending on the diamines used. The glass transition temperatures of aromatic homopolyimides were above 271degreesC, while the glass transition temperatures of the copolyimides increased with an increase in the 2, 2', 3, 3'-BPDA-component. The effects of the chemical structure of the polymer chain on the solubility were investigated. It was found that the solubility of BPDA-based polyimides could be improved by the introduction of flexible units, nonlinear and non-coplanar units, and copolymerization. The polyimides with nonlinear and non-coplanar units derived from 2, 2', 3, 3'-BPDA appeared to have prominently enhanced solubility in polar aprotic solvents and polychlorocarbons when compared with the homopolyimide derived from 3, 3', 4, 4'-BPDA.

Aromatic poly(ester imide)s and poly(amide imide)s having 1,1 '-binaphthyl-2,2 '-diyls in the main chain

Full Paper: Two new 1,1'-binaphthyl-2,2'-diyl-based dianhydrides, i.e., 2,2'-bis(3,4-dicarboxybenzamido)-1,1'-binaphthyl dianhydride (BNDADA) and 2,2'-bis(3,4-dicarboxybenzoyloxy)-1,1'-binaphthyl dianhydride (BNDEDA), were synthesized and polymerized with various aromatic diamines to afford polyimides through the traditional two-step method. The polyimides with inherent viscosities ranging from 0.27 to 0.70 dl . g(-1) showed excellent solubilities in polar solvents such as DMAc, DMSO and NMP etc., except of the poly(ester imide) prepared from BNDEDA and benzidine. Poly(ester imide)s based on BNDEDA can also be readily dissolved in weakly polar solvents such as THF, CH2Cl2 and CHCl3. The glass transition temperatures of these polyimides are in the range of 210-310 degrees C; the 5% weight loss temperatures are in the range of 390-465 degrees C in nitrogen and 384-447 degrees c in air. These polymers from light yellow, tough films that were transparent above 365 nm. The effects of different flexible units attached in the 2- and 2'-positions, i.e., amide, ester and ether, on the properties of the polyimides obtained are discussed.

Nanocrystalline SnO2 synthesised by means of hydrothermal precipitation

Nanocrystalline SnO2 with different particle sizes has been prepared by means of hydrothermal precipitation. The resulting SnO2 nanometer size powders, which are basically spherical in shape according to TEM, are tetragonal in structure with space group P4/mnm. Calculation shows that the crystallite size of SnO2 increases with increase of the calcination temperature, but that the average crystal lattice distortion rate decreases with increase of crystallite size. The smaller the particle, the bigger the crystal lattice distortion and the slower the crystal growth rate. Weight loss analysis indicates the prepared SnO2 is very slightly impure.

Synthesis and thermal polymerization of a novel stilbene-maleimide AB-monomer

A novel AB-monomer, 3-maleimidostilbene (ST-MAI), was synthesized. DSC investigation indicated that the ST-MAI monomer melted at 127 degrees C and thermally polymerized in the temperature range of 180 similar to 300 degrees C. LR investigation on the thermal polymerization processes proved that the thermal polymerization included not only copolymerizaiton between stilbene and maleimide, but also homopolymerization of maleimide. The largest reaction conversion of maleimide and stilbene unit in a ST-MAI monomer was about 82% and 50% respectively. The glass transition temperature of cured ST-MAI resin was 234 degrees C, determined by DSC. The decomposition temperatures for 10% weight loss was above 430 degrees C in both air and nitrogen atmospheres.

Synthesis and characterization of aromatic dianhydrides and polyesterimides derived from 4-hydroxyphthalic anhydride

4-Hydroxyphthalic anhydride, prepared from 4-chlorophthalic anhydride, was reacted with trimellitic anhydride monoacid chloride or arylene diacid chloride to give aromatic ester-containing dianhydrides (EDAs). These dianhydrides were characterized by element analysis, melt point, FTIR and H-1-NMR. A series of aromatic poly (amic ester acid)s was synthesized by polycondensation of these EDAs and various diamines in polar organic solvent. The inherent viscosity of poly (amic ester acid)s ranged from 0.55 to 0.89 dL/g, indicating the intermediate to higher molecular weight. Polyesterimides having glass transition temperatures between 184-219degreesC were produced by thermal imidization of corresponding poly (amic ester acid)s. These polymers were fairly resistant to organic solvent, but some of them were soluble in phenol solvents. Thermogravimetric analyses revealed that these polyesterimides were stable up to 400degreesC, and the 5% weight loss temperatures were recorded in the range of 432-483degreesC in air atmosphers and 451-490degreesC in nitrogen.

Crosslinking of polyimides via spirodilactone unit in polymer backbone

A new approach for the crosslinking of polyimides via the lactamization of spirodilactone unit in polyimide backbone was studied by two means: model reaction and the comparison of the properties of the polyimide precursors to those of the crosslinking polymers. Polyimides 4 and 5 were soluble in N,N'dimethylacetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO), N'-methylpyrrolidone (NMP), and other common organic solvents, whereas their corresponding crosslinking polymers were insoluble in these solvents. The glass transition temperatures for polyimide 5 and its crosslinking polymer were 262 degrees C and 291 degrees C, whereas those for polyimide 4 and its crosslinking polymer were 265 degrees C and 360 degrees C. The weight-loss rate of the crosslinling polymers was apparently slower than that of the precursors when the temperature was >400 degrees C. The 10% weight-loss temperature for the polyimides 4 and 5 was <500 degrees C, whereas that for the crosslinking polymers was close to or above 600 degrees C. The results indicate that this type of crosslinking polymer has good thermal properties. The temperature for the formation of lactam was above 180 degrees C. (C) 1999 John Wiley & Sons, Inc.

Optically active poly(amide-imide)s containing axially dissymmetric 1,1 '-binaphthyl moieties

Novel optically active aromatic poly(amide-imide)s (PAIs) were prepared from newly synthesized 2,2'-bis(3,4-dicarboxybenzamido)-1,1'-binaphyl dianhydride ((+/-)-, (S)-, and (R)-BNDADA). PAIs based on dianhydride monomers with different ee % were investigated with respect to their structures and chiroptical properties. These polymers were highly soluble in polar aprotic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, pyridine, etc., and showed high glas s transition temperatures of 287-290 degrees C and 5% weight loss temperatures of 450-465 degrees C in nitrogen. Optically active PAIs exhibited high specific rotations, excellent optical stabilities, and a dependence of optical activities on temperature. Investigations on chiroptical properties indicated that chiral conformation was possessed by optically active PAIs. (C) 1999 John Wiley & Sons, Inc.

Synthesis and properties of aromatic polyimides derived from 2,2,' 3,3 '-biphenyltetracarboxylic dianhydride

2,2,'3,3' -Biphenyltetracarboxylic dianhydride (2,2,'3,3'-BPDA) was prepared by a coupling reaction of dimethyl 3-iodophthalate. The X-ray single-crystal structure determination showed that this dianhydride had a bent and noncopolanar structure, presenting a striking contrast to its isomer, 3,3,'4,4'-BPDA. This dianhydride was reacted with aromatic diamines in a polar aprotic solvent such as N,N-dimethylacetamide (DMAc) to form polyamic acid intermediates, which imidized chemically to polyimides with inherent viscosities of 0.34-0.55 dL/g, depending on the diamine used. The polyimides from 2,2,'3,3'-BPDA exhibited a good solubility and were dissolved in polar aprotic solvents and polychlorocarbons. These polyimides have high glass transition temperatures above 283 degrees C. Thermogravimetric analyses indicated that these polyimides were fairly stable up to 500 degrees C, and the 5% weight loss temperatures were recorded in the range of 534-583 degrees C in nitrogen atmosphere and 537-561 degrees C in air atmosphere. All polyimides were amorphous according to X-ray determination. (C) 1999 John Wiley & Sons, Inc.