Preparation of highly porous heat-resistant polybenzoxazole network films and their electrical conductivities

Highly porous rigid polybenzoxazole (PBO) network films were prepared using a precursor-mediated fabrication method. The obtained PBO network films possessed high porosities of ~40%, as calculated from their apparent densities. In addition, the 5%-weight-loss temperatures of the films were ≥570°C under nitrogen atmosphere, demonstrating an excellent thermal stability. The electrical conductivities of the obtained PBO network films and phosphoric-acid-doped PBO network films were also evaluated. In addition, PBO network films containing pyridine rings were prepared and subjected to phosphoric acid doping. The resultant films were found to exhibit the highest conductivities of the films considered in this study owing to proton conduction both between phosphate groups and between the pyridine rings. The highest conductivity was found for a film prepared from a phosphoric-acid-doped PBO network containing pyridine rings, that is, 2.09 × 10^?1 S/cm at 150°C, which was higher than that of Nafion ? . Therefore, these films can be used at higher temperatures than that of Nafion ? .     

Synthesis and properties of novel heat-resistant fluorescent conjugated polymers with bisindolylmaleimide

Novel conjugated polymers with bisindolymaleimide were synthesized via simple metal-free condensation polymerization. The polymers exhibited high glass transition temperatures and decomposition temperatures with considerable luminescent properties.     

Synthesis and combined properties of novel fluorinated cationic surfactants derived from hexafluoropropylene dimer

Three novel fluorinated surfactants with branched short fluorinated tails as hydrophobic groups, ammonium oxide as polar groups are prepared. Surface tension measurement shows that these fluorinated surfactants are ideal compounds to design new formulations in fire-fighting field.     

New heat-resistant polymers derived from azomethine bismaleimides and maleimide-terminated azomethine prepolymers

A novel class of bismaleimides containing azomethine linkages was synthesized by reacting the monomaleamic acid derived from an aromatic diamine with terephthaldehyde (TPA) in a molar ratio 2 : 1 and subsequent cyclodehydration. In addition, a series of maleimide-terminated azomethine prepolymers (MTAPs) was synthesized. More particularly, 4,4′-diaminodiphenylsulfone (DDS) reacted with TPA in nonstoichiometric molar quantities (2 : 1 or 5 : 4 or 8 : 7) to prepare amine-terminated azomethine prepolymers (ATAPs). The latter reacted with maleic anhydride and then cyclodehydrated. Furthermore, a maleimide-crosslinkable azomethine prepolymer (MCAP) was synthesized by reacting tris(3-aminophenyl)phosphine oxide with an equimolar amount of maleic anhydride and subsequently with TPA. The polymer precursors were characterized by IR, ¹H-NMR, DTA, and inherent viscosity. The thermal stability of the cured resins was evaluated by TGA and IGA. The thermal properties of the cured resins derived from the MTAPs were compared with those of the ordinary polyazomethine prepared from the reaction of DDS with TPA. It was shown that crosslinking of these polymer precursors during their curing was attained both via the maleimide and azomethine double bonds.     

Preparation of phytoactive polymers derived from mono-and bispiperidols with growth-stimulating properties

Optimal conditions for the synthesis of phytoactive polymers from mono-and bispiperidols and maleic anhydride copolymers were found. The growth-stimulating activity of these polymers was tested on arid cultures.     

Synthesis and properties of luminophores derived from fluorinated biphenyls

A procedure was developed for the synthesis of dimethyl 2-fluoro-and 2,2′-difluorobiphenyl-4,4′-dicarboxylates. The latter were converted into fluorinated 4,4′-bis[(E)-2-(1,3-benzoxazol-2-yl)ethenyl]-and 4,4′-bis[5-(4-octyloxyphenyl)-1,3,4-oxadiazol-2-yl]biphenyls which showed strong luminescence in the crystalline state and in solution; their spectral properties were examined.     

Synthesis and characterization of fluorinated polyimides derived from novel unsymmetrical diamines

Two kinds of aromatic, unsymmetrical diamines with ether-ketone group, 3-amino-4′-(4-amino-2-trifluoromethylphenoxy)-benzophenone and 4-amino-4′-(4-amino-2-trifluoromethylphenoxy)-benzophenone, were successfully synthesized with two different synthetic routes. Then, they were polymerized with 4,4′-oxydiphthalic anhydride, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, and 2,2′-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride to form a series of fluorinated polyimides via a conventional two-step thermal or chemical imidization method. The resulting polyimides were characterized by measuring their solubility, viscosity, mechanical properties, IR-FT, and thermal analysis. The results showed that the polyimides had inherent viscosities of 0.48-0.68 dl/g and were easily dissolved in bipolarity solvents and common, low-boiling point solvents. Meanwhile, the resulting strong and flexible polyimide films exhibited excellent thermal stability, e.g., decomposition temperatures (at 10% weight loss) are above 575 °C and glass-transition temperatures in the range of 218-242 °C. The polymer films also showed outstanding mechanical properties, such as tensile strengths of 86.5-132.8 MPa, elongations at break of 8-14%, and initial moduli of 1.32-1.97 GPa. These outstanding combined features ensure that the polymers are desirable candidate materials for advanced applications.     

Synthesis and GC-MS study of fluorinated esters derived from thrimethylolpropane

Zol-gel process was used to synthesize equilibrium mixtures of mono-, di-, and trimester derived from trimethylolpropane and perfluorocarboxylic acids. The elution order of the components of the mixtures from a weakly polar HP-5 column was established. The mass spectra of the synthesized compounds were studied. The GC-MS parameters of the products were compared with the respective parameters of their nonfluorinated analogs. The characteristics of the fluorinated esters have features determined by the esterification degree and the nature of the perfluoroalkyl groups, due to which these compounds can be identified in mixtures.     

Unified study of the different physical properties of amorphous polymers

Uptil now it has not been possible to explain the different physical properties of amorphous polymers using a model based on a single conceptual scheme. In this paper, a phenomenological model is proposed which tries to explain the mechanical, optical and thermal properties (both thermal conductivity and expansivity) of amorphous polymers. The model has similarities with the composite model, proposed by the present authors, which has proved to be successful in interpreting the different physical properties of semicrystalline polymers. The present model considers the bulk form of the polymer as an aggregate of microscopic units possessing intrinsic physical properties. On drawing, the development of anisotropy in different physical properties is supposed to be due to the development of preferred orientation of these units. The development of the preferred orientation has been estimated directly from birefringence data. The agreement between the calculated and experimental values of the elastic modulus, thermal conductivity and thermal expansivity of PVC, PMMA and PS is found to be reasonable good.     

Studies in heterocyclic polymers. Part VI. A weight-loss study of the formation of a polybenzoxazole

The cyclisation of an aromatic poly(o-hydroxyamide) to form polybenzoxazole has been studied by combining isothermal weight-loss and thermogravimetric analyses. The thermogravimetric data were analysed by the method of Gyulai and Greenhow [4] to derive values for the apparent activation energy of the cyclisation process which was found to double at about 50% conversion (74–155 kJ mole^?1. A similar result was observed when the process was studied in the presence of low concentrations of p-toluene sulphonic acid, which appears to have a moderate catalytic effect upon the cyclisation process. The apparent order of reaction of the process has been found to be close to 2, contrary to previous studies which have assumed it to be unimolecular.     

Synthesis and mechanical properties of novel photosensitive polyimides

This paper surveys novel photoimageable polyimides (PHIMPI), with emphasis on synthesis. Details of the chemistry and synthesis techniques on PHIMPI are discussed. A number of associated issues such as swelling, storage stability, shrinkage, photospeed, solvent developability, moisture absorption, thermal expansion and mechanical properties are presented. Most of the photoimageable polyimides that are commercially suitable to date are negative-acting, although recent developments in positive-acting PHIMPI are included.     

标牌用光敏树脂的制备和性能

本文对光敏树脂的合成进行了初步研究，比较了几种单体对光固化速度和光固化产品性能的影响，并对如何选择混合交联单体的配比，以便得到性能优异的软质光敏标牌产品的工作进行了探索。     

Synthesis and characterization of novel fluorinated thermoplastic polyurethane with high transmittance and superior physical properties

Three novel series of transparent fluorinated thermoplastic polyurethane (FTPU) elastomers based on 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), polytetramethylene glycol (PTMG), polycaprolactone (PCL) and 4,4′-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene] bisphenol (BPAF) were synthesized by two-step solution polymerization. The FTPU were characterized by Fourier transform infrared spectrometry (FTIR), UV-Visible spectrometry (UV-Vis), wide angle X-ray diffraction (WAXD), atomic force microscopy (AFM), thermogravimetric analysis (TGA), and mechanical tests. The FTIR results indicate that the micro-phase separation and hydrogen bonding strength increase with increasing fluorine content, which are proved by the results of AFM and WAXD. The UV-Vis tests show high transmittance of FTPU films which is affected by crystallization easily. The TGA and mechanical tests indicate that thermal stability and mechanical properties of FTPU are improved significantly with the introduction of BPAF.     

Synthesis and optical and electroluminescent properties of novel conjugated polyelectrolytes and their neutral precursors derived from fluorene and benzoselenadiazole

Novel copolymers derived from amino‐functionalized fluorene‐ and selenium‐containing heterocycles [2,1,3‐benzoselenadiazole (BSeD)] were synthesized by the palladium‐catalyzed Suzuki coupling method. Their quaternized salt polyelectrolytes of corresponding compositions were obtained by a postpolymerization treatment. The resulting copolymers were soluble in polar solvents. An efficient energy transfer due to exciton trapping on the BSeD sites was observed. Devices from such copolymers emitted orange‐red light peaked at 560–610 nm. All the polymers showed good device performance with high‐work‐function metal Al as a cathode without the use of an additional electron‐injection layer and are promising candidates for polymer light‐emitting diode applications. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2521–2532, 2006     

Cyclic polymers: Synthetic strategies and physical properties

Syntheses of cyclic polymers including cyclic homopolymers, cyclic block copolymers, sun‐shaped polymers, and tadpole polymers are discussed on the basis of a differentiation between synthetic methods and synthetic strategies (e.g., polycondensation, ring–ring equilibration, or ring‐expansion polymerization). Furthermore, all synthetic methods are classified as kinetically or thermodynamically controlled reactions. Characteristic properties of cyclic polymers such as smaller hydrodynamic volume, lower melt viscosities, and higher thermostabilities are compared to the properties of their linear counterparts. Furthermore, the nanophase separation of cyclic diblock copolymers is discussed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 251–284, 2010     

Comparative study of the photodegradation of polybenzoxazoles and related model compounds. Stabilization of polybenzoxazoles

Polybenzoxazoles (PBO) are thermally stable polymers whose possible use under space conditions as a transparent coating aboard spacecraft is restricted by their photodegradability. This photodegradability, which results in a loss of optical properties, is due to the structural features of benzoxazoles as well as to the presence of residual impurities from the synthesis (ketones, esters, amides). Suitable structural changes, which were intrinsic (increase in the conjugation) or extrinsic (addition of nickel salts able to complex the benzoxazole units), allowed the PBO photochemical stability to be increased and subsequently their optical transparency to be maintained. The fluorescence inhibition observed when nickel salts were added suggests that, in this case, stabilization results from a singlet-singlet energy transfer. The effect of the various structural factors investigated on the stability of polybenzoxazoles was correlated with the photochemical behavior of the corresponding model compounds.     

Synthesis and properties of fluorene‐based fluorinated polymers

Fluorene‐based polymers containing various fluorinated benzene (fluorobenzene, p‐difluorobenzene, and tetrafluorobenzene) moieties were synthesized. In addition, perfluorooctylation of poly‐[(9,9‐dioctylfluorene‐2,7‐diyl)‐co‐(fluorene‐2,7‐diyl)] was carried out to afford fluorene‐based polymers with perfluorooctyl moiety at the 9‐position on the fluorene ring. To evaluate the effect of fluorine moiety, polymers containing nonfluorinated benzene moieties and nonfluorinated octyl groups were synthesized. The photoluminescence measurements indicated that all these polymers exhibited blue emission in solution, but a polymer containing a perfluorooctyl group did not emit in the film state. Polymers containing various fluorinated benzene moieties showed higher fluorescence quantum yields and thermal stability than those containing nonfluorinated benzene. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3143–3150, 2001     

Preparation and surface properties of novel low surface free energy fluorinated silane-functional polybenzoxazine films

A novel fluorinated silane-functional benzoxazine monomer is synthesized, and the structure is characterized by FTIR and (1)H NMR. Chemical bonds Si-O-Si linkage between the benzoxazine monomer and the substrate are identified through the variation of water contact angles. The low surface free energy calculation and mechanism of the benzoxazine polymer films are proved through contact angle measurement and FTIR. The film formation property and thermal stability of the polybenzoxazine are also investigated. These results clearly show that this novel polybenzoxazine can not only bond to the substrate but also possess even lower surface free energy which is 15.5 mJ/m(2). The polymer also possesses well thermal stability with a glass transition temperature of 188 °C and the 5% weight loss temperatures of 276 °C.