Thermally stable polymers containing 1,3,4-oxadiazole units obtained from Huisgen reaction

Thermally stable polymers containing 1,3,4-oxadiazole units have been synthesized through Huisgen reaction of the aromatic/aliphatic bis-tetrazole compounds with the aromatic/aliphatic bis-acid chlorides in pyridine as solvent.The obtained polymers are insoluble or slightly soluble even in polar aprotic solvents such as DMSO and DMF.Relatively high inherent viscosity values（0.61-1.33 dL/g,in 0.125%H₂SO₄ at 25℃） were observed for these compounds.Thermal analyses of the polymers using DSC and TGA techniques showed that the polymers have improved thermal stabilities.The glass transition temperature has not been observed in the fully aromatic polymers,but the polymers obtained from 5-[6-（1H-tetrazol -5-yl）hexyl]-lH-tetrazole（Ⅳ） showed very clear T_g.A model reaction was also investigated and the resulting bis-1,3,4-oxadiazole compound was characterized by conventional spectroscopy methods.     

Synthesis and characterization of novel soluble and thermally stable polyamides based on pyridine monomer

Nucleophilic aromatic substitution reaction of 4-aminophenol and also 5-amino-1-naphthol with 2,6-dichloropyridine in N-methyl-2-pyrrolidone (NMP) as solvent, in the presence of potassium carbonate, afforded two aromatic ether diamines. Eight soluble, thermally stable polyamides were prepared by polycondensation reaction of the obtained diamines with aromatic and aliphatic diacid chlorides including terephthaloyl chloride (TPC), isophthaloyl chloride (IPC), adipoyl chloride (AC), and sebacoyl chloride (SC). The prepared monomers and polymers were characterized by conventional spectroscopic methods. Physical and thermal properties of the polymers, such as thermal behavior, thermal stability, solution viscosity, and solubility behavior were also studied.     

Synthesis of novel low-viscosity liquid epoxidized aromatic hyperbranched polymers

Low-viscosity liquid epoxidized aromatic hyperbranched polymers are synthesized by the reaction between epichlorohydrin (ECH) and carboxy-end hyperbranched polymers prepared from low-cost products trimellitic anhydride (B₃ TMA) and dihydroxy alcohols (A₂). The low-viscosity property, especially the lowest viscosity of epoxidized aromatic hyperbranched polymers is only 350 cp which has not reported among epoxidized aromatic hyperbranched polymers before, make them can be used to coatings and adhesion fields without organic solvent hopefully. The properties of the epoxidized aromatic hyperbranched polymers are measured by GPC, FT-IR and viscometer.     

Synthesis and characterization of N-phenylated aromatic polyureas from dianilino compounds and aromatic diisocyanates

N-phenylated aromatic polyureas were synthesized by the polyaddition of dianilino compounds to aromatic diisocyanates in sym-tetrachloroethane at around 100°C. Factors that influence the reaction, such as monomer concentration, reaction solvent, catalyst, temperature, and time, were studied to optimize the conditions for the preparation of high molecular weight polymers. Compared with the analogous unsubstituted aromatic polyureas, the N-phenylated polyureas were almost amorphous and soluble in a variety of solvents and had low glass transition temperatures. Some of the polymers could be cast into transparent flexible films from chloroform solutions.     

聚二乙烯苯的取代反应研究

以悬浮聚合法制得一系列高交联聚二乙烯苯树脂，通过改变反应试剂、催化剂、反应溶剂考察了聚二乙烯苯树脂进行亲电取代反应的规律．结果表明，聚二乙烯苯树脂可发生亲电取代反应，反应程度较低．聚（对－二乙烯苯）的反应程度高于聚（间－二乙烯苯）．     

含苯乙炔基的可交联聚芳醚酮交替共聚物的合成与热性能

以耐高温高性能树脂-聚芳醚酮作为研究对象, 从改善材料的加工工艺性及提高材料的使用温度出发, 对含有苯乙炔基的交替共聚物进行了系统研究. 实验结果表明, 该系列聚合物固化前具有较好的溶解性, 固化过程中显示出较好的热稳定性, 固化后具有较高的玻璃化转变温度和优异的热稳定性与热氧稳定性, 且降低聚合物的分子量没有对固化物的热性能产生明显影响, 在高性能复合材料基体树脂方面具有潜在的应用价值.     

Stereoselective Polymerization of Aromatic Vinyl Polar Monomers

Polar vinyl polymers, a class of polymers with polar groups as side chains, have significant advantages over conventional nonpolar polyolefin materials in terms of viscosity, toughness, interfacial properties (dyeability and printability), and compatibility with solvents or other polymers. Among them, aromatic polar vinyl polymers are of interest because of their good heat resistance properties. In addition, stereoselective polymerization of aromatic polar vinyl monomers has been rapidly developed because the steric structure of the polymer has a significant impact on its physical properties. In this paper, we review the research progress of stereoselective polymerization catalysts for aromatic polar vinyl monomers in recent years, discuss in detail the influence of ligand structure, electronic effect of substituents, spatial site resistance effect, central rare earth metal species and polymerization solvents on the activity and stereoselectivity of polymerization reactions, and explore the possible mechanism of polymerization reaction.     

Synthesis and properties of carbazole‐layered polymers

New aromatic ring‐layered polymers consisting of carbazole as a layered aromatic group and xanthene as a scaffold were designed and synthesized via the Sonogashira–Hagihara coupling reaction. Their optical and electrochemical behaviors were investigated in detail; the results showed that these polymers could be used as hole‐transporting materials. Polymers with nitrobenzene moieties at the polymer chain ends quenched the emission from the layered carbazoles to the nitrobenzene termini; thus, the polymers acted as the molecular wire that transferred photoexcited energy and/or electrons to the polymer termini. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4279–4288, 2009     

Poly(diphenylsiloxy)arylazines. I. Synthesis and characterization

The synthesis of poly(diphenylsiloxy)arylazines and the preparation of the necessary aromatic aldehyde and azine precursors are described. This new family of polymers was prepared by a modified melt-condensation reaction of hydroxyl-substituted phenyl-and naphthylazines with bis(anilino)diphenylsilane. The resulting polymers have been characterized by elemental analysis, gel-permeation chromatography, vapor-phase osmometry, and absorption spectroscopy. Assignment of a polymer backbone composed of alternating diphenylsiloxane and arylazine moieties was made on the basis of the infrared absorption bands and by comparison of the fluorescence and absorption spectra of the polymers with those of model compounds. The molecular weight of the polymers was found to depend on temperature, reaction time, and the ratio of monomers. The formation of low molecular weight products was avoided by maintaining reaction temperatures below the decomposition point of the arylazine and by keeping the ratio of silylamine to arylazine at about 3:1. Molecular weights as high as 38,000 and extents of conversion of 85% were obtained by the described melt condensation procedure. The molecular weight of another member of the family was increased from 4600 to 8100 by a post-polymerization scheme, involving the reaction of aromatic hydroxyl and anilinosilane endgroups. Significant crosslinking via ortho hydroxyl groups during the polymerization of tetrahydroxyarylazines can be ruled out because of the solubility of the polymers in chloroform or tetrahydrofuran and on the basis of their fluorescence spectrum.     

Reversible Dimerization and Polymerization of a Janus Diradical To Produce Labile C−C Bonds and Large Chromic Effects

Conducting polymers can be synthesized by irreversible diradical monomer polymerization. A reversible version of this reaction consisting of the formation/dissociation of σ‐dimers and σ‐polymers from a stable quinonoidal diradical precursor is described. The reaction reversibility is made by a quinonoidal molecule which changes its structure to an aromatic species by forming weak and long intermolecular C?C single bonds. The reaction provokes a giant chromic effect of about 2.5 eV. The two opposite but complementary quinonoidal and aromatic tautomers provide the Janus faces of the reactants and products which produces the observed chromic effect. A reaction mechanism is proposed to explain the variety of final products starting with structurally very similar reactants. These reversible reactions, covering an unusual regime of weak covalent supramolecular bonding, yield products which might be envisaged as novel molecular and polymeric soft matter phases.     

Parabanic polymers obtained by the cyclocondensation reaction of polyureas containing 2,6-pyridyl structure

The polymers containing 1,3-imidazolidine-2,4,5-trione rings on the macromolecular backbone are known for a few years and named poly(parabanic acid)s. The paper presents some polymers and model compounds with urea and/or parabanic structures, as a result of the cyclocondensation reaction of the urea derivatives containing 2,6-pyridyl rest, with the oxalyl chloride. The 2,6-pyridyl radical has an acid acceptor character that determines an important distinct influence on the cyclocondensation reaction. The influence of the reaction conditions (temperature, time, beside of the presence or absence of pyridine (Py)) on the progress of the cyclocondensation was studied. The advance of the reaction was followed by IR spectra. The products were characterized by the elemental analysis, ¹H NMR and IR spectra, solubilities and viscosity measurements. Thermal properties were determined by thermogravimetric analyses and differential scanning calorimetry. The analytical and spectral data demonstrated that, in absence of Py, the cyclocondensation performed almost completely only in the case of the aliphatic polyureas, while, in the same conditions, the aromatic polymers were only partly transformed. By using the Py as catalyst, both aromatic and aliphatic polyureas can be transformed into parabanic polymers at above 90% transformation degree (TD). A calculation method of the TD based on the IR spectroscopy was discussed.     

Polymer syntheses via aromatic nitro displacement reaction

Nucleophilic displacement of activated aromatic nitro groups with aryloxy anion is a versatile and useful reaction for the synthesis of aromatic ethers. Preparation of various aromatic monomers and polymers containing ether linkages is described.     

Synthesis and thermal properties of disiloxane-arylene polymers by dehydrocoupling polymerization of bis(dimethylsilyl)arylene with water

Disiloxane-arylene polymers having phenylene, biphenylene, and fluorenylene groups as arylene units were synthesized by dehydrocoupling polymerization of corresponding bis(silane) derivatives with water. The reactivity of Si-H was not affected by the structure of aromatic groups in the reaction. The polymers containing biphenylene and fluorenylene units are amorphous and show higher glass transition temperatures than the polymer from 1,4-bis(dimethylsilyl)benzene.     

Synthesis of aromatic polyimines by the condensation of aromatic dialdehyde and diamine

Film-forming aromatic polyimines were prepared by low temperature solution polymerization of aromatic dialdehyde and aromatic diamine usingm-cresol. The polymerization proceeded rapidly to give high molecular weight polyimine solutions. Fibrous polymers were precipitated by pouring the solutions into anhydrous methanol. Lemon yellow-to-orange films were cast in situ from the reaction solutions. The polymers showed typical C=N stretching absorption near 1620 cm^?1 in infrared spectra and had high glass transitions of over 200 ?C but showed low crystallinity.     

Adapting semiconducting polymer doping techniques to create new types of click postfunctionalization

After the historical development from the insoluble polyacetylene film to soluble and processible aromatic polymers, donor-acceptor-type aromatic polymers have recently emerged as a new class of semiconducting polymers. The polymer energy levels and band gaps can be tuned by the appropriate selection of the donor and acceptor moieties, and some of these polymers showed good optoelectronic or photovoltaic performances. The conventional synthetic method for achieving donor-acceptor-type aromatic polymers is based on the metal-catalyzed polycondensation between donor-type monomers and acceptor-type co-monomers. In this tutorial review, a new methodology for introducing donor-acceptor chromophores into semiconducting polymers is described. The donor-acceptor structures are constructed in the main chains and side chains of semiconducting polymers using a polymer reaction based on high-yielding addition reactions between the electron-rich alkynes and strong acceptor molecules, such as tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). Considering the p-type doping features of TCNE and TCNQ, the experimental procedure is the same as the conventional doping technique for semiconducting polymers. However, the resulting donor-acceptor type polymers are chemically stable due to the absence of unstable unpaired electrons (polarons). The donor-acceptor alternating polymers were achieved in one step from the precursor poly(aryleneethynylene)s and poly(arylenebutadiynylene)s. When the side chain alkynes were post-functionalized, the polymer energy levels were controlled by the species and amount of the employed acceptor molecules. These atom-economic acceptor additions satisfy most of the requirements of the "click chemistry" concept. In contrast to the conventional click chemistry reactions, the reactions between electron-rich alkynes and acceptor molecules provide a wide variety of polymers with promising optoelectronic applications.     

One-step polymerization of polytrithiocarbonate using phase-transfer catalyst

A series of aliphatic and aromatic polytrithiocarbonates was prepared using a novel “one-pot” synthesis procedure employing a phase-transfer catalyst. The starting reagents were either an aliphatic or an aromatic dihalide and an excessive amount of carbon disulfide. The effects of the phase-transfer catalyst and reaction conditions on yield were studied. The structure and composition of the polymers and reaction side-products were determined from infrared, ultraviolet, ¹H-NMR spectra, and elemental analyses. The polymers were further characterized by viscosity measurement and thermal analysis. © 1993 John Wiley & Sons, Inc.     

C−N Coupling Reactions on Graphene with Aromatic Macromolecules and the Spatial Conformation of Grafted Macromolecules

The fabrication of advanced graphene-based nanocomposites with high-performance polymers requires covalent modification of graphene with aromatic macromolecules. Herein, C−N coupling reactions between fluorinated graphene (FG) and aromatic polyamides containing the benzimidazole moiety are successfully achieved. The optimized conditions are presented based on the nucleophilic behavior of the C−N coupling reaction on graphene. Different from the C−N coupling reaction between two small aromatic molecules, the conformation of grafted aromatic polyamide after reaction changes from torsional to paralleled alignment on graphene with the molecular length increment. Non-covalent interactions between graphene and aromatic polyamides result in this conformational change owing to the extended π systems of graphene and aromatic polyamides, and the synergistic effect of covalent and non-covalent interactions is put forward. As a consequence, graphene dispersibility is greatly enhanced in the solution of aromatic polyamide.     

Modification of polymers via electrophilic aromatic substitution

Three vinyl monomers, 2,4,6-trimethoxystyrene, 4-(N,N-dimethylamino)styrene, and N-methyl-2-vinylpyrrole, were synthesized via the Wittig reaction from the corresponding aldehyes. These monomers were homopolymerized by radical polymerization using α,α′-azoisobutyronitrile (AIBN) as initiator at 60°C. The reaction of these polymers with 4-phenyl-1,2,4-triazoline-3,5-dione (phTD) and 4-methyl-1,2,4-triazoline-3,5-dione (MeTD) was investigated. Although polytrimethoxystyrene reacts slowly with PhTD at room temperature, the other two polymers react fast and lead to the incorporation of the triazolinedione unit into the side chain of the polymer via electrophilic aromatic substitution. The reaction of bistriazolinediones (BTD) with these polymers was performed in dimethylformamide using 10–20% molar concentration of the BTD. The resulting crosslinked polymers are insoluble in polar as well as nonpolar solvents. Some physical properties of the unmodified and modified polymers were studied.     

Further polymers derived from bisazlactones and tetraamino compounds

New polymers containing benzimidazole in the polymeric backbone were obtained from the reaction of bis(oxazolones) with known and with a novel aromatic tetraamine. The polymers have inherent viscosities in the range of 0.1-0.4 dL/g (in DMF 30°C).     

Ionic Liquids as Novel Reaction Media for the Synthesis of Condensation Polymers

The use of ionic liquids as novel solvents for the synthesis of condensation polymers was investigated. A series of ionic liquids including new ones was synthesized and purified. 1,3‐Dialkylimidazolium‐based ionic liquids seem to be suitable reaction and activating media for the synthesis of high‐molecular‐weight aromatic polyimides and polyamides. Inherent viscosities of the polymers obtained in 1,3‐dialkylimidazolium bromides range from 0.52 to 1.35 dL/g.