Heterocyclic polymers characterization

Since Robinson [1] discovered cholesteric liquid-crystal phases in concentrated a-helical polypeptide solutions, lyotropic liquid crystallinity has been reported for such polymers as aromatic polyamides, heterocyclic polymers, DNA, cellulose and its derivatives, and some helical polysaccharides. These polymers have a structural feature in common, which is elongated (or asymmetric) shape or chain stiffness characterized by a relatively large persistence length. The minimum persistence length required for lyotropic liquid crystallinity is several nanometers1. 

Polybenzimidazoles are heterocyclic, thermoplastic and basic polymers characterized by at least one aromatic unit, which confers high mechanical and thermal stability (Tg > 400 °C). As already introduced, the most investigated basic unit of this class of polymers is poly [2,2 -(m-phenylene)-5,5 -bibenzimidazole]... 

Work in our laboratory in the past few years has been concerned with the use of acetylene chemistry, both to aid the processing of aromatic heterocyclic polymers and to pro-, vide such materials a method by which they could become tougher and more durable in structural applications. The most attractive feature of the acetylenic carbon carbon triple bond is its capability to undergo various ionic and free radical addition reactions, leading to highly fused thermally stable aromatic systems. This paper will review our work on acety-lene containing aromatic heterocyclic polymers with respect to synthesis and characterization, as well as some already determined mechanical properties as composites and adhesives. 

Bartolotta A, Di Marco G, Lanza M, Carini G, D Angelo G, Tripodo G, Fainleib A M, Slinchenko E A, Shtompel V 1 and Privalko V P. (1999) Synthesis and physical characterization of semi-IPNs of linear polyurethane and heterocyclic polymer network, Polym Eng Sci 39 549-558. 

XT Then certain allyl halides react with a suitable inorganic salt in the presence of a heterocyclic monomer, polymerization ensues (J). If the halide is a polymeric halide, graft copolymer results. The objectives of the present work are (1) to synthesize and characterize such graft copolymers and (2) to test some of their mechanical properties and relate them to the content of branch which has been grafted from the polymer. 

Double helical DNA is a water-soluble polymer that contains an electronically well-coupled stack of aromatic heterocyclic base pairs. This review describes efforts in our laboratory to characterize electron-transfer reactions between transition metal complexes bound by intercalation within the 7r-stack of DNA. Much information is available concerning the structure, synthesis, and methods of characterization of this polymer. Also, research in our laboratories has been directed toward describing the photophysical and photochemical properties of metal complexes bound to DNA. Using these metal complexes to probe the DNA 7r-way, we are now in a position to ask Is DNA a molecular wire ... 

In general, carbocyclic aromatic polymers yield more carbonized products than heterocyclic ones. Susceptibility of polymers to carbonization under pyrolysis conditions is characterized by the so-called coke number Van Krevelen concluded that the tendency for carbonization may be regarded as an additive resultant of the contributions of the individual functional groups in the monomer units. The contribution of a group is expressed in carbon equivalents contributed by each group to the coke residue, CR, per monomer unit ... 

On the other hand, polymer-supported task-specific ILs in which the imidazolium cations couple L-proline via the ionic-pair interaction have also been synthesized and applied in metal scavenging and heterogeneous catalysis. The novel materials displayed considerable ability for metal scavenging onto their surface [e.g., Cul, Pd(OAc)2, Pd and IrCh] without the aid of a non-immo-bilized ionic liquid. Moreover, attempts to use these materials in the Cul-cat-alyzed N-arylation of nitrogen-containing heterocycles revealed that these systems are characterized by a much higher activity and recycling ability than... 

The ionic conductivities of sulfonated polyetherketone/imidazole (pyrazole) systems were first studied by Kreuer et al. [161]. The intercalation of imidazole (pyrazole) into the polymer with Bronsted add functions was shown to produce a high protonic conductivity (ca. 10 S cm ). However, the volatility of these heterocycles hampers their application for high-temperature PEMFCs. In order to improve the thermal stability, the immobilization of these heterocyde systems was evaluated [162-164]. When Schuster et al. characterized the conductivity of imidazole-terminated ethylene... 

In the Phillips process, polyphenylene sulfide (PPS) is obtained from the polymerization mixture in the form of a fine white powder, which, after purification, is designated Ryton V PPS. Characterization of this polymer is complicated by its extreme insolubility in most solvents. At elevated temperatures, however, Ryton V PPS is soluble to a limited extent in some aromatic and chlorinated aromatic solvents and in certain heterocyclic compounds. The inherent viscosity, measured at 206°C in 1-chloronaphthalene, is generally 0.16, indicating only moderate molecular weight. The polymer is highly crystalline, as shown by x-ray diffraction studies (9). The crystalline melting point determined by differential thermal analysis is about 285°C. 

In phosphazene chemistry, preparation and reactions of small molecule, linear phosphazenes continue to attract interest. This year numerous papers have explored the utility of the aza-Wittig reaction in the synthesis of complex molecules with particular reference to nitrogen heterocycles. In cyclophosphazene chemistry, the shift of emphasis to materials which are monomers themselves or models for phosphazene polymers is apparent. The synthesis and characterization of poly(phosphazenes) is an active area with extensive interest in phosphazene based polyelectrolytes being noted. Solid state NMR has been shown to be a valuable tool for the study of both structure and phase changes in poly(phosphazenes). 

Epoxy resins are among the most important of the high performance thermosetting polymers and have been widely used as structural adhesives and matrix for fiber composites. Epoxy resins are characterized by the presence of epoxide groups before cure, and they may also contain aliphatic, aromatic, or heterocyclic structures in the backbone. The epoxy group can react with amines, phenols, mercaptans. 

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