Aromatic heterocyclic polymer

Chemistry, reaction mechanisms, and properties have been extensively reviewed.4,5,10-20 Hie present chapter deals witii only one type of fully cyclized aromatic heterocyclic polymers die high-molecular-weight linear polymer witii a special emphasis on die synthesis and structure—property relationships for specific applications. 

It has been shown that miscible polymer blends and copolymerization offer complementary routes to polymer systems of tailored properties. The recognition that miscibility (at least in a transient sense) is much more common with aromatic heterocyclic polymers than is observed with low temperature flexible... 

Aromatic-Heterocyclic Polymers Research at United States Air Force... 

AROMATIC-HETEROCYCLIC POLYMERS RESEARCH AT UNITED STATES AIR FORCE WRIGHT LABORATORY RECENT DEVELOPMENTS... 

One of the first all-aromatic heterocyclic polymers to undergo development as a high temperature adhesive was a polybenzimidazole (PBI). In 1961, Vogel and Marvel (1)... 

Polyimidazopyrrolone (ladder pyrrone, polypyrrolone) n. An aromatic, heterocyclic polymer that results from the reaction of an aromatic dianhydride with a tetramine. Due to the double-chain or ladder-hke structure, these polymers have outstanding resistance to radiation, chemicals, and heat (no weight loss to 550°C). However, this structure also makes them difficult to process. To overcome this difficulty pyrrone pre-polymers in the form of solutions and salt-like powders have been made available. The powders can be molded under conditions that complete the cychzation or conversion of the ladder-hke molecular structure during the molding cycle. The cychzation reaction generates water, which must be removed from the part. 

Aromatic heterocyclic polymers such as polypyrrole and polythiophene have low ionization potentials and low electron affinities [1, 2]. An early theoretical study on the electronic properties of these polymers indicated that electron affinity is mainly affected by substitution on the heteroatom whereas ionization potential is mainly affected by substitution on the backbone [9], Later theoretical studies on polythiophene indicated that chemical transformation of thienyl sulfur to the corresponding thienyl-5-oxide or thienyl-5,5-dioxide would deeply affect the electronic properties of the polymer as a result of the increase in both electron affinity (EA) and ionization potential (IP) [10, 11],... 

Molecular composites development has been concentrated primarily in physical blend systems in which rigid-rod aromatic-heterocyclic polymers functioned as the... 

Among the very large number of chemically different aromatic and aromatic-heterocyclic polymers synthesized within the last decade, only a few exhibit any crystallinity and therefore have melting points. Among... 

The introduction of heteroaromatic units into polymer backbones has played a major role in the advancement of high performance materials. This strategy has resulted in a number of aromatic heterocyclic polymers and aromatic-heteroaromatic polyamides. For example, Marvel s preparation of polybenzimidazole or Kvenzel s work in which oxadiazole rings were incorporated in aromatic polyamides. We now report the preparation of poly(imidazoleamides), a new class of heteroaromatic polyamides based on cyanoimidazoles. 

Hanley TR, Helminiak TE, Benner CL (1978) Expansion of aromatic heterocyclic polymers in salt solution. J Appl Polym Sci 22 2965-2978... 

Tan L, Arnold F, Dang T et al (1994) Pseudo-ladder rigid-rod polymers tfihydroxy pendant benzothiazole aromatic heterocyclic polymer and copolymers. Polymer 35 3091-3101... 

Polyimide fiber is made from an aromatic heterocyclic polymer, and P84 is the brand name of the polyimides manufactured by Evonik Fibers with a trilobal fiber cross section (Fig. 2.25). P84 is a fully imidized polyimide derived from aromatic dianhydrides and aromatic diisocyanates and has a glass transition temperature of 315°C. The fibers start to carbonize at temperatures beyond 370°C. Due to the aromatic structure, the polymer and fibers are inherently nonflammable. An FOl of 38% can be measured. P84 can be used for temperatures up to 260°C, depending on the environment [71]. Typical properties of P84 are introduced in Table 2.67. 

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. 

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