Other Heterocyclic Polymers

Thermal and thermo-oxidative degradation have been studied as a function of chemical structure in poly(phenylquinoxaline) and poly(naphthylimido phenyl-quinoxaline). The introduction of the naphthalene units is claimed to decrease thermal stability, but to increase thermo-oxidative stability. The thermal degradation of polyhexazocyclanes and suitable model compounds has been 

Zurakowski-Orszagh and S. Kobiela, Polimery (Warsaw), 1979, 24, 14 (Chem. Abstr., 1979, 91, 40 069). 

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However, some of the basic problems of polypyrrole and of the other heterocyclic polymers act to limit the performance of the lithium/polymer battery, and thus its wide applicability. These are essentially slow kinetics, self-discharge and low energy content. 

The 2,5-coupling of thiophene monomeric units leads to two possible structures for poly thiophene—a linear and a coiled structure. If the sulfur atoms are oriented trans to each other, a linear polymer results as illustrated in Fig. 13a. If the atoms are cis to each other, the coil structure is favored as shown in Fig. 13b [265,266]. Other heterocyclic polymers [265], such as polypyrrole, are believed to form linear structures. Hence, a linear structure would seem favored for polythiophene. However, the possibility of an alternative structure is quite interesting and two studies have provided some possible evidence for a coil-type structure. 

A hydraulic fracturing fluid containing guar gum or other natural polymers can be stabilized against bacterial attack by adding heterocyclic sulfur... 

A change of architecture is another route that enables diversification of the properties of aliphatic polyesters. This review will focus on star-shaped, graft, macrocyclic, and crosslinked aliphatic polyesters. It must be noted that the ROP of lactones has been combined with several other polymerization mechanisms such as ROP of other heterocyclic monomers, ionic polymerization, ROMP, and radical polymerization. Nevertheless, this review will not cover these examples and will focus on polymers exclusively made up of poly(lactone)s. 

A wide range of polymers based on other heterocyclic 5-membered rings have been investigated, including oxadiazole, pyrazole, triazole, tetrazole, and thiophene [Bass et al., 1987 Briffaud et al., 2001 Cassidy, 1980 Critchley et al., 1983 Gebben et al., 1988 Ueda and Sugita, 1988],... 

Considerable research effort has been devoted in recent years to the use of chloral derivatives for the synthesis of linear heterocyclic polymers. Of these, the most common are aromatic polyimides [1-12], Many of these polymers have been synthesised from compounds like 4,4 -diaminobenzophenone, and other diamines, which, as demonstrated in the previous chapter, can be obtained from chloral. Polyimides prepared from these diamines were largely synthesised by the conventional two-step procedure [11, 12] involving mild reaction of the diamines with the bis(phthalic)anhydrides, isolation of poly(o-carboxy)amide (PCA) prepolymers, and then processing into products followed by thermal or chemical imidisation [13—16] (Scheme 3.1). Some properties of polyimides prepared from 4,4 -diaminobenzophenone are provided in Table 3.1. 

Finally, addition polymerization of suitably substituted furans allows incorporation of the furan nucleus into heterocyclic polymers (77MH1102). 2-Vinylfuran apparently exhibits free radical polymerizability comparable with that of styrene, although rates, yields and degrees of polymerization are low under all conditions except for emulsion polymerization. Cationic polymerization is quite facile and leads not only to the poly(vinylfuran) structure (59), as found in free radically produced polymers, but also to structures such as (60) and (61) in which the furan nucleus has become involved. Furfuryl acrylate and methacrylate undergo free radical polymerization in the manner characteristic of other acrylic esters. 

Relatively few simple pyrimidine monomers have been incorporated into heterocyclic polymers (70MI11100). By far the greatest efforts with this ring system have involved polymerizable derivatives of nucleic acid bases and related compounds (81MH1102). The majority of this work has involved the synthesis and free radical polymerization of suitable vinyl- and acrylic-functional monomers, e.g. (134)-(136), although epoxy and other derivatives have also been studied. A number of the polymers exhibit base-paired complex formation with natural nucleic acid polymers or synthetic analogues, have found use in... 

Heterocyclic polymers containing the 1,4-dioxane ring have been mentioned only briefly in the literature. Cationic addition polymerization of 1,4-dioxene (151) produces polymer (152 Scheme 48) which, along with other poly(l,2-dialkoxyethylenes), is reported to form polymeric complexes with poly(methacrylic acid) (79MI11109). 

One of the time honored polymer modification reactions resulting in heterocyclic polymer formation is reaction of a poly(diene) with maleic anhydride or a maleimide (B-64MI11100). Two modification techniques have, in general, been employed—one catalyzed or initiated, the other not. Although most reports deal with modifications using maleic anhydride, A-alkylmaleimides are reported to behave in a completely analogous fashion. 

As discussed in Chapter 3, some other inorganic polymers also contain phosphorus atoms.47 They are derived from the basic phosphazene structure described in Chapter 3, and are obtained by the ring-opening polymerization of heterocyclic compounds in which one of the disubstituted phosphorus atoms is replaced by another moiety. Specifically, introduction of a carbon atom can yield poly(carbophosphazenes), with the repeat unit shown in 6.49. Alternatively, replacement with a sulfur atom can yield a poly(thiophosphazene) (6.50). Relatively little is known about these polymers at the present time 47... 

The Raillard group at Affymax developed a multigram synthesis of a 2,5-diketopiperazine and other heterocyclic systems by employing a high-load Merri-field resin transformed into polymer-supported valine, which was used as the amino component in an Ugi-4CR to gave the target diketopiperazine 137 after cleavage of 136 from the resin [77] (Scheme 2.49). 

One of the characteristic properties of BBB, BBL, and many other similar heterocyclic polymers is their limited solubility. As far as is now known, BBB is soluble only in strong acids such as concentrated sulfuric, benzenesulfonic, methanesulfonic, and concentrated phosphoric acid and in certain aqueous reagents discussed below, in which a chemical reaction modifies the polymer. The vat dyestuffs below ... 

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