With aromatic backbones preparation

Various phosphonated block and graft copolymers have been prepared in order to obtain membranes with high local concentrations of phosphonic acid. The block copolymers have mainly been based on phosphonated and non-phosphonated vinyl monomers, whereas the graft copolymers have been based on polymers with aromatic backbones such as PAESs, poly(phenylene oxide) (PPO), and PBI, from which phosphonated vinyl monomers have been grafted. 

Stability and performance of AEM prepared using poly(4-vinyl pyridine-costyrene), quaternized with 1-bromooctane, and deposited on fibrous woven paper was unsatisfactory [189]. Sanchez and coauthors [190] discussed problems related to the use of certain AEMs. They pointed out that the so-called Hoffman degradation that involves attack of a hydroxyl on a-hydrogen in p-position to a quaternary ammonium attached to an aliphatic chain may cause its removal, followed by release of a tertiary amine and formation of a double bond at the end of a broken chain. Attachment of DABCO on short leash prevented chain break due to Hoffman degradation, but release of DABCO and generation of a double bond attached to the chain could take place. Perhaps thermal cross-linking by DABCO of poly(vinyl benzyl chloride) may solve this problem. Sulfonated polymers prepared by polymerization or copolymerization of phosphazene, siloxans, styrene, vinylidene fluoride, and various monomers with aromatic backbones, and possibly with aliphatic spacers, have been used. Various imides as well as PPS, PEK, PEEK, PSU, PEEKK, and PPSU can also be used [190,191]. 

Chemical modifications of PPO by electrophilic substitution of the aromatic backbone provided a variety of new structures with improved gas permeation characteristics. It was found that the substitution degree, main chain rigidity, the bulkiness and flexibility of the side chains and the polarity of the side chains are major parameters controlling the gas permeation properties of the polymer membrane. The broad range of solvents available for the modified structures enhances the possibility of facile preparation of PPO based membrane systems for use in gas separations. 

The NMR spectra of copolymers prepared by simultaneous oxidation of the two phenols and those prepared by sequential oxidation, in either order, are almost identical. The methyl peak is broadened, as is the peak caused by the protons of the pendant phenyl rings centered at 8 7.20 ppm, and all show the same peaks for aromatic backbone protons in about the same intensity ratios. The polymer obtained by oxidizing a mixture of DMP and the separately prepared homopolymer of MPP with a cuprous bromide-tetramethylbutanediamine catalyst, the procedure considered to have the best chance of producing a block copolymer, was completely random. 

Other high-performance epoxy resins have been synthesized with the goal of achieving higher-temperature performance. Initially epoxy novolacs, which have a more rigid aromatic backbone and a higher epoxide functionality, were prepared. 

Polynaphthoylenebenzimidazoles containing 1,3,4-oxadiazole and benzoxa-zole cycles in the backbone structures were prepared [123] by the interaction of bisfnaphthalic anhydrides) containing the previously mentioned heterocycles with aromatic bis o-phenylenediamines) according to Scheme 51. 

In order to prepare polydiacetylenes with aromatic rings directly attached to the polymer backbone an interesting strategy has been employed. The aromatic ring is attached to one position of the diyne and a functionality for proper self-assembly (Fig. 1) is attached to the other position of the di5me. A carbamate functionality has commonly been used to provide the proper supramolecular stnictiu-e (Fig. 5). Advantages of this scheme are that the reduced nonbonded interactions... 

The poly(phenylene oxide)s are also referred to as polyoxyphenylenes and poly(phenylene ether)s. Variations in the configuration of the ether group, ie, ortho, meta, or para, and in the extent and type of substitution, eg, alkyl, halo, etc, on the aromatic backbone give rise to a large number of possible homo- and copolymers. The polymers with para-oriented ethers have been studied most extensively and several have significant utility. Poly(2,6-dimethyl-l,4-phenylene oxide) [25134-01-4] (DMPPO), prepared by General Electric by the oxidative coupling polymerization of 2,6-dimethylphenol, is marketed as PPO resin. Blends of... 

Indacenedithiophenes (IDTs) are a class of molecules that are isoelectronic to the IF family (Figure 2.16). Incorporation of sulfur into aromatic backbones is an established method to improve processability and stability to ambient conditions and modify electronics [84-86]. IDTs 34a and 35a were prepared by the Haley group and exhibited red-shifted absorptions and deepened LUMO energy levels compared with 28q. Benzannulated derivatives 34b and 35b were further red-shifted with LUMO energy levels estimated at —4.03 and —3.84eV, respectively. 

These observations are consistent with the difficulty that aromatic substituted diacetylenes have in undergoing a topochemical polymerization. The preparation of single crystal polydiacetylenes with aromatic substituents directly attached to the polymer backbone remains a challenge for supramolecular synthesis. 

The general utility of one-pot macrocyclization conditions was demonstrated by the satisfactory preparation of other circularly folded aromatic pentamers 20b-e, sharing the same aromatic backbone but differing by exterior side chains (Table 9.5). Because the solubility of monomers 19c-e is not as good as 19a and 19b containing alkyl side chains, more CH2CI2 (6 ml in Table 9.11 vs. 3 ml in Table 9.4) is needed to dissolve 19c-e. With the use of more solvent, yield for 20a decreases from 25 % (entry 12, Table 9.4) to 23 % (entry 1, Table 9.5) and 20b-e aU can be produced satisfactorily with a respective yield of 18, 12, 10, and 16 %. 

Jiang s group [68] prepared fluorinated hb-PAEK end-capped with nickel phtha-locyanine and checked the material for NLO applications. The third-order nonlinear coefficient was found to have a value of 0.98 x 10 " esu, which the authors attributed to the dual contributions of nonlinear absorption and refraction of the molecules. Moreover, the obtained value was found to be almost five times larger than that of other metallophthalocyanines [314] due to presence of the hyperbranched structure, the aromatic backbone, and the number of end-functionalities. 

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