Polycondensed systems, aromaticity

Intensive development of applied research activities in the field of lyotropic LC polymer systems was observed in the mid-1960s and 1970s, when novel families of aromatic polyamides were obtained. These polymers are usually prepared by the polycondensation of aromatic diacyl dihalide (HalOCAr COHal) with an aromatic diamine (H2NAr NH2) in solution, according to the reaction... 

The preparation of aramids by direct polycondensation of aromatic diamines with aromatic dicarboxylic acids using triphenyl phosphite and pyridine as condensing agents has been well documented. This method was used here to polymerize the commercially available diamines, 4,4 -oxydianiline (ODA) and 1,4-phenylenediamine (PDA), with 10,11,15, and 16. Polymers obtained with this method formed fibrous precipitates on pouring the reaction mixtures into stirring methanol. Essentially quantitative yields were obtained for all systems evaluated. High molecular weight... 

Trost and Ghadiri19 have found a Lewis-acid-mediated intramolecular cyclization of allyl sulfones. When the allyl sulfone 40 is treated with A1C13, polycondensed aromatic system 41 can be obtained in good yield (equation 24). The mechanism probably involves... 

Monomers employed in a polycondensation process in respect to its kinetics can be subdivided into two types. To the first of them belong monomers in which the reactivity of any functional group does not depend on whether or not the remaining groups of the monomer have reacted. Most aliphatic monomers meet this condition with the accuracy needed for practical purposes. On the other hand, aromatic monomers more often have dependent functional groups and, thus, pertain to the second type. Obviously, when selecting a kinetic model for the description of polycondensation of such monomers, the necessity arises to take account of the substitution effects whereas the polycondensation of the majority of monomers of the first type can be fairly described by the ideal kinetic model. The latter, due to its simplicity and experimental verification for many systems, is currently the most commonly accepted in macromolecular chemistry of polycondensation processes. 

Polyimides are prepared from the polycondensation reaction between an aromatic dianhydride and oxydianiline (Fig. 1). In this paper, we will use the above polymer as typical of all PI coatings. All experimental results quoted here were obtained with this system. 

In this review the nomenclature and numbering originally given by Newman 1( will be used. As an example the numbering of hexahelicene is given. In the example the quaternary carbon atoms are not numbered, but on addition of a group at these carbon atoms they are numbered as usual in polycondensed aromatic systems. For the x-ray analyses (and also i3C-NMR etc), the quarternary carbon atoms are numbered separately. 

The rearrangement accompanied by the elimination of ketone R OMe gave, as a rule, good yields of naphthalenes 556 (Table XII)438,439 and was extended to the synthesis of polycondensed aromatic systems 557, 558, and (559), as demonstrated by Eqs. (36-38). 

The mechanochemical polycondensation reaction has been studied using heterochain polymer systems—polyethylene terephthalate poly-(e-caprolactam), cellulose, etc.—characterized by end groups that can be activated to increase their own number by mechanochemical destruction of corresponding polymers. The mechanochemical destruction was done in the presence of some suitable condensing agents, such as aliphatic and aromatic diamines and fatty acid dichlorides. 

The application of Heck coupling polycondensation is not limited to the synthesis of poly(arylene vinylene)s via the alkenylation of haloarenes in simple monomer systems but includes a variety of self- and cross-coupling reactions involving reactants with various functionalities. For instance, the polycondensation of diiodoarene with bis(acrylamido)arene by the Pd(OOCCH3)2—P (o-C6H4—CH3)3 catalyst yields respective aromatic polycinnamamide [106] ... 

The polycondensation of l,l -dicarboxycobalticenium chloride with aromatic diamines in molten antimony trichloride at 150-175 °C gave polyamides containing the cobalticenium tetrachloroantimonate(V) salt system in the repeating unit (Eq. 5)9. ... 

A detailed study of the chemical constitution of the products revealed that their composition is influenced by temperature but not by pressure or the nature of the catalyst. With increased reaction temperature there was a decrease in total and acidic oxygen concentrations in the asphaltenes and a corresponding increase in both aromatic content and the C/H ratio. This observation is consistent with the loss of aliphatic side chains from the polycondensed ring systems. 

Polymeric N202-chelates may be obtained by polyreaction of a bifunctional low molecular N202-chelate instead of constructing the chelate system during polycondensation. But only few results show a new way for the future. Bifunctional low molecular dielates (136) solved in NaOH were condensed with bifunctional aromatic acid chlorides solved in CH2Q2 by interfacial polycondensation >. Insoluble polychelates (137) were obtained (Eq. 69). 

Crude oil residues and bitumen are colloidal disperse systems. In these systems, high-molecular solid structure units (asphaltenes) are dispersed in an oily phase (maltenes) (see section 8.2). In industrial thermal cracking processes, these units precipitate as coke. Coke formation is caused by polycondensation reactions of aromatic cores of asphaltenes, which lose the paraffinic periphery. The main objective of a substantial portion of this chapter is to show how deep cracking of bitumen at low temperature can be achieved without coke formation (i.e., without polycondensation of asphaltenes). The main reactions of asphaltenes that lead to coke formation are described. Also described are ways to reduce the negative influence of these reactions on the process. 

From Figure 9.10, it is seen that during the thermal treatment of pure model compounds, polycondensation is the only reaction that occurs. In contrast to this, during the co-treatment of the model compound with polypropylene, the flouren is decomposed. This decomposition reaction proceeds via the bridged-ring system, because one-ring aromatic compounds were found in the reaction product in case b) of Figure 9.10. 

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