Polyhydrazides preparation

Carbazole-containing PODs have been obtained (53) by cyclodehydration (in the presence of POCl3) of polyhydrazides prepared by polycondensation of IV-ethyl-3,6-carbaZoledicarbonyl chloride with dihydrazides of the corresponding dicarboxylic acids. Thermal decomposition of the polymers containing aliphatic units occurs at 365-380°C, compared to 400-405°C for polymers containing aromatic units. 

Carboxylic acid hydiazides are prepared from aqueous hydrazine and tfie carboxylic acid, ester, amide, anhydride, or halide. The reaction usually goes poody with the free acid. Esters are generally satisfactory. Acyl halides are particularly reactive, even at room temperature, and form the diacyl derivatives (22), which easily undergo thermal dehydration to 1,3,4-oxadiazoles (23). Diesters give dihydtazides (24) and polyesters such as polyacrylates yield a polyhydrazide (25). The chemistry of carboxyhc hydrazides has been reviewed (83,84). 

Oligomer 163 represents a stabilizer having PA chain with pendant phenolic moiety [31], Pendant hindered piperidine or piperazine moieties were attached to oligomeric stabilizers having polysulfonamide, polyurea (e.g. 164), or PA (e.g. 165) unis [213]. Polyhydrazide 166 was tested as HD AO and copper deactivator in PP [214]. Poly (nitrophenylene-carbazide disulfide) 167 was prepared for thermal stabilization of PVC. Phosphorus containing crosslinkable polymers having polyamide, polyimide and polyurea chains were prepared for flame and heat resistant applications [215]. 

Interfacial reactions have been employed using the reactions of dicar-boxylic acid chlorides with diamines to form polyamides, with hydrazine and hydrazides to form polyhydrazides disulphonyl halides have been used to prepare polysulphonamides diisocyanates and glycols have been used to prepare polyurethanes interfacially (Section 7) and diisocyanates and diamines have been reacted interfacially to form polyureas [6] (Section 8). Polyesters prepared by this technique were discussed in Section 5.7. 

Major contributions to the synthesis of aromatic polyamides were made by Morgan, Kwolek and coworkers ( 1.- ) G. N. Milford prepared the aromatic polyamide and J. W. Richter synthesized the polyhydrazides and polyamide-hydrazide discussed in this paper (.7). Other investigators have also contributed extensively to the synthesis and characterization of aromatic polyamides for example, Preston and coworkers at Monsanto (8-10). Important contributions to the polyamide synthesis literature have also been made by Australian, Canadian, European, Japanese and Russian scientists (11). 

Polyamide, polyurea, polyhydrazide and polyurethane materials having modified surfaces, which are antimicrobial, are prepared using selective UV photon irradiation, high energy electron irradiation or low energy eleetron irradiation. 

The polycondensation reaction is more profitably utilized in the preparation of polyhydrazides and poly(amide-hydrazides) with high molecular weights 19 which are difficult to be produced by the phosphorylation reaction with triphenyl phosphite and pyridine20. The results of the polycondensation reaction of p-aminoben-zoylhydrazide(p-ABH) with dicarboxylic acids in the presence of triphenyl phosphite and LiCl are listed in Table 11. 

The term "condensation polymers" was introduced by W. H. Carothers in his early work on the preparation of polyesters and polyamides to distinguish this class of polymers from vinyl polymers made by addition reactions. Condensation polymers were defined as polymeric molecules that may be converted by hydrolysis, or its equivalent, into monomers that differ from the structural units by one molecule of H2O, HCl, NHj, etc. This broad definition includes many polymers made by ring-opening or addition reactions, for example, lactone and lactam polymers, polyurethanes, polyureas, polyimides, and polyhydrazides, as well as polymers made by true condensation reactions. 

Polyhydrazides were prepared by the general procedure of Frazer (1) from dihydrazides and diacid chlorides in amide solvents (Fig. 1) ... 

Other Extended Chain Polyhydrazides. The polyhydrazide system based on terephthaloyl, chloro-terephthaloyl, 2,5-pyridinedioyl and oxalyl units was examined by the preparation of polymers and determination of their ability to form liquid crystalline solutions in aqueous tetramethylammonium hydroxide. The acyl groups are coded T, ClT,... 

Another extended-chain polyhydrazide which contains no rings was prepared from oxalic di-hydrazide and trans,trans-muconvl dichloride (last formula of Table IV). The polymer had an Tinh value of 0.33 and dissolved in tetramethylammonium hydroxide to form only isotropic solutions. With a higher molecular weight sample, optically anisotropic solutions should be attained. Other possible components for this purpose are fumaroyl and acetylenedioyl (Table IV). ... 

N-Substituted Polyhydrazides Several poly-hydrazides were prepared in which each hydrazide link had one N-methyl substituent (Table VIII). Only isotropic solutions were obtained in the aqueous organic bases. The nitrogen substituent presumably provides a more flexible type of amide link and changes the nature of the solvent association (see next section). 

There are only a few communications in the literature on the fabrication of fibers from LC polymers of a different chemical structure than aromatic polyamides and heterocyclic polyarylenes of the type of PBT or PBO, and they primarily concern aromatic polyhydrazides. These polymers can be considered polyamides prepared with hydrazine as the diamine. LC solutions of polyhydrazides based on terephthalic and oxalic acids have been prepared in both aqueous solutions of organic bases (secondary amines or quaternary ammonium bases) and in concentrated sulfuric acid [57]. In sulfuric acid, polyhydrazides are unstable and undergo hydrolytic decomposition, but the copolyhydrazide based on oxalic, chloro-, and terephthalic acids form relatively stable LC solutions in sulfuric acid... 

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