Poly Schiff bases

The interaction of PCSs with nucleophilic reagents was studied by us we took the reactions of hydrazine and phenylhydrazine with polyazines, poly(schiff base)s, and other polymers containing conjupted C=N bonds as an example40,41, U7,258. ... 

Interaction of PCSs with electron acceptors and donors results in molecular complexes with partial or complete charge transfer. In particular, detailed investigations involved charge transfer complexes (CTC) of poly (schiff base), polyazines, products of thermal transformations of PAN and a number of other PCSs129, 238, 241 243, 267. ... 

Fig. 18. Electronic absorption spectra of a poly(schiff base) obtained by polycondensation of 4,4 -diacetyldiphenyl sulfide and p-phenylenediamine (1) and of its complex with iodine (2)...

CTC formation is accompanied by a volume contraction129. Thus, poly(schiff base)s having no side groups give complexes with a density 10—15% higher than that calculated on an additivity assumption. 

X-ray diffraction analysis of crystalline poly(schiff base)s and their low molecular models shows that the formation of molecular complexes is accompanied by an increase in interplanar distances and, in a number of cases, by complete amor-phization. Molecular complexes of poly(schiff base)s with Br2 decompose with time, because of the bromination of the donor components, forming C—Br bonds. Substitution of hydrogen by bromine in phenyl groups occurs only in cases in which these groups are not included into the main polymeric chain. 

We have already pointed out that the reduction in conjugation efficiency in PCSs is followed by a short-wave shift of the CTC transfer band. This accounts for the fact that poly(schiff base)s and polyazines having conjugated sections separated by oxygen and sulfur atoms are characterized by a short-wave shift of the transfer band of CTC with all acceptors compared to the respective polymers having no interruption of the conjugated chain. This shift may reach 20-50 nm. 

Bearing in mind the semiconductive properties of PCSs one might expect that these substances, being p-type semiconductors in air, possess photosensitizing activity. We, indeed, have demonstrated40 that PCSs, such as poly(schiff base)s, salts of poly(propynoic acid), or polyquinoline, are active photosensitizers of... 

Structure of the chiral poly-Schiff base [14] has been studied by NMR spectroscopy.29 It was shown that poly-Schiff bases have an interesting feature their chiral forms can be self-assembled into nanometer-size fibrous architecture, while their racemic analogues did not show any self-assembling properties. 

Another group of polyconjugated photoconductive polymers reported in the literature are poly(Schiff-bases)33, polycondensates of aromatic diamines and... 

Test strips were prepared by oxidation of cellulose with KIO4 to a polyaldehyde, followed by condensation with 1-naphthylamine to a poly-Schiff base and reduction with NaBH4 to an immobilized naphthylamine cellulose derivative, which is mechanically stabilized on a polypropylene sheet. PAA can be detected on addition of nitrite to the test solution and contacting with the strip, where azo dyes are formed. Quantitative analysis can be carried out by diffuse reflectance spectroscopy. The method was applied to pharmaceutical preparations with RSD better than 30%246. 

Low molecular weight Schiff base complexes of many metals are well known and in the case of aromatic ligands these tend to have high thermal stability. Polymeric Schiff bases likewise have been well reported, and although many of these have the Schiff base appended as a substituent on a vinyl polymer backbone, others have the Schiff base residue as part of the mainchain. The latter continue to complex metals very well [140, 141] and one early paper reports the use of a Mn(II) polymeric complex in the aerobic oxidation of cumene at 30-100°C [142]. Indeed there is an implication in the paper that the polymer complex is stable to 200°C when complexed O2 tends to be liberated. Wohrle s group have also studied polymeric Schiff bases extensively, again mostly with pendant groups. However, they have reported a mainchain poly Schiff base [143], its complexation with Co(II), Ni(II) and Cu(II), and use of the supported complexes as catalysts in quadricyclane isomerisation to norbornadiene. 

Monomeric dihydrazides were prepared by the reaction of 2,4-D and CMPA derivatized tartrate and glutarate with hydrazine hydrate, and polymerized by reactions with HMDI to form polyureas. These monomeric derivatives were also polymerized with terephthaldehyde to form poly(Schiff base)s containing herbicide moieties (Scheme 3.11) [136]. The effect of structure and of the aqueous environment on the hydrolysis rates of 2,4-D from the polymers were investigated under various conditions. 

Chart I. Synthesis of poly(Schiff base) from benzil. 

We have succeeded in synthesizing polydiphenylacetylene with Schiff base end groups with different length and structure. Their photoluminescent properties have been investigated. It is clear that better experimental conditions (proper solvent or solvent mixture, proper catalyst, etc.) are necessary for the preparation of poly(Schiff bases) with a similar structure. This is the aim of our future investigations. 

Method 4. Polymerization of Diacetyl and / -Phenylenediamine The polycondensation of diacetyl with p-phenylenediamine yields a dark-brown, amorphous powder that is soluble in dimethylformamide, formic acid, and sulf uric acid. Its structure was thought to be a poly(Schiff base). However, ozonization and infrared studies demonstrated that the most probable structure of the polymer was [23] (33). Since diacetyl dimerizes to a product which yields p-xyloquinone in basic medium, the polymer [23] could have arisen from the reaction of p-xyloquinone with the diamine (53). 

TABLE VI[ —continued Metal-Containing Poly(Schiff Bases)... 

Poly-SchifF bases containing DCZB units in the main chain (26b) were synthesized by the direct polycondensation of rran5-l,2-bis(3-formyl-9-carbazolyl)cyclo-butane with aromatic diamines [217]. Complexation of the polymers (26b) with iodine produces cation-radical salts which result from an electron transfer from DCZB moieties to iodine. The undoped polymers are insula-... 

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