Benzothiazole polymers

The benzoxazole and the benzothiazole polymers which received most attention are the cis and trans isomers, respectively. PBT, which has been the object of most of the work, is prepared by first synthesizing 2,5-dimercapto-l,4-phenylenediamine PPD is converted into the bis-thiourea with ammonium... 

By reduction in the degree of polymerisation. To produce processable rubbers the original polymers are masticated with substances such as benzothiazole disulphide and tetramethylthiuram disulphide. The more severe degradation techniques to produce liquid polysulphides are mentioned below. 

When two polymers interact or react with each other, they are likely to provide a compatible, even a miscible, blend. Epoxidized natural rubber (ENR) interacts with chloro-sulfonated polyethylene (Hypalon) and polyvinyl chloride (PVC) forming partially miscible and miscible blends, respectively, due to the reaction between chlorosulfonic acid group and chlorine with epoxy group of ENR. Chiu et al. have studied the blends of chlorinated polyethylene (CR) with ENR at blend ratios of 75 25, 50 50, and 25 75, as well as pure rubbers using sulfur (Sg), 2-mercapto-benzothiazole, and 2-benzothiazole disulfide as vulcanizing agents [32]. They have studied Mooney viscosity, scorch... 

Aromatic poly(benzothiazole)s are thermally and thermooxidatively stable and have outstanding chemical resistance and third-order nonlinear optical susceptibility. Aromatic poly(benzothiazole)s can be spun into highly-oriented ultrahigh strength and ultrahigh modulus fibers. However, this type of polymer is insoluble in most organic solvents. Therefore, hexafluoroisopropylidene units are introduced in the polymer backbone to obtain soluble or processable aromatic poly(benzothiazole)s. 

The aromatic poly(benzothiazole) from 15 and 29 is almost amorphous and easily soluble in strong acids such as concentrated sulfuric acid and methane-sulfonic acid.26 It also dissolves in organic solvents such as HMPA and o-chlorophenol. The increased solubility and amorphous nature of this polymer is also ascribed to reduced intermolecular forces and to looser packing owing to the presence of highly distorted diphenylhexafluoroisopropylidene units in the polymer backbone. 

The process that makes the chemistry, properties, and applications of elastomers so different from other polymers is cross-linking with sulfur, commonly called vulcanization. The modem method of cross-linking elastomers involves using a mixture of sulfur and some vulcanization accelerator. Those derived from benzothiazole account for a large part of the market today. Temperatures of 100-160°C are typical. 

A few other PAEH have been reported. One disclosure concerned PAE containing pendent benzoxazole and benzothiazole units [49]. The activated difluoro benzazole monomers, 2-(2,6-difluorophenyl)benzoxazole or benzothiazole, were prepared from the reaction of 2,6-difluorobenzoyl chloride with 2-aminophenol or 2-aminothiophenol in polyphosphoric acid. By H NMR, the benzazole unit was shown to have a greater electron-withdrawing effect on the 2-phenyl group than on the benzo ring [49]. Only a few polymers were reported. As an example, the polymer of structure 12 had an intrinsic viscosity of 0.45 (NMP at 30 °C) and Tg of 170°C [49],... 

Synthesis of polyimides containing benzothiazole-2-sulfide groups was carried out using high-temperature polycyclocondensation in w-cresol in accordance with Scheme 5.7 [41, 44]. All the polyimide synthesis reactions were homogeneous and yielded polymers having reduced viscosities Pred = 0.29-0.42 dl/g, Tg = 215-265 °C and 10% weight loss temperature = 325-400 °C (Table 5.9). 

All the resulting polyimides were soluble in NMP polyimides based on dianhydride A were also soluble in THF, while polyimides derived from dianhydride 6F showed solubility in THF and chloroform. A positive influence of benzothiazole-2-yl side groups on polymer solubility was also reported in the literature [45, 46]. 

Several molecules which can undergo intramolecular proton transfer in the excited state have been found to be unusually photostable. Thus, for example, 2-hydroxybenzophenone is used as a photostabilizer in polymers while benzophenone itself is photoactive (Kysel, 1969). In crystalline 2-(2 -hydroxyphenyl)benzothiazole and its derivatives [3] a proton is transferred in the excited state from an... 

Fig. 10.24 Structures of polymers absorbing beyond 600 nm (a) poly(dithieno(3,4-b 2, 3 -d)thiophene), (b) tbiophene/isothianaphthalene copolymers, and (c) a thienyl-pyrrole/benzothiazole copolymer.

Abstract Benzimidazoles, benzothiazoles and benzooxazoles are privileged structural units not only in the pharmaceutical industry but also in several other fields such as agricultural, electronic, and polymer chemistry. This ring system is present in numerous antioxidant, antiparasitic, antihelmintics, antiproliferative, anti-HIV, anticonvulsant, anti-inflammatory, antihypertensive, antineoplastic and antitrichinellosis activities. Owing to the immense importance of benzimidazoles, efforts have been made from time to time to generate various derivatives of these compounds. These methods have been well described in this Chapter. 

Polymers of benzoquinone, some tin-containing polymers, like poly(dialkyl tin maleate), zinc or cadmium containing polycondensates of 8-hydroxyquinoline with formaldehyde, polymers containing phosphorus, Ar,Ar -diphenylguanidine, 4-ami-no-1,2,3-triazole, benzothiazole, benzimidazole, benzothiazolone or dithiocarba-mate moieties were reported as thermostabilizers for PVC [67, 325-327]. 

Polymers containing heterocycles in the backbone include a variety of compounds, as the diversity of heterocyclic molecules is quite large. The polymers from this class may contain groups derived from furan, thiophene, pyrrole, isoindole, benzimidazole, benzothiazole, benzoxazole, quinoxaline, etc. Macromolecules with a ladder backbone containing, for example, a phenoxazine unit in their structure also are known. Amino thermosetting resins from melamine can be considered as polymers containing heterocycles in their structure. 

Chang S M, Tzeng Y J, Wu S Y, Li K Y and Hsueh K L, Emission of white light from 2-(2 hvdroxvphenyl) benzothiazole in polymer electroluminescent devices Thin Solid Films, 477,1-2, (April 2005), 38-41... 

Organoiron polynorbornenes incorporating benzothiazole dyes into the side chains have also been prepared.273 These polymers displayed max = 511 nm in DMF and max = 608 nm, with a shoulder at 574 nm upon addition of a hydrochloric acid solution. 

The most frequently used material is divinylbenzene/styrene. This polymer has been used for the enrichment of compounds like benzothiazol, malathion, atrazine, disulfoton, 2-(methylthio)-benzothiazol, and A-butylbenzene sulfonic acid from river water. In comparison with other... 

Little is known about the stracture of phaeomelanins. Although the presence of 1,4-benzothiazine units in these pigment polymers is generally accepted, the other postulates, i.e. incorporation of benzothiazole and tetrahydroisoquinoline units into the pigment backbone, need further investigations (59). 

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