Thermotropic poly

The synthesis and liquid crystalline properties are presented of two classes of chiral (I-n) and prochiral (Il-m) thermotropic poly(ester 0-sulfide)s. The nematic mesophase behavior of the polymers I-n exhibits distinct even-odd alternations with chemical structure and is compared with that of closely related poly(ester 0-sulfide)s Ill-n and IV-m. 

The asymmetric oxidation reaction of prochiral poly(ester 0-sulfide)s to optically active poly(ester 0-sulfoxide)s can be accomplished with almost theoretical chemoselactivity and moderate to high enantioselectivity degrees. While the asymmetric oxidation of prochiral sulfides should not be a preparative method for chiral sulfoxides, we expect that the structure of the parent polymers might be specifically designed for the preparation of chiral thermotropic poly(ester 0-sulfoxi-de)s. 

Kricheldorf has reported the synthesis of lyotropic poly(amide-imide)s and poly(benzoxazole-amide)s. These were prepared by the polycondensation of N,N-bis(trimethylsilyl)-p-phenylenediamine or N,AT -bis(trimethylsilyl)-3,3 -dim-ethylbenzidine with the diacyl chloride of trimellitimide of p-aminobenzoic acid, or the imide formed from p-amino benzoic acid and terephthalic acid. Lyotropic behaviour was observed in cone, sulphuric acid solution [38]. A series of thermotropic poly(imide-amide)s was prepared based on trimellitimides formed from trimellitic anhydride and an a, -bis(4-aminophenoxy) alkane with carbon chain lengths 9-12. Melting points were in the range 250-300 °C. They formed smectic A phases and tended to degrade around the isotropisation temperatures (around 350 °C). Pendant methyl groups or occupied meta- groups tended to prevent mesophase formation [39]. Novel LC poly(imide-amides) have also been synthesised from new diamine spacers derived from linear diaminoalkanes and 4-nitrophthalic anhydride. A smectic and nematic phase were observed when 4,4 -biphenyl dicarboxylic acid was used as co-monomer [40]. 

Table 8. Thermotropic poly(etherimide)s prepared at Liverpool University...

Table 10. Thermotropic poly(etherimide)s based on biphenyl tetracarboxylic imide...

A series of thermotropic poly(amide-imide)s were synthesised [38] from diamines produced by alkylation of silylated 4-nitrophenol with oc,co-dibromoal-kanes, followed by hydrogenation of the resulting a,co-bis(nitrophenoxy)al-kanes. The diamines were reacted with trimellitic anhydride chloride in boiling m-cresol to produce polymer structure 21. 

Ballauff M (1986) Rigid rod pdymers having flexible side chains. I. Thermotropic poly(l,4-phenylene-2,5-dialkoxyterephthalate) s. Makromol. Chem. Rapid Commun. 7 407... 

Ballauff M, Schmidt GF (1987) Rigid rod polymers having flexible side chains. 3. Structural investigations on a novel layered mesophase formed by thermotropic poly(l,4-phenylene-2,5-dialkoxyterephthalate)s. Mol. Liq. Cryst. 147 163... 

X.-G. Li and M.-R. Huang, Thermal degradation kinetics of thermotropic poly(p-oxybenzoate-co-p,p -hi >hcny e.rte.. eiep Ab2Aste)fibet,JoumalofAppliedPolymerScience, 71,1923(1999). 

A fifth factor is certainly ease of preparation and in this characteristic the melt prepared thermotropic polymers are particularly favored. All of the polymers described thus far may be made in a conventional melt acidolysis process starting with the acetoxy derivatives of the hydroxyl containing monomers used. A typical polymerization scheme is shown in Figure 8, the preparation of the two component polyester derived from the acetylated hydroxybenzoic and hydroxynaphthoic acids. The polymerization may be carried out with or without added catalysts. The poly(ester-amides) commented on here, and the more recently reported aromatic, thermotropic poly(ester-carbonates) and poly(ester-imides), may all be synthesized in a similar manner. 

Rozes L (1996) Synthesis of thermotropic poly(polyester-61ocA -polyether)s, Thesis, University of Paris. 

Rozes L, Tessier M and Marechal E (1996) Synthesis and characterization of thermotropic poly (polyesters-block-polyethers, Proc Int Symp Poly condensation 96, Paris, p. 334. 

Li XG, Huang MR (1999) Thermal decomposition kinetics of thermotropic poly (oxybenzoate-co-oxynaphthoate) Vectra copolyester. Polym Degrad Stab 64 81-90... 

The fact that the chemical shift anisotropy is a tensor has also been used by Oulyadi et al to study the orientation of thermotropic poly-siloxanes. NMR spectra obtained in the presence of high-power proton decoupling and in the absence of magic-angle sample spinning have been recorded for comb polysiloxanes of the... 

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