OXYNAPHTHOATE COPOLYMER

Results are presented of an investigation of the use of linear-temp, controlled pyrolysis with subsequent analysis of the pyrolysates (volatiles and residues) by 18V electron-impact mass spectrometry and FTIR spectrometry to provide information on the thermal degradation mechanisms of aromatic polyesters, in particular polyhydroxybenzoic acid and oxybenzoate-oxynaphthoate copolymer (Vectra). 13 refs. 

Early studies of the thermal degradation of so-called polyarylates were covered by Neiman [100] and Ehlers and co-workers [101]. Since then, several highly aromatic and specifically liquid crystalline (mesogenic) polyesters have been examined in terms of their anaerobic thermal degradation characteristics. These inclnde homopolymers of hydroxybenzoic acids [102-105] copolymers of hydroxybenzoic acid with hydroxynaphthoic acid [105-108] polymers which are essentially copolymers of hydroxybenzoic acid and alkyene terephthalates [107-118] copolymers of hydroxybenzoic acid with other aromatic polyesters [119-122] phenolic and bisphenolic terephthalates [123-127] poly(oxynaphthoate)s [128] and liquid crystal polyesters (LCP) containing unsaturated acids as part of a copolyester chain [129-131]. 

Poly(oxybenzoate-co-oxynaphthoate). Figure 2.64 represents an even more complicated polymer system. In this case the macromolecule is the random copolymer poly(oxybenzoate-co-oxynaphthoate), a high-strength material (Vectra ). 

In this section, copolymers of polyethylene are discussed, starting with low-density, branched polyethylene and culminating with crystallization, melting, and annealing of poly(ethylene-co-octene-l), also described as linear-low-density polyethylene, LLDPE. Furthermore, partial phase diagrams of poly(ethylene terephthalate-co-oxybenzoate), PETcoOB, andpoly(oxybenzoate-co-oxynaphthoate), POBcoON, are presented. The latter systems are examples of increasing chain stiffness by cocrystalUzation which leads to mesophase behavior (see Sect. 5.5). 

PETcoOB and POBcoON. A second example of thermal analysis of copolymers involves the two systems, poly(ethylene terephthalate-co-oxybenzoate), PETcoOB, and poly(oxybenzoate-co-oxynaphthoate), POBcoON. The structural formulas of the CRUs are as follows ... 

Of special importance is in this case that the backbone of the copolymer can change chemically by trans-esterification (see Fig. 3.47). In fact, heating poly(ethylene terephthalate) and acetoxybenzoic acid in the melt is a common synthetic route to PETcoOB. The inclusion of oxybenzoate groups makes poly(ethylene terephthalate) increasingly stiffer (see Fig. 1.50). In POBcoON, oxynaphthoate adds an additional off-set of the large zig-zag of the benzoate. As a result of this chain stiffening, the PETcoOB with more than 30 mol-% oxybenzoate shows an anisotropic melt, as for a nematic main-chain liquid crystal (see Fig. 5.136) and the system POBcoON has a mesophase character over the whole concentration range. 

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