Poly 7-hydroxybenzoate

Figure 9.19 Relative thickness of microstructural layers of a 3 mm thick injection-moulded ruler of liquid-crystalline poly(/7-hydroxybenzoic acid-co-ethylene terephthalate). The axial moduli ( ) of the materials in the different layers are shown. Drawn after data from Hedmark et al. (1988).

Copolymerization can be employed in a similar fashion to modify the properties of the homopolymer of /7-hydroxybenzoic add (5-6). Poly(/ -hydroxybenzoic acid) is an infusible polymer which can be shaped only by compression sintering. A melt processable variation of this high modulus, thermally stable material can be made, however, by copolymerizing an ester of 5-6 with equimolar quantities of terephthalic acid (5-7) and biphenol (5-8) to produce an aromatic polyester which can be fabricated at temperatures near400 C but still retain many useful properties at 300°C. 

PEEK showed extreme thermal stability, but when blended with a liquid crystalline poly(hydroxybenzoic/naphthoic acid) copolymer, LCP, there is a measurable reduction in this property [Mehta and Isayev, 1991]. 

There is a further very important class of main-chain liquid-crystal polymers that differ from those discussed above by being random copolyesters based on polymers such as poly(hydroxybenzoic acid) -fO— —C=0), where — — represents a para-disubstituted benzene ring (para-phenylene unit). The random copolymers include units of various other forms containing phenylene or naphthylene rings and their introduction reduces the crystallinity and melting point considerably without necessarily lowering the value of Polymers of these types have... 

Macroconformations consisting of two or three helices intertwined with each other are also sometimes called super helices or super secondary structures. An example is deoxyribonucleic acid, which forms a double helix from two complementary chains, each in the form of a helix (see Section 29). With synthetic polymers, both it-poly(methyl methacrylate) and poly(/ -hydroxybenzoic acid) appear to form double helices. Triple helices are, for example, formed by the protein, collagen (see Section 30). 

Sugijama, H., Lewis, D., White, J. Structural Characteristics, Rheological Properties, Extrusion and Melt Spinning of 60/40 Poly(Hydroxybenzoic Acidcoethylene Terephtalate). 

Figure 10.9 Polarized photomicrograph of oriented Vectra A950 (poly (hydroxybenzoic acid-co-hydroxy naphthoic acid)). The arrow indicates the shear direction.

Figures. Cross-polarization MAS CNMR spectrum of poly(hydroxybenzoic acid) as a function of contact time (in ms). All spectra were obtained from 2K FTs of 1(XX) FID accumulations at a 3,5 s repetition time. (Reprinted with permission from C.A. Fyfe et ai [14].)...

Many thanks are given to the Tennessee Eastman Corporation for the donation of the p(ET/HBA) copolymers, poly(ethyleneterephthalate-hydroxybenzoic acid), and to the Hoechst-Celanese Corporation for donation of the Vectra polymer RD-501 p(HBA/HNA/TA/HQ), poly(hydroxybenzoic acid-r-hydroxynaphthoic acid-r-terephthalic acid-r-hydroquinone). 

Poly(hydroxybenzoic acid)/copolyesterether elastomer microcomposites were imaged and it was shown that time and the solvent used to make the composite result in different morphologies. When solvents with high affinities for the elastomer were used, the resultant composite showed imiform dispersion of that material. With poor solvents, the elastomer was observed to aggregate into nommiform aggregates (111). 

Most polymer blends that are commercial products in the industry are partially miscible. Partially miscible polymer blends are those that exhibit some shift from their pure component glass transition temperatures. Thus, a binary miscible blend will exhibit one glass transition temperature [1], and a partially miscible blend may exhibit two distinct glass transition temperatures other than their pure component values [2,3]. Some experimental systems such as polyethylene terepthalate (PET) and poly-hydroxybenzoic (PHB), polycarbonate (PC), and styrene acrylonitrile (SAN) have been reported [4]. Very little mathematical description of partially miscible systems is available in the literature. 

Poly(d-hydroxy-2-naphthoic acid-co-4-hydroxybenzoic acid) [81843-52-9]... 

Industrial Thermotropic LGPs. Vectran, poly(6-hydroxy-2-naphthoic acid- o-4-hydroxybenzoic acid) [81843-52-9] is currendy the only thermotropic fiber which is commercially available (13). Vectran is synthesized by the melt acidolysis of/ -acetoxybenzoic acid and 6-acetoxy-2-naphthoic acid. 

The first rigid-rod polyester poly(4-hydroxybenzoic acid) (PHBA, Ekonol) was commercially introduced by 1970.162 However, this polyester, like the... 

Poly(hydroxyalkanoic acid)s (PHAs), 27, 31, 41-43 biodegradable, 90 Poly(4-hydroxybenzoic acid) (PHBA), 49-50... 

In order to make polymers behave as liquid crystals it is necessary to introduce some structural rigidity. A typical polymer which has the required rigidity is poly(phenylenetetraphthalamide) (10.7). This material belongs to a class of polymer known as the aramids. Other liquid crystalline polymers are the thermotropic polyesters derived from /7-hydroxybenzoic acid, p, p -biphenol and terephthalic acid (10.8). 

Poly(p-hydroxybenzoate) (PHB)-poly(ethylene terephthalate) (PET), P(HB80-ET20) (Rodrun 5000) or P(HB60-ET40) (Rodrun 3000) (Unitika Company, Japan)... 

E4 poly[(4-hydroxybenzoic acid)-co-hydroquinone-co-(terephthalic acid)]... 

Poly(l,4-oxybenzoyl) (LII) [IUPAC poly(oxy-l,4-phenylenecarbonyl), obtained by selfreaction of p-hydroxybenzoic acid, and the various aramids (Sec. 2-8f) were among the first LC polymers studied. The experience in commercializing poly(l,4-oxybenzoyl) and the... 

Poly(arylene ether benzoxazole)s were also synthesized from the reaction of bis[(4-hydroxyphenyl)benzoxazole]s and activated aromatic difluoro monomers as shown in Eq. (7) [28,29]. The bis[(4-hydroxyphenyl)benzoxazole]s were readily prepared by condensation of the appropriate bis(o-aminophenol) (e.g. 3,3 -dihydroxy-4,4 -diaminobiphenyl) with phenyl-4-hydroxybenzoate in diphenyl sulfone at 260°C. Under proper conditions, the less expensive 4-hydroxybenzoic acid can be used in place of the phenyl ester to provide high yields of the desired bis[(4-hydroxyphenyl)benzoxazole]s. As presented in Table 9, the hexafluoroisopropylidene (6F) containing polymers were amorphous. These polymers were prepared in DMAc. However, the polymers derived from 6,6 -bis[2-(4-hydroxyphenyl)benzoxazole] were prepared in diphenyl sul-... 

Poly(arylene ether benzimidazole)s have received more attention than any other PAE containing heterocyclic units. This is due primarily to their unique combination of properties even at relatively low molecular weights and their potential for use in several high performance applications. The initial report in 1991 involved polymers from the reaction of 3 different bis[(4-hydroxy-phenyl)benzimidazole]s with various activated aromatic difluoro monomers as shown in Eq. (10) [37]. The bis[(4-hydroxyphenyl)benzimidazole]s were prepared from the reaction of aromatic bis(o-diamines) and phenyl-4-hydroxybenzoate in diphenyl sulfone. The use of 4-hydroxybenzoic acid would obviously reduce the... 

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