Crystalline polymers Poly

Scheme 10 Liquid crystalline polymer poly(I7) and its precursors...

Kijima, M. Kinoshita, L Hattori, T. Shirakawa, H. Synthesis of a novel liquid crystalline polymer, poly(2,5-didecyloxy-l,4-phenylenebutadiynylene). J. Mater. Chem. 1998, 5(10), 2165-2166. 

The re-entrant or Tammann loop-shape phase diagram as observed in proteins is also found in other systems and has been connected to exothermic disordering [88]. In this particular case, nematic - smectic A transitions in liquid crystals and the phase behaviour of a crystalline polymer, poly(4-methyl-pentene-l), the phase behaviour can be understood by... 

K. Akagi, H. Shirakawa, Liquid crystalline polymers, poly(acetylene) derivatives, in The Polymeric Materials Encyclopedia. Synthesis, Properties and Applications, ed. J. C. Salamone, CRC Press, Boca Raton, FL, 1996, Vol. 5, pp. 3669-3675. 

In this work, the structure, morphology and crystallization behavior of a semi-crystalline polymer, poly(ethylene oxide), PEO, when mixed with natural montmorillonite (Na -MMT) are studied [9]. The structure of the hybrids was investigated by X-ray diffraction (XRD), the thermal properties by Differential Scanning Calorimetry (DSC) and the kinetics of crystallization by isothermal Polarized Optical Microscopy (POM) and isothermal DSC. It is known that for PEO /... 

Higashimura H, Fujisawa K, Moro-oka Y, Namekawa S, Kubota M, Shiga A, Uyama H, Kobayashi S (2000) New crystalline polymers poly(2,5-dialkyl-l,4-phenylene oxide)s. Macromol Rapid Commun 21 1121-1124... 

Vittoria V, Russo R, Decandia F, Magagnini PL, Bresci B (1991) Transport-properties of a side-chain liquid-crystalline polymer— poly(4-acryloyloxy biphenyl). J Polym Sci Polym Phys 29 1163-1168... 

Kiss, G., In situ composites blends of isotropic polymers and thermotropic liquid crystalline polymers . Poly. Science (RAPRA) London, 5/12-13/1982, paper 25.1 (1982). 

Weiss, R.A., Wansoo, H., Nicolais, L., Novel reinforced polymers based on blends of polystyrene and a thermotropic liquid crystalline polymer . Poly Eng Sci V27,684-691 (1987). 

The conducting polymer poly(sulfur nitride) is unusual in that it is crystalline, consisting of chains of sulfur and nitrogen packed in parallel. 

Polyoxyethylene. Synthetic polymers with a variety of compositionaHy similar chemical stmctures are as follows. Based on polarity, poly(oxymethylene) (1) would be expected to be water soluble. It is a highly crystalline polymer used in engineering plastics, but it is not water-soluble (see... 

Polymer Ferroelectrics. In 1969, it was found that strong piezoelectric effects could be induced in the polymer poly(vinyhdene fluoride) (known as PVD2 or PVDF) by apphcation of an electric field (103). Pyroelectricity, with pyroelectric figures of merit comparable to crystalline pyroelectric detectors (104,105) of PVF2 films polarized this way, was discovered two year later (106.)... 

Unlike most crystalline polymers, PVDF exhibits thermodynamic compatibiUty with other polymers (133). Blends of PVDF and poly(methyl methacrylate) (PMMA) are compatible over a wide range of blend composition (134,135). SoHd-state nmr studies showed that isotactic PMMA is more miscible with PVDF than atactic and syndiotactic PMMA (136). MiscibiUty of PVDF and poly(alkyl acrylates) depends on a specific interaction between PVDF and oxygen within the acrylate and the effect of this interaction is diminished as the hydrocarbon content of the ester is increased (137). Strong dipolar interactions are important to achieve miscibility with poly(vinyhdene fluoride) (138). PVDF blends are the object of many papers and patents specific blends of PVDF and acryflc copolymers have seen large commercial use. 

It has, however, been possible to find solvents for some polar crystalline polymers such as the nylons, poly(vinyl chloride) and the polycarbonates. This is because of specific interactions between polymer and solvent that may often occur, for instance by hydrogen bonding. 

Although it is a polar polymer, its electrical insulating properties at room temperature are good even at high frequencies owing to the fact that since room temperature is well below the transition temperature dipole orientation is severely restricted. Some data on the crystallinity of poly(ethylene terephthalate) are presented in Table 25.5. 

Poly acetals are highly crystalline polymers. The number of repeating units ranges from 500 to 3,000. They are characterized by high impact resistance, strength, and a low friction coefficient. 

Poly(phenyleneethynylene)s, 482 optically active, 516-517 synthesis of, 496-500, 502 Poly(m-phenylene isophthalamide), 136 synthesis of, 185-186 Poly(l,4-phenylene terephthalate) liquid crystalline polymers, 51 Poly(para-phenylene)s, 472. See also Poly (p -pheny lene)... 

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). 

Other hand, when an equimolar mixture of 2,5-DSP and l OEt is recrystallized from benzene, yellow crystals, comprising 2,5-DSP and l OEt in a molar ratio of 1 2, deposit. In the DSC curve of this crystal, a single endothermic peak is observed at 166°C, which is different from the melting point of either 2,5-DSP (223°C) or l OEt (156°C). Furthermore, the X-ray powder diffraction pattern of the crystal is quite different from those of the homocrystals 2,5-DSP and l OEt. Upon irradiation the cocrystal 2,5-DSP-l OEt affords a crystalline polymer (77i h = 1.0 dl g in trifluoroacetic acid). The nmr spectrum of the polymer coincides perfectly with that of a 1 2 mixture of poly-2,5-DSP and poly-1 OEt. In the dimer, only 2,5-DSP-dimer and l OEt-dimer are detected by hplc analysis, but the corresponding cross-dimer consisting of 2,5-DSP and l OEt is not detected at all (Hasegawa et al., 1993). These observations by nmr and hplc indicate that the photoproduct obtained from the cocrystal 2,5-DSP-l OEt is not a copolymer but a mixture of poly-2,5-DSP and poly-l OEt in the ratio 1 2. 

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