Crystal Phases of Polymers

Stmctural changes in the orthorhombic-to-hexagonal phase transition of PE crystals were investigated in the course of heating to the melting point. The IR and spectral patterns characteristic of the hexagonal phase were confirmed. In particular, the bands characteristic of the disordered short trans segments (shorter than 

The defect density of states of the tight (110) fold in PE is calculated. Modes of the (110) fold calculated at 1348,1342 and 1288 cm and are assigned to IR bands at 1346-1347 cm i and 1342-1343 cm and near 1295 cm. The (110) folds (approximately g g ggtg) also contribute to the gtg/gtg bands at 1368 cm, where g = +60° and g = -60° from the plane of the C-C backbone and t = trans. In contrast to the (200) fold, the (110) fold does not exhibit a localised gap mode near 700 cm. The observed IR bands are assigned to the defect modes of the (110) fold (373). The (110) folds are folds in the crystal plane and (200) folds lie along the (200) crystal plane. 

The phase transition in an ethylene-tetrafluoroethylene alternating copolymer from the orthorhombic to the hexagonal structure is a result of the generation and propagation of conformational collective defects (182). 

Syndiotactic poly-p-methylstyrene (PPMS) exhibits various crystalline forms and clathrate stmctures. Bands due to the syndiotactic stereostmcture and bands typical of the two different chain conformations are observed in the CTystalline structures as well as bands sensitive to intermolecular interactions typical of the different modes of chain packing (350). 

In polyamide 66, normalised absorbances of the bands at 924 and 1136 cm were plotted against density and the intercept at zero absorbance provided a density of 1.26 g/crtP, which was very close to the crystalline density. The 924 and 1136 cm bands are assigned to the conformation in the amorphous phase. The assignments of the bands at 936 and 1200 cm to the conformation in the crystalline phase were confirmed (31). 

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Amorphous phase, of polymers, 20 400 Amorphous polymers, 10 203 crystallization of, 19 844 Amorphous red selenium, 22 74 Amorphous regions, in fibers, 11 171 Amorphous resins, use in thermoforming, 19 555... 

Cocrystallization in copolymers of a-olefins. II — Butene-1 copolymers and polybutene type II—I crystal phase transition. Polymer 7, 23 (1965). 

The orthorhombic crystal phase of polyethylene has, like most polymer crystals, pronounced anisotropic properties. The elastic moduli along the three orthogonal crystallographic directions of the orthorhombic unit cell are at 23 °C 3.2 GPa along a and 3.9 GPa along b according to Sakaruda et al. [14] and 240-360 GPa along c [14, 15, 16]. The thermal expansion coeffi-... 

The first part of the book discusses formation and characterization of the microemulsions aspect of polymer association structures in water-in-oil, middle-phase, and oil-in-water systems. Polymerization in microemulsions is covered by a review chapter and a chapter on preparation of polymers. The second part of the book discusses the liquid crystalline phase of polymer association structures. Discussed are meso-phase formation of a polypeptide, cellulose, and its derivatives in various solvents, emphasizing theory, novel systems, characterization, and properties. Applications such as fibers and polymer formation are described. The third part of the book treats polymer association structures other than microemulsions and liquid crystals such as polymer-polymer and polymer-surfactant, microemulsion, or rigid sphere interactions. 

Wissbrun earlier observed a very long relaxation time and high elasticity for anisotropic melts of aromatic polyesters, as well as several other types of flow anomalies. Unfortunately, in most of these earlier studies, the rheological behavior of liquid crystal melts of polymers could not be directly compared with that of the isotropic phase of the same polymers because of their high clearing temperatures. 

Since the sensitivity of pulse NMR is very high and H Ti values for usual polymers are less than 1 s due to the spin diffusion, rapid measurements with short repetition times are possible. This gives us the real time measurement of nonequilibrium phenomena such as crystallization in the polymer. The crystallization process of polymers has been studied by an optical microscope, dilatometry and X-ray diffraction. These methods only gives static information about the crystallization process. The pulse NMR measurements provide both the fraction and the molecular mobility of each phase. Figures 7.19 and 7.20 show the temperature change of the fractions and T2 values of crystalline, interfacial and amorphous components for poly(e-caprolactone)... 

The purpose of this chapter is to explain theoretically the formation of liquid crystal phases in polymer systems and to provide the basic concepts for designing and synthesizing liquid crystalline polymers. Liquid crystalline polymers combine features of both polymers and liquid crystals, thus we discuss the materials from two sides liquid crystallinity and polymer properties. Theoretical descriptions have encountered many difficulties in the past. One is that the present theoretical understanding of neither polymers or liquid crystals is complete. 

In addition to barotropic liquid crystals of flexible polymers, there are also a few reports on the observation of the liquid crystalline phase of polymers containing no mesogenic units of rigid rods. Aharoni (1988), for example, was very lucky to have found a series of the following polymers that form a thermotropic liquid crystal phase. 

Several authors have analyzed the miscibility of iPP and PB-1, by means of different analytical approaches. Piloz et al. (16) found a single, composition-dependent, glass transition behavior for these blends, and concluded that they are compatible in the amorphous state. Sjegmann (17,18) reported that the composition dependence of tensile properties evidences a high degree of compatibility of iPP and PB-1 and observed a marked effect of the composition on the morphology of melt-crystallized samples. Conversely, the analysis of the crystallized blends indicates the presence of separated crystal phases of the two polymers, even if a mutual influence during the crystallization cannot be excluded. 

The solid products of the thermolysis of PAA-NP and NiPAcr (Table 3.2) are the mixture of two phases in the partially X-ray-amorphous matrix. One of them is a well-crystallized phase of metallic Ni, and another is the particularly crystallized phases of nickel oxide (for NiPAcr) and nickel carbide (for PAA-Ni ). For all the polymers, decarboxylation of metal-containing groups is a source of the largest portion of the total gaseous products. The major product is CO2 ... 

It has been noted [31] that the crystallization rate of polymers increases by up to six orders of magnitude when the crystallization event occurs when the polymer is under an applied stress rather than in a quiescent state. This large increase in crystallization rate is accompanied by a change in crystal habit, the shape of the crystalline phase produced transformed, over a narrow stress regime, from a spherulitic (spherically symmetrical) to a columnar habit (see Figure 1.5). 

Table IV shows that the values of transition temperatures Tg j slightly decrease with increasing n, which is probably due to the effect of internal plas-tification and was frequently observed in the case of comb-like polymers (21), The evaluation of the thermal effect inherent In this transition for PChMAA-II gave the value of 0,76-0,08 cal/g, which agrees well with the values of heats of melting, corresponding to the liquid crystalline phase-isotropic melt transition for low-molecular liqtdd crystals ( ), However, in contrast to the latter, which, as a rule, crystallize during cooling (see, for example, Pi re 33. the liquid crystalline phase of polymers vitrifies while cooled (Figure 5). In other words, in the case of polymers, the structure of the liquid C3 ystalline phase...

Keywords Polymer crystallization NMR of polymers Polyethylene Hexagonal phases Nanostructured materials Confined polymers Crystal engineering Nanochannels... 

The discussion of metastable, semicrystalline phases of polymers and their irreversible melting is based on the two early papers Wunderlich B (1964) A Thermodynamic Description of the Defect Solid State of Linear High Polymers. Polymer 5 125-134 and The Melting of Defect Polymer Crystals. Polymer 5 611-624. A later review and expansion is given in Wunderlich B (1997) Metastable Mesophases. Macromol Symp 113 51-65. 

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