Crystal structure polystyrene

A comparison of the crystal structures, NMR and IR spectra of various Yb(ll) and calcium complexes demonstrated that they were strikingly similar, a reflection of the nearly identical radii of Ybz+ and Ca2+.25 Nevertheless, the dibenzylytterbium(ll) analog of 127 produces polystyrene of high syndiotacticity (r= 94.9%, rr= 90.0%), whereas 127 itself yields only atactic or slightly syndiotactic polymer. A difference in Yb-L and Ca-L bond strengths, despite their similar lengths, has been proposed as the source of the difference.315... 

In the crystal structures of many other isotactic polymers, with chains in threefold or fourfold helical conformations, disorder in the up/down positioning of the chains is present. Typical examples are isotactic polystyrene,34,179 isotactic poly(l-butene),35 and isotactic poly(4-methyl-l-pentene).39,40,153,247... 

De Rosa, C. Guerra, G. Petraccone, V. Pirozzi, B., Crystal structure of emptied clathrate form (8e form) of syndiotactic polystyrene, Macromolecules 1997, 30, 4147 4152... 

G. Natta, P. Corradini, I. W. Bassi. Crystal structure of isotactic polystyrene ,... 

Monodisperse spherical colloids and most of the applications derived from these materials are still in an early stage of technical development. Many issues still need to be addressed before these materials can reach their potential in industrial applications. For example, the diversity of materials must be greatly expanded to include every major class of functional materials. At the moment, only silica and a few organic polymers (e.g., polystyrene and polymethylmethacrylate) can be prepared as truly monodispersed spherical colloids. These materials, unfortunately, do not exhibit any particularly interesting optical, nonlinear optical or electro-optical functionality. In this regard, it is necessary to develop new methods to either dope currently existing spherical colloids with functional components or to directly deal with the synthesis of other functional materials. Second, formation of complex crystal structures other than closely packed lattices has been met with limited success. As a major limitation to the self-assembly procedures described in this chapter, all of them seem to lack the ability to form 3D lattices with arbitrary structures. Recent demonstrations based on optical trapping method may provide a potential solution to this problem, albeit this approach seems to be too slow to be useful in practice.181-184 Third, the density of defects in the crystalline lattices of spherical colloids must be well-characterized and kept below... 

Experiments by Hachisu et al. [36] for the order-disorder transition of polystyrene particles in electrolyte solution are in agreement with this theory, as verified by Russel [49]. Experiments [45,46] confirm the FCC structure for the ordered phase at high particle density. The softness of the interparticle interaction alters the crystal structure to the BCC stimcture [45,46], in agreement with the theoretical findings displayed in Figure 11.13. 

As isotactic polystyrene has a simUar crystal structure to that of polyethylene, the concept of the intramolecular cydization may be applied to the degradation of the former to account for the formation of the products of degradation. Let the three-unit one turn radical form the cyclic compound (VIH) by the interaction of the Qi and C 6 atoms. The cyclic compound (VIII) may lose hydrogens to other free radicsds to form 1,3,5-triphenyl-benzene (IX). 

Carlson, R.J. and Asher, S.A., Characterization of optical diffraction and crystal structure in mono-disperse polystyrene colloids, AppZ. Spectmsc., 38, 297, 1984. 

Fig. 14 a, b Chemical structures of a poly (ethylene glycol)-Wock-poly(a, P-aspartate) (PEG- -PAsp) and polyethylene glycol)-Wock-poly(a, P-aspartamide) (PEG-b-PAspA), b poly (ethylene oxide)-Wocfc-polystyrene-protoporphyrin IX (PEO- -PS-PPIXZn) and crystal structure of horse radish peroxidase (HRP) the arrow marks the positioning of the cofactor... 

ANL s ultrasonic viscometer is a nonintrusive in-line device that measures both fluid density and viscosity. The design of the viscometer is based on a technique that measures acoustic and shear impedance. The technique was first applied by Moore and McSkimin (1970) to measure dynamic shear properties of solvents and polystyrene solutions. The reflections of incident ultrasonic shear (1-10 MHz) and longitudinal waves (1 MHz), launched toward the surfaces of two transducer wedges that are in contact with the fluid, are measured. The reflection coefficients, along with the speed of sound in the fluid, are used to calculate fluid density and viscosity. Oblique incidence was commonly used because of better sensitivity, but mode-converted waves often occur in wedges that do not exhibit perfect crystal structure and lack well-polished surfaces. For practical applications, we use the normal-incidence arrangement. 

Ishihara et al. reported in 1986 that syndiotactic polystyrene can be prepared with the aid of organic or inorganic titanium compounds activated with methylaluminoxane [177]. There is much greater incentive to commercialize syndiotactic polystyrene than the isotactic one. This is because isotactic polystyrene crystallizes at a slow rate. That makes it impractical for many industrial applications. Syndiotactic polystyrene, on the other hand, crystallizes at a fast rate, has a melting point of 275°C, compared to 240°C for the isotactic one, and is suitable for use as a strong structural material. 

Whereas most of the early work on crystallization, etc., were concerned with predominantly isotactic chains, the recent developments in synthetic methodologies have enabled the preparation of highly syndiotactic polymers [13,14]. Since the high stereoregularity of these syndiotactic polymers facilitates their crystallization, several papers have been published on the x-ray crystal structure and polymorphism of syndiotactic polystyrene [15-18]. The chain conformation in the crystalline state has also been analyzed using NMR [19]. Similarly, the crystal structure of syndiotactic polypropylene has also been studied by a number of authors [20-22]. 

De Rosa C, Guerra G, Petraccone V, Corradini P (1991) Crystal Structure of the a-Form of Syndiotactic Polystyrene. Polymer Journal 23 1435-1442... 

Chatani Y, Shimane Y, Ijitsu T, Yukinari T (1993) Structural study on S3mdiotactic polystyrene 3. Crystal structure of planar form I. Pol3mier 34 1625-1629... 

These polymers illustrate the complexity of predicting the crystal structure of these polymers. Although polystyrene, with its bulky phenyl side group, is normally considered to be an amorphous polymer, the isotactic form of the polymer forms a helix and a crystalline structure. Usually the density of the... 

As for solution growth, the lateral hahits of melt-grown crystals reflect both the underlying crystal structure and the kinetics of growth. Thus i-polystyrene... 

Load-deformation curves for polyethylene and polystyrene are shown in Fig. 5.2. Polyethylene necks and cold draws in the manner described above (5.N.1). As it is a semi-crystalline polymer, yielding involves considerable disruption of th.e crystal structure. Slip occurs... 

Finally, a few comments about the uniqueness of polymer crystal structures and phase space localization are warranted. Almost all crystallizable polymers exhibit polymorphism, the ability to form different crystal structures as a result of changes in thermodynamic conditions (e.g., temperature or pressure) or process history (e.g., crystallization conditions) [12]. Two or more polymorphs of a given polymer result when their crystal structures are nearly iso-energetic, such that small changes in thermodynamic conditions or kinetic factors cause one or another, or both, to form. Polymorphism may arise as a result of competitive conformations of the chain, as in the case of syndiotactic polystyrene, or as a result of competitive packing modes of molecules with similar conformations, as in the case of isotactic polypropylene. In some instances, the conformational change may be quite subtle isotactic polybutene, for example, exhibits... 

Chatani, Y., Inagaki, T., Shimane, Y, Shikuma, H. Structural study on syndiotac-tic polystyrene 4. Formation and crystal structure of molecular compound with iodine. Polymer, 34(23), 4841 845 (1993). 

De Rosa, C., Rapacciuolo, M., Gnerra, G., Petraccone, V., Corradini, P. On the crystal structure of the orthorhombic form of syndiotactic polystyrene. Polymer,... 

De Rosa, C, Rizzo, P, de Ballesteros, O. R., Petraccone, V, Guerra, G. Crystal structure of the clathrate delta form of syndiotactic polystyrene containing 1,2-dichloroethane. Polymer, 40, 2103-2107 (1999). 

Tarallo, O., Petraccone, V. On the crystal structure of the clathrate forms of syndiotactic polystyrene containing carbon disulfide and iodine. Macromol. Chem. Phys., 205(10), 1351-1360 (2004). 

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