Polycarbonate chain

Why is it necessary to cap off the polycarbonate chains with a monofunctional molecule when producing the polymer via interfacial polymerization ... 

The structure of tha polycarbonate chain Is analyzed from tha point of view of the spatial configurations. It follows that the molecule can be treated as a freely rotating chain consisting of a succession of virtual bonds (lvp) 7.0 A In length, jointed at angles (SI of ca. 112°. 

The helical parameters corresponding to the various skeletal conformations of the blsphenol A polycarbonate chain are calculated. Combining these results with the conformational energy calculations shows that flat-helical and extended conformations are of equal energy for this chain. In addition, cyclic structures are also found to be stereochemically possible. The small values of the characteristic ratio of the unperturbed end-to-end distance and its temperature coefficient are attributed to the equal energy of the flat-helical and extended-helical, as well as the nonhelical, conformers. 

A study parallel to the one discussed in this article focused on the problem of the internal plasticization of the polycarbonate chain by the incorporation of more flexible repeating units. 

The heat of melting and the entropy of melting can be calculated, from the depression of the crystalline melting point by the plasticizer. The high melting point of the polycarbonate is due essentially to a low entropy of fusion, undoubtedly caused by the high rigidity of the polycarbonate chain. 

Aryl-aliphatic copolyamide Bisphenol A polycarbonate Chain disentanglement craze N-Cyclohexyl maleimide unit... 

The nanotubes were first oxidized in nitric acid before dispersion as the acidic groups on the sidewalls of the nanotubes can interact with the carbonate groups in the polycarbonate chains. To achieve nanocomposites, the oxidized nanotubes were dispersed in THF and were added to a separate solution of polycarbonate in THF. The suspension was then precipitated in methanol and the precipitated nanocomposite material was recovered by filtration. From the scanning electron microscopy investigation of the fracture surface of nanotubes, the authors observed a uniform distribution of the nanotubes in the polycarbonate matrix as shown in Figure 2.3 (19). 

Figure 1 Schematic representation of the polycarbonate chain showing the trans— trans (a) and trans—cis (b) conformations of the carbonate group. The low energy phenylene rotation pathway is denoted by the arrows. (From Ref. 29.)...

Fig. 14. Schematic representation of the deformation of an average polycarbonate chain above T.

REDOR was also applied to examine the structure and dynamics of interfaces of heterogeneous polymer blends. A heterogeneous blend was prepared from [carbonyl- C]polycarbonate and poly(p-fluorostyren-co-styrene) copolymer of p-fluorostylene. The blend was formed by coprecipitation from chloroform into methanol. A fluorine dephased REDOR signal indicates that the 1 polycarbonate chain in 20 exists at the interface, suggesting that the polycarbonate phase is embedded in a continuous polystyrene matrix which is 200 A thick or 400 A in diameter [54],... 

Kozlov, G. V. Dolbin, I. V Shogenov, V. JQi. Zaikov, G. E. Estimation of end-to-end distances for a polycarbonate chain within the framework of the fractional derivatives theory. In book Fractal Analysis of Polymers From Synthesis to Composites. Ed. Kozlov, G. Zaikov, G. Novikov, V. New York, Nova Science Publishers, Inc. 2003, 123-130. 

Dolbin, I. V Sargaeva, T. N. Kozlov, G. V. Shogenov, V. Kh. The end-to-end distance estimation for polycarbonate chain within the framework of the theory of fractaional derivatives. Proceedings of All-Russian Sci. Conf Perspective-2004. NaPchik, KBSU, 2004,3,178-181. 

In this process, it is thought that a two-step polymerization reaction is involved [11]. In the first step an adduct of the catalyst and a growing polycarbonate chain is formed in the organic phase, e.g. ... 

Hydrocarbon Ions and molecules. In contrast to polycarbon chain molecules which cannot be detected by radioastronomy, the closely related molecules of the type C H, for which rotational transitions are... 

The hydrocarbon ions required for this build-up can be derived from the hydrogenation of (odd) polycarbon-chain Ions, the protonation of neutral (odd) polycarbon-chain molecules, H elimination reactions of C with polyacetylenes or Hg elimination reactions of CH3 with polyacetylenes (28). Experimental evidence for nitrogen entrainment in this fashion is... 

The unsaturated phenol is highly reactive and gives rise to coloured products. This decomposition may be repressed by the use of a molar excess of diphenyl carbonate in the ester interchange reaction. In this way, initial esterification and consequent stabilization of the bisphenol A occurs more rapidly. When an excess of diphenyl carbonate is used, the initial products are low molecular weight polycarbonate chains terminated with phenyl carbonate groups. When these low molecular weight polymers are heated above 250°C under... 

Detailed mechanistic studies on C02/epoxide promoted by various A1 porphyrin initiators in the presence of a nucleophile concluded on a mono-metallic pathway with the polycarbonate chain growing on one side of the (Porph)Al backbone and with the opposite side being occupied by the Al-coordinated Lewis base cocatalyst (Scheme 10) [37]. In particular, investigations on a (TPP)A1X/DMAP catalytic systems for CO2/PO copolymerization showed that coordination of the nucleophile/... 

In the rare situation of a homogeneous polymer blend, interactions involving dissimilar macro-radical/macromolecule pairs are theoretically possible. Interactions in the homogeneous two-component system PMMA/bisphenol A polycarbonate have been explained on the basis of PMMA radical attack on the polycarbonate chain. 

Benzoin methyl ethers have been incorporated into a polycarbonate chain. The synthesis was achieved by polycondensing bisphenol A with phosgene in the presence of 4,4 -dihydrobenzoin methylether [216]. Irradiation of the resulting poly condensate in the presence of methyl methacrylate... 

Fig. 7. Stylized representation of "very local" order of a few polycarbonate chains as proposed by Schaefer et al. (reproduced with permission). Local lattice distortion permits 180° ring flipping. 

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