Poly expansion

In the second quarter of the twentieth century, with the development of poly(vinyl chloride), nylon, polyurethane, and other polymers, many new and improved leather-like materials, so-called coated fabrics (qv), were placed on the market. Shortages of leather after World War 11 led to the expansion of these leather-like materials ("man-made" leathers) to replace leather in shoes, clothing, bags, upholstery, and other items. DurabiUty and waterproof quahties superior to leather made coated fabrics advantageous, in spite of imperfection in breathabihty and flexibiUty. Demands for shoes, clothing, and other items are stiU increasing due to growing world population and urbanization. 

Vinyl-Coated Fabrics. Leather substitutes are designed to imitate the appearance of leather with its grain surface. This requirement has been accomphshed by coating substances that are capable of forming a uniform film, and was first met by plasticized poly(vinyl chloride) (PVC). A leather-like material termed vinyl-coated fabric was developed in the 1930s in the United States and Germany. Shortages of leather after World War 11 spurred the expansion of this material. 

As alternatives to the isentropic efficiencies for the turbomachinery components, tjt and Tjc. which relate the overall enthalpy changes, small-stage or poly tropic efficiencies (Tjpj and Tjpc) are often used. The pressure-temperature relationship along an expansion line is then p T = constant, where z = [y y OtJpt]-... 

For the synthesis of the complex natural product, the terminus six-membered ketone 55 had to be transformed into an oxepane ring. For this necessary transformation, the authors were attracted by the single-carbon homologation of a pyr-anone (a sort of ring-expansion) because, in prindple, it could be used in an iterative sense at any stage of the 6-endo cydization in their poly-TH P-based synthetic approach for the synthesis of trans-fused 6,7,6 (THP-oxepane-THP) and 6,7,7 (THP-oxepane-oxepane) ring systems [28]. Treatment of ketone 55 with TMSCHN2... 

In a series of papers culminating in the report of a total synthesis of hemibrevetoxin B, Nakata and co-workers utilised a zinc catalysed ring expansion of poly-substituted tetrahydropyrans, exemplified by the transformation of 34 to 35 (Scheme 7) <96TL213, 96TL217, 96TL6365>. 

PP-g-MA) silicate nanocomposites and intercalated thermoset silicate nanocomposites for flame-retardant applications were characterised by XRD and TEM [333], XRD, TEM and FTIR were also used in the study of ID CdS nanoparticle-poly(vinyl acetate) nanorod composites prepared by hydrothermal polymerisation and simultaneous sulfidation [334], The CdS nanoparticles were well dispersed in the polymer nanorods. The intercalation of polyaniline (PANI)-DDBSA (dodecylbenzene-sulfonate) into the galleries of organo-montmorillonite (MMT) was confirmed by XRD, and significantly large 4-spacing expansions (13.3-29.6A) were observed for the nanocomposites [335],... 

From equation 3.31, work done by gases as a result of poly tropic expansion... 

The behaviour in solution of the first type of polyions compared with that of uncharged molecules is more involved in that the coil expansion is affected not only by the solvent but also by the electric field formed by the polyion itself, by the counterions and by the ions of other low-molecular-weight electrolytes, if present in the solution. Infinite charge dilution cannot be achieved by diluting the poly electrolyte solution, as a local high-intensity... 

Figure 3. NMR of isotactic poly(MMA) in CDCI3 at 300 K with 1% TMS. Upper trace is x8 vertical expansion.

Foams for woodland and grass fire-fighting have been developed with low drainage (water loss from foam) and high expansion (volume of foam per volume of starting liquid), two parameters traditionally considered to be inversely proportional. The stabilizing additive is poly (methyl vinyl ether/maleic anhydride), thought to cross-react with fatty alcohol components of the foam base via the anhydride function. 

While studies have repeatedly demonstrated that IL-1 and TNF-a are potent inductors of bone loss after OVX, the role of IL-6 is more uncertain. The IL-6-deficient mouse does not lose bone mass after OVX, although it has increased bone turnover (Poli et al. 1994), while the mouse overexpressing IL-6 does not present osteoporosis, which seems to be a contradiction (Kitamura et al. 1995). Moreover, neutralizing antibodies against IL-6 prevents an increase in osteoclast number after OVX (Kimble et al. 1997 Jilka et al. 1992), although it does not prevent bone loss after OVX, nor does it diminish in vivo bone resorption (Kimble et al. 1997). All this suggests that IL-6 contributes to the expansion... 

The MALDI spectrum of a polymer sample in which all chains possess the same backbone allows identification of the end-groups present at the chain ends. This type of analysis is referred to as end-group analysis. An example will be helpful. Figure 15.1 reports the MALDI spectrum of a poly(bisphenolA carbonate) (PC for short) sample [7], It displays a series of peaks from 2 up to 16 kDa, the most intense ones in the region from 5 up to 7 kDa. It also displays peak assignment and an expansion of the spectral region from 3.0 up to 3.7 kDa. Peaks at 3034, 3288, and 3542 are labeled as A and are due to PC chains terminated with phenolcarbonate on both sides. Peaks at 3168, 3422, and 3676 are labeled as B and are due to PC chains terminated with phenolcarbonate on one side and bisphenol-A on the other. Peaks at 3048, 3302, and... 

Figure 15.1. MALDI spectrum of a polycarbonate sample along with peak assignment. In the inset, an expansion of the spectral region from 3.0 up to 3.7 kDa is shown. (Reproduced from Puglisi, C. et al., 1999. Analysis of Poly(bisphenol A Carbonate) by Size Exclusion Chromatography/Matrix-Assisted Laser Desorption/lonization. I. End Group and Molar Mass Determination. Rapid Communications in Mass Spectrometry, 13 2260-2267. With permission of John Wiley Sons, Inc.)...

Scheuermann, T., Schulz, B., Blume, A., Wahle, E., Rudolph, R., and Schwarz, E. (2003). Trinucleotide expansions leading to an extended poly-L-alanine segment in the poly (A) binding protein PABPN1 cause fibril formation. Protein Sci. 12, 2685-2692. 

Shinchuk, L. M., Sharma, D., Blondelle, S. E., Reixach, N., Inouye, H., and Kirschner, D. A. (2005). Poly-(L-alanine) expansions form core /1-sheets that nucleate amyloid assembly. Proteins 61, 579-589. 

The ring-expansion carbonylation of epoxides is the most widely studied field in the epoxide carbonylation chemistry since the product lactones are highly attractive targets particularly, /1-lactones are useful compounds due to their versatility in organic synthesis [ 14,15] as well as their utilization as monomers to produce poly(3-hydroxyalkanoate)s, naturally occurring biodegradable polyesters [16-19]. 

Poly(3-hydroxyalkanoate)s have potential for application to engineering plastics endowed with biodegradable nature. One of the synthetic approaches to the polyesters is the ring-opening polymerization of -substituted /3-lactones which can be effectively produced by ring-expansion carbonylation of epox-... 

The presence of multiple C C moieties in di- and poly-ynes hints at a vast potential for expansion of this chemistry. Recent developments in the chemistry and material properties of these complexes have led to a surge of interest in the chemistry of these highly unsaturated ligands. Some of these results have been the subject of several recent short reviews and highlight articles. 

Liu and Zhong introduced a number of QSPR models based on molecular connectivity indices [151, 152], In a first iteration, the researchers developed polymer-dependent correlations descriptors were calculated for a set of solvents and models were developed per polymer type [151], Polymer classes under consideration were polystyrene, polyethylene, poly-1-butene, poly-l-pentene, poly(4-methyl-l-pentene), polydimethylsiloxane, and polyisobutylene. As the authors fail to provide any validation for their models, it is difficult to asses their predictive power. In a subsequent iteration and general expansion of this study, mixed and therefore more general models based on the calculated connectivity indices of both solvent and polymers were developed. While it is unclear from the paper which polymer representation was used for the calculation of the connectivity indices, the best regression model (eight parameter model) yields only acceptable predictive power (R = 0.77, = 0.77, s = 34.47 for the training set, R = 0.75... 

Fig. 40 Synthesis of cyclic poly((3-lactone) by metal-free ring-expansion polymerization...

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