Poly cycloalkanes

An alkane, by definition, has the formula C H(2 +2). Cycloalkanes and polycycloalkanes, by definition, contained fewer hydrogen atoms and instead contain rings. The number of rings in a (poly)cycloalkane is determined as follows ... 

Take the formula for the ring compound of interest, and the formula of the alkane with the same number of carbons, and subtract the number of hydrogens in the former from the number of hydrogens in the latter. Divide the resulting number by 2. The number thus obtained is the number of rings in the (poly)cycloalkane. As an example, consider dicyclohexylmethane ... 

The microstructure of the discussed cycloaliphatic polymers concerns the cis-trans geometrical isomerism of the rings and the relative stereochemistry between the rings. A modified Bovey m-r nomenclature [507] provides a useful description of the microstructure of poly(methylene-l,3-cycloalkane)s, where capital letters (M for mesogenic, R for racemic) denote the stereochemistry of the rings and lower case letters ( m and r) denote the relative stereochemistry between the rings [503], Therefore, cA-isotactic, tram-isotactic, cA-syndiotactic and tram-syndiotactic cyclopolymers may be formed. As in many other cases, 13C NMR spectroscopy reveals information about both the tacticity of the polymer and the ratio of cis to treins rings. 

As shown in Table 6.1.10, the pyrolysate contains alkanes, alkenes, some alkadienes and cycloalkanes (as identified by the MS library search). As expected, the comparison of the retention times in Table 6.1.10 with those from Table 6.1.1 and Table 6.1.8 shows that the compounds in the three pyrolysates, although all hydrocarbons, are not similar. This is also illustrated in Figure 6.1.30, which shows a time window from 20 min. to 40 min. of the pyrograms for poly(propylene-alt-ethylene) and for polyethylene and polypropylene. 

Simple Authors alkanes Congested alkanes C3 Cycloalkanes (size) C4 C5--C7 C8-C12 Poly- cyclics Con- jugated Alkenes Alkynes alkenes Silanes Thianes Halides Ketones Aromatic Acid deriv. 

As in the case of cycloalkanes, the types of motion in the homologous series of phenylenes is strongly size dependent. Figure 5.1 shows the thermal transition temperatures as a function of phenylene groups and in Table 5.1 the transition entropies are listed. The first member of the series shows no thermal transitions below the melting temperature (Sect. 5.1.1). With the second and third, a condis phase becomes obvious (Sect. 5.1.2) and with the fifth, liquid crystalline states exist in addition (Sect. 5.1.3). Poly-p-phenylene (Sect. 5.1.4) is the limiting member of these molecules. 

In addition, thermodynamics plays an important role. The basic thermochemical parameters are summarized in Figure 13.1 for the polymerization of simple cycloalkanes (CH2) leading to poly(methylene). The data present the theoretical free energy of polymerization (AG ) at 25 °C as a function of the cycle size (the first data point corresponds to the polymerization of ethylene) [22]. The results were calculated based on the thermochemical parameters of the putative monomers and of poly(m)ethylene. With the exception of cyclohexane, all cycloalkanes display negative free energies of polymerization. Noteworthy in this regard is the very low AG° obtained for cyclopropane and cyclobutane, with free energies of polymerization even lower than for ethylene. 

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