Polymer homologous series, defined

In the development of inorganic chemistry, on the other hand, homologous series have played a less important part. The only well-defined series which have been studied are the siloxanes (RaSiOln and the phos-phonitrilic chlorides (PNCU), based respectively on the isoelectronic repeating units SiO and PN. They each form extensive series of both cyclic and related linear polymers. Each includes an element of principal quantum number 3, a feature which accounts for some resemblances between the two groups, and which requires an extension of the ideas derived from the organic field. 

Secondary structural variables, including the nature of the polymer backbone, will only be elucidated by synthesizing complete and homologous series of well-defined polymers. As discussed previously, only a few of the poly(vinyl ether)s, polynorbor-nenes and polymethacrylates contain both identical mesogens and spacers. These systems confirm the above trends. For example, when (4 -n-butoxyphenoxycarbo-nyl)phenoxy mesogens are attached to polymethacrylate and poly(vinyl ether) back-... 

An alternative method uses a concept called critical surface tension, proposed by Fox and Zissman to characterize the surface energy of solids. A plot cosine of the contact angle (cos 6), and liquid—vapor surface tension (yiv), yields a straight line for a homologous series of liquids (Fig. 3.5). Nonho-mologous liquids yield a curved line that may not be easily extrapolated. The intercept of the line at cos (0) equal to one is defined as the critical surface tension of the polymer (yc). Values of 18 dynes/cm for... 

As can be seen from the above discussions, the chain dimensions and the particle scattering function of ein unperturbed wormlike chain at infinite dilution are expressed as functions of two independent parameters L and q. Since L is proportional to the molecular weight M, it turns out that these properties of a series of homologous polymers in the unperturbed state are determined by M, q, and Ml. Here, Ml is defined by... 

The homology here is the hydroxyl group, one of the two end groups in the sense of macromolecular chemistry. In the homologous polymer series concept it is the central methylene groups which are decisive. They define the series, and the chemical nature of the end groups is of secondary interest. 

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