Turn-over number polymers

Random distribution of a significant number of hydrophilic NVIAz units along the polymer chain could result in uniform hydrophilization. This, in turn, could lead to a loss of ability for the coil-globule transition, which is caused by the hydrophobic interactions. As a result, such copolymers should be water-soluble over a wide temperature range. 

Clearly, an enormous number of new polymers have and continue to be synthesized using ROMP reactions. The development of the new generation of single-site aUcylidene catalysts has introduced a new level of control over ROMP chemistry. Control of polymer microstructure should, in turn, result in a better understanding of the interplay between microstmcture and macroscopic properties. The use of living ROMP chemistry is still in its infancy. It will be interesting to observe whether or not useful materials can be developed from this chemistry. 

The crystal orbital approach (see ref. 94 for a review of the recent computational developments in this field) has dominated the electronic structure calculations on polymers for several years. However, the recently published reports on the finite-cluster calculations reveal that the latter methodology has several definite advantages over the traditional approach. Let P(N) be an extensive property of a finite cluster X-(-A-)j -Y, where N is the number of repeating units denoted by A, while X and Y stand for terminal groups. The corresponding intensive properties, p(N) = P(N)/N, are known only for integer values of N. However, provided the polymer in question is not metallic, P(v) can be approximated by a smooth function p(v) of v = 1/N, which in turn can be extrapolated to v = 0 yielding the property of the bulk polymer. 

Fortunately, the use of mass spectrometry for polymer analysis took on a new dimension at the turn of the century. Figure 1 lists the number of polymer mass spectrometry publications in the CAplus (Chemical Abstracts) database over the years 1965-2000. Up until the mid-1990s there was a steady— but not dramatic— increase in the number of articles. Starting in 1995, however, there has been a marked increase in the number of polymer mass spectrometry reports in the literature. Also the number of symposia and conferences devoted to the subject has grown considerably in the last few years. 

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