Synthetic helical polymers: conformation and function.

Polyisocyanates, long studied as theoretical models for wormlike chains in dilute solution and liquid crystals, differ from their biological helical analogs in the absence of a pre-determined helical sense. These polymers have an unusual sensitivity to chiral effects that arises from a structure in which alternating right- and left-handed long helical blocks are separated by infrequent and mobile helical reversals. Statistical thermodynamic methods yield an exact description of the polymer and the cooperative nature of its chiral properties. Minute energies that favor one of the helical senses drive easily measurable conformational changes, even though such energies may be extremely difficult to calculate from structural theory. In addition, the chiral nature of the polymer can be used to test theoretical ideas concerned with cholesteric liquid crystals, one of which solves the problem of assigning the helical sense.

https://science.sciencemag.org/content/sci/268/5219/1860.full.pdf

A Helical Polymer with a Cooperative Response to Chiral Information

Stereoisomerie des chaines macromoleculaires; la contribution de la spectroscopie RMN a la stereochimie macromoleculaire; analyse conformationnelle; chiralite dans les polymeres; controle stereochimique au cours de polymerisation

The Stereochemistry of Linear Macromolecules

In recent years polyurethanes have been confronted with several challenges. Some of these challenges have been overcome with the development of new catalysts. This review article covers recent developments in the field of polyurethane catalysis. An overview of the different types of catalysts, their applications, and their actuation mechanisms, followed by a general survey of the stability of one‐component polyurethane systems in which the latent catalyst is already incorporated is presented.

Raymond F. Tietz

Papers

The homopolymerization of monoisocyanates

Reduction Products of the Rubremetinium Cation1

Relative Rates of Migration of Aryl Groups in the Schmidt Reaction of Benzhydrols1