Ring-opening polymerization substituent effects

H. Kamitakahara and F. Nakatsubo, Substituent effect on ring-opening polymerization of regioselectively acylated 1,4-anhydro-a-D-glucopyranose derivatives, Macromolecules, 29 (1996) 1119-1122. 

The results show that the presence of bulky substituent on a polymer chain may effectively inhibit the termination proceeding by this mechanism. The results presented at this point may be summarized as follows chain transfer to polymer is a general feature of cationic ring-opening polymerization although for different systems the contribution of this reaction may vary only in some systems this process results in termination (These systems involve, e.g., cyclic amines (3- and 4-membered) and cyclic sulfides (3- and 4-membered) and the contribution of the reaction is reduced for substituted chains. 

W., Mikes, F., Guo, Y, Koike, Y, and Okamoto, Y. (2004) Free-radical polymerization of dioxolane and dioxane derivatives effect of fluorine substituents on the ring opening polymerization. J. Polym. Sci., Part A Polym. Chem., 42, 5180. 

The inhibitory effects of polar functional groups are not nearly as pronounced when the substituent is attached to a strained cycloalkene, where the release of ring strain provides a significant driving force for its metathesis. The norbornene ring system polymerizes easily by ring opening thus, numerous functionalized polymers have been prepared by the sequence depicted in Eq. (61). Many of these polymers hold some potential for commercialization and hence the bulk of this work is reported in the patent literature. 

By comparison unsubstituted lactones such as propiolactone (G) polymerize more slowly and molecular weights are lower. The authors believe propagation is slower, the carboxylate anion formed from pivalolactone ring opening being more nucleophilic because of the inductive effect of the two methyl substituents. 

In recent studies of styrene oxide polymerization reactions we found the phenyl substituent to have a significant Influence on the course of the polymerization process, too. In our particular case, however, the influence is due not only to steric factors, but also to the inductive effects of the phenyl ring, which Influences directly the course of the oxirane ring-opening reaction. 

The polymerization of endo- and exo-2 tert. -butyl-T Oxa bicyclo-[2.2, l]heptane have been studied T. As expected the large substituent very effectively shields the neighbouring carbon from nucleophilic attack of the monomer and the ring opening occurs only at the bridge head carbon. 

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