L-Alanine Induced Chiral Single-Stranded Helical Polynorbornenes
Date Issued
2010
Date
2010
Author(s)
Kao, Ming-Jui
Abstract
The purpose of this thesis is to design and synthesis single-stranded helical polynorbornenes (PNBs) appended with chiral alanine and anthracene chromophores and further use photophysical methods to study the helicity of these polymers and interactions between pendant
Hydrogen bonding plays an important role for the helical structure of these polymers. Bisamidic linkers are essential to ensure the bisignate CD curves for these polymers. Single amidic linkage may be not strong enough to hold the pendants in proper orientation, and therefore polymers with with such linkers are CD inactive. Exciton coupling method at the absorptions for the anthracene and 4-aminobenzamide chromophores is used to depict the helicity of the polymers.
Because hydrogen bond networks bring the pending adjacent groups into a fixed orientation, the chiral center would induce the right-handed or left-handed helical direction of every monomeric unit. Therefore the random copolymer from the copolymerization of a mixture of (R)- and (S)-enantiomeric monomers with a enantiomeric excess cannot produce PNBs with a single-handed helical conformation. This helical PNB system does not follow Majority rule.
Subjects
Helical Polynorbornenes
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