Spectroscopic evidence for diastereomeric helical segments of polysilane bearing enantiopure (S)- and (R)-3,7-dimethyloctyl groups

Autor:	Akihiro Ohira, Roopali Rai, Anubhav Saxena, Michiya Fujiki
Rok vydání:	2004
Předmět:	chemistry.chemical_classification Circular dichroism education.field_of_study Polymers and Plastics Organic Chemistry Population Wurtz reaction chemistry.chemical_compound Enantiopure drug chemistry Helix Polymer chemistry Materials Chemistry Side chain Polysilane education Alkyl
Zdroj:	Journal of Polymer Science Part A: Polymer Chemistry. 42:4518-4527
ISSN:	1099-0518 0887-624X
DOI:	10.1002/pola.20378
Popis:	We synthesized two optically active helical polysilanes, poly[(S)-3,7-dimethyloctyl-3-phenylpropylsilane] (PS1) and poly[(R)-3,7-dimethyloctyl-3-phenylpropylsilane] (PS2), bearing a flexible and rodlike silicon main chain and enantiopure alkyl side chains with (S)- and (R)-chiral centers, respectively, at the γ-positions. PS1 and PS2 underwent a thermodriven helix–helix transition at 10 °C in isooctane. Circular dichroism (CD) and UV studies demonstrated the transition characteristics, such as the transition temperature, population of right- and left-handed helical motifs, global shape, and screw pitch. At −80 °C, the dissymmetry ratio suggested that a preferential right-handed or left-handed screw sense was present in the polymer chains of PS1 and PS2, respectively. However, above the transition temperature, the appearance of a bisignate cotton band in the CD spectra suggested that both right-handed screw-sense, tight helical segments and left-handed screw-sense, loose helical segments coexisted in the same chains of PS1 and PS2. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4518–4527, 2004
Databáze:	OpenAIRE
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