Document Detail

Azo Monomers Exhibiting Low Layer Shrinkage at the SmA-SmC Transition and trans-cis Light-Induced Isomerization.
MedLine Citation:
PMID:  23197425     Owner:  NLM     Status:  In-Data-Review    
Methacrylic monomers containing a (phenylene)azobenzene unit substituted with a lateral cyano group and alkyl chains of different length are synthesized and characterized by NMR techniques. Their liquid-crystalline properties are studied by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. All monomers exhibit a mesomorphic behavior that extends over wide temperature ranges with nematic and orthogonal or tilted smectic-type mesophases, depending on the length of the terminal chain. The smectic structures are determined to be single-layered with a low layer shrinkage (<5 %) at the SmA-SmC transition. This atypical behavior is attributed to the combination of a high smectic order promoted by both π-π and bond dipole-bond dipole interactions between cyano-substituted central cores, and a low correlation between neighboring layers arising from dispersive forces between the end groups (methacrylic group and alkyl chain) of the monomer. On the other hand, the trans-cis isomerization of monomers is induced in solution by irradiating with a UV lamp. High cis-isomer contents (≥96 %) are obtained at the photostationary state, which is reached in a relatively short time (40 s).
Tonatiuh García; Leticia Larios-López; Rosa Julia Rodríguez-González; José Román Torres-Lubián; Dámaso Navarro-Rodríguez
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Chemphyschem : a European journal of chemical physics and physical chemistry     Volume:  13     ISSN:  1439-7641     ISO Abbreviation:  Chemphyschem     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2012-11-30     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100954211     Medline TA:  Chemphyschem     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  3937-44     Citation Subset:  IM    
Copyright Information:
Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Departamento de Materiales Avanzados, Centro de Investigación en Química Aplicada, Blvd. Enrique Reyna H. 140, Saltillo Coahuila 25253 (México).
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