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Effect of Double Branching in α,ω‐Substituted Oligothiophenes on Thermal Solid‐State Properties
Author(s) -
Gülcher Jochen,
Vill Roman,
Braumüller Markus,
Rahimi Khosrow,
de Jeu Wim H.,
Mourran Ahmed,
Ziener Ulrich
Publication year - 2017
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201700046
Subject(s) - branching (polymer chemistry) , chemistry , melting point , solid state , crystallography , dendrimer , linker , polymer chemistry , stereochemistry , organic chemistry , computer science , operating system
A systematic series of septi‐, noni‐ and undecithiophenes and the corresponding pre‐oligomers with five different dendrimer‐like branched end‐groups have been synthesized and their thermal solid‐state properties investigated. The substituents vary in terms of the lengths of the linkers between the silicon branching points. Comparison of the compounds in the series reveals that the linker connecting the oligomeric core with the first branching point has the strongest effect on the thermal properties. Furthermore, the relatively large volume of the substituents causes surprisingly low overall transition enthalpies and entropies for the oligomers of 10–20 kJ mol –1 and 15–40 J mol –1 K –1 , respectively, whereas the pre‐oligomers with interrupted conjugation display values in the range of 15–40 kJ mol –1 and 40–100 J mol –1 K –1 , respectively. Polarizing optical microscopy (POM) revealed textures pointing to smectic and columnar liquid‐crystalline phases but X‐ray and AFM data of a representative example are typical of cubic phases.