Liquid Crystalline Properties of Polyguanidines

Modified polyguanidines were prepared, and their liquid crystalline properties were studied using optical polarizing microscopy and X-ray diffraction. Parameters examined include chirality, the uniformity of the lengths of side chains, and attached side-chain mesogens. If the side chains on the repe...

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Bibliographic Details
Published in:Macromolecules 2004-11, Vol.37 (22), p.8286-8292
Main Authors: Kim, Jeonghan, Novak, Bruce M., Waddon, Alan John
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Organic polymers
Physicochemistry of polymers
Polymers with particular structures
Preparation, kinetics, thermodynamics, mechanism and catalysts
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Summary:Modified polyguanidines were prepared, and their liquid crystalline properties were studied using optical polarizing microscopy and X-ray diffraction. Parameters examined include chirality, the uniformity of the lengths of side chains, and attached side-chain mesogens. If the side chains on the repeat units are identical, then polymer has a more ordered structure in both solution and the solid state. Uniform lengths of the side chains are also important. Poly(N,N‘-di-n-hexylguanidine), poly-I, exhibited a lyotropic smectic texture in contrast to a nematic texture of poly(N-(rac)-2-phenylethyl)-N‘-methylguanidine) (poly-( rac -II)). Optically pure poly(N-((R)-2-phenylethyl)-N‘-methylguanidine) (poly-( R- II)) formed a cholesteric texture, whereas the corresponding racemic polyguanidine, poly-( rac- II), formed a nematic texture. Additionally, poly-( R -II) displayed a mesophase at a lower critical concentration than either poly-I or poly-( rac- II), implying that poly-( R- II) is stiffer than these two other derivatives. Poly(N-6-((4‘-methoxyphenylazo)phenyl-4-oxy)hexyl-N‘-n-hexylguanidine) (poly-IV), one of combined liquid crystalline structures (liquid crystalline backbone plus liquid crystalline side chains), displayed a lyotropic nematic texture presumably due to the strong dipolar−dipolar interaction between the main chain and side chains that folds the appendages parallel to the molecular axis. Poly(N-12-((4‘-methoxybiphenyl-4-oxy)dodecyl-N‘-n-dodecylguanidine) (poly-V) and poly(N,N‘-di-n-dodecylguanidine) (poly-VI) exhibited thermotropic liquid crystalline behavior.
ISSN:0024-9297
1520-5835
DOI:10.1021/ma0493527