We report an efficient method for extraction of anionic polysaccharides (PS) from
cyanobacteria, Aphanothece sacrum; we used a hot alkaline solution (0.01 N NaOH) as an elution
solvent in the first step of the extraction and isopropanol as a precipitation solvent in the last step.
Thin fibers of PS were obtained at a high yield (50-80 % to the weight of the raw cyanobacterial
sample). The spectroscopy and elemental analyses indicated the PS contains fucose, uronic acids
(14.2 % by a carbazole-sulfuric acid method), a sugar unit containing amides. The solution of PS
with a concentration of 1 wt% showed a very high viscosity (80 000cps) implying a high molecular
weight, and a strong macroscopic birefringence with a texture typical of nematic liquid crystals was
confirmed by crossed-polarizing microscopy (more than 0.5 wt%). The PS from A. sacrum may form
a special structure rigid-rod enough to show LC phase and macroscopic birefringence.
Photosensitive, liquid crystalline (LC) polymers were prepared by in-bulk polymerization of phytomonomers such as cinnamic acid derivatives. The p-coumaric acid (4HCA) homopolymer showed a thermotropic LC phase where a photoreaction of [2+2] cycloaddition occurred by ultraviolet irradiation. LC phase was exhibited only in a low molecular weight state but the polymer was too brittle to materialize. Then we copolymerized 4HCA with multifunctional cinnamate, 3,4 dihydroxycinnamic acid (caffeic acid; DHCA), to prepare the hyperbranching architecture. Many branches increased the apparent size of the polymer chain but kept the low number-average molecular weight. P(4HCA-co-DHCA)s showed high performances which may be attained through the entanglement by in-bulk formation of hyperbranching, rigid structures. P(4HCA-co-DHCA)s showed a smooth hydrolysis, an in-soil degradation and a photoreaction cross-linking from conjugated cinnamate esters to aliphatic esters. The change in photoconversion degree tuned the polymer performance and chain hydrolysis.
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