Ct. Andrade et al., Comparative study on structural features of alpha chitin from Xiphopenaeuskroyeri and its precipitated product from phosphoric acid solution, J APPL POLY, 83(1), 2002, pp. 151-159
A sample of a chitin was obtained from shells of the shrimp Xiphopenaeus kr
oyeri by demineralization and deproteinization processes. This sample of na
tive a chitin (NC) was dissolved in concentrated phosphoric acid and recove
red by precipitation in an alkaline aqueous solution, giving rise to a samp
le named PC. Solid-state carbon-13 nuclear magnetic resonance (C-13-NMR), X
-ray diffraction, and atomic force microscopy (A-FM) techniques were used t
o compare both samples and to investigate structural changes in a chitin un
der the action of phosphoric acid. C-13-NMR experiments and X-ray diffracti
on results revealed a high crystalline order in both samples. Structural di
fferences were due to the higher distance between adjacent chains along the
b axis and the consequent decrease in the number of intermolecular hydroge
n bonds in the sample recovered from solution. While remarkable supramolecu
lar differences could be observed in the fibrillar crystals of the NC sampl
e, the PC sample was characterized by only one type of morphology. (C) 2002
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