Cellulose crystallite sizes in diploid and tetraploid native cotton

Abstract

Cellulose crystallite sizes in directions perpendicular to (101), (101 V ), and (002) planes, have been estimated from X-ray powder diffraction patterns. The diffraction peaks were resolved using the FIT X-ray diffraction data analysis program (written by SOCABIM, Siemens DIFFRAC AT Software System, Siemens, Germany). The complete data for all the three equatorial planes was analyzed for 2u, d values, full width at half-maximum (FWHM), and the normalized area under the three diffraction peaks, for seven cotton cultivars grown at four different locations in India in different crop years. The mean crystallite sizes were determined using the Scherrer equation. The reference standard included degummed and purified ramie fibers for relative crystallinity estimation in cotton cultivars. It has been observed that, though the computed crystallite sizes corresponding to (101), (101 V ), and (002) planes vary within individual varieties with location and year of growth, the combined average crystallite size corresponding to (101) and (101 V ) planes taken together for individual varieties from all locations and crop years is close to the combined average crystallite size corresponding to the (002) planes, irrespective of the species of cotton. The values of the average relative crystallinity with respect to highly oriented degummed and purified ramie fibers of individual varieties from all locations and crop years do not significantly vary between varieties and species of cotton. It is visualized that variations in crystallite sizes arise as a result of the differences in the amount of cellulose synthesized within fibers of individual varieties and their disposition within the matrix of their developing fibers.

Caracterização química e estrutural de fibra de sisal da variedade Agave sisalana

“…Segundo Sao et al [38] , as propriedades mecânicas dos materiais lignocelulósicos são fortemente dependentes do índice de cristalinidade dos mesmos. Nas últimas décadas, a medida do índice de cristalinidade tem recebido muita atenção por razões de aplicações comerciais e devido à importância que estes materiais vêm despertando na área industrial [39] . A composição química das fibras, a variação do índice de cristalinidade (Ic) e as curvas de raios X ao longo do comprimento da fibra de sisal são apresentadas na Tabela 1 e na Figura 1, respectivamente.…”

Microfibril diameter in celery collenchyma cellulose: X-ray scattering and NMR evidence

“…Using the Scherrer equation the broadening of the 200 diffraction peak can be used to estimate the lateral extent of the lattice, with some uncertainty due to other contributions to broadening. Such estimates are well correlated (Newman 1999) with NMR estimates of microfibril diameter for primary-wall cellulose and for cellulose from cotton, flax and ramie, where the Scherrer diameter is larger at 4-6 nm (Wada et al 1995;Moharir and Kiekens 1998) and the proportion of the C-4 NMR signal assigned to crystalline interior chains is correspondingly greater (Atalla and Vanderhart 1984;Vië tor et al 2002;Sturcova et al 2004).…”

Diffraction evidence for the structure of cellulose microfibrils in bamboo, a model for grass and cereal celluloses

“…Evidence has emerged, first from 13 C NMR spectroscopy [ 7 - 9 ] and more recently from other spectroscopic and scattering technologies [ 10 - 15 ], for partially ordered cellulose microfibrils no more than about 3 nm in diameter. Cellulose microfibrils of that size have been reported from unlignified primary cell walls [ 13 , 15 ] and from gymnosperm xylem, which is dominated by lignified secondary cell walls [ 7 , 10 , 16 ], although cotton, flax and certain other materials composed of relatively pure cellulose contain thicker microfibrils [ 14 , 17 , 18 ]. A 3 nm microfibril is too thin to accommodate the 36 chains formerly assumed to be present in microfibrils emerging from the 6-membered ‘rosette’ responsible for cellulose biosynthesis [ 19 ].…”