X-ray crystallographic, scanning microprobe X-ray diffraction,and cross-polarized/magic anglespinning ¹³C NMR studies of the structure of cellulose III _II

The X-ray crystallographic structure of cellulose IIIn is characterized by disorder; the unit cell (space group P2 ₁, α = 4.45 Å, b = 7.64 Å, c = 10.36 A, αa= β = 90°, γ = 106.96°) is occupied by one chain that is the average of statistically disordered antiparallel chains. ¹³C CP/MAS NMR studies reveal the presence of three distinct molecular conformations that can be interpreted as a mixture of two different crystal forms, one equivalent to cellulose III _I and another with two independent glucosyl conformations in the asymmetric unit. Both X-ray crystallographic and ¹³C NMR spectroscopic results are consistent with an aggregated microdomain structure for cellulose This structure can be generated from a new crystal form (space group P2 ₁; α = 4.45 Å, b = 14.64 Å, c = 10.36 Å, α =β = 90°, y = 90.05°; two crystallographically independent and antiparallel chains; gt hydroxymethyl groups) by multiple dislocation defects. These defects produce microdomains of the new crystal form and cellulose III _I that scanning microprobe diffraction studies show are distributed consistently through the cellulose III _I fiber.