2.9. Determination of molecular weights
The cellulose samples were dissolved in 1 M cupriethylenediamine diluted from the 3 M stock solution purchased from Prolabo (France). The viscosimetric average degree of polymerisation (DPv) of cellulose samples was calculated from the intrinsic viscosities of the corresponding solutions at 25 C, using the relationship (Rinaudo, 1968): ½g ¼ 0:891DP0v:936.
2.10. Solid state NMR spectroscopy
The NMR experiments were performed on a Bruker Avance spectrometer (13C frequency of 100 MHz), using proton dipolar decoupling (DD), magic angle spinning (MAS) and cross-polarisation (CP). CP transfer was achieved using a ramped amplitude sequence (RAMPCP) for an optimised total contact time of 2 ms. The spinning speed was set at 6 kHz, sweep width 50,000 Hz, recycle delay 4 s and 10,000 scans. The 13C chemical shifts were measured relative to the carbon chemical shift of the glycine carboxyl group (176.0 ppm).