Cellulose deuterated

The nature of the bonds between cellulosic fibres in paper has been the subject of some controversy over many years. The early and now largely discredited view was that paper derived its strength merely from mechanical entanglement of the fibres. However, experiments in which paper is formed from non-aqueous solvents produce sheets with very poor strength properties and have thus tended to disprove this conjecture. In the mid-1950s deuteration experiments were carried out which demonstrated that of the order of 0.4-2% of all hydroxy groups are additionally bonded in paper as compared with the unbonded fibres. This observation led to the view that... 

By using a mathematical treatment formally analogous to that of Spurlin (79) for the substitution of cellulose derivatives, the following equations are derived for the mole fractions of individual deuterated guaiacols as a function of time ... 

Nuclear Magnetic Resonance (NMR) - NMR spectra of cellulose nitrate-g-poly(methyl methacrylate) and cellulose nitrate were recorded in deuterated acetone using Perkin-Elmer-R-32 (90 MHz). 

Next, a correlation among Sa, Xam(X), the fraction of the accessible part (by heavy water) at equilibrium, as determined by the deuteration IR method, Xac(IR)> ar)d the relative amount of the higher field peaks of the C4 carbon peaks, Xh(NMR), were examined for samples having cellulose crystal form II, so as to clarify the factors contributing to Sa. In this case, Xi,(NMR) was estimated from Eq. (60) ... 

Corte and Schraschek (444a) used IR shifts on deuteration of cellulose to calculate binding energy in paper sheets. The values were of the proper order of magnitude but lower than experimental results. These authors also review the theories of paper strength and conclude that H bonds play a major part in it. Other workers (1788, 2225, 2224) have studied the same problem. 

The use of this deuteration technique can be extended to investigate chemical substitution in cellulose with a view to determining whether the reaction has occurred in crystalline regions as well as in amorphous, and what the effect of substitution is on the hydrogen-bonding system of the residual hydroxyl groups in the regions where substitution has occurred. 

Early deuteration studies - were limited by the fact that the rate and extent of the exchange between deuterium oxide and the hydroxyl groups in cellulose had to be determined by density measurements, whereas an... 

Deuteration has also been used as a gravimetric method for determining accessibility, the results for cotton being in exact agreement with those of Valentine. The linear relationship which exists between moisture sorption and the fraction of material found to be amorphous to infrared has been confirmed for thirteen different t5qies of cellulose, and it is suggested that a difference in the ratio of moisture regain to amorphous content between samples of cellulose I and cellulose II reflect differences in their sorption behavior and, hence, in the structure of their amorphous... 

Figure 6. Infrared spectra of deuterated bacterial cellulose (solid line) and rehydrogenated bacterial cellulose (dashed line) (16)...

Figure 1 shows a 50 MHz CP/MAS C NMR spectrum of ramie cellulose and a stick-type nmr spectrum of low molecular weight cellulose( DP <10) In deuterated dimethyl sulfoxide solution(DMSO) (8 ) (The broken and solid lines In the CP/MAS spectrum will be explained below.). As already reported(9,10), the assignments for the Cl, C4 and C6 carbons are relatively easy, based on analogies with the solution state spectrum. However, It should be noted that these resonance lines shift downfleld by 2.3-9.6 ppm In the solid state compared to the solution state. The cause of such large downfleld shlfts(to be explained In the next section) Is attributed to the different conformations about the P-l,4-glycosldlc linkage and the exo-cyclic C5-C6 bond in which these carbons are Involved. 

Fig. 5 IR spectra of the deuterated allomorphs in OD stretching region. A I, valonia cellulose, B IV prepared from IHi (C), C IHi from A, D II, ophane, E Hn from D, F IVxi E.

The authors wish to thank Dr. H. L. Crespi for furnishing the sample of deuterated bacterial cellulose and for his advice concerning the growth of algae in heavy water, and Dr. U. P. Agarwal for the many helpful discussions he contributed to this work. Portions of this work were used by J. H. Wiley as partial fulfillment of the requirements for the Ph.D. degree at The Institute of Paper Chemistry. 

It will be observed that the moisture regain and deuteration determinations yield lower values for degree of order than the chemical reaction techniques. As will be discussed later Zeronian et al. p) have demonstrated it is feasible to use the moisture regain technique in a manner which will permit differentiation between sorption on crystallite surfaces and sorption in the disordered regions of the cellulose. When allowance was made for the sorption on the crystallite surfaces they found the degree of order for cotton and mercerized cotton was similar to those found by the acid hydrolysis technique. 

Deuteration. When cellulose is treated with saturated deuterium oxide vapor at roan ten rature, the easily accessible hydroxyl groi exchange re idly, and a less accessible coi xxient exchanges more slowly. Other hydroxyl groups do not exchange. The easily accessible hydroxyl groiq>s have been equated with the amorphous... 

Fig. 11. Neutron-diffiaction pattern recorded on a normal (OH, left) and on a deuterated (OD) sample of cellulose ip. ...

Fig. 12. X-Ray and neutron fiber-diffraction patterns recorded from native cellulose (OH) and frilly deuterated (OD) cellulose samples. The difference in the scattering properties of hydrogen and deuterium (indicated by the red circles) allows the precise location of the electron density (shown in blue), which corresponds to the position of hydrogen atoms in the crystalline lattice. (See Color Plate 5.)...

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