THE FINE STRUCTURE OF VALONIA MICROFIBRIL GEL PERMIATION CHROMATOGRAPHIC STUDIES OF VALONIA CELLULOSE

Abstract

The fine structure of the microfibril of Valonia macrophysa is discussed based on the changes of molecular weight distribution curves, _??_w and_??_w/_??_n of acid hydrolysis residues. Valonia macrophysa was treated with various concentration of NaOH at 20°C for 2 hrs and in few cases for 72 hours. Then, those treated samples were acid hydrolyzed with 4N-HCI at boiling point for different length of time.
The_??_w and _??_w/_??_n were calculated from the distribution curve. The molecular weight distribution of the hydrolysis residue was measured by gel permeation chromatography.
The elution curve of the hydrolysis residue of unmercerized Valonia shows the unimodal curve with the tail in the low molecular weight region. The values are 6000 and 2.47 for leveling off_??_w (leveling off_??_v obtained viscometrically is 2000) and_??_w/_??_n respectively.
The elution curve of the hydrolysis residue of Valonia pre-treated with 0_??_16% concentration of NaOH solutions shows the same unimodal curve as that of unmercerized Valonia, and the quantity of the low molecular weight fractions increase with the increment of NaOH concentration.
The hydrolysis residue of the sample treated with 16_??_20% concentration of NaOH solutions shows bimoda_??_ curve. It is interesting to note that the position of the peak in the high molecular weight region does not shift to low molecular weight region with higher alkaline concentration or longer hydrolysis period, but the area under this peak increases with longer period of hydrolysis, and that in the low molecular weight region decreases. Hence, it is clear that owing to disappearance of the peak in the low molecular weight region, the value of _??_w of a partial mercerized sample becomes eventually equal to the value of leveling off _??_w of unmercerized sample after longer hydrolysis times. The experimental results indicate, in other word, that the microfibril can not be cut in shorter period than about 1 μ calculated from leveling off _??_μ of unmercerized sample.
The elution curve obtained from hydrolysis residue of the sample treated with NaOH solution of concentration more than 20% shows the unimodal distribution curve in the side of low molecular weight.
Changes in the _??_w obtained above correspond with those of _??_v, although both values are not equal.
On the basis of these experiments, it suggests that the Valonia microfibril is composed of extended chains and that defect consisting of chain-end dislocation does not exist at random throughout the microfibril, but generally at intervals of about 1 μ.