Konjac glucomannan (KM) is a water soluble glucomannan with high molar mass. KM aqueous solution shows extremely high viscosity. KM can be depolymerized by chemical hydrolysis. The molar mass of hydrolyzed KM decreased with increase of acid concentration and hydrolysis time. The acid hydrolysis led chain scission of KM, but introduced no significant new chemical groups into the structure. KM molecular chain was hydrolyzed randomly by acid hydrolysis. The viscosity of KM aqueous solutions decreased with decreasing molar mass. KM solution changed to Newtonian fluid with decreasing molar mass at low concentration. KM with molar mass less than 320 kDa was Newtonian fluid in semi-dilute region. KM aqueous solution showed two kinds of critical overlap concentration of C* and C**. C* is onset of shrinkage of the polymer coils and C** is the critical concentration to attain their limiting size. The overlapping and entanglement of KM chains with high molar mass occurred at lower concentration as compared to those of KM with low molar mass.

Konjac glucomannan (KM) is a water soluble glucomannan with high molar mass. KM aqueous solution shows extremely high viscosity. KM can be depolymerized by chemical hydrolysis. The molar mass of hydrolyzed KM decreased with increase of hydrolysis time. The acid hydrolysis led chain scission of KM, but introduced no significant new chemical groups into the structure. The weight-averaged molar mass,M w , of original KM and that of 30 min hydrolyzed KM were 1.0 x 10 6 Da and 6.0 x 10 3 Da, respectively. The weight-averaged radius of gyration, R G , of original KM was 98.0 nm. The R G value decreased with increase of hydrolysis time and then reached to below 10 nm at 20 min of hydrolysis time. SPM image of original KM molecular chain showed string-like pattern. The contour length and the chain height of original KM were 1193 nm and 1.2 nm, respectively. The chain height scarcely changed regardless of molar mass, but the contour length decreased significantly with increase of hydrolysis time. The chain lengths of KM with M w of 5.9 x 10 5 Da and 1.8 x 10 5 Da were 688 nm and 268 nm, respectively.