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 γ-rays irradiation. The molar mass of original KM was 1020 kDa. The molar mass of irradiated KM decreased significantly with increase of absorbed dose up to 2 kGy and then decreased gradually. The molar mass of 10 kGy irradiated KM was 236 kDa. The radius of gyration (R G ) of original KM was 98.0 nm. The R G value decreased significantly with increase of the dose up to 2 kGy and then reached to 46.4 nm at 10 kGy of absorbed dose. KM molecules were solvated in the form of random coils in water. The flexibility of molecular chain increased with increasing temperature. SPM image of original KM molecular chain showed rod-like pattern. The chain length and thickness of original KM was 1150 nm and 1.04 nm, respectively. The chain length decreased significantly with decrease of molar mass. However, the chain height scarcely changed regardless of molar mass. The chain lengths of low molar mass KM with 507 kDa and 236 kDa were 440 nm and 250 nm, respectively.

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