A feasible method to determine the critical DS for modified polysaccharide derivativesʹ gelation by gel point, tg

The process of determining a critical DS to a polymerʹs gelation is a key link in identifying degradable polymersʹ cross-linking behaviors. A feasible method was developed from the rheological technique. In principle, it was a new application of gel point, tg, in an overlapping field of polymersʹ modification and characterization, by which the gelling properties of carboxyl methylated guar gum (CMGG) and locust bean gum (CMLBG) were dynamically investigated by identifying their tg. Differing from the routine research in rheology or synthesis chemistry, the present study focused on neither pure tg nor pure DS but on their interrelation. The results demonstrated that CMGG/CMLBGʹs gel points could be observed only when their DS were 0.2. However, it was not guaranteed to yield the tested polymersʹ gel points unless the investigation was performed on a plateau region. Two preconditions, DS≤0.2 and ω=3–60 rad s−1, must be satisfied simultaneously besides γ of 0.5% was maintained in order to obtain the expected gel point. Since DS was regarded as a contradictory focus related to the polymersʹ hydrophilicity and cross-linking behavior, the value DS=0.2 was exactly the upper limit of CMGG/CMLBGʹs gelation. The significance of the present study rests not only in the first successful attempt in determining galactomannan-based derivativesʹ DScritical but also in its universal application for other polysaccharide-based derivatives because of a similarity in structure.