DSC and TMA Studies of Polysaccharide Physical Hydrogels

Abstract

Various kinds of polysaccharides found in a wide variety of plants, bacteria, crustaceans and insects form hydrogels via physical aggregation in aqueous media. The major mass of hydrogels is water filled, ca. 95~99.5 %, in a network structure, although the solid shape of the gel is maintained. In this paper, firstly the wide range of gelation mechanism is briefly described, and then thermal analysis of representative gel-forming polysaccharides, such as carrageenan, alginate, galactomannan, and pectin, is introduced. By differential scanning calorimetry (DSC), gel-sol and sol-gel transition temperature of thermoreversible hydrogels are measured and phase diagram is established. It is suggested that binary systems showing sinusoidal gel-sol-gel transition are capable of being assembled. By thermomechanical analysis (TMA), dynamic modulus (E') at around 1 x10 4 Pa of thermo-irreversible hydrogels was obtained using a sample holder designed to measure the viscoelastic properties in water. Reliable coordination is shown between the results obtained by DSC and TMA. In this review, current research and several topics on thermal properties of polysaccharide physical hydrogels are introduced.

Development of functional active films from blend of gelatin with crude orange juice pomace pectin: Test for packaging of virgin olive oil

“…The lowest Tg value (63. Accordingly, it was reported by Iijima et al 91 that the Tg value of highly dried methoxylated pectin is at approximately 150 C. As the methylation degree of SOPP is over 60%, its Tg value would be higher than that of gelatin, which may explain the thermal stability enhancement in the blend films, compared to the control film CFG (100/0). 82 The polyanion-complex due to ionic interactions between positively charged gelatin and negatively charged pectin, 81 resulting in more thermal-resistant films.…”

Building an extensible cell wall

“…Within native cell walls, the physical state of pectins—intermixed as they are with cellulose, xyloglucan, glycoproteins and other polymers—is not so clear, and it is uncertain whether they undergo gel–sol transitions characterized in pure HG isolates ( Ngouemazong et al, 2012 ). Such transitions can be measured as endothermic events by differential scanning calorimetry ( Iijima et al, 2021 ), but there seems to be only a single report of such a potential transition in growing cell walls ( Lin et al, 1991 ). In pectin-rich primary cell walls from apple ( Malus pumila ) fruit, no evidence of gel–sol transition was detected ( Aguilera et al, 1998 ).…”

Polysaccharide-Based Hydrogels for Wound Dressing: Design Considerations and Clinical Applications

“…In chemistry, the gelation process is known as the progressive crosslinking of polymer chains in the reaction system into one gigantic molecule with ‘infinite’ size( Gao, Peng, & Mitragotri, 2021 ). The abundance of functional groups of polysaccharides enables the formation of hydrogels by physical ( Iijima, Hatakeyama, & Hatakeyama, 2021 ) or chemical crosslinking ( Figure 1A ). ( Ahmad et al, 2019 ; Nie et al, 2019 ) Physical method generally refers to the cross-link of polysaccharide polymers by weak interaction forces such as H-bonding, Van der Waals interactions, hydrophobic forces and molecular entanglements ( Francesko et al, 2018 ; Iijima et al, 2021 ), whereas chemical gelling often involves the covalent bonding between polysaccharide polymers or polysaccharide polymer and the corresponding crosslinker, including condensation reactions, enzymatic crosslinking, disulfide crosslinking, click chemistry, polymerization, etc ( Aeridou et al, 2020 ; Meng & Edgar, 2016 ; Mo et al, 2021 ).…”

“…The abundance of functional groups of polysaccharides enables the formation of hydrogels by physical ( Iijima, Hatakeyama, & Hatakeyama, 2021 ) or chemical crosslinking ( Figure 1A ). ( Ahmad et al, 2019 ; Nie et al, 2019 ) Physical method generally refers to the cross-link of polysaccharide polymers by weak interaction forces such as H-bonding, Van der Waals interactions, hydrophobic forces and molecular entanglements ( Francesko et al, 2018 ; Iijima et al, 2021 ), whereas chemical gelling often involves the covalent bonding between polysaccharide polymers or polysaccharide polymer and the corresponding crosslinker, including condensation reactions, enzymatic crosslinking, disulfide crosslinking, click chemistry, polymerization, etc ( Aeridou et al, 2020 ; Meng & Edgar, 2016 ; Mo et al, 2021 ). Whether it is chemical crosslinking or physical crosslinking, the chemical mechanism of its crosslinking is forming interchain linkages, native or pre-anchored functional groups on one polymer chain must react with the corresponding groups on another chain using stepwise crosslinking chemistries ( Gao et al, 2021 ).…”