Thermoreversible and irreversible

Thermoreversible and Irreversible Physical Gels from Biopolymers... 

Low methoxyl pectins (< 50% esterified) form thermoreversible gels in the presence of calcium ions and at low pH (3 - 4.5) whereas high methoxyl pectins rapidly form thermally irreversible gels in the presence of sufficient (e.g., 65% by weight) sugars such as sucrose and at low pH (< 3.5) the lower the methoxyl content, the slower the set. 

Corresponding DLS and rheology studies to prove the validity of the Eq. (18) were performed on another thermoreversible system (three mixtures made of xanthan gum and locust bean gum (XG/LBG) (Richter et al. 2004b, 2005) and on the irreversibly radical chemical cross-linking system (W-vinylcaprolactam/ 2-hydroxylethyl- methacrylate/allylmethacrylate) (Richter et al. 2004c). 

In chemical gels the network connection (crosslink) is usually a covalent bond, which leads to a thermally irreversible gel. When the crosslinking is purely physical in nature, a physical gel is formed which is thermally reversible. There have been at least two excellent works published in the last few years. Reversible Polymeric Gels and Related Systems by Russo [2] and Thermoreversible Gelation of Polymers and... 

---