Determination of Molecular Weight of Agars and Effect of the Molecular Weight on the Glass Transition

Abstract

A novel procedure to determine the molecular weight (MW) and MW distributions for various agars is described. The MW values of commercial agars, an agarose, an agaropectin, and hydrolyzed agaroses were determined by size exclusion chromatography-low angle laser light scattering, using 4.0 M guanidine hydrochloride as eluent to avoid gelation. The MW for the commercial agars was between 106 400 and 243 500 with polydispersity between 1.283 and 6. 600. The MW of the agarose separated from a commercial agar was lower than that of the agaropectin. To prepare agaroses with different MW values, the obtained agarose was hydrolyzed. The MW of the agarose decreased with hydrolysis time, and the polydispersity, on the contrary, increased. The glass transition temperature (T(g)) of agarose with different MW values and that of agaropectin were measured by differential scanning calorimetry. The T(g) of the agarose was higher than that of the agaropectin with higher MW. The T(g) of agarose increased with MW.

Investigation of polymer electrolyte based on agar and ionic liquids

“…It was already reported that glass transition in agar samples can be found or observed in the range of temperature between 60 and 130°C depending on the molecular mass and moisture content [27,28]. However, no linebase changes were observed in the agar matrix used for this study.…”

Biopolymer agar‐agar doped with NH4SCN as solid polymer electrolyte for electrochemical cell application

“…However, it is thought that a maximum change in heat flow occurs at the midpoint of T g and that the midpoint is approximately the mean value of the distribution . It has already been reported that glass transition in agar samples can be observed in the range of temperature between 60 and 130 °C depending on the molecular mass and moisture content …”

“…It is well‐known that the glass transition does not occur at a single temperature, but at a range of temperatures. There are many articles showing T g as a temperature range . However, it is thought that a maximum change in heat flow occurs at the midpoint of T g and that the midpoint is approximately the mean value of the distribution .…”

Information Architecture Practice: An Interview with Gayle Curtis, Modem Media

“…SAA‐20 and SAG‐20 films showed broader peaks at their T g while a narrower peak was observed in SPG‐20 film. Unlike Phytagel, agar is a mixture of agarose and agaropectin and they showed different glass transition temperatures with agarose showing a higher T g than agaropectin 38. These two different components in agar may lead to a broader tan δ peak at its T g .…”