Starch Aerogels: A Member of the Family of Thermal Superinsulating Materials.

Starch aerogels were prepared via dissolution in water (thermomechanical treatment), retrogradation, solvent exchange, and drying with supercritical CO2. Amylose content in starches was varied from 0 to 100%. The aerogels' bulk density, morphology, specific surface area, thermal conductivity, and mechanical properties under compression were investigated. Pea starch aerogels had one of the highest specific surface area and lowest density and thermal conductivity (0.021-0.023 W/m·K), with the latter indicating that a new thermal superinsulation material was obtained. A detailed study of the influence of processing parameters on pea starch aerogels properties showed the importance of retrogradation time which decreases specific surface area and increases mechanical properties and thermal conductivity. Finally, a comparison of starch aerogel thermal conductivity with that of other bioaerogels is performed.

Synthesis and properties of fatty acid starch esters.

Being completely bio-based, fatty acid starch esters (FASEs) are attractive materials that represent an alternative to crude oil-based plastics. In this study, two synthesis methods were compared in terms of their efficiency, toxicity and, especially, product solubility with starch laurate (C12) as model compound. Laurates (DS>2) were obtained through transesterification of fatty acid vinylesters in DMSO or reaction with fatty acid chlorides in pyridine. The latter lead to higher DS-values in a shorter reaction time. But due to the much better solubility of the products compared to lauroyl chloride esterified ones, vinylester-transesterification was preferred to optimize reaction parameters, where reaction time could be shortened to 2h. FASEs C6-C18 were also successfully prepared via transesterification. To determine the DS of the resulting starch laurates, the efficient ATR-IR method was compared with common methods (elementary analysis, (1)H NMR). Molar masses (Mw) of the highly soluble starch laurates were analyzed using SEC-MALLS (THF). High recovery rates (>80%) attest to the outstanding solubility of products obtained through transesterification, caused by a slight disintegration during synthesis. Particle size distributions (DLS) demonstrated stable dissolutions in CHCl3 of vinyl laurate esterified - contrary to lauroyl chloride esterified starch. For all highly soluble FASEs (C6-C18), formation of concentrated solutions (10 wt%) is feasible.