Calorimetric evaluation of the glass transition in hydrated, linear and branched polyanhydroglucose compounds

摘要: By comparing glass transition temperatures, Tg, determined by differential scanning calorimetry (midpoint of heat capacity step at 3 °C.mn−1) on powders varying water contents for different polysaccharides, the influence molecular weight, degree branching and (1–4) vs (1–6) glycosidic linkage ratio upon depression Tg is illustrated, thus extending results former studies. Due to both doubts concerning change its transition, when dispersed in such media, limitations second-order entropy-based derivations, effect plasticization described Couchman's correlation degenerated form, which similar Gordon-Taylor formulation. Strong enthalpy relaxation effects are observed following aging treatments temperatures below, even far below Tg. This makes it necessary erase history moisture-conditioned samples and, thus, only second DSC scan presented. As expected, linear chains appear favor chain-chain interactions induce partial crystallinity; branched molecules display lower values, due chain end effects, as well flexibility points. The three dihedrals present α(1–6) linkages seem depress a fashion internal plasticization. case α(1–4) amylose bearing grafted fructoses examined first towards tailored structures, designed optimize mechanical properties (as chemically modified polysaccharides) inhibit recrystallization. extension ciliated structures (sparse brushes) proposed target biosynthesis optimization.