Université de Nantes, Oniris, CNRS, GEPEA, UMR 6144, F- 44470 Carquefou, France; Institut de Chimie Moléculaire de Reims, CNRS UMR 7312, Université de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex, France.
Institut de Chimie Moléculaire de Reims, CNRS UMR 7312, Université de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex, France.
Carbohydr Polym. 2023 Apr 15;306:120607. doi: 10.1016/j.carbpol.2023.120607. Epub 2023 Jan 20.
Paramylon is a linear β-1,3-glucan produced by the microalgae Euglena Gracilis. Due to its native crystalline structure, involving hexagonally packed triple helices, paramylon is neither water soluble nor thermoplastic. While such properties are generally obtained by chemical modification of paramylon, the present work demonstrates that using ionic liquid/water mixtures as solvents or plasticizers may be an alternative: A mixture of water with cholinium glycinate (40:60) allowed: i) obtaining paramylon solutions at 80 °C, that form reversible ionogels upon cooling at 20 °C, when used as a solvent, and ii) the thermomechanical processing of paramylon below 100 °C by extrusion and hot-press into transparent films, when used as a plasticizer. The thermoplastic paramylon obtained consists of an amorphous matrix, self-reinforced by oriented triple helices packed as nanofibers. This results in a storage modulus ranging from 300 to 450 MPa at 25 °C, depending on the plasticizer content, and in a tensile strain at break of 27 %. For storage times larger than 1 month, a recrystallization of paramylon is observed, with an unidentified crystalline structure different from the native one. Recrystallized samples can be reprocessed into amorphous films by hot pressing.
海藻糖是一种由绿眼虫产生的线性β-1,3-葡聚糖。由于其天然的结晶结构，涉及六边形排列的三重螺旋，海藻糖既不溶于水也不具有热塑性。虽然这些特性通常可以通过海藻糖的化学修饰来获得，但本工作表明，使用离子液体/水混合物作为溶剂或增塑剂可能是一种替代方法：水与胆碱甘氨酸（40:60）的混合物允许：i）在 80°C 下获得海藻糖溶液，当用作溶剂时，在冷却至 20°C 时形成可逆的离子凝胶，以及 ii）在低于 100°C 时通过挤出和热压成透明薄膜进行海藻糖的热机械加工，当用作增塑剂时。所获得的热塑性海藻糖由无定形基质组成，该基质通过排列成纳米纤维的定向三重螺旋自增强。这导致在 25°C 时储能模量在 300 到 450 MPa 之间变化，具体取决于增塑剂的含量，断裂时的拉伸应变达到 27%。对于大于 1 个月的储存时间，观察到海藻糖的再结晶，具有不同于天然结构的未识别的结晶结构。再结晶的样品可以通过热压重新加工成无定形薄膜。
