Smart Materials and ‡Nanophysics, Istituto Italiano di Tecnologia , Via Morego 30, 16163 Genova, Italy.
ACS Appl Mater Interfaces. 2015 Feb 18;7(6):3742-53. doi: 10.1021/am508515z. Epub 2015 Feb 5.
Designing starch-based biopolymers and biodegradable composites with durable mechanical properties and good resistance to water is still a challenging task. Although thermoplastic (destructured) starch has emerged as an alternative to petroleum-based polymers, its poor dimensional stability under humid and dry conditions extensively hinders its use as the biopolymer of choice in many applications. Unmodified starch granules, on the other hand, suffer from incompatibility, poor dispersion, and phase separation issues when compounded into other thermoplastics above a concentration level of 5%. Herein, we present a facile biodegradable elastomer preparation method by incorporating large amounts of unmodified corn starch, exceeding 80% by volume, in acetoxy-polyorganosiloxane thermosets to produce mechanically robust, hydrophobic bioelastomers. The naturally adsorbed moisture on the surface of starch enables autocatalytic rapid hydrolysis of polyorganosiloxane to form Si-O-Si networks. Depending on the amount of starch granules, the mechanical properties of the bioelastomers can be easily tuned with high elastic recovery rates. Moreover, starch granules considerably lowered the surface friction coefficient of the polyorganosiloxane network. Stress relaxation measurements indicated that the bioelastomers have strain energy dissipation factors that are lower than those of conventional rubbers, rendering them as promising green substitutes for plastic mechanical energy dampeners. Corn starch granules also have excellent compatibility with addition-cured polysiloxane chemistry that is used extensively in microfabrication. Regardless of the starch concentration, all of the developed bioelastomers have hydrophobic surfaces with lower friction coefficients and much less water uptake capacity than those of thermoplastic starch. The bioelastomers are biocompatible and are estimated to biodegrade in Mediterranean seawater within three to six years.
设计具有耐用机械性能和良好耐水性的基于淀粉的生物聚合物和可生物降解复合材料仍然是一项具有挑战性的任务。尽管热塑性（解结构）淀粉已作为石油基聚合物的替代品出现，但在潮湿和干燥条件下其尺寸稳定性差，广泛限制了其在许多应用中作为首选生物聚合物的使用。另一方面，未经修饰的淀粉颗粒在与其他热塑性塑料复合时，浓度超过 5%时，会出现不相容、分散性差和相分离问题。在此，我们提出了一种简便的可生物降解弹性体制备方法，即将大量未经修饰的玉米淀粉（体积超过 80%）掺入乙酰氧基聚有机硅氧烷热固性树脂中，以制备机械强度高、疏水性生物弹性体。淀粉表面上自然吸附的水分能够使聚有机硅氧烷自动催化快速水解，形成 Si-O-Si 网络。根据淀粉颗粒的数量，生物弹性体的机械性能可以很容易地进行调整，具有高弹性恢复率。此外，淀粉颗粒还大大降低了聚有机硅氧烷网络的表面摩擦系数。应力松弛测量表明，生物弹性体的应变能耗散因子低于传统橡胶，使它们成为有前途的塑料机械能阻尼器的绿色替代品。玉米淀粉颗粒还与广泛用于微加工的加成型硅氧烷化学具有极好的相容性。无论淀粉浓度如何，所有开发的生物弹性体都具有疏水性表面，其摩擦系数较低，吸水率比热塑性淀粉低得多。生物弹性体具有生物相容性，估计在 3 到 6 年内可在地中海海水中生物降解。
