SusChEM: Rheology of Cellulose and other Biopolymers in Ionic Liquids

SusChEM：离子液体中纤维素和其他生物聚合物的流变学

• 批准号: 1506589
• 负责人: Ralph Colby
• 金额: $ 34.5万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-15 至 2020-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1506589&HistoricalAwards=false
• 关键词: SusChEM; Rheology; Cellulose; other; Biopolymers

AbstractNon-Technical: Cellulose is the most abundant renewable polymeric natural resource on our planet. For many years cellulose has been chemically modified to make it water-soluble or at least water-dispersible, enabling solution processing of cellulose. However, the modifications are expensive and inhibit the crystallization of cellulose that imparts final mechanical properties. Ionic liquids are nonvolatile solvents and recently, certain ionic liquids have been found to dissolve native cellulose. There is a large inductrial research effort aimed at fiber spinning and other solution processing operations on unmodified cellulose with companies developing large patent portfolios on cellulose/ionic liquid solutions. In support of such technologies, a fundamental study of the flow properties of cellulose solutions in ionic liquids is planned. Since there are several unusual aspects of cellulose/ionic liquid rheology, including a seemingly large effect of trace amounts of water, this research may be transformative and enabling. This study will provide a basis for understanding the rheology of native cellulose, enabling it to be processed in ionic liquid solutions. This green processing scheme allows cellulose to be processed without chemical modification, which is already known to produce fibers with superior mechanical properties, and ionic liquids are nonvolatile and routinely water-extracted from the cellulose to be 99% recovered without use of any volatile organic solvents. Consequently, ionic liquid solutions may provide a viable pathway to high modulus polymer products from renewable resources that are non-petroleum based.Technical: At a given concentration, ionic liquid solutions have higher viscosity than aqueous solutions and are slightly more elastic (longer relaxation time); both are advantageous for stability of coating and fiber spinning operations. The planned rheology experiments will thoroughly characterize the viscoelastic response of cellulose in three ionic liquids (one that appears to be a theta-solvent and another that preliminary data suggests to be a good solvent) over wide ranges of temperature and concentration. While the concentration dependences of viscosity, relaxation time and terminal modulus of dry cellulose/ionic liquid solutions in linear response have the expected scalings, the linear viscoelasticity is quite sensitive to small quantities of water. Additionally, unexpected results are observed in stronger shear flows relevant to coating, fiber spinning and other solution processing; the shear viscosity is significantly larger than the linear viscosity from oscillatory shear, whereas conventional polymer solutions either show the two to be identical or find the shear viscosity is lower from chain alignment in shear. This will be explored in detail using X-ray scattering in shear flow to detect alignment of cellulose chains. The PI and his team will also begin to explore the solution rheology of other polysaccharides (chitin/chitosan, the second-most abundant polymeric natural resource on the planet) in ionic liquids.

摘要非技术：纤维素是地球上最丰富的可再生聚合物自然资源。 多年来，纤维素经过化学改性，使其具有水溶性或至少具有水分散性，从而能够对纤维素进行溶液加工。 然而，这种改性是昂贵的，并且会抑制赋予最终机械性能的纤维素的结晶。 离子液体是非挥发性溶剂，最近发现某些离子液体可以溶解天然纤维素。 目前，针对未改性纤维素的纤维纺丝和其他溶液加工操作进行了大量的工业研究，公司开发了有关纤维素/离子液体解决方案的大量专利组合。 为了支持此类技术，计划对离子液体中纤维素溶液的流动特性进行基础研究。 由于纤维素/离子液体流变学有几个不寻常的方面，包括痕量水的看似巨大的影响，因此这项研究可能具有变革性和可行性。 这项研究将为了解天然纤维素的流变学提供基础，使其能够在离子液体溶液中进行加工。 这种绿色加工方案允许在不进行化学改性的情况下加工纤维素，众所周知，化学改性可以生产出具有优异机械性能的纤维，并且离子液体是非挥发性的，并且通过常规水从纤维素中提取，可以在不使用任何挥发性有机溶剂的情况下回收99% 。 因此，离子液体溶液可以提供一条从非石油基可再生资源生产高模量聚合物产品的可行途径。技术：在给定浓度下，离子液体溶液比水溶液具有更高的粘度，并且弹性稍强（松弛时间更长） ）；两者都有利于涂层和纤维纺丝操作的稳定性。 计划中的流变学实验将彻底表征纤维素在三种离子液体（一种似乎是θ溶剂，另一种初步数据表明是良好溶剂）中在较宽的温度和浓度范围内的粘弹性响应。 虽然线性响应中干纤维素/离子液体溶液的粘度、弛豫时间和末端模量的浓度依赖性具有预期的比例，但线性粘弹性对少量的水相当敏感。 此外，在与涂层、纤维纺丝和其他溶液加工相关的更强剪切流中观察到意想不到的结果；剪切粘度明显大于振荡剪切产生的线性粘度，而传统聚合物溶液要么显示两者相同，要么发现剪切粘度因剪切中的链排列而较低。 我们将使用剪切流中的 X 射线散射来检测纤维素链的排列，对此进行详细探索。 首席研究员和他的团队还将开始探索离子液体中其他多糖（甲壳素/壳聚糖，地球上第二丰富的聚合自然资源）的溶液流变学。