Rheo-Optics of Stress-Structure Coupling in Complex Fluids

复杂流体中应力-结构耦合的流变光学

• 批准号: 9802610
• 负责人: Jan van Egmond
• 金额: $ 25万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-08-01 至 1999-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9802610&HistoricalAwards=false
• 关键词: Rheo; Optics; Stress; Structure; Coupling

ABSTRACT Proposal Number: CTS-9802610 Principal Investigator: van Egmond This is a grant to develop a better understanding of the coupling between rheology and the development of structure, especially in soft materials that undergo phase transitions and other morphological changes. These materials include polymer systems such as compatible and incompatible blends, solutions, and gels. Other important materials include liquid crystals (LC's) with applications such as polymer dispersed LC droplets for LC display screens and micellar systems with a wide variety of applications in controlled drug delivery, as drag reducing agents in pumped fluids, and as templates for the manufacture of mesoporous silica-based sieves of unprecedented selectivity. Further, it is also important that real-time, on-line instruments that can measure structure during processing be developed. This technology would be of immense value in assuring product quality and reducing waste through a combination of simulation and model-based control schemes. Two key objectives are addressed by this research: (1) the development of novel optical instruments that are crucial for the detection of real-time three dimensional structure and stress in flowing multicomponent polymeric materials; and (2) the characterization of mechanisms through which rheology interacts with phase transitions, structural fluctuations and fluid mechanical instability in model multicomponent polymer and micelles systems. These objectives will be achieved through a combination of non-intrusive optical techniques (birefringence, dichroism and light scattering) to measure molecular and mesoscopic structural evolution, mechanical rheometry to measure macroscopic stress, and modeling. This array of instrumentation will be used to study flow instabilities that occur in complex materials such as polymer solutions that undergo apparent "flow-induced phase separation". According to preliminary results, the driving mechanism for these instabilitie s is the coupling between viscoelastic stresses, convection, and stresses associated with anisotropic meso-structure. The relevance of this work rests on the need to understand instabilities and heterogeneities that occur during the processing of complex materials such as polymer blends. 2 1

摘要建议编号：CTS-9802610首席研究员：范·埃格蒙德这是一项拨款，旨在更好地了解流变学和结构发展之间的耦合，特别是在经历相变和其他形态变化的软材料中。这些材料包括聚合物体系，如相容和不相容的共混物、溶液和凝胶。其他重要材料包括液晶(LC)，用于液晶显示屏的聚合物分散液滴和胶束系统，在受控药物输送中具有广泛的应用，作为泵送流体中的减阻剂，以及用作制造具有前所未有选择性的介孔二氧化硅筛的模板。此外，开发能够在加工过程中测量结构的实时、在线仪器也很重要。这项技术将通过模拟和基于模型的控制方案相结合，在确保产品质量和减少浪费方面具有巨大的价值。这项研究涉及两个关键目标：(1)开发对实时检测流动的多组分聚合物材料的三维结构和应力至关重要的新型光学仪器；(2)表征流变学与模型多组分聚合物和胶束体系中的相变、结构波动和流体机械不稳定性相互作用的机制。这些目标将通过非侵入性光学技术(双折射、二向色性和光散射)来测量分子和介观结构的演变、机械流变学来测量宏观应力和建模来实现。这种仪器阵列将用于研究复杂材料中发生的流动不稳定性，例如经历明显的“流动诱导相分离”的聚合物溶液。根据初步结果，这些不稳定性的驱动机制是粘弹性应力、对流和与各向异性细观结构有关的应力之间的耦合。这项工作的相关性在于需要了解在聚合物混合物等复杂材料的加工过程中发生的不稳定性和异质性。2 1