Deformation-induced changes in segmental dynamics of polymer glasses prepared by melt stretching and stress aging

熔融拉伸和应力老化制备的聚合物玻璃的变形引起的链段动力学变化

• 批准号: 2002959
• 负责人: Mark Ediger
• 金额: $ 47.05万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2002959&HistoricalAwards=false
• 关键词: Deformation; induced; changes; segmental; dynamics

NON-TECHNICAL SUMMARY:Polymer glasses are important materials due to their high transparency, the low energy input required for molding them into particular shapes, their stiffness, and their resistance to breakage. Polymer glasses are used in applications as diverse as advanced aircraft composites and eyeglass lenses. The planned research will investigate how polymer glasses respond when they are subjected to large forces. In particular, the experiments will use lasers and microscopes to measure how the polymer molecules rearrange when a polymer glass is deformed. Current theories and computer simulations have identified this molecular motion as a key quantity that must be understood to determine if a polymer glass will stretch, deform, or break. The polymer glasses to be used will be processed in special ways (stretched at high temperature or deformed at low temperature) to critically test these simulations and theories. The proposed experiments should lead to more reliable models for the prediction of the mechanical properties of polymer glasses. This in turn may have a significant economic impact because of the broad potential of these lightweight materials. The students involved in this project will learn how to characterize polymer glasses and improve the properties of materials. All personnel supported by this grant will participate in a program to increase the number of highly qualified students from underrepresented groups that enter Ph.D. programs in the U.S.TECHNICAL SUMMARY:The deformation properties of polymer glasses are extremely challenging to predict as a result of the nonlinear nature of the deformation and the nonequilibrium nature of the glass. Here it is proposed to measure segmental mobility in polymer glasses during deformation using an optical photobleaching method that provides access to the rotational correlation function of an ensemble of dilute probe molecules. Deformation can increase segmental mobility in polymer glasses by more than a factor of 1000, and an understanding of this enhanced mobility is a key requirement for accurate modeling of the mechanical properties of polymer glasses. For the proposed work, polymer glasses will be prepared by melt quenching so that subsequent mobility measurements during deformation can disentangle the influences of yield and strain hardening on segmental mobility. The proposed work will also test whether deformed polymer glasses can show indications of overaging, i.e., physical aging that occurs at an accelerated rate as a result of applied stress. Finally, the generality of the results obtained in tensile deformation will be tested by performing optical measurements of segmental mobility during shear deformation. The proposed experiments can provide a molecular-level test of theoretical descriptions of polymer glass deformation. The experimental results obtained, in comparison with theory and simulation, should lead to an enhanced fundamental understanding of the deformation of polymer glasses. All personnel supported by this grant will participate in a program to increase the number of highly qualified students from underrepresented groups that enter Ph.D. programs in the U.S..This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

非技术摘要：聚合物玻璃是重要的材料，因为它们的透明度很高，将它们成型为特定形状所需的低能量输入，它们的刚度以及对破裂的抵抗力。聚合物眼镜用于等级飞机复合材料和眼镜镜片的应用。计划的研究将调查聚合物玻璃在受到大力量时的反应。特别是，实验将使用激光和显微镜来测量聚合物分子在变形时如何重新排列。当前的理论和计算机模拟已将这种分子运动确定为一个关键量，必须理解，以确定聚合物玻璃是否会伸展，变形或破裂。要使用的聚合物玻璃将以特殊的方式（在高温下或在低温下变形）进行严格测试这些模拟和理论。提出的实验应导致更可靠的模型，以预测聚合物玻璃的机械性能。 反过来，由于这些轻质材料的广泛潜力，这可能会产生重大的经济影响。 参与该项目的学生将学习如何表征聚合物眼镜并改善材料的特性。这笔赠款支持的所有人员将参加一项计划，以增加进入博士学位的代表性不足的团体的高素质学生人数。美国技术摘要中的程序：由于变形的非线性性质和玻璃的非平衡性质，聚合物玻璃的变形特性非常具有挑战性。在这里，建议在变形过程中使用光漂白方法测量聚合物玻璃中的分段迁移率，该方法可访问稀释探针分子集合的旋转相关函数。 变形可以使聚合物玻璃杯中的分段迁移率提高1000倍以上，并且了解这种增强的迁移率是准确建模聚合物玻璃的机械性能的关键要求。对于拟议的工作，聚合物玻璃将通过熔融淬火来制备，以便在变形过程中随后的迁移率测量可以解散产量和应变硬化对节段迁移率的影响。拟议的工作还将测试变形的聚合物玻璃是否可以显示出过度分娩的迹象，即由于施加的应力而以加速速率发生的物理衰老。 最后，将通过在剪切变形过程中对分段迁移率进行光学测量来测试在拉伸变形中获得的一般性。提出的实验可以提供对聚合物玻璃变形的理论描述的分子级检验。与理论和仿真相比，获得的实验结果应导致对聚合物玻璃变形的基本理解。这笔赠款支持的所有人员将参加一项计划，以增加进入博士学位的代表性不足的团体的高素质学生人数。美国的计划。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的评论标准来评估值得支持的。

项目成果

Segmental Dynamics in the Strain-Hardening Regime for Poly(methyl methacrylate) Glasses with and without Melt Stretching

• DOI: 10.1021/acs.macromol.2c01442
• 发表时间: 2022-09
• 期刊: Macromolecules
• 影响因子: 5.5
• 作者: Enran Xing;Trevor Bennin;M. Razavi;M. Ediger

Overaging with Stress in Polymer Glasses? Faster Segmental Dynamics despite Larger Yield Stress!

• DOI: 10.1021/acs.macromol.2c01338
• 发表时间: 2022-11
• 期刊: Macromolecules
• 影响因子: 5.5
• 作者: M. Razavi;Enran Xing;M. Ediger

Rejuvenation Versus Overaging: The Effect of Cyclic Loading/Unloading on the Segmental Dynamics of Poly(methyl methacrylate) Glasses

• DOI: 10.1021/acs.macromol.0c01489
• 发表时间: 2020-09
• 期刊: Macromolecules
• 影响因子: 5.5
• 作者: Trevor Bennin;Enran Xing;J. Ricci;M. Ediger

Multistep Deformation Experiment and Development of a Model for the Mechanical Behavior of Polymeric Glasses

• DOI: 10.1021/acs.macromol.2c00711
• 发表时间: 2022-07
• 期刊: Macromolecules
• 影响因子: 5.5
• 作者: G. Medvedev;Enran Xing;M. Ediger;J. Caruthers