Studies on Polymer Glasses, Melts, and Solutions

聚合物玻璃、熔体和溶液的研究

• 批准号: 0804593
• 负责人: Jane Lipson
• 金额: $ 30万
• 依托单位: Dartmouth College
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-09-15 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0804593&HistoricalAwards=false
• 关键词: Studies; Polymer; Glasses; Melts; Solutions

TECHNICAL SUMMARY:This award supports research and education in studies of polymer glasses, melts, and solutions. The award is being support by the Division of Chemistry and the Division of Materials Research. The activity largely resides in two areas, polymer phase transitions and the impact of deuteration and local branching on the miscibility of polymer solutions and blends.Polymer thin films are studied which exhibit a glass transition where the polymer transforms from a glassy to a rubbery solid upon heating, a phenomenon which is usually explained through local relaxations. Though a glass transition is not itself unusual, the recent observation that the presence of a substrate and/or a free surface may have a long-range and significant impact on the glass transition of the polymer stimulates this research. The research develops theoretical models and computer simulations to address questions such as the why shifts in the glass transition of polymeric films may persist over tens of nanometers from the surface or substrate. There are two scenarios investigated. In one, the polymer film is supported by a substrate, in which case the glass transition of the film has been observed to occur tens of degrees above the bulk temperature. Conversely, the influence of a surface leads to a steep drop in the glass transition, particularly when the film is free-standing (has two free surfaces). In all cases the magnitude of the temperature shift depends on the choice of polymer and the film thickness. This proposal outlines a new model for the glass transition of thin film polymers, one which will address both the magnitude of the temperature shifts and the length scales over which they occur.The second area of research focuses on the impact of deuteration and local branching on the miscibility of polymer solutions and blends. The replacement of hydrogen for deuterium is employed in small angle neutron scattering experiments to study such systems. This isotopic exchange has an impact on miscibility which ranges from essentially nil to extremely significant. In the research carried out here, a theoretical analysis is outlined which will lead to a predictive tool for assessing the anticipated effect of deuteration. Another local change results in measurable shifts in miscibility is the incorporation of branches. These variations in local chain connectivity are characteristic of polyolefins. Research done here builds upon initial evidence that the theoretical methods developed to study deuteration effects can also apply for this category of structural change.The effort undertaken has broader impacts with both technological and educational consequences. In this work the theoretical tools developed by the PI to study complex fluids will be used to make testable predictions on polymer glasses and mixtures. The outcome is that a more sophisticated combination of strategies, accessible to the materials community, will be available in solving problems relating to understanding connections between microscopic structure and macroscopic behavior. The polymer thin films studied here are the subject of significant interest due to their potential for application in areas such as optics, catalysis, and electronics, as well as their ubiquitous presence in polymer nanocomposites. The polyolefins specifically are a class of polymers which have wide industrial application. The research activities involve graduates and postdoctoral fellows who are being trained in computer simulations methods and associated theory of polymer materials. Research results are disseminated through conference presentations by the PI and her research group at national meetings and in refereed publications. The PI's efforts in research and teaching mentorship have resulted in an increase in the number of women in the ranks of graduate and postgraduate students and in faculty.NONTECHNICAL SUMMARY:This award supports research and education in studies of polymer materials. The award is being support by the Division of Chemistry and the Division of Materials Research. The activity largely resides in two areas, polymer phase changes and the mixing properties of polymer solutions and blends.Polymer thin films are studied which exhibit a glass transition where the polymer transforms from a glassy to a rubbery solid upon heating. Though a glass transition is not itself unusual, the recent observation that the presence of a surface may have a significant impact on the glass transition of the polymer stimulates this research. The research develops theoretical models and computer simulations to address questions such as the why shifts in the surface structure of polymeric films may persist deep into the film. There are two scenarios investigated. In one, the polymer film is supported by a substrate, in which case the glass transition of the film has been observed to occur tens of degrees above the usual temperature. Conversely, the influence of a surface leads to a steep drop in the glass transition onset, particularly when the film is free-standing (has two free surfaces). In all cases the magnitude of the temperature shift depends on the choice of polymer and the film thickness. This proposal outlines a new model for the glass transition of thin film polymers, one which will address both the magnitude of the temperature shifts and the length scales over which they occur.The second area of research focuses on the impact of deuteration and local branching on the mixing of polymer solutions and blends. In the research carried out here, a theoretical analysis is outlined which will lead to a predictive tool for assessing the anticipated effects. One factor investigated is the changes in mixing properties when the polymer molecules have side branches as opposed to being primarily long chains which is a characteristic of polyolefins. Research done here builds upon initial evidence that the theoretical methods developed in previous studies can also apply for this category of structural change.The effort undertaken has broader impacts with both technological and educational consequences. In this work the theoretical tools developed by the PI to study complex fluids will be used to make testable predictions on polymer glasses and polymer mixtures. The outcome is that a more sophisticated combination of strategies, accessible to the materials community, will be available in solving problems relating to understanding connections between molecular level structure and behavior of the material as a whole. The polymer thin films studied here are the subject of significant interest due to their potential for application in areas such as optics, catalysis, and electronics, as well as their ubiquitous presence in polymer nanocomposites. The polyolefins specifically are a class of polymers which have wide industrial application. The research activities involve graduates and postdoctoral fellows who are being trained in computer simulations methods and associated theory of polymer materials. Research results are disseminated through conference presentations by the PI and her research group at national meetings and in refereed publications. The PI's efforts in research and teaching mentorship have resulted in an increase in the number of women in the ranks of graduate and postgraduate students and in faculty

技术概述：该奖项支持聚合物玻璃，熔体和解决方案的研究和教育。该奖项由化学部和材料研究部支持。这种活性主要存在于两个方面，即聚合物相变以及氘化和局部分支对聚合物溶液和共混物的混相性的影响。研究了聚合物薄膜表现出玻璃化转变，即聚合物在加热时从玻璃状固体转变为橡胶状固体，这种现象通常通过局部松弛来解释。虽然玻璃化转变本身并不罕见，但最近观察到，衬底和/或自由表面的存在可能对聚合物的玻璃化转变产生长期而重要的影响，这激发了这项研究。该研究开发了理论模型和计算机模拟，以解决诸如为什么聚合物薄膜的玻璃化转变可能会从表面或衬底持续数十纳米的问题。这里调查了两种情况。在一种情况下，聚合物薄膜由衬底支撑，在这种情况下，已经观察到薄膜的玻璃化转变发生在比本体温度高几十度的地方。相反，表面的影响导致玻璃化转变的急剧下降，特别是当薄膜是独立的（有两个自由表面）时。在所有情况下，温度变化的幅度取决于聚合物的选择和薄膜的厚度。本提案概述了薄膜聚合物玻璃化转变的新模型，该模型将解决温度变化的幅度和它们发生的长度尺度。第二个研究领域集中在氘化和局部分支对聚合物溶液和共混物的混相的影响。在小角中子散射实验中，采用氢代氘的方法对这类体系进行了研究。这种同位素交换对混相的影响从基本为零到极其显著。在这里进行的研究中，概述了一个理论分析，这将导致评估氘化预期效果的预测工具。另一个导致可测量的混相变化的局部变化是分支的合并。这些局部链连通性的变化是聚烯烃的特征。这里的研究建立在初步证据的基础上，这些证据表明，用于研究氘化效应的理论方法也适用于这类结构变化。所进行的努力在技术和教育方面都产生了更广泛的影响。在这项工作中，PI开发的用于研究复杂流体的理论工具将用于对聚合物玻璃和混合物进行可测试的预测。结果是，材料界可以使用更复杂的策略组合来解决与理解微观结构和宏观行为之间的联系有关的问题。由于聚合物薄膜在光学、催化和电子学等领域的应用潜力，以及它们在聚合物纳米复合材料中的普遍存在，因此，本文所研究的聚合物薄膜是一个非常有趣的主题。聚烯烃是一类具有广泛工业应用的聚合物。研究活动涉及研究生和博士后，他们正在接受计算机模拟方法和聚合物材料相关理论的培训。研究成果通过PI及其研究小组在国家会议上的会议报告和经评审的出版物传播。PI在研究和教学指导方面的努力使研究生和研究生以及教员中的妇女人数有所增加。非技术总结：该奖项支持高分子材料研究的研究和教育。该奖项由化学部和材料研究部支持。活性主要存在于两个方面，聚合物的相变化和聚合物溶液和共混物的混合特性。研究了具有玻璃化转变的聚合物薄膜，其中聚合物在加热时从玻璃状转变为橡胶状固体。虽然玻璃化转变本身并不罕见，但最近观察到表面的存在可能对聚合物的玻璃化转变产生重大影响，这激发了这项研究。该研究开发了理论模型和计算机模拟来解决诸如为什么聚合物薄膜表面结构的变化可能会持续到薄膜深处等问题。这里调查了两种情况。在一种情况下，聚合物薄膜由衬底支撑，在这种情况下，已经观察到薄膜的玻璃化转变发生在比通常温度高几十度的地方。相反，表面的影响导致玻璃化转变开始的急剧下降，特别是当膜是独立的（有两个自由表面）时。在所有情况下，温度变化的幅度取决于聚合物的选择和薄膜的厚度。本提案概述了薄膜聚合物玻璃化转变的新模型，该模型将解决温度变化的幅度和它们发生的长度尺度。第二个研究领域集中在氘化和局部分支对聚合物溶液和共混物混合的影响。在这里进行的研究中，概述了理论分析，这将导致评估预期效果的预测工具。研究的一个因素是当聚合物分子具有侧分支而不是主要是长链时混合性能的变化，这是聚烯烃的特征。这里所做的研究建立在初步证据的基础上，即以前研究中发展的理论方法也可以适用于这类结构变化。所进行的努力在技术和教育方面都产生了更广泛的影响。在这项工作中，PI开发的用于研究复杂流体的理论工具将用于对聚合物玻璃和聚合物混合物进行可测试的预测。结果是，一个更复杂的策略组合，材料社区可以访问，将可用于解决有关理解分子水平结构和材料整体行为之间联系的问题。由于聚合物薄膜在光学、催化和电子学等领域的应用潜力，以及它们在聚合物纳米复合材料中的普遍存在，因此，本文所研究的聚合物薄膜是一个非常有趣的主题。聚烯烃是一类具有广泛工业应用的聚合物。研究活动涉及研究生和博士后，他们正在接受计算机模拟方法和聚合物材料相关理论的培训。研究成果通过PI及其研究小组在国家会议上的会议报告和经评审的出版物传播。PI在研究和教学指导方面的努力使研究生和研究生以及教员中的妇女人数有所增加