Rational Design of Internal Interfaces in Multicomponent Polymer Blends

abstractcts - 9805852 n。对多组分聚合物共混物的微观结构和内部界面进行了系统的实验研究。尽管对这些系统进行了数年的研究，但许多基本问题仍未解决。最近的理论研究[Schick， 1997, and Muthukumar， 1997]表明在两种均聚物和一种嵌段共聚物的相对简单的混合物中存在多种复杂相。预测相与在油/水/表面活性剂混合物中发现的相相似，并且具有高密度的内部界面。这些理论对导致这些结构的参数（分子量、温度等）做出了明确的、可实验验证的预测。将对聚烯烃共混物进行实验。模型材料，其分子量和组成是基于理论处方，将通过阴离子聚合合成。表征微结构的主要手段是中子和光散射。内部界面的曲率和界面厚度等属性将由静态散射实验确定。选择性标记和对比匹配将被用于关注多组分混合物中的特定组分。特别是，使用标记嵌段共聚物，如果双嵌段是一种活性界面剂并涂覆在内部界面上，则可以直接研究界面。由于缓慢的动力学和亚稳中间结构的存在，在聚合物体系中达到平衡并不总是可能的。通过时间分辨散射实验研究共混物从相图的一个区域淬火到另一个区域时的结构演变。主要目标是确定导致调制相形成的条件[Bates， 1997]：具有长程有序的多组分有序相，以及缺乏长程有序的周期性结构的微乳液。在多组分聚合物共混物中缺乏连贯的界面设计策略是公认的。我们打算获得的基本知识将是朝着制定这种战略迈出的一步。新材料也可能从我们的实验中出现。在油水体系中，有序相由于其固体性质而没有受到太多关注。聚合物基有序材料在需要固体性质的结构应用中可能很有价值。内部界面的热力学稳定性将导致更好的加工特性。剪切诱导的相变可能导致在静态条件下无法获得的新形态

ABSTRACTCTS-9805852N. BalsaraPolytechnic U. @ NYA systematic experimental study of microstructure and internal interfaces in multicomponent polymer blends is proposed. In spite of several years of research on these systems, many fundamental issues remain unresolved. The proposed work is motivated by recent theoretical work [Schick, 1997, and Muthukumar, 1997] that indicate the presence a variety of complex phases in relatively simple mixtures of two homopolymers and a block copolymer. The predicted phases are similar to those found in oil/water/surfactant mixtures, and are characterized by a high density of internal interfaces. These theories make explicit and experimentally testable predictions of the parameters (molecular weight, temperature, etc.) that will lead to these structures. Experiments will be conducted on polyolefin blends. Model materials, with molecular weights and compositions that are based on theoretical prescriptions, will be synthesized via anionic polymerization. The main characterization tools of microstructure will be neutron and light scattering. The curvature and other attributes such as interfacial thickness of the internal interfaces will be determined from static scattering experiments. Selective labeling and contrast matching will be used to focus on specific components in the multicomponent blends. In particular, the use of a labeled block copolymer, will enable a direct study of the interface, if the diblock is an active interfacial agent and coats the internal interfaces. Achieving equilibrium in polymer systems is not always possible, due to slow kinetics and the presence of metastable intermediate structures. Time-resolved scattering experiments will be conducted to study the evolution of structure when the blends are quenched from one region of the phase diagram to another. The main goal is to identify the conditions that lead to the formation of modulated phases [Bates, 1997]: multicomponent ordered phases that possess long range order, and microemulsions which are periodic structures that lack long-range order.The absence of coherent strategies for designing interfaces in multicomponent polymer blends is well recognized. The fundamental knowledge that we propose to obtain will be a step toward developing such strategies. New materials may also emerge from our experimentation. In oil/water systems ordered phases have not received much attention due to their solid-like properties. Polymer-based ordered materials may he valuable in structural applications where solid-like properties are necessary. The thermodynamic stability of the internal interfaces will lead to better processing characteristics. Shear-induced phase transitions may lead to a new morphologies that were not accessible under quiescent conditions.***