Melt-Miscible Polyethylene Block Copolymers

熔融混溶聚乙烯嵌段共聚物

• 批准号: 1402180
• 负责人: Richard Register
• 金额: $ 56万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1402180&HistoricalAwards=false
• 关键词: Melt; Miscible; Polyethylene; Block; Copolymers

TECHNICAL SUMMARY:Hydrocarbon polymers exhibiting a low interaction energy density (X, proportional to the Flory-Huggins interaction parameter) against polyethylene (PE) will be developed; combining these polymers with PE in the form of block copolymer can lead to either higher-strength semicrystalline plastics, or easily-processed melt-miscible thermoplastic elastomers, depending on polymer composition and block architecture. Recently, it has been shown that certain polymers prepared via ring-opening metathesis polymerization (ROMP) of norbornene derivatives followed by catalytic hydrogenation show a relatively low X against PE, though those particular ROMP polymers have glass transition temperatures (Tg) slightly below room temperature, hence providing no mechanical reinforcement. This project will investigate other substituted norbornenes, including polymers with phenyl, cyclohexyl, and norbornyl sidegroups, all of which show Tg well above room temperature. Interaction strengths between these polymers, collectively denoted as "PX", and between these polymers and linear PE (LPE, prepared by hydrogenation of ROMP polycyclopentene), will be measured via the synthesis of well-defined block copolymers, at targeted molecular weights, and measurements of the melt phase behavior, including the thermotropic order-disorder transition temperature, by small-angle x-ray scattering. Random copolymer blocks will be employed to tune the solubility parameter of the norbornene-based PX block, to promote miscibility with LPE. The measured interaction energy densities will be interpreted within a solubility parameter framework if found to obey regular mixing (generating a solubility parameter "ladder" where each "rung" is a novel ROMP polymer), or within a ternary mixing framework if found to mix irregularly. These frameworks will, in turn, permit the design of PE-containing materials -- through selection of block chemistries and lengths -- which will form homogeneous, easily-processed melts. Two particular architectures will be explored, as "test beds" for the property modifications which can be achieved through the incorporation of high-Tg PX blocks: PX-LPE-PX triblocks with a majority crystallizable midblock, and LPE-PX-rubber-PX-LPE pentablocks, with a majority rubbery midblock. NON-TECHNICAL SUMMARY:Polyethylene (PE) is far and away the most ubiquitous synthetic polymer -- 39 billion pounds produced in the US in 2012 (and increasing, with the availability of ethylene from shale gas) -- and is familiar in daily life in applications ranging from milk jugs to weatherproofing sheet to hip replacements. PE is also combined with other polymers, in the form of a block copolymer -- where the two polymers are covalently bound -- in numerous specialty applications, including thermoplastic elastomers (TPEs): rubbers which can be melt-processed and recycled. In TPEs, melt-miscibility between the blocks facilitates melt-processing, greatly diminishing the amount of energy required. The present work seeks to develop a polymer which is both melt-miscible with PE and which has a glass transition temperature (softening point) above room temperature, to impart the strength characteristic of glassy polymers to the final block copolymer. The proposed work will provide an integrated research and educational experience for three to four graduate students and three to six undergraduates. Students will become expert in the synthesis of well-defined polymers, macromolecular characterization, structural characterization by small-angle x-ray scattering, polymer mixing thermodynamics, and polymer mechanical properties and structure-property relationships. By having students work across all phases of the project, from synthesis to test application, they gain a "big picture" outlook which will serve them well as a future foundation. The PI and students will engage the general public through science outreach, on the Princeton University campus and nearby schools, most immediately through the development of a large-auditorium "Polymer Show" to debut in 2014. A specific aim is to promote interest in, and appreciation for, polymeric materials science and technology among middle school students, including those in the Trenton public school system.

技术概述：将开发与聚乙烯（PE）具有低相互作用能密度（X，与Flory-Huggins相互作用参数成正比）的碳氢聚合物；将这些聚合物与PE以嵌段共聚物的形式结合，根据聚合物的组成和嵌段结构，可以得到高强度的半结晶塑料或易于加工的熔融混溶热塑性弹性体。最近，有研究表明，通过降冰片烯衍生物的开环分解聚合（ROMP）和催化加氢制备的某些聚合物对PE的X值相对较低，尽管这些特定的ROMP聚合物的玻璃化转变温度（Tg）略低于室温，因此没有提供机械增强。该项目将研究其他取代的降冰片烯，包括苯基、环己基和降冰片基侧基的聚合物，所有这些聚合物的Tg都远高于室温。这些聚合物（统称为“PX”）之间的相互作用强度，以及这些聚合物与线性聚乙烯（LPE，由ROMP聚环戊烯加氢制备）之间的相互作用强度，将通过合成定义明确的嵌段共聚物来测量，在目标分子量下，以及通过小角度x射线散射测量熔融相行为，包括热致有序-无序转变温度。随机共聚物嵌段将用于调整降冰片烯基PX嵌段的溶解度参数，以促进与LPE的混相。测量的相互作用能量密度，如果发现服从规则混合，将在溶解度参数框架内解释（生成溶解度参数“阶梯”，其中每个“梯级”是一种新的ROMP聚合物），或者如果发现不规则混合，将在三元混合框架内解释。反过来，这些框架将允许设计含有pe的材料——通过选择块化学物质和长度——这将形成均匀的、易于加工的熔体。将探索两种特殊的体系结构，作为可以通过结合高tg PX块来实现属性修改的“试验台”：具有大部分可结晶性中间块的PX- lpe -PX三块和具有大部分橡胶中间块的lpe -PX- PX- lpe五块。非技术总结：聚乙烯（PE）无疑是最普遍的合成聚合物——2012年在美国生产了390亿磅（随着页岩气中乙烯的可用性，这一数字还在增加）——在日常生活中，从牛奶罐到防风化板再到髋关节置换术，都有很常见的应用。PE也与其他聚合物结合，以嵌段共聚物的形式，两种聚合物共价结合，在许多特殊应用中，包括热塑性弹性体（TPEs）：可以熔融加工和回收的橡胶。在tpe中，块体之间的熔体混相有利于熔体加工，大大减少了所需的能量。目前的工作旨在开发一种聚合物，它既可以与PE熔融混溶，又具有高于室温的玻璃化转变温度（软化点），从而将玻璃化聚合物的强度特性赋予最终的嵌段共聚物。拟议的工作将为3至4名研究生和3至6名本科生提供综合研究和教育经验。学生将精通聚合物的合成、大分子表征、小角度x射线散射的结构表征、聚合物混合热力学、聚合物力学性能和结构-性能关系。通过让学生在项目的所有阶段工作，从合成到测试应用，他们获得了一个“大局观”，这将为他们未来的基础服务。PI和学生们将在普林斯顿大学校园和附近的学校通过科学宣传吸引公众，最直接的方式是开发一个大型礼堂的“聚合物展”，将于2014年首次亮相。一个具体的目标是促进中学生对聚合物材料科学和技术的兴趣和欣赏，包括特伦顿公立学校系统的学生。