Magnetically-Driven Orientation of Multiphase Polymer Systems: A Ligand-Functionalized, Magnetic Nanoparticle Approach

多相聚合物系统的磁驱动取向：配体功能化的磁性纳米粒子方法

• 批准号: 0967559
• 负责人: Richard Spontak
• 金额: $ 30万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-05-01 至 2014-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0967559&HistoricalAwards=false
• 关键词: Magnetically; Driven; Orientation; Multiphase; Polymer

Proposal Number: 0967559P.I.: Richard SpontakInterest in dispersing inorganic nanoparticles (NPs) in polymeric matrices continues to increase as a viable and facile means by which to enhance the mechanical, optical, electrical, and magnetic properties of organic polymers. While many studies have focused on using the (co)polymer matrix to spatially modulate the NPs, the overarching objective of the present proposal is to demonstrate the feasibility of using field aligned surface functionalized magnetic nanoparticles (NPs) to direct phase orientation and therefore generate new multiphase polymer morphologies with potentially new anisotropic properties. The effects of magnetic NP chains formed in homogeneous polymer mixtures by externally applied, uniform magnetic fields, on the nano/microstructure during (micro)phase separation will be explored in two systems: polymer blends and block copolymers composed of polystyrene and poly(methyl methacrylate) (PS/PMMA). We hypothesize that, due to the formation of NP chains along the field direction, the blends will form highly elongated phase domains or possibly layers instead of conventional spheroidal domains, whereas the lamellae in the copolymer will align with the NPs to form large grain sizes (with a reduced number of defects). The NP surfaces with native long chained aliphatic functional groups are expected to agglomerate at the interface in both systems and thus serve as stabilizing sites. This prediction will be verified using magnetic (Co and Fe3O4) NPs under magnetic fields of up to 20 kOe to induce formation of linear NP chains. These NP chains, responsible for observed ferrofluid behavior, are predicted to template formation of the interface through their pinning behavior. To explore a different regime of thermodynamic behavior, NPs will be functionalized with oligostyrene (OS) or oligo(methyl methacrylate) (OMMA) to impart selective solubility in one of the polymer species. The field aligned nano/microstructures will be compared for magnetic NP chain formation at the interface versus within one of the (micro)domains. Binary core Au/Fe3O4 NPs will also be prepared. Owing to the distinct Au and Fe3O4 surface chemistries, each half will be independently functionalized one half with OPS, and the other with OMMA, to form Janus NPs. The possibility of altering interfaces with oriented Au/Fe3O4 NPs will be explored. Multiscale molecular dynamics simulations complementing experiments will be performed to (i) provide a theoretical framework of the dynamics of NP chain formation and (ii) guide experimental design by establishing operational thresholds.Intellectual Merit: The proposed research will significantly enhance the current understanding of the role that NPs can serve to pin or align phase boundaries in heterogeneous polymer systems. Use of magnetic-field aligned NP chains to template formation of oriented lamellar phase boundaries will be of interest for further studies and applications, since there exists a great need to achieve greater control over morphological orientation in multiphase polymer systems.Broader Impact: The results from the proposed research will be incorporated into two courses at NCSU. In addition to enriching the undergraduate and graduate curriculum through student participation, we plan outreach programs to local students at the K-12 levels through the Kenan Fellows Program at NCSU. The PIs will endeavor to attract underrepresented and minority students from the RISE (incoming freshman students) and Pack Promise (low income students provided with tuition wavers, research positions, and academic support) programs at NC State. The PIs have successful experience recruiting exemplary students from such student groups.

提案编号：0967559 P.I.：在聚合物基体中分散无机纳米粒子（NPs）的兴趣继续增加，作为一种可行和简便的手段，通过它来增强有机聚合物的机械，光学，电学和磁学性能。虽然许多研究都集中在使用（共）聚合物基质空间调制的纳米粒子，本提案的首要目标是证明使用场对准的表面功能化的磁性纳米粒子（纳米粒子），以指导相取向的可行性，因此产生新的多相聚合物形态与潜在的新的各向异性性能。磁性NP链在均匀聚合物混合物中形成的外部施加的，均匀的磁场，在（微）相分离过程中的纳米/微观结构的影响将在两个系统中探索：聚合物共混物和嵌段共聚物组成的聚苯乙烯和聚（甲基丙烯酸甲酯）（PS/PMMA）。我们假设，由于沿沿着场方向形成NP链，共混物将形成高度伸长的相域或可能的层，而不是传统的球状域，而共聚物中的层状结构将与NP对齐，以形成大的晶粒尺寸（具有减少的缺陷数量）。具有天然长链脂肪族官能团的NP表面预期在两个系统中的界面处聚集，从而充当稳定位点。这一预测将验证使用磁性（Co和Fe 3 O 4）纳米粒子在磁场高达20千奥斯特诱导形成线性NP链。这些NP链，负责观察到的铁磁流体的行为，预测模板形成的界面，通过他们的钉扎行为。为了探索热力学行为的不同机制，将用低聚苯乙烯（OS）或低聚（甲基丙烯酸甲酯）（OMMA）官能化NP，以赋予在聚合物物种之一中的选择性溶解度。将比较场对准的纳米/微米结构在界面处与在（微）域之一内的磁性NP链形成。还将制备二元核Au/Fe 3 O 4 NPs。由于Au和Fe 3 O 4表面化学性质不同，每一半将独立地用OPS官能化，另一半用OMMA官能化，以形成Janus NP。改变界面与定向Au/Fe 3 O 4纳米颗粒的可能性将被探索。多尺度分子动力学模拟补充实验将进行（一）提供一个理论框架的NP链形成的动力学和（二）通过建立操作thresholds.Intellectual优点指导实验设计：拟议的研究将显着提高目前的理解的作用，NP可以作为针或对齐相边界在非均相聚合物系统。使用磁场对齐NP链模板形成的定向层状相边界将是进一步的研究和应用的兴趣，因为存在着很大的需要，以实现更大的控制形态取向多相聚合物systems.Broader影响：从拟议的研究结果将被纳入两个课程在NCSU。除了通过学生参与丰富本科生和研究生课程外，我们还计划通过NCSU的凯南研究员计划向K-12级别的当地学生提供外展计划。PI将奋进吸引来自北卡罗来纳州RISE（新生）和Pack Promise（低收入学生提供学费减免，研究职位和学术支持）计划的代表性不足和少数民族学生。 PI有成功的经验，从这些学生团体招募模范学生。