Investigating Nanoparticle Organization in Polymer Matrices during Reaction-Induced Phase Transitions and Material Processing
Investigating Nanoparticle Organization in Polymer Matrices during Reaction-Induced Phase Transitions and Material Processing
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DOI：
10.1021/acsami.1c14830
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发表时间：
2021-08-25
影响因子：
9.5
通讯作者：
Hickey, Robert J.
中科院分区：
文献类型：
--
作者：
LaNasa, Jacob A.;Neuman, Anastasia;Hickey, Robert J.
控制聚合物基质中纳米颗粒的组织一直是一个长期存在的问题，并直接影响到材料的性能。在大多数情况下，简单地混合纳米颗粒和聚合物会导致大范围的聚集，从而产生有害的影响。物理混合纳米粒子和聚合物等独立组分的另一种方法是在单相单体/纳米粒子混合物中进行聚合。在这里，我们报道了纳米颗粒在杂化材料中的聚集机理，在杂化材料中，金纳米颗粒最初均匀分散在单体混合物中，然后在聚合和材料加工过程中经历两步聚集过程。具体地说，首先在甲基丙烯酸甲酯(MMA)溶液中合成了油胺功能化的金纳米颗粒(AuNP)，然后利用偶氮二异丁腈(AIBN)引发的自由基聚合制备了AuNP和聚甲基丙烯酸甲酯(PMMA)杂化材料。所产生的产物很容易被压制以获得纳米颗粒组织被定义为均匀分散或聚集的块状薄膜。聚合反应在不同的温度(T)和MMA体积分数(Phi(MMA))下进行，以系统地影响最终的纳米粒子分散状态。在MMA的聚合和后续的材料加工过程中，最初均一的AuNP/MMA混合物在聚合过程中经历了PMMA和油胺之间的大相分离，但AuNP分散在油胺相中。然后，当材料经过真空干燥和压制处理时，纳米颗粒聚集在油胺相中。通过结合使用透射电子显微镜(TEM)和小角X射线散射(SAXS)来跟踪纳米粒子在聚合和加工步骤中的组织结构。金纳米粒子在PMMA块体薄膜中的分散状态最终由PMMA和油胺相混合的热力学决定，但纳米粒子的聚集机理发生在与材料聚合和加工相对应的两个步骤中。Flory-Huggins混合理论用于支持PMMA和油胺的相分离。报道的结果强调了非平衡过程和平均场近似的结合如何揭示了通过反应诱导相变合成的杂化材料中纳米粒子的聚集。
Controlling nanoparticle organization in polymer matrices has been and is still a long-standing issue and directly impacts the performance of the materials. In the majority of instances, simply mixing nanoparticles and polymers leads to macroscale aggregation, resulting in deleterious effects. An alternative method to physically blending independent components such as nanoparticle and polymers is to conduct polymerizations in one-phase monomer/nanoparticle mixtures. Here, we report on the mechanism of nanoparticle aggregation in hybrid materials in which gold nanoparticles are initially homogeneously dispersed in a monomer mixture and then undergo a two-step aggregation process during polymerization and material processing. Specifically, oleylamine-functionalized gold nanoparticles (AuNP) are first synthesized in a methyl methacrylate (MMA) solution and then subsequently polymerized by using a free radical polymerization initiated with azobis(isobutyronitrile) (AIBN) to create hybrid AuNP and poly(methyl methacrylate) (PMMA) materials. The resulting products are easily pressed to obtain bulk films with nanoparticle organization defined as either well-dispersed or aggregated. Polymerizations are performed at various temperatures (T) and MMA volume fractions (Phi(MMA)) to systematically influence the final nanoparticle dispersion state. During the polymerization of MMA and subsequent material processing, the initially homogeneous AuNP/MMA mixture undergoes macrophase separation between PMMA and oleylamine during the polymerization, yet the AuNP are dispersed in the oleylamine phase. The nanoparticles then aggregate within the oleylamine phase when the materials are processed via vacuum drying and pressing. Nanoparticle organization is tracked throughout the polymerization and processing steps by using a combination of transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). The resulting dispersion state of AuNPs in PMMA bulk films is ultimately dictated by the thermodynamics of mixing between the PMMA and oleylamine phases, but the mechanism of nanoparticle aggregation occurs in two steps that correspond to the polymerization and processing of the materials. Flory-Huggins mixing theory is used to support the PMMA and oleylamine phase separation. The reported results highlight how the integration of nonequilibrium processing and mean-field approximations reveal nanoparticle aggregation in hybrid materials synthesized by using reaction-induced phase transitions.