Characterizing the Areal Density and Desorption Kinetics of Physically Adsorbed Polymer in Polymer Nanocomposite Melts
Characterizing the Areal Density and Desorption Kinetics of Physically Adsorbed Polymer in Polymer Nanocomposite Melts
复制标题
DOI：
10.1021/acs.macromol.9b02205
复制
发表时间：
2020-04-14
期刊：
影响因子：
5.5
通讯作者：
Winey, Karen, I
中科院分区：
文献类型：
--
作者：
Bailey, Eric J.;Griffin, Philip J.;Winey, Karen, I
在聚合物纳米复合材料(PNC)中，纳米粒子(NPs)和聚合物之间的界面区域是增强性能的基础，而这些结合聚合物层的时间稳定性对于扩展PNC性能的控制是必要的。利用离子散射技术，将聚(2-乙烯基吡啶)(P2VP)与26 nm二氧化硅纳米颗粒混合，通过分离和直接测量自由聚合物和聚合物在熔融状态下完全吸附在吸引纳米颗粒上的比例，研究了结合聚合物层的寿命。通过对沉积在大块聚合物基质上的PNC薄膜进行热处理，PNC中的游离聚合物迅速扩散到底层基质中，而熔体中自发形成的结合聚合物仍留在NPs中。通过结合链的分数与NP表面积的关联，我们的分析表明，结合的聚合物链类似于R-g从NP表面延伸到熔体中。计算的熔体中吸附链占据的平均NP表面积远小于对孤立链的预测或在NP聚合物溶液中的测量。结合聚合物的分数随退火时间的增加而减少，并且在较高的温度和较低的相对分子质量下下降得更快。这项工作表明，离子散射法可以定量地测量熔融状态下与纳米粒子结合的聚合物的链尺度结构和动力学。这一新信息提供了基本的见解，并使PNC的设计在制造和使用过程中具有更高的热稳定性。
The interfacial regions between nanoparticles (NPs) and polymers in polymer nanocomposites (PNCs) underlie enhanced properties, and the temporal stability of these bound polymer layers is necessary for extended control on PNC performance. Using ion scattering techniques and poly(2-vinyl pyridine) (P2VP) mixed with 26 nm silica NPs, we investigate the lifetime of the bound polymer layer by separating and directly measuring the fraction of free polymer and polymer adsorbed to attractive NPs entirely in the melt state. By annealing thin PNC films deposited on bulk polymer matrices, free polymer from the PNC rapidly diffuses into the underlying matrix while the spontaneously formed bound polymer in the melt remains with the NPs. By correlating the fraction of bound chains with the NP surface area, our analysis shows that bound polymer chains extend similar to R-g from the NP surface into the melt. The calculated average NP surface area occupied by adsorbed chains in the melt is much smaller than predicted for an isolated chain or measured in an NP-polymer solution. The bound polymer fraction decreases as a function of annealing time and decreases more rapidly at higher temperatures and for lower molecular weights. This work demonstrates that ion scattering methods can quantitatively measure the chain-scale structure and dynamics of polymers bound to NPs in the melt state. This new information provides fundamental insights and enables the design of PNCs with greater thermal stability during fabrication and use.