Polymer diffusion in a polymer nanocomposite: effect of nanoparticle size and polydispersity
Polymer diffusion in a polymer nanocomposite: effect of nanoparticle size and polydispersity
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DOI：
10.1039/c2sm25269d
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发表时间：
2012-01-01
期刊：
影响因子：
3.4
通讯作者：
Composto, Russell J.
中科院分区：
文献类型：
--
作者：
Gam, Sangah;Meth, Jeffrey S.;Composto, Russell J.
采用弹性反冲检测法，测量了氘化聚苯乙烯（dPS）的示踪剂在含有平均粒径d(n)为28.8 nm和12.8 nm的二氧化硅纳米复合材料中的扩散。大小NP的体积分数（phi(NP)）范围分别为0 ~ 0.5和0 ~ 0.1。在NPs体积分数相同的情况下，由于NPs之间的粒子间距离（ID）减小，dPS的示踪剂扩散随着NP尺寸的减小而减小。减少的扩散系数，定义为纳米复合材料中示踪剂相对于纯PS的扩散系数（D/D-0），与约束参数，即ID（D(n)）相对于示踪剂尺寸，ID(D(n))/2R(g)绘制，几乎坍塌到主曲线上，尽管D/D-0略大于多分散，较小的NPs。使用SAXS中NP大小的对数正态分布，当多分散性（sigma）从1增加到1.39时，较小NP的平均ID在phi(NP) 0.1处增加25%。考虑到聚合物的多分散性，约束参数更好地反映了NP间距对聚合物扩散的影响。这些实验表明，聚合物示踪剂在聚合物纳米复合材料中的扩散是由约束参数经验捕获的，并且由于NP多分散性导致的平均ID的增加对尺寸分布较窄的模型NP系统具有次要影响。然而，对于多分散性相当大的商业体系，粒径分布的影响会显著增加内径，进而影响聚合物动力学。
The tracer diffusion of deuterated polystyrene (dPS) is measured in a polystyrene nanocomposite containing silica nanoparticles (NPs), with number average diameters d(n) of 28.8 nm and 12.8 nm, using elastic recoil detection. The volume fractions of the large and small NPs (phi(NP)) range from 0 to 0.5, and 0 to 0.1, respectively. At the same volume fraction of NPs, the tracer diffusion of dPS is reduced as NP size decreases because the interparticle distance between NPs (ID) decreases. The reduced diffusion coefficient, defined as the tracer diffusion coefficient in the nanocomposite relative to pure PS (D/D-0), plotted against the confinement parameter, namely ID(d(n)) relative to tracer size, ID(d(n))/2R(g), nearly collapses onto a master curve, although D/D-0 is slightly greater for the more polydisperse, smaller NPs. Using a log normal distribution of NP size from SAXS, the average ID of the smaller NPs is shown to increase by 25% at phi(NP) 0.1 as polydispersity (sigma) increases from 1 to 1.39. By accounting for polydispersity, the confinement parameter better represents the effect of NP spacing on polymer diffusion. These experiments demonstrate that polymer tracer diffusion in polymer nanocomposites is empirically captured by the confinement parameter and that an increase in the average ID due to NP polydispersity has a secondary effect on model NP systems with a narrow distribution of sizes. However, for commercial systems, where polydispersity can be quite large, the effect of size distribution can significantly increase ID which in turn will influence polymer dynamics.