Mobility of Polymer-Tethered Nanoparticles in Unentangled Polymer Melts
Mobility of Polymer-Tethered Nanoparticles in Unentangled Polymer Melts
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DOI：
10.1021/acs.macromol.8b02138
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发表时间：
2019-02-26
期刊：
影响因子：
5.5
通讯作者：
Rubinstein, Michael
中科院分区：
文献类型：
--
作者：
Ge, Ting;Rubinstein, Michael
发展了聚合物系留纳米粒子(NP)在非纠缠聚合物熔体中运动的标度理论。我们根据NP直径d和接枝聚合物链(Tail)R-Tail的大小确定了两种类型的标度区域。在一种情况下，由于尾部的摩擦系数比运动较小的粒子的摩擦系数低，系留粒子的运动主要由裸露的粒子控制。在粒子占优势的情况下，束缚NP的均方位移(MSD)与时间的关系可以近似为裸露NP的(Bare)。在另一种情况下，当尾巴的摩擦系数超过粒子的摩擦系数时，系留的NP运动由尾巴主导，时间长于交叉时间tau*。在尾部占主导地位的情况下，MSD仅对t<；tau*接近(Bare)。T>；tau*的单尾NP的MSD(Tail)近似为单体在自由尾的MSD(Tail)，而t>；tau*的多尾NP的MSD(STAR)近似为星形聚合物支化点的MSD(Star)。在尾部占优势的情况下，In的时间依赖关系呈现出两个性质不同的次扩散区域。T&t；tau*的第一个亚扩散区域来自于粒子与熔体链之间的动力学耦合。当粒子参与尾巴的动力学时，t>；tau*的第二个次扩散区域发生。对于具有松散接枝链的NPs，在NP周围存在一个高斯刷区域，在该区域中，高斯构象中的链条经历了没有流体动力耦合的Rouse动力学。在尾部为主的情况下，松散接枝的多尾NPs的交叉时间tau*随着尾部数量的增加而减少。对于具有密集接枝链的NPs，尾部是相互流体动力耦合的。致密接枝多尾纳米颗粒扩散的流体动力学半径可用颗粒和尾巴尺寸之和来近似。
A scaling theory is developed for the motion of a polymer-tethered nanoparticle (NP) in an unentangled polymer melt. We identify two types of scaling regimes depending on the NP diameter d and the size of a grafted polymer chain (tail) R-tail. In one type of regime, the tethered NP motion is dominated by the bare NP, as the friction coefficient of the tails is lower than that of the less mobile particle. The time dependence of the mean square displacement (MSD) of the tethered NP in the particle-dominated regime can be approximated by (bare) for the bare NP. In the other type of regimes, the tethered NP motion is dominated by the tails when the friction coefficient of the tails surpasses that of the particle at times longer than the crossover time tau*. In a tail-dominated regime, the MSD approximate to (bare) only for t < tau*. of a single-tail NP for t > tau* is approximated as the MSD (tail) of monomers in a free tail, whereas of a multitail NP for t > tau* is approximated as the MSD (star) of the branch point of a star polymer. The time dependence of in a tail-dominated regime exhibits two qualitatively different subdiffusive regimes. The first subdiffusive regime for t < tau* arises from the dynamical coupling between the particle and the melt chains. The second subdiffusive regime for t > tau* occurs as the particle participates in the dynamics of the tails. For NPs with loosely grafted chains, there is a Gaussian brush region surrounding the NP, where the chain strands in Gaussian conformations undergo Rouse dynamics with no hydrodynamic coupling. The crossover time tau* for loosely grafted multitail NPs in a tail-dominated regime decreases as the number of tails increases. For NPs with densely grafted chains, the tails are hydrodynamically coupled to each other. The hydrodynamic radii for the diffusion of densely grafted multitail NPs are approximated by the sum of the particle and tail sizes.