Effect of Physical Nanoconfinement on the Viscosity of Unentangled Polymers during Capillary Rise Infiltration
Effect of Physical Nanoconfinement on the Viscosity of Unentangled Polymers during Capillary Rise Infiltration
复制标题
物理纳米约束对毛细管上升渗透过程中未纠缠聚合物粘度的影响
DOI：
10.1021/acs.macromol.8b00966
复制
发表时间：
2018-07-24
期刊：
影响因子：
5.5
通讯作者：
Lee, Daeyeon
中科院分区：
文献类型：
--
作者：
Hor, Jyo Lyn;Wang, Haonan;Lee, Daeyeon
我们研究了物理约束对聚合物粘度和未纠缠聚合物在毛细管上升渗透（CaRI）过程中的玻璃化转变温度（T-g）的作用。CaRI通过毛细作用热驱动聚合物渗透到密集堆积的纳米颗粒薄膜的空隙中，诱导聚合物的极端纳米限制。我们分别通过使用不同的聚合物分子量和不同的纳米颗粒大小来调整约束比（CR），即聚合物旋转半径与纳米颗粒填料中平均孔隙半径的比值。我们发现，在弱相互作用纳米颗粒的间隙中，物理约束未纠缠的聚合物导致粘度相对于体粘度增加了2个数量级以上，聚合物T-g增加了32 K。粘度和T-g的增加都随着CR的增加而增加，并且在CR近似于1时达到饱和。黏度与T-g增加之间的相关性表明，平移链动力学的减缓与纳米约束下聚合物节段运动的减少直接相关。这些发现强调了理解极端纳米限制对聚合物的输运和热性能的影响的重要性，即使在弱相互作用系统中也是如此，这反过来将为优化所得到的CaRI纳米复合薄膜的加工参数和性能提供指导。
We investigate the role of physical confinement on the polymer viscosity and the glass transition temperature (T-g) of unentangled polymers undergoing capillary rise infiltration (CaRI). CaRI thermally drives polymer infiltration into the voids of densely packed nanoparticle films via capillarity, inducing extreme nanoconfinement of the polymer. We tune the confinement ratio (CR), defined as the ratio of the polymer radius of gyration to the average pore radius in the nanoparticle packing, by using different polymer molecular weights and by varying the nanoparticle size constituting the packing, respectively. We show that physical confinement of unentangled polymers in the interstices of weakly interacting nanoparticles leads to increased viscosity by more than 2 orders of magnitude relative to the bulk viscosity and to increased polymer T-g by 32 K. The increase in both viscosity and T-g increases with CR and saturates at CR similar to 1. The correlation between the viscosity and T-g increase suggests that the slowdown in translational chain dynamics is directly correlated to the decreased polymer segmental motion under nanoconfinement. These findings emphasize the importance of understanding the effect of extreme nanoconfinement on the transport and thermal properties of polymers, even in weakly interacting systems, which in turn will provide guidelines in optimizing processing parameters and properties of the resulting CaRI nanocomposite films.