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 ∼ 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.

中文翻译：

---

纳米限制对毛细管上升渗透过程中未缠结聚合物粘度的影响

我们研究了物理限制作用对聚合物粘度和玻璃化转变温度（T _g）未缠结的聚合物正在经历毛细管上升渗透（CaRI）。CaRI通过毛细作用将聚合物渗透热驱动到紧密堆积的纳米颗粒薄膜的空隙中，从而引起聚合物的极端纳米约束。我们分别通过使用不同的聚合物分子量和通过改变构成填充物的纳米颗粒尺寸来调整限制率（CR），定义为聚合物旋转半径与纳米颗粒填充物中的平均孔半径之比。我们表明，在弱相互作用的纳米粒子的间隙中对未缠结的聚合物进行物理限制会导致相对于整体粘度增加2个数量级以上的粘度，并使聚合物T _g增加32K。粘度和T均增加_g随CR而增加，并在CR〜1处饱和。粘度和T _g的增加之间的关系表明，平移链动力学的减慢与纳米约束下聚合物链节运动的减少直接相关。这些发现强调了即使在弱相互作用的系统中，也必须了解极端纳米限制对聚合物的传输和热性能的影响，这反过来将为优化所得CaRI纳米复合膜的工艺参数和性能提供指导。