We measured the local glass transition temperature T_g(z) of polystyrene (PS) as a function of distance z from a silica substrate with end-grafted chains using fluorescence, where competing effects from the free surface have been avoided to focus only on the influence of the tethered interface. The local T_g(z) increase next to the chain-grafted substrate is found to exhibit a maximum increase of 49 ± 2 K relative to bulk at an optimum grafting density that corresponds to the mushroom-to-brush transition regime. This perturbation to the local T_g(z) dynamics of the matrix is observed to persist out to a distance z ≈ 100–125 nm for this optimum grafting density before bulk T_g is recovered, a distance comparable to that previously observed by Baglay and Roth [J. Chem. Phys.2017, 146, 203307] for PS next to the higher-T_g polymer polysulfone.

中文翻译：

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优化束缚链的接枝密度以改变聚苯乙烯在二氧化硅基材附近的局部玻璃化转变温度：蘑菇相对于刷子的优势

我们使用荧光测量了聚苯乙烯 (PS) 的局部玻璃化转变温度T _g ( z ) 作为与具有末端接枝链的二氧化硅基板的距离z的函数，其中避免了来自自由表面的竞争效应，仅关注于系留接口的影响。在对应于蘑菇到刷子过渡状态的最佳接枝密度下，发现链接枝基板旁边的局部T _g ( z ) 增加相对于体积最大增加 49 ± 2 K。观察到这种对矩阵局部T _g ( z ) 动力学的扰动持续到一定距离z ≈ 100–125 nm，因为此最佳接枝密度在恢复体积T _g之前，该距离与 Baglay 和 Roth 先前观察到的距离相当 [ J. Chem. 物理。2017 , 146 , 203307] 用于 PS 旁边的更高T _g聚合物聚砜。