Temperature dependent perylene fluorescence as a probe of local polymer glass transition dynamics
Temperature dependent perylene fluorescence as a probe of local polymer glass transition dynamics
复制标题
温度依赖性苝荧光作为局部聚合物玻璃化转变动力学的探针
DOI：
10.1039/d2sm00552b
复制
发表时间：
2022
期刊：
影响因子：
3.4
通讯作者：
Roth, Connie B.
中科院分区：
文献类型：
--
作者：
Han, Yixuan;Roth, Connie B.
我们证明了在大块聚合物基体中掺杂的苝荧光发射光谱的温度依赖性如何对周围聚合物段的局部玻璃化转变动力学敏感。聚焦于第一个荧光峰，我们发现第一个荧光峰和自参考区（SRR）之间的强度比IRatio(T) = IPeak(T)/ISRR具有温度依赖性，这是由于受激发的苝染料的非辐射衰变途径受其与周围聚合物段的分子间碰撞的影响。对于不同的聚合物基体，聚甲基丙烯酸甲酯（PMMA）、聚苯乙烯（PS）、聚2-乙烯基吡啶（P2VP）和聚碳酸酯（PC），我们证明了IRatio(T)在聚合物的玻璃化转变温度Tg以上表现出非Arrhenius行为，而在聚合物基体的Tg以下表现出恒定的活化能E，表明苝对聚合物基体α-弛豫动力学的敏感性。这种温度依赖性的转变使我们能够确定周围聚合物基体的苝定义的局部Tperyleneg，该Tperyleneg与已知聚合物的Tg值非常吻合。我们类似于Williams-Landel-Ferry （WLF）方程定义了一个荧光强度位移因子，并利用文献中聚合物基质的WLF参数来量化将荧光强度比转换为由传统WLF位移因子描述的有效时标比所需的校准因子cf。这项工作开辟了一种新的表征方法，可用于绘制纳米级聚合物材料玻璃化转变的局部动力学响应，使用适当的共价附着在聚合物链上。
We demonstrate how the temperature dependence of perylene's fluorescence emission spectrum doped in bulk polymer matrices is sensitive to the local glass transition dynamics of the surrounding polymer segments. Focusing on the first fluorescence peak, we show that the intensity ratio IRatio(T) = IPeak(T)/ISRR between the first peak and a self referencing region (SRR) has a temperature dependence resulting from the temperature-dependent nonradiative decay pathway of the excited perylene dye that is influenced by its intermolecular collisions with the surrounding polymers segments. For different polymer matrices, poly(methyl methacrylate) (PMMA), polystyrene (PS), poly(2-vinyl pyridine) (P2VP), and polycarbonate (PC), we demonstrate that IRatio(T) exhibits a transition from a non-Arrhenius behavior above the glass transition temperature Tg of the polymer to an Arrhenius temperature dependence with constant activation energy E below the Tg of the polymer matrix, indicating perylene's sensitivity to cooperative α-relaxation dynamics of the polymer matrix. This transition in temperature dependence allows us to identify a perylene defined local Tperyleneg of the surrounding polymer matrix that agrees well with the known Tg values of the polymers. We define a fluorescence intensity shift factor in analogy with the Williams–Landel–Ferry (WLF) equation and use literature WLF parameters for the polymer matrix to quantify the calibration factor cf needed to convert the fluorescence intensity ratio to the effective time scale ratio described by the conventional WLF shift factor. This work opens up a new characterization method that could be used to map the local dynamical response of the glass transition in nanoscale polymer materials using appropriate covalent attachment of perylene to polymer chains.