Dynamic Polymer Free Volume Monitored by Single-Molecule Spectroscopy of a Dual Fluorescent Flapping Dopant
Dynamic Polymer Free Volume Monitored by Single-Molecule Spectroscopy of a Dual Fluorescent Flapping Dopant
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DOI：
10.1021/jacs.1c06428
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发表时间：
2021-08-27
影响因子：
15
通讯作者：
Saito, Shohei
中科院分区：
文献类型：
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作者：
Goto, Yuma;Omagari, Shun;Saito, Shohei
双荧光扑动分子探针（N-FLAP）的单分子光谱（SMS）实现了聚苯乙烯局部自由体积动力学的实时纳米级监测。SMS研究是通过氮取代对先前报道的扑动分子进行结构改进而实现的，从而提高了探针的亮度（22倍）。在玻璃跃迁以上5 K温度的聚苯乙烯薄膜中，单个N-FLAP分子的光谱在短波和长波形式之间频繁地跳跃，后者表明分子在激发态下的平面化。对观测到的光谱跳变进行了统计分析，以揭示分子环境的动力学。结合MD和QM/MM计算表明，只有在分子附近有足够大的聚合物自由体积（至少大于280埃）时，才会发生扑动探针的激发态平面化，并且这种自由体积平均持续1.2 s。
Single-molecule spectroscopy (SMS) of a dual fluorescent flapping molecular probe (N-FLAP) enabled real-time nanoscale monitoring of local free volume dynamics in polystyrenes. The SMS study was realized by structural improvement of a previously reported flapping molecule by nitrogen substitution, leading to increased brightness (22 times) of the probe. In a polystyrene thin film at the temperature of 5 K above the glass transition, the spectra of a single N-FLAP molecule undergo frequent jumps between short- and long-wavelength forms, the latter one indicating planarization of the molecule in the excited state. The observed spectral jumps were statistically analyzed to reveal the dynamics of the molecular environment. The analysis together with MD and QM/MM calculations show that the excited-state planarization of the flapping probe occurs only when sufficiently large polymer free volume of more than, at least, 280 angstrom(3) is available close to the molecule, and that such free volume lasts for an average of 1.2 s.