Frasca Franklin, Duhamel Jean
Institute for Polymer Research, Waterloo Institute for Nanotechnology, Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada.
Polymers (Basel). 2025 Jul 18;17(14):1979. doi: 10.3390/polym17141979.
Series of pyrene-labeled diols (Py-DOs) and polyols (Py-POs) were synthesized by coupling a number () of 1-pyrenebutyric acids to diols and polyols to yield series of end-labeled linear ( = 2) and branched ( > 2) oligomers, respectively. Pyrene excimer formation (PEF) between an excited and a ground-state pyrene was studied for the Py-DO and Py-PO samples by analyzing their fluorescence spectra and decays in tetrahydrofuran, dioxane, ,-dimethylformamide, and dimethyl sulfoxide. Global model-free analysis (MFA) of the pyrene monomer and excimer fluorescence decays yielded the average rate constant (<>) for PEF. After the calculation of the local pyrene concentration ([]) for the Py-DO and Py-PO samples, the <>-vs.-[] plots were linear in each solvent, with larger and smaller slopes for the Py-DO and Py-PO samples, respectively, resulting in a clear kink in the middle of the plot. The difference in slope was attributed to a bias for PEF between pyrenes close to one another on the densely branched Py-PO constructs resulting in lower apparent [] and <> values. This study illustrated the ability of PEF to probe how steric hindrance along a main chain affects the dynamic encounters between substituents in multifunctional oligomers such as diols and polyols.
通过将多个1-芘丁酸与二醇和多元醇偶联，分别合成了一系列芘标记的二醇（Py-DO）和多元醇（Py-PO），以产生一系列末端标记的线性（n = 2）和支化（n>2）低聚物。通过分析芘标记的二醇和多元醇样品在四氢呋喃、二氧六环、N，N-二甲基甲酰胺和二甲基亚砜中的荧光光谱和衰减，研究了激发态芘与基态芘之间的芘激基缔合物形成（PEF）。芘单体和激基缔合物荧光衰减的全局无模型分析（MFA）得出了PEF的平均速率常数（k<>）。在计算了芘标记的二醇和多元醇样品的局部芘浓度（[p]）之后，k<>对[p]的图在每种溶剂中都是线性的，芘标记的二醇和多元醇样品的斜率分别较大和较小，导致图中间出现明显的拐点。斜率的差异归因于在密集支化的Py-PO结构上彼此靠近的芘之间PEF的偏差，导致较低的表观[p]和k<>值。这项研究说明了PEF探测主链上的空间位阻如何影响二醇和多元醇等多功能低聚物中取代基之间动态碰撞的能力。
