Diffusion ordered ¹H-NMR spectroscopy (DOSY) is a useful, non-destructive technique for analysing polymer hydrodynamic size and intrinsic/solution viscosity. However, to date there has been no investigation of DOSY under variable temperature conditions that allow trends in polymer conformation to be determined. Poly(2-ethyl-2-oxazoline) (P(EtOx)) is a hydrophilic polymer that has the potential to replace poly(ethylene glycol) (PEG) in biomedical applications. Applying DOSY to a series of narrow-distribution P(EtOx) revealed that the apparent hydrodynamic radii scaled with molecular weight as expected. By altering the temperature of the solution the trends in Flory-type exponents were determined, enabling the determination of the power laws related to the coil-globule conformation of linear polymers directly from NMR data. These measurements were complicated by the onset of convection currents at higher temperatures, which impose a limit to the effective measurement range of ca. 10–35 °C. It was revealed that P(EtOx) had a more expanded random coil conformation than PEG, and it trended towards θ conditions at the lower critical solution temperature. In comparison, PEG was approximately in θ-conditions at room-temperature. This shows the use, and limitations of DOSY in polymer conformation analysis, and applies it to P(EtOx), a polymer which has not been analysed in this manner before.

中文翻译：

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通过 NMR 光谱测定聚合物构象：D2O 中聚（2-乙基-2-恶唑啉）和聚（乙二醇）的比较扩散有序 1H-NMR 光谱


扩散有序 ¹ H-NMR 光谱 (DOSY) 是一种有用的非破坏性技术，用于分析聚合物流体动力学尺寸和特性/溶液粘度。然而，迄今为止，还没有在可变温度条件下对 DOSY 进行研究，从而确定聚合物构象的趋势。聚(2-乙基-2-恶唑啉) (P(EtOx)) 是一种亲水性聚合物，有潜力在生物医学应用中取代聚乙二醇 (PEG)。将 DOSY 应用于一系列窄分布 P(EtOx) 表明，表观流体动力学半径与预期的分子量成正比。通过改变溶液的温度，确定了弗洛里型指数的趋势，从而能够直接从 NMR 数据确定与线性聚合物的线圈-球体构象相关的幂律。这些测量因较高温度下对流电流的出现而变得复杂，这限制了约 100 kHz 的有效测量范围。 10–35°C。结果表明，P(EtOx) 具有比 PEG 更扩展的无规卷曲构象，并且在较低临界溶液温度下趋向于 θ 条件。相比之下，PEG 在室温下大约处于 θ 条件。这显示了 DOSY 在聚合物构象分析中的用途和局限性，并将其应用于 P(EtOx)，这是一种以前从未以这种方式分析过的聚合物。