O'Connell Róisín A, Sharratt William N, Aelmans Nico J J, Higgins Julia S, Cabral João T
Department of Chemical Engineering, Imperial College London, South Kensington, London SW7 2AZ, United Kingdom.
Buchem B.V., Minden 60, Apeldoorn 7327 AW, Netherlands.
Macromolecules. 2022 Feb 8;55(3):1050-1059. doi: 10.1021/acs.macromol.1c02030. Epub 2022 Jan 18.
We investigate the conformation of poly(2,6-diphenyl--phenylene oxide) (PPPO) in good and mixed solvents by small-angle neutron scattering (SANS) across its ternary phase diagram. Dichloromethane was selected as a "good" solvent and heptane as a "poor" solvent whose addition eventually induces demixing and polymer precipitation. Below the overlap concentration *, the polymer conformation is found to be well described by the polymer-excluded volume model and above by the Ornstein-Zernike expression with a correlation length ξ which depends on the concentration and solvent/nonsolvent ratio. We quantify the decrease in polymer radius of gyration , increase in ξ, and effective χ parameter approaching the phase boundary. Upon flash nanoprecipitation, the characteristic particle radius (estimated by scanning electron microscopy, SEM) is found to scale with polymer concentration as well as with nonsolvent content. Significantly, the solution volume per precipitated particle remains nearly constant at all polymer concentrations. Overall, our findings correlate ternary solution structure with the fabrication of polymer nanoparticles by nonsolvent-induced phase separation and precipitation.
我们通过小角中子散射（SANS）研究了聚（2,6 - 二苯基 - 对亚苯基氧化物）（PPPO）在良溶剂和混合溶剂中的构象，并跨越其三元相图。选择二氯甲烷作为“良”溶剂，庚烷作为“不良”溶剂，添加庚烷最终会导致相分离和聚合物沉淀。在重叠浓度*以下，发现聚合物构象可以很好地用聚合物排除体积模型来描述，而在其之上则用具有相关长度ξ的奥恩斯坦 - 泽尼克表达式来描述，该相关长度ξ取决于浓度和溶剂/非溶剂比。我们量化了聚合物回转半径的减小、ξ的增加以及接近相界时有效χ参数的变化。通过快速纳米沉淀法，发现特征颗粒半径（通过扫描电子显微镜，SEM估算）与聚合物浓度以及非溶剂含量成比例。值得注意的是，在所有聚合物浓度下，每个沉淀颗粒的溶液体积几乎保持恒定。总体而言，我们的研究结果将三元溶液结构与通过非溶剂诱导相分离和沉淀制备聚合物纳米颗粒联系起来。
