Neal Thomas J, Parnell Andrew J, King Stephen M, Beattie Deborah L, Murray Martin W, Williams Neal S J, Emmett Simon N, Armes Steven P, Spain Sebastian G, Mykhaylyk Oleksandr O
Department of Chemistry, The University of Sheffield, Dainton Building, Sheffield S3 7HF, U.K.
Department of Physics and Astronomy, The University of Sheffield, Hicks Building, Sheffield S3 7RH, U.K.
Macromolecules. 2021 Feb 9;54(3):1425-1440. doi: 10.1021/acs.macromol.0c02341. Epub 2021 Jan 22.
A range of amphiphilic statistical copolymers is synthesized where the hydrophilic component is either methacrylic acid (MAA) or 2-(dimethylamino)ethyl methacrylate (DMAEMA) and the hydrophobic component comprises methyl, ethyl, butyl, hexyl, or 2-ethylhexyl methacrylate, which provide a broad range of partition coefficients (log ). Small-angle X-ray scattering studies confirm that these amphiphilic copolymers self-assemble to form well-defined spherical nanoparticles in an aqueous solution, with more hydrophobic copolymers forming larger nanoparticles. Varying the nature of the alkyl substituent also influenced self-assembly with more hydrophobic comonomers producing larger nanoparticles at a given copolymer composition. A model based on particle surface charge density (PSC model) is used to describe the relationship between copolymer composition and nanoparticle size. This model assumes that the hydrophilic monomer is preferentially located at the particle surface and provides a good fit to all of the experimental data. More specifically, a linear relationship is observed between the surface area fraction covered by the hydrophilic comonomer required to achieve stabilization and the log value for the hydrophobic comonomer. Contrast variation small-angle neutron scattering is used to study the internal structure of these nanoparticles. This technique indicates partial phase separation within the nanoparticles, with about half of the available hydrophilic comonomer repeat units being located at the surface and hydrophobic comonomer-rich cores. This information enables a refined PSC model to be developed, which indicates the same relationship between the surface area fraction of the hydrophilic comonomer and the log of the hydrophobic comonomer repeat units for the anionic (MAA) and cationic (DMAEMA) comonomer systems. This study demonstrates how nanoparticle size can be readily controlled and predicted using relatively ill-defined statistical copolymers, making such systems a viable attractive alternative to diblock copolymer nanoparticles for a range of industrial applications.
合成了一系列两亲性统计共聚物，其中亲水组分是甲基丙烯酸（MAA）或甲基丙烯酸2-（二甲氨基）乙酯（DMAEMA），疏水组分包括甲基丙烯酸甲酯、乙酯、丁酯、己酯或2-乙基己酯，这些共聚物具有广泛的分配系数（log ）。小角X射线散射研究证实，这些两亲性共聚物在水溶液中自组装形成结构明确的球形纳米颗粒，疏水性更强的共聚物形成更大的纳米颗粒。改变烷基取代基的性质也会影响自组装，在给定的共聚物组成下，疏水性更强的共聚单体产生更大的纳米颗粒。基于颗粒表面电荷密度的模型（PSC模型）用于描述共聚物组成与纳米颗粒尺寸之间的关系。该模型假设亲水单体优先位于颗粒表面，并且与所有实验数据都拟合得很好。更具体地说，观察到实现稳定所需的亲水共聚单体覆盖的表面积分数与疏水共聚单体的log 值之间存在线性关系。对比变化小角中子散射用于研究这些纳米颗粒的内部结构。该技术表明纳米颗粒内部存在部分相分离，约一半可用的亲水共聚单体重复单元位于表面，而核心富含疏水共聚单体。这些信息使得能够开发出一种改进的PSC模型，该模型表明阴离子（MAA）和阳离子（DMAEMA）共聚单体体系中亲水共聚单体的表面积分数与疏水共聚单体重复单元的log 之间具有相同的关系。这项研究表明，使用相对不明确的统计共聚物可以很容易地控制和预测纳米颗粒的尺寸，使得此类体系成为一系列工业应用中双嵌段共聚物纳米颗粒的可行且有吸引力的替代物。
