Stoichiometry of electrostatic complexes determined by light scattering
Stoichiometry of electrostatic complexes determined by light scattering
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DOI：
10.1021/ma062887a
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发表时间：
2007-06-12
期刊：
影响因子：
5.5
通讯作者：
Berret, J.-F.
中科院分区：
文献类型：
--
作者：
Berret, J.-F.
本文报道了用静态和动态光散射的方法研究了带相反电荷的聚合物与无机纳米颗粒之间的静电络合作用。研究的纳米颗粒是柠檬酸盐包覆的氧化铈（CeO2，纳米铈）、氧化铁（γ - fe2o3，磁铁矿）和掺铕钒酸钇（Eu:YVO4）纳米晶体，尺寸在10纳米范围内。对于聚合物，我们使用了不同分子量的阳离子中性二嵌段共聚物（聚（丙烯酸三甲基铵乙酯）-b-聚（丙烯酰胺），以下简称PTEA-b-PAM）。对于这三种胶体分散体，我们发现静电络合可以在100 nm范围内形成稳定的纳米颗粒团簇。通过系统测量散射强度与X、纳米颗粒与聚合物的混合比来监测络合作用。对于CeO2/PTEA(5K)-b-PAM（30K）、γ - fe2o3 /PTEA(5K)-b-PAM（30K）、γ - fe2o3 /PTEA(11K) -b-PAM（30K）、Eu:YVO4/PTEA(2K)-b-PAM（60K）和Eu:YVO4/PTEA(5K)-b-PAM（30K）这5对纳米粒子/聚合物，我们发现了一个独特的行为：散射强度在中间X范围内表现出一个尖锐而突出的峰。为了解释这种行为，我们开发了一个模型，该模型假设，无论X如何，混合聚集体都以固定的聚合物与纳米颗粒的比例形成。结果与模型在五个系统上的一致性很好。不同分子量的结果表明，混合聚集体的化学计量是由相反电荷之间的静电相互作用控制的。该模型可以推导出混合聚集体的分子量和化学计量。
We report on the electrostatic complexation between oppositely charged polymers and inorganic nanoparticles investigated by static and dynamical light scattering. The nanoparticles put under scrutiny were citrate-coated nanocrystals of cerium oxide (CeO2, nanoceria), of iron oxide (gamma-Fe2O3, maghemite), and of europium-doped yttrium vanadate (Eu:YVO4) with sizes in the 10 nm range. For the polymers, we have used cationic-neutral diblock copolymers (poly(trimethylammonium ethyl acryl ate)-b-po ly(acryl amide), hereafter referred to as PTEA-b-PAM) with different molecular weights. For the three colloidal dispersions, we show that the electrostatic complexation gives rise to the formation of stable nanoparticle clusters in the 100 nm range. The complexation was monitored by systematic measurements of the scattering intensity vs X, the mixing ratio between nanoparticles and polymers. For five nanoparticle/polymer pairs, namely CeO2/PTEA(5K)-b-PAM(30K), gamma-Fe2O3/PTEA(5K)-b-PAM(30K), gamma-Fe2O3/PTEA(11K) -b-PAM(30K), Eu:YVO4/PTEA(2K)-b-PAM(60K), and Eu:YVO4/PTEA(5K)-b-PAM(30K), we found a unique behavior: the scattering intensity exhibits a sharp and prominent peak in the intermediate X range. To account for this behavior, we have developed a model which assumes that, regardless of X, the mixed aggregates are formed at a fixed polymer-to-nanoparticle ratio. The agreement between the results and the model is excellent on the five systems. Results at different molecular weights suggest that the stoichiometry of the mixed aggregates is controlled by the electrostatic interactions between the opposite charges. The model allows to derive the molecular weight and the stoichiometry of the mixed aggregates.