Formation of colloidal dispersions of organic materials in aqueous media by solvent shifting
Formation of colloidal dispersions of organic materials in aqueous media by solvent shifting
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DOI：
10.1021/la034173o
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发表时间：
2003-08-05
期刊：
影响因子：
3.9
通讯作者：
Whitesides, TH
中科院分区：
文献类型：
--
作者：
Brick, MC;Palmer, HJ;Whitesides, TH
本文描述了通过“溶剂转移”程序制备水不溶性有机材料的胶体分散体，其中有机溶质在与水混溶的有机溶剂中的浓缩溶液被分散到大量含有胶体稳定剂的水性（非溶剂）本体溶液中。在大多数研究案例中，溶质以 0.1-0.5 μm 的无定形颗粒形式分离。颗粒尺寸与局部过饱和度（即溶质进料浓度与本体中平衡溶解度的瞬时值之比）密切相关，并且还表现出对溶质进料浓度的弱依赖性。根据沉淀条件的系统变化获得的结果，包括水相中有机溶剂的量、溶质进料浓度和混合条件，根据颗粒形成机制进行了讨论，包括将进料溶液分散为小液滴，然后在界面处溶剂/水反扩散。这种相互扩散导致溶剂质量迅速下降，通过旋节线分解导致局部液-液相分离。该机制被证明与非晶态（无定形）颗粒的优先形成以及观察到的颗粒尺寸和形成速率的变化一致。
This paper describes the preparation of colloidal dispersions of water-insoluble organic materials by a "solvent-shifting" procedure, in which a concentrated solution of an organic solute in a water-miscible organic solvent is dispersed into a large volume of aqueous (nonsolvent) bulk solution containing colloidal stabilizers. In the majority of cases studied, the solute separates as 0.1-0.5 mum amorphous particles. The particle size is strongly correlated with the local supersaturation, i.e., the ratio of the solute feed concentration to the instantaneous value of the equilibrium solubility in the bulk, and also shows a weak dependence on the solute feed concentration. The results obtained on systematic variation of the precipitation conditions, including the amount of organic solvent in the aqueous phase, the solute feed concentration, and the mixing conditions, are discussed in terms of a mechanism of particle formation comprising dispersion of the feed solution as small droplets, followed by solvent/water counterdiffusion at the interface. Rapidly decreasing solvent quality, resulting from this interdiffusion, leads to local liquid-liquid phase separation by spinodal decomposition. This mechanism is shown to be consistent with the preferential formation of noncrystalline (amorphous) particles and with the observed changes in particle size and formation rate.