Microfluidic approach to the formation of internally porous polymer particles by solvent extraction.
Microfluidic approach to the formation of internally porous polymer particles by solvent extraction.
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DOI：
10.1021/la404506b
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发表时间：
2014-02
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影响因子：
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通讯作者：
Takaichi Watanabe;Carlos G Lopez;J. Douglas;T. Ono;J. Cabral
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作者：
Takaichi Watanabe;Carlos G Lopez;J. Douglas;T. Ono;J. Cabral
我们报道了通过使用微流体的选择性溶剂萃取控制形成直径从几十微米到数百微米的内部多孔聚电解质颗粒。通过正面光聚合制备的耐溶剂微器件通过载体溶剂相(C)将二元聚合物(P)/溶剂(S1)混合物包裹在一起，形成具有明确半径和低多分散性的塞子；然后将悬浮液与选择性萃取溶剂(S2)接触，该溶剂与C和S1可混溶，但不能与P相容，从而从液滴中提取S1。随后的相转化产生了表面光滑但内部结构高度多孔的聚合物胶囊。根据液体提取时间的不同，这一阶段可以在芯片内原位进行，也可以在外部S2槽中非原位进行。双峰聚合物塞是使用不对称的倒T形接头实现的。在本演示中，我们使用水(S1)、十六烷(C)和甲乙酮(S2)形成聚苯乙烯磺酸钠(P)颗粒。我们测量了液滴提取速度作为液滴大小和聚合物浓度的函数，并提出了一个简单的比例模型来指导颗粒形成。我们发现，从液滴中形成颗粒所需的提取时间与初始聚合物浓度无关，而与初始液滴大小成正比。对于所有聚合物浓度，得到的颗粒大小与初始液滴大小呈线性关系，从而可以精确控制颗粒大小。内部颗粒多孔结构表现出从致密的表面皮肤到基本上中空的核心的聚合物密度梯度。通过改变初始液滴组成至15wt%的聚合物，可实现10%至50%的平均颗粒孔隙率。这种颗粒在功能材料、光学材料和涂层材料中具有潜在的应用。
We report the controlled formation of internally porous polyelectrolyte particles with diameters ranging from tens to hundreds of micrometers through selective solvent extraction using microfluidics. Solvent-resistant microdevices, fabricated by frontal photopolymerization, encapsulate binary polymer (P)/solvent (S1) mixtures by a carrier solvent phase (C) to form plugs with well-defined radii and low polydispersity; the suspension is then brought into contact with a selective extraction solvent (S2) that is miscible with C and S1 but not P, leading to the extraction of S1 from the droplets. The ensuing phase inversion yields polymer capsules with a smooth surface but highly porous internal structure. Depending on the liquid extraction time scale, this stage can be carried out in situ, within the chip, or ex situ, in an external S2 bath. Bimodal polymer plugs are achieved using asymmetrically inverted T junctions. For this demonstration, we form sodium poly(styrenesulfonate) (P) particles using water (S1), hexadecane (C), and methyl ethyl ketone (S2). We measure droplet extraction rates as a function of drop size and polymer concentration and propose a simple scaling model to guide particle formation. We find that the extraction time required to form particles from liquid droplets does not depend on the initial polymer concentration but is rather proportional to the initial droplet size. The resulting particle size follows a linear relationship with the initial droplet size for all polymer concentrations, allowing for the precise control of particle size. The internal particle porous structure exhibits a polymer density gradient ranging from a dense surface skin toward an essentially hollow core. Average particle porosities between 10 and 50% are achieved by varying the initial droplet compositions up to 15 wt % polymer. Such particles have potential applications in functional, optical, and coating materials.