Article pubs.acs.org/Langmuir
Reliable Synthesis of Monodisperse Microparticles: Prevention of Oxygen Diffusion and Organic Solvents Using Conformal Polymeric Coating onto Poly(dimethylsiloxane) Micromold Jae-Min Jeong,†,§ Myung Seok Oh,‡,§ Bong Jun Kim,‡ Chang-Hyung Choi,† Bora Lee,‡ Chang-Soo Lee,*,† and Sung Gap Im*,‡ †
Department of Chemical Engineering, Chungnam National University, Yuseong-gu, Daejeon 305-764, Republic of Korea Department of Chemical and Biomolecular Engineering & KI for NanoCentury, Korea Advanced Institute of Science and Technology, Yuseong-gu, Daejeon 305-701, Republic of Korea
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ABSTRACT: An effective polymeric thin film deposited by initiated chemical vapor deposition (iCVD) process was presented and its application as a barrier film on the PDMS micromold blocking the penetration of oxygen and organic solvents was investigated. With this barrier film, we were able to synthesize monodisperse polymeric particles of sizes down to 3 μm, which has been reported to be extremely challenging with bare PDMS micromold. The polymeric barrier film on the PDMS micromold enabled this successful synthesis of microparticles by effectively blocking the diffusion of oxygen, which is a well-known radical quencher in radical polymerization, through the PDMS micromold. Furthermore, the iCVD barrier film substantially decreased the penetration of various organic solvents such as acetone, tert-butanol, PDMS oil, and decane as well as organic substances including fluorescent molecules like rhodamine B and fluorescein isothiocyanate (FITC). Therefore, the polymeric barrier film coated on PDMS micromold via iCVD process will broaden the application of PDMS to microfluidic area for the synthesis of smaller microparticles with various organic substances.
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INTRODUCTION
size distribution is still eagerly researched from academia and industry. Recently, several approaches to synthesize monodisperse microparticles were reported. Membrane emulsification technique based on the ejection of disperse polymeric phase through a porous membrane was introduced to produce monodisperse droplets and particles.15 The most advanced system, microfluidic method for the generation of monodisperse emulsion droplets, enabled the facile control of the size of the produced emulsion droplets by the combination of driving pressures of the two immiscible fluids, geometry of microchannels, and interfacial properties between disperse and continuous fluid.7,16,17 Most recently, the micromolding technique using poly(dimethylsiloxane) (PDMS) has enabled easy and reproducible synthesis of monodisperse microparticles.18 Unlike microfluidics, the synthesis procedure eliminated the need for flow control and the recycling of materials was feasible. However, the method based on the PDMS micromolds is not yet applied to produce highly monodisperse microparticles at smaller scale (
