(62g) Synthesis of Polymer Beads Necklaces in a Microfluidic Device

Polymer particles synthesis has long been the focus of a very intensive research because from painting formulation to drugs delivery they cover a wide range of applications. So far, polymer particles were mainly prepared by either heterogeneous polymerization processes (emulsion, suspension, supercritical fluid) or by precipitation processes in a non solvent. Although, these two processes lead to polymer particules having a different size domain, they induce a large particle size distribution. Recently, microfluidic processes have been considered because of their unique capacity to generate billions of microdroplets with a very narrow size distribution. Indeed, if the microdroplets generated are polymerizable media, it is possible to obtain billions of polymer particles with well-defined characteristics like size, shape and morphology. The advantage is even greater considering the fact that the particle size can be simply adjusted by tuning the continuous phase and dispersed phase flow rates.

The work presented here aims at the synthesis of polymer beads necklaces. We are also interested to get necklaces with different compositions and structures like plain (a), alternated (b) or block (c) arrangement of two different polymer beads within the necklace (cf. figure, blue and red spheres represent two different polymer microparticles).

Necklaces are formed from polymer microparticles as follow: first, alternate formation of two different polymerizable microdroplets is promoted at a cross-junction; then the microdroplets are polymerized by free radical copolymerization using a photo or thermal initiator. By mixing a functional comonomer in each monomer phase, one obtains two differents polymer microparticles bearing on their surface an antagonistic chemical group capable to form a covalent bond by condensation reaction. Then, each reactive bead is individually and alternately confined in a channel in such a way that each microparticle get into contact with two other microparticles. Finally, the chemical reaction between the reactive groups is promoted resulting in a covalent bond between the microparticles and the formation of the polymer beads necklace. By varying the amount of crosslinking agent and the nature of the monomer (styrenic, acrylate), it is possible to adjust some of the physical properties of each beads like viscosity and rheological characteristics.

In this work, it was demonstrated that the use of microfluidic devices allow the synthesis of totally new polymer materials like polymer beads necklaces with a large range of morphologies and properties.