Textured and Hierarchically Constructed Polymer Micro- and Nanoparticles

Abstract

Microfluidic techniques allow for the tailored construction of specific microparticles, which are becoming increasingly interesting and relevant. Here, using a microfluidic hole-plate-device and thermal-initiated free radical polymerization, submicrometer polymer particles with a highly textured surface were synthesized. Two types of monomers were applied: (1) methylmethacrylate (MMA) combined with crosslinkers and (2) divinylbenzene (DVB). Surface texture and morphology can be influenced by a series of parameters such as the monomer–crosslinker–solvent composition, surfactants, and additives. Generally, the most structured surfaces with the simultaneously most uniform particles were obtained in the DVB–toluene–nonionic-tensides system. In a second approach, poly-MMA (PMMA) particles were used to build aggregates with bigger polymer particles. For this purpose, tripropyleneglycolediacrylate (TPGDA) particles were synthesized in a microfluidic co-flow arrangement and polymerized by light- irradiation. Then, PMMA particles were assembled at their surface. In a third step, these composites were dispersed in an aqueous acrylamide–methylenebisacrylamide solution, which again was run through a co-flow-device and photopolymerized. As such, entities consisting of particles of three different size ranges—typically 0.7/30/600 µm—were obtained. The particles synthesized by both approaches are potentially suitable for loading with or incorporation of analytic probes or catalysts such as dyes or metals.

Four-Level Structural Hierarchy: Microfluidically Supported Synthesis of Polymer Particle Architectures Incorporating Fluorescence-Labeled Components and Metal Nanoparticles

“…In addition, the viscosity of the carrier phase influences the monomer droplet formation and size of the formed particles. As in our previous work, viscosity at higher methylcellulose concentrations and poly-TPGDA microparticles became smaller under the same flow conditions…”

“…In the case of copolymerization, different concentrations of acrylic acid (5, 10, 20% v/v) were added into the TPGDA monomer phase, and particles were polymerized as described in Section (III). It was found previously that the optimal concentration of acrylic acid in the monomer phase was 10% . Despite the fact that particle binding was more efficient in the case of a higher acrylic acid concentration (20%), the formed microparticles were more polydisperse.…”

“…As we found previously, at a 1200/70 μL/min flow rate ratio of carrier to monomer phase, PMMA particles with a mean size of about 800 nm and a positive surface charge with a ζ potential of +35 mV were obtained. Variable flow rates and pDADMAC concentration strongly influence the particle size; therefore, polymer particle sizes can be tuned from 800 down to 100 nm . By decreasing the monomer phase flow rate at a constant carrier flow rate, the particle polydispersity increased from 8 to 15% as the size of the particle decreased.…”

“…The size of hydrogel particles can be tuned by changing the monomer/carrier phase flow rate ratio. As we found previously, at a constant monomer rate of −30 μL/min, the particle size can be reduced from 1000 to around 500 μm by increasing the carrier flow rate from 300 to 1200 μL/min, resulting in a change of dispersity of particle size from 7.5 to 12% …”

“…Using an aqueous acrylamide solution as a matrix for particle or composite encapsulation, a mechanical contact of an embedded material with the environment can be prevented while still allowing diffusion of molecules into and out of a hydrogel particle . A beneficial property of polyacrylamide is that composite-embedded hydrogel microparticles can be dried and re-wet again without damaging the composites . Also, this way, composite particles can be stored without mechanical damage for a long time. , Moreover, the hydrogel matrix allows diffusion of macromolecules in- and outside the matrix .…”