Abstract
Within the very large range of porous polymers and a related immense scope of applications, we investigate here a specific route to design soft porous polymers with controlled porosity: we use aqueous-based formulations of oligomers with mineral particles which are solidified into a hydrogel upon photo-polymerization; the embedded particles are then chemically etched and the hydrogel is dried to end up with a soft porous polymeric scaffold with micron-scale porosity. Morphological and physical features of the porous polymers are measured and we demonstrate that the porosity of the final material is primarily determined by the amount of initially dispersed sacrificial particles. In addition, the liquid formulations we use to start with are convenient for a variety of material forming techniques such as microfluidics, embossing, etc., which lead to many different morphologies (monoliths, spherical particles, patterned substrates) based on the same initial material.
Highlights
The porosity in polymers may emerge from a variety of physical or chemical routes, e.g., phase separation [1], foaming [2], emulsion templating [3], sacrificial particles [4] . . . It leads to important functionalities such as light weight, insulation, permeability, etc. that find numerous applications.Specific material forming processes may add up to more functionalities: spherical particles are useful for instance for chromatography, drug delivery, acoustics [5], whereas thin films of can be used as membranes for filtration; fibers are useful for fabric and promising for tissue engineering [6]; eventually, porous polymers become increasingly appealing for 3D printing [7]
We study the critical steps that lead to a solid porous polymer starting from an aqueous dispersion: optimization of the formulation containing the oligomers, the sacrificial particles and water; photo-curing of turbid dispersions; removal of the particles [4]; drying; and features of the final porosity
We provide evidence that the porosity of the dried polymer perfectly relates to the initial quantity of the sacrificial particles; connected or disconnected porosity could possibly be produced depending on the initial formulation
Summary
Specific material forming processes may add up to more functionalities: spherical particles are useful for instance for chromatography, drug delivery, acoustics [5], whereas thin films of can be used as membranes for filtration; fibers are useful for fabric and promising for tissue engineering [6]; eventually, porous polymers become increasingly appealing for 3D printing [7]. In most of these applications, the features of the porosity are of prime importance, namely and at minima its size, distribution, connectivity, specific surface, etc. Due to the specific rheological nature of the formulations (low viscosity, negligible yield-stress), we demonstrate that these fluids can be formed under a large variety of structures using advanced techniques such as for instance soft embossing and microfluidics
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