Polymeric nanoporous materials fabricated with supercritical CO₂ and CO₂-expanded liquids

Abstract

Both academia and industries have put great efforts into developing non-destructive technologies for the fabrication of polymeric nanoporous materials. Such non-destructive technologies developed with supercritical CO2 (scCO2) and CO2-expanded liquids (CXLs) have been attracting more and more attention because they have been demonstrated to be green and effective media for porous polymer preparation and processing. In this tutorial review, we present several such new technologies with scCO2 and CXLs, which have the capacity to prepare polymeric nanoporous materials with unique morphologies. The fabricated nanoporous polymers have significantly improved the performance of polymeric monoliths and films, and have found wide applications as templates, antireflection coatings, low-k materials, tissue engineering scaffolds and filtration membranes. This tutorial review also introduces the associated characterization methods, including the imaging, scattering and physisorption techniques.

Hollow‐Structured Materials for Thermal Insulation

“…Many other models based on the Knudsen number have also been proposed to empirically describe the influence of spatial confinement on the gas thermal conductivity in small voids of HSMs. [3d,10] The “corrected” effective thermal conductivity of gases confined in small voids allows us to more accurately describe the contribution of gases in an HSM to the overall thermal conductivity of the HSM. For an HSM with a defined shape and volume, the voids occupy only a fraction of volume of the HSM, which is usually described as porosity, Π.…”

“…The dependence of high thermal insulation performance of aerogels on the existence of voids (or hollow structures) has stimulated great efforts in developing new thermal‐insulation materials by generating hollow structures (e.g., voids and bubbles) in bulk materials and composites. Although some review articles have summarized the progress in fabricating various thermal‐insulation materials including aerogels, polymer foams, and composite films, a review with a perspective on the general structure–property relationship between the hollow structures and reduction of thermal conductivity in all insulation materials is still absent. Herein, we present a comprehensive and timely overview on the present thermal‐insulation materials containing hollow structures with an emphasis on the structure–property relationship.…”

Design of controlled release systems for THEDES—Therapeutic deep eutectic solvents, using supercritical fluid technology

“…The use of scCO 2 for the development of enhanced biomaterials for pharmaceutical and/or biomedical applications has been reported in different reviews (Duarte et al, 2009a,b;Knez et al, 2011;Salerno and Pascual, 2015;Zhang et al, 2014). CO 2 is the most commonly used solvent at supercritical conditions due to its low critical parameters (T c = 31.1 C and P c = 73.8 bar) and to the fact that it is environmentally benign, non-toxic, non-flammable, non-corrosive, readily available and inexpensive.…”

Nanomembrane Materials Based on Polymer Blends

“…While polymer coatings are relatively easy to deposit, they are unable to withstand high temperatures and harsh chemical environments. In the past decades, different methods have been developed to control the porosity, pore shape and size of nanoporous polymer materials, including hard/soft template, self-assembly, and high internal phase emulsion (HIPE) polymerization [111]. Amongst the characterization methods that can be used for this purpose are electro-spinning, gas sorption, mercury injection, permeation test, and optical methods (direct observation).…”