Materials processing in supercritical carbon dioxide: surfactants, polymers and biomaterialsElectronic supplementary information (ESI) available: video clips relating to work carried out in the Howdle research group. See http://www.rsc.org/suppdata/jm/b3/b315262f/

Abstract

Supercritical carbon dioxide (scCO 2 ) is a unique solvent with a wide range of interesting properties. This review focuses upon recent advances in the use of scCO 2 in materials synthesis and materials processing. In particular, we consider the advances made in three major areas. First the design and application of new surfactants for use in scCO 2 , which enable the production of metal nanoparticles, porous polymers and polymers of high molecular weight with excellent morphology. Second the development of new polymer processing and polymer blend technologies in scCO 2 , which enable the synthesis of some very complex polymer composites and blends. Finally, the application of scCO 2 in the preparation of novel biomedical materials, for example biodegradable polymer particles and scaffolds. The examples described here highlight that scCO 2 allows facile synthesis and processing of materials, leading to new products with properties that would otherwise be very difficult to achieve.

Sorption and Swelling of Poly(D,L‐lactic acid) and Poly(lactic‐co‐glycolic acid) in Supercritical CO2

“…[2][3][4][5][6][7][8][9] The interaction between scCO 2 and the polymer leads to a plasticization of the polymer also at low temperatures: a small amount of CO 2 dissolved in the polymer is in fact sufficient to strongly reduce its glass transition temperature and viscosity. [10] Under these conditions, the incorporation of bioactive compounds can be achieved, since the polymer can be easily penetrated.…”

Thermodynamics and Kinetic Processes of Polymer Blends and Block Copolymers in the Presence of Pressurized Carbon Dioxide

“…CO 2 is attractive in this process for several reasons: i) its ability to increase the diffusion rates of penetrants in polymers, ii) its temperature-and pressure-tunable solvent strength, which can be used to control the degree of substrate swelling, iii) its use to control monomer/initiator partitioning between the fluid phase and the swollen polymer matrix, and iv) its facile removal from the resultant polymer blend by simple depressurization. This procedure has been previously reviewed, [42,50] but is further explored here due to recent advances. Rajagopalan and McCarthy [201] have identified several benefits of this strategy: i) most polymers swell, but do not dissolve, in CO 2 and can thus serve as substrates; ii) any monomer that can be dissolved in CO 2 is suitable; iii) polymerization can be performed throughout the bulk of the substrate or just at the surface; iv) the blend composition can be tailored by adjusting operating variables such as the monomer and initiator concentrations, as well as the reaction and exposure times, pressures, and temperatures; and v) the technique can be used to generate interpenetrating networks (IPNs) or semi-IPNs.…”

“…This conventional nucleation and growth mechanism competes with CO 2 escape to the atmosphere, in which case it immediately follows that CO 2 diffusivity in the polymer is a consideration of paramount importance. Several reviews [40,42,43,[47][48][49][50] provide relevant details of scCO 2 -induced microcellular foaming and microcellular foams produced from homopolymers with or without fillers in both batch and continuous operations.…”

One Step Preparation of Controlled Drug Release Systems in Supercritical Carbon Dioxide

“…The "green" properties of carbon dioxide have provided the driving force to develop a number of new applications. [11][12][13][14][15] In the present study, N-vinylpyrrolidone (VP) was chosen as a comonomer due to its well-known biocompatibility, hydrophilicity and good complexation ability. A proper fractionation led to desired LCST of copolymers.…”