Synthesis of highly cross-linked poly(diethylene glycol dimethacrylate) microparticles in supercritical carbon dioxide

MIP Synthesis and Processing Using Supercritical Fluids

Supercritical fluid technology provides a clean and straightforward way for the preparation of high affinity polymeric materials. Molecularly Imprinted Polymers (MIPs) as dry, free-flowing powders are obtained in a one-step synthetic route yielding molecular recognition materials for several applications. Herein, we describe the experimental procedures involved in the scCO₂-assisted MIP development: synthesis, template desorption, impregnation, and membrane preparation. MIP applications are described putting in evidence the advantages of MIP development using supercritical fluid technology.

Development of itaconic acid-based molecular imprinted polymers using supercritical fluid technology for pH-triggered drug delivery

A novel pH-responsive molecularly imprinted polymer (MIP) based on Itaconic acid:Ethylene glycol dimethacrylate was developed as a potential body-friendly oral drug delivery system for metronidazole (MZ), a pH-independent drug. MIP performance was evaluated in a simulated oral administration situation, at pHs 2.2 and 7.4. Itaconic acid-based copolymers were synthesized using two different molar ratios of template:monomer:crosslinker (T:M:C), 1:5:25 and 1:5:50, in supercritical carbon dioxide (scCO₂) in high yields. Further, impregnation of MZ was performed in scCO₂ environment. Morphological and chemical properties of the copolymers produced were assessed by SEM, Morphologi G3 and FTIR analyses. Non-molecularly imprinted polymer (NIP) matrices presented swelling over time in opposition to the molecularly imprinted ones. In the scCO₂-impregnation process, MIPs showed a significant molecular recognition towards MZ, presenting higher drug uptake ability with MZ loading of 18-61 wt% in MIPs, compared to 7-20 wt% in NIPs. In vitro drug release experiments presented different release profiles at the different pHs, where MZ-MIPs could release higher amounts of MZ at the lowest pH than at pH 7.4.

Supercritical carbon dioxide design strategies: from drug carriers to soft killers

The integrated use of supercritical carbon dioxide (scCO(2)) and micro- and nanotechnologies has enabled new sustainable strategies for the manufacturing of new medications. 'Green' scCO(2)-based methodologies are well suited to improve either the synthesis or materials processing leading to the assembly of three-dimensional multifunctional constructs. By using scCO(2) either as C1 feedstock or as solvent, simple, economic, efficient and clean routes can be designed to synthesize materials with unique properties such as polyurea dendrimers and oxazoline-based polymers/oligomers. These new biocompatible, biodegradable and water-soluble polymeric materials can be engineered into multifunctional constructs with antimicrobial activity, targeting moieties, labelling units and/or efficiently loaded with therapeutics. This mini-review highlights the particular features exhibited by these materials resulting directly from the followed supercritical routes.

Integrated desulfurization of diesel by combination of metal-free oxidation and product removal by molecularly imprinted polymers

The desulfurization of diesel containing dibenzothiophene (DBT) is achieved based on the combination of Brønsted acid catalyzed oxidation of DBT by H₂O₂ and the selective removal of the oxidized products using a molecularly imprinted polymer (MIP) produced in supercritical carbon dioxide.

Tuning smart microgel swelling and responsive behavior through strong and weak polyelectrolyte pair assembly

The layer-by-layer (LbL) assembly of polyelectrolyte pairs on temperature and pH-sensitive cross-linked poly(N-isopropylacrylamide)-co-(methacrylic acid), poly(NIPAAm-co-MAA), microgels enabled a fine-tuning of the gel swelling and responsive behavior according to the mobility of the assembled polyelectrolyte (PE) pair and the composition of the outermost layer. Microbeads with well-defined morphology were initially prepared by synthesis in supercritical carbon dioxide. Upon LbL assembly of polyelectrolytes, interactions between the multilayers and the soft porous microgel led to differences in swelling and thermoresponsive behavior. For the weak PE pairs, namely poly(L-lysine)/poly(L-glutamic acid) and poly(allylamine hydrochloride)/poly(acrylic acid), polycation-terminated microgels were less swollen and more thermoresponsive than native microgel, whereas polyanion-terminated microgels were more swollen and not significantly responsive to temperature, in a quasi-reversible process with consecutive PE assembly. For the strong PE pair, poly(diallyldimethylammonium chloride)/poly(sodium styrene sulfonate), the differences among polycation and polyanion-terminated microgels are not sustained after the first PE bilayer due to extensive ionic cross-linking between the polyelectrolytes. The tendencies across the explored systems became less noteworthy in solutions with larger ionic strength due to overall charge shielding of the polyelectrolytes and microgel. ATR FT-IR studies correlated the swelling and responsive behavior after LbL assembly on the microgels with the extent of H-bonding and alternating charge distribution within the gel. Thus, the proposed LbL strategy may be a simple and flexible way to engineer smart microgels in terms of size, surface chemistry, overall charge and permeability.

Molecular Interactions and CO2-Philicity in Supercritical CO2. A High-Pressure NMR and Molecular Modeling Study of a Perfluorinated Polymer in scCO2

The carbon and fluorine chemical shifts of mixtures of carbon dioxide and Krytox, a carboxylic acid end-capped perfluorinated polyether used as stabilizer for the dispersion polymerization of methyl methacrylate, have been studied using high-pressure, high-resolution nuclear magnetic resonance. 13C and 19F spectra were measured in the density region between 0.54 and 0.73 g.cm(-3) at 334 K for different solutions of Krytox in scCO2 (0.22, 1.13 and 1.72 w/w %). An in-house developed high-pressure apparatus with the capability to change in situ the sample composition was used for this purpose using a 10 mm polyether ketone NMR tube. The nature of CO2-Krytox interaction was assessed both by comparing the CO2 deltaC variation of neat CO2 with that of mixtures with increasing surfactant composition and by the analysis of Krytox 19F corrected chemical shifts in terms of medium magnetic susceptibility. Ab initio calculations, at the second-order Møller-Plesset level of theory to include the effects of electron correlation, were performed to access and compare the nature of the interactions between CO2 and perfluorinated and nonfluorinated analogue model molecules. Both experimental 13C and 19F HP-NMR results and molecular modeling studies support a F...CO2 site-specific Lewis acid-Lewis base interaction model. A positive entropic variation for the formation of CO2-fluorinated solute complex is advanced as an explanation for the higher solubility of perfluorinated molecules when compared to the nonfluorinated analogues.