Macromolecular surfactants for supercritical carbon dioxide applications: Synthesis and characterization of fluorinated block copolymers prepared by nitroxide‐mediated radical polymerization

Abstract

Poly(perfluorooctyl‐ethylenoxymethylstyrene) (PFDS) and poly(1,1,2,2‐tetrahydroperfluorodecyl acrylate) (PFDA) homopolymers as well as poly(styrene)‐b‐poly(perfluorooctyl‐ethylenoxymethylstyrene) (PS‐b‐PFDS) and poly(styrene)‐b‐poly(1,1,2,2‐tetrahydroperfluorodecyl acrylate) acrylate) (PS‐b‐PFDA) block copolymers of various chain lengths were synthesized by nitroxide‐mediated radical polymerization in the presence of either 2,2,6,6‐tetramethyl‐1‐piperidinyloxy free radical (TEMPO) in the case of FDS monomer or N‐tert‐butyl‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl)‐N‐oxyl (DEPN) in the case of the FDA monomer. The molar composition of the block copolymers was determined by elemental analysis and proton NMR while the blocky structure was checked by SEC analysis in trifluorotoluene. Block copolymers PS‐b‐PFDS (3.6K/60K) and PS‐b‐PFDA (3.7K/43K) were soluble in neat CO2 at moderate pressure and temperature, indicating the formation of micelles. Similar block copolymers with a longer PS block such as PS‐b‐PFDA (9.5K/49K), corresponding to a lower CO2‐philic/CO2‐phobic balance, were insoluble in neat CO2 but could be solubilized in the presence of styrene as a cosolvent. Additionally, surface and bulk properties of PS‐b‐PFDA were investigated, indicating the same surface tension as for the PFDA homopolymer (γLV = 10.3 mN/m) and a bulk nanostructured morphology. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3537–3552, 2004

“Green” Atom Transfer Radical Polymerization: From Process Design to Preparation of Well-Defined Environmentally Friendly Polymeric Materials

“…A multitude of chemical transformations have been successfully carried out in scCO 2 , including polymerizations. [371][372][373] Most polymers are not soluble in this medium, but polymerization reactions can be conducted efficiently in it, provided that suitable surfactants [374][375][376] (with a CO 2 -philic segment and a segment miscible with the polymer) are used to prevent flocculation. The removal of the solvent leads to a freely flowing polymer powder.…”

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

“…[239,240,243,248,253] Wignall has provided a detailed review of these self-organizing copolymer systems and the methods employed in their structural analysis. [256] Although novel CO 2 -philic block copolymers continue to be developed by emerging synthetic strategies, [257] the copolymers described above have thus far only been observed to form spherical micelles in the presence of scCO 2 . Using a slightly different approach wherein self-organized copolymers are dissolved in scCO 2 and then reprecipitated upon depressurization, Frankowski et al [258] have exposed block copolymer nanotubes formed from a poly(ferrocenyldimethylsilane) 19 -b-PDMS 72 copolymer in a selective organic solvent to scCO 2 to track changes in morphology as functions of saturation time, pressure, and temperature.…”

Dispersion copolymerization of acrylonitrile‐vinyl acetate in supercritical carbon dioxide

“…One possible explanation is that, under lower pressure, the reaction condition does not arrive at the cloudpoint (defined as the reversible onset of a fully opaque solution) of the stabilizer. 43 Therefore, the stabilizer does not exhibit its function during reaction. Once the reaction condition arrives at the cloud-point, the increase of ScCO 2 pressure has no clear effect on yield.…”

“…There exists two possible explanation that the stabilizer's solubility in ScCO 2 increased along with increasing pressure. 43 The fluorinated block can stretch adequately to result in heightening critical precipitation molecular weight. The critical precipitation molecular weight means that polymers with a molecular weight larger than a certain critical value precipitate and begin to coagulate to form unstable particles.…”