Supercritical carbon dioxide copolymers

De Simone et al. synthesized poly(fluoroalkyl acrylate)-based block copolymers for use as lipophilic/C02-philic surfactants for carbon dioxide applications [181]. The particle diameter and distribution of sizes during dispersion polymerization in supercritical carbon dioxide were shown to be dependent on the nature of the stabilizing block copolymer [182]. 

Buhler, E. Dobrynin, A. V. DeSimone, J. M. Rubinstein, M. Light-Scattering Study of Diblock Copolymers in Supercritical Carbon Dioxide C02 Density-Induced Micellization Transition. Macromolecules 1998, 31, 7347-7355. Bunyard, W. C. Romack, T. J. DeSimone, J. M. Perfluoropolyether Synthesis in Liquid Carbon Dioxide by Hexafluoropropylene Photooxidation. Macromolecules 1999, 32, 8224-8226. 

Londono, J. D. Dharmapurikar, R. Cochran, H. D. Wignall, G. D. McClain, J. B. Betts, D. E. Canelas, D. A. DeSimone, J. M. Samulski, E. T. Chillura-Martino, D. Triolo, R. The Morphology of Block Copolymer Micelles in Supercritical Carbon Dioxide by Small-Angle Neutron and X-ray Scattering. 

Well ordered mesoporous silicate films were prepared in supercritical carbon dioxide.[218] In the synthesis in aqueous or alcoholic solution, film morphology of preorganized surfactants on substrate cannot be fully prescribed before silica-framework formation, because structure evolution is coincident with precursor condensation. The rapid and efficient preparation of mesostructured metal oxides by the in situ condensation of metal oxides within preformed nonionic surfactants can be done in supercritical CCU- The synthesis procedure is as follows. A copolymer template is prepared by spin-coating from a solution containing a suitable acid catalyst. Upon drying and annealing to induce microphase separation and enhance order, the acid partitions into the hydrophilic domain of the template. The template is then exposed to a solution of metal alkoxide in humidified supercritical C02. The precursor diffuses into the template and condenses selectively within the acidic hydrophilic domain of the copolymer to form the incipient metal oxide network. The templates did not go into the C02 phase because their solubility is very low. The alcohol by-product of alkoxide condensation is extracted rapidly from the film into the C02 phase, which promotes rapid and extensive network condensation. Because the template and the metal oxide network form in discrete steps, it is possible to pattern the template via lithography or to orient the copolymer domains before the formation of the metal oxide network. 

Colina, C.M., Hall, C.K., and Gubbins, K.E., Phase behavior of PVAC-PTAN block copolymer in supercritical carbon dioxide using SAFT, presented at the 9th International Conference on Properties and Phase Equilibria for Product and Process Design, Kurashiki, Japan, May 20-25, 2001, 2001. 

Duxbury Christopher, J., Wang, W., de Geus, M., Heise, A., and Howdle Steven, M. (2005) Can block copolymers be synthesized by a single-step chemoenzymatic route in supercritical carbon dioxide J. Am. Chem. Soc., 127 (8), 2384-2385. 

To confirm Stejskal and Kratochvil s theories of chemical composition distribution, graft copolymers of methyl methacrylate (MMA) and MMA-terminated PDMS were first synthesized by free-radical procedures by the Virginia Tech researchers. Any unincorporated PDMS macromonomer was then stripped with supercritical carbon dioxide and finally the polymer was... 

Figure 9.14 Gel permeation chromatograms of PMMA-g-PDMS copolymer before and after extraction with supercritical carbon dioxide. GPC trace of extract (PDMS macromonomer) is shown, too (Hell-stern, 1989).

Two PMMA-g-PDMS copolymers were also prepared with roughly similar composition (20 wt% and 26 wt% PDMS) and with the same molecular weight PDMS grafts (M = 10,000) by free radical polymerization and by anionic polymerization. The copolymers were first extracted of any unincorporated methacryloxy-terminated PDMS using supercritical carbon dioxide then they were fractionated with supercritical chlorodifluoromethane. Each fraction was characterized in the same manner as described for the three polymers depicted in figure 9.15 and the results are shown in figure 9.16 (DeSimone et al., 1990). The differences in chemical composition distribution profiles of the copolymers... 

Figure 9.18 Gel permeation chromatograms of fractions of PMMA-g-PDMS copolymer fraction 1 obtained with supercritical carbon dioxide and fractions 2, 3, 4 obtained with supercritical chlorodifluoromethane (Hellstern, 1989).

Figure 9.28 Cel permeation chromatograms of a 5,000 molecular weight aminopropyl-terminated poly-(dimethyD-co-(diphenyl)siloxane parent copolymer containing 25wt% diphenyl substituents and of fraction 2 obtained with supercritical ethane at 150°C and 300 bar after reaction with supercritical carbon dioxide at 80°C and 100 bar (refer to data in table 9.17) (Elsbernd et al., 1990b).

Heise, Palmans, de Geus, Villarroya and their collaborators (17,41,42) have been working on a chemoenzymatic cascade synthesis to prepare block copolymers. They combine enzymatic ring-opening polymerization (eROP) and atom transfer radical polymerization (ATRP). The synthesis of block copolymers was successful in two consecutive steps, i.e., eROP followed by ATRP. In the one-pot approach, block copolymers could be obtained by sequential addition of the ATRP catalyst, but side reactions were observed when all components were present from at the onset of reactions. A successful one-pot synthesis was achieved by conducting the reaction in supercritical carbon dioxide. 

We investigated the chemoenzymatic synthesis of block copolymers combining eROP and ATRP using a bifunctional initiator. A detailed analysis of the reaction conditions revealed that a high block copolymer yield can be realized under optimized reaction conditions. Side reactions, such as the formation of PCL homopolymer, in the enzymatic polymerization of CL could be minimized to < 5 % by an optimized enzyme (hying procedure. Moreover, the structure of the bifunctional initiator was foimd to play a major role in the initiation behavior and hence, the yield of PCL macroinitiator. Block copolymers were obtained in a consecutive ATRP. Detailed analysis of the obtained polymer confirmed the presence of predominantly block copolymer structures. Optimization of the one-pot procedure proved more difficult. While the eROP was compatible with the ATRP catalyst, incompatibility with MMA as an ATRP monomer led to side-reactions. A successfiil one-pot synthesis could only be achieved by sequential addition of the ATRP components or partly with inert monomers such as /-butyl methacrylate. One-pot block copolymer synthesis was successful, however, in supercritical carbon dioxide. Side reactions such as those observed in organic solvents were not apparent. 

Catalytic Hydrogenation of Olefins in Supercritical Carbon Dioxide Using Rhodium Catalysts Supported on Fluoroacrylate Copolymers... 

Lopez-Castillo, Z. K. Flores, R. Kani, I. Fackler, Jr.,J. P. Akgerman, A. Fluoroacrylate Copolymer Supported Rhodium Catalysts for Hydrogenation Reactions in Supercritical Carbon Dioxide. Ind. Eng. Chem. Res., 2002,41, 3075-3080... 

ZHA ZMng, Y., Gangwani, K.K., and Lemert, R.M., Sorption and swelling of block copolymers in the presence of supercritical carbon dioxide, J. Supercrit Fluids, 11, 115, 1997. 

LAC Lacroix-Desmazes, P., Andre, P., Desimone, J.M., Ruzette, A.-V., and Boutevin, B., Macromolecular surfactants for supercritical carbon dioxide applications Synthesis and characterization of fluorinated block copolymers prepared by nitroxide-mediated radical polymerization (experimental data by P. Lacroix-Desmazes), J. Polym. Sci. Part A Polym. Chem., 42, 3537, 2004. 

MA2 Ma, Z. and Lacroix-Desmazes, P., Dispersion polymerization of 2-hydroxyetlryl methacrylate stabilized by a hydrophilic/C02-philic poly (ethylene oxide)-6-poly(l,l,2,2-tetrahydroperfluorodecyl acrylate) (PEO-Zr-PFDA) diblock copolymer in supercritical carbon dioxide (experimental data by P. Lacroix-Desmazes), Polymer, 45, 6789, 2004. 

Samulski and J. M. DeSimone, Critical micelle density for the self-assembly ofblock copolymer surfactants in supercritical carbon dioxide, iongmihr 16(2) 416 (2000). 

B. Wang, M. Wang, Z. Xing, H. Zeng, G. Wu, Preparation of radiation crosslinked foams from low-density polyethylene/ethylene vinyl acetate (LDPE/EVA) copolymer blend with a supercritical carbon dioxide approach. J. Appl. Polym. Sci. 127, 912-918 (2013)... 

Fig. 2.5 Impact of the copolymer composition on the solubility of ethylene/methylacrylate-copolymers (EMA) in supercritical carbon dioxide. Subscripts Indicate the amount of methylacrylate monomers in the copolymer in mol%. Experimental data from [6].

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