Scott presents three papers at the American Institute of Chemical Engineers (AIChE) 2005 Conference entitled, "Nanoparticle Filled Rubbery Polymer Membranes for CO2 Sequestration", "Permeability Enhancement in Nanoparticle Filled Polymeric Membranes", Permeability Enhancement in Nanoparticle Filled Polymeric Membranes, and "Nanoparticle-Induced Desilylation of Substituted Acetylene Polymers to Prepare Gas Separation Membranes with Exceptional Chemical Resistance".
Nanoparticle Filled Rubbery Polymer Membranes for CO2 Sequestration
Co-authors Scott Matteucci, Haiqing Lin, Benny D. Freeman, Victor Kusuma, M.J. Yacaman, Sumod Kalakkunnath (University of Kentucky), and Douglass Kalika (University of Kentucky)
Abstract
Traditionally, the addition of impermeable particles to rubbery polymeric membranes reduces light gas and vapor permeability as particle loading increases. This phenomenon is well known for barrier materials, and there are numerous models, such as the one derived by Maxwell, that accurately predict the permeability loss of membranes filled with impermeable particles.[1]
Recently, nonporous metal oxide nanoparticles (primary particle diameter as low as 2.5 nm) have been dispersed in rubbery polymer to make membranes that have over an order of magnitude higher light gas (i.e., CO2, N2, O2, H2) permeability with little or no change in selectivity relative to the neat polymer, which runs counter to traditional filler rubbery polymers. For example, the CO2 permeability was 1100 barrers in filled 1,2-butadiene as compared to 52 barrers for the unfilled polymer. For both materials, the CO2/N2 selectivity was 14, at 35 oC and 3.4 atm. Nanoparticle filled poly(ethylene oxide) membranes reached permeabilities as high as 1700 barrer while maintaining a CO2/N2 selectivity of 25, at 35 oC and 3.4 atm. The degree of permeability enhancement is particle loading dependant, with maximum particle loading over 50 weight percent for some materials. Nanocomposites have been prepared with different polymer matrices (e.g., polar, non-polar, and crosslinked rubbery polymers) and different particle surface chemistries (e.g., MgO, SiO2, TiO2, etc.). These materials have been characterized using light gas sorption and permeation to monitor gas transport properties as well as SEM and TEM to characterize particle distribution within the polymer matrix.
Furthermore, nanocomposites with rubbery matrices often exhibit significantly improved gas transport behavior at low temperatures. Both light gas permeability and selectivity increases substantially with decreasing temperature. However, in some of these materials the gas transport enhancements are limited by the onset of nanoparticle-induced polymer crystallization, as characterized by permeation and DSC experiments.
[1] R. M. Barrer, J. A. Barrie and M. G. Rogers, Heterogenous Membranes: Diffusion in Filled Rubber, Journal of Polymer Science, Part A: Polymer Chemistry, 1 (1963) 2565-2586
Permeability Enhancement in Nanoparticle Filled Polymeric Membranes
Co-authors Scott Matteucci, Haiqing Lin, Benny D. Freeman, Victor Kusuma, M.J. Yacaman, Sumod Kalakkunnath (University of Kentucky), Douglass Kalika (University of Kentucky), and Anita Hill (CSIRO, Manufacturing & Infrastructure Technology).
Abstract
Traditionally, the addition of impermeable particles to rubbery polymeric membranes reduces light gas and vapor permeability as particle loading increases. This phenomenon is well known for barrier materials, and there are numerous models, such as one derived by Maxwell, that accurately predict permeability decrease in membranes filled with impermeable particles.[1]
Recently, nanoparticle filled polymers have been prepared that have over an order of magnitude higher light gas (i.e., CO2, N2, O2, H2) permeability with little or no change in selectivity relative to that of the unfilled polymer, which runs counter to traditional filled polymers. This phenomena has been observed in a broad range of polymeric materials, from high free volume stiff-chain polyacetylenes and crosslinked poly(ethylene oxide) to commodity materials such as 1,2-polybutadiene and poly(ethylene-co-1-octene). The degree of permeability enhancement is polymer and particle loading dependent, and our studies include a wide range of polymer and particle chemistries, including situations where the polymer and particle can react. Moreover, nanocomposite light gas permeability and selectivity are highly dependent on nanoparticle surface chemistry. The nanoparticles are nonporous and are primarily from the metal oxide family (MgO, SiO2, TiO2, etc.). Some of the particles are available as small as 2.5 nm primary particle diameter. These nanocomposites have been characterized using light gas sorption and permeation to monitor gas transport properties as well as SEM and TEM to characterize particle distribution within the polymer matrix.
Using appropriate nanoparticle and polymer combinations permits preparation of nanocomposite membranes that are over 90 weight percent nanoparticles. In such instances, it has been necessary to investigate fractional free volume and membrane void space behavior to characterize the structure of materials with such extremely high nanoparticle loadings.
[1] R. M. Barrer, J. A. Barrie and M. G. Rogers, Heterogenous Membranes: Diffusion in Filled Rubber, Journal of Polymer Science, Part A: Polymer Chemistry, 1 (1963) 2565-2586.
Nanoparticle-Induced Desilylation of Substituted Acetylene Polymers to Prepare Gas Separation Membranes with Exceptional Chemical Resistance
Co-authors Scott Matteucci, Roy Raharjo, Benny D. Freeman, T. Sakaguchi (Kyoto University) and T. Masuda (Kyota University)
Abstract
Many membrane applications require separation of organic vapors from permanent gases.[1] Such separations include the purification of natural gas and hydrogen recovery in refineries. Potential membrane candidate materials include substituted polyacetylenes, which have permeation and selectivity properties that are desirable for organic vapor removal from permanent gases. For instance, the mixed gas n-butane/CH4 selectivity is 48 and the pure n-butane permeability is 80,000 barrer in poly(1-trimethylsilyl-1-propyne) (PTMSP).[2] Moreover, both n-butane/CH4 selectivity and n-butane permeability increase when surface treated fumed silica nanoparticles have been dispersed in the polymer.[2] The utility of substituted polyacetylenes for these applications is limited by poor membrane chemical stability towards organic liquids and vapors. PTMSP, poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene] (PTMSDPA), poly(4-methyl-2-pentyne) and poly(methylacetylene) readily dissolve in industrially relevant organic components (toluene, hexane, etc.) that could be present in industrial feed streams to the membrane.[3-6] However, polyacetylenes such as poly(acetylene) and poly(diphenylacetylene) (PDPA) are insoluble in most organic solvents.[6,7] Currently, the only reported method for making PDPA is to desilylate PTMSDPA using trifluoroacetic acid, so these chemically stable materials cannot be prepared as membranes via conventional processing protocols. Although the resulting material is chemically stable, the permeability and n-butane/permanent gas selectivity decrease significantly.[8] We discovered a method for preparing partially desilylated polyacetylene nanocomposites. Basic nanoparticles (e.g., MgO), when dispersed in polymers such as PTMSDPA, remove trimethylsilyl groups from the polymer backbone. Small molecule compounds were also used to demonstrate the desilylation reaction. Then, the polyacetylenes were partially desilylated using nanoparticles. When possible, the products of the reaction were characterized using XPS, FTIR, and NMR. Gas transport properties were characterized. Interestingly, nanoparticle-desilylated polymers are insoluble in common hydrocarbon solvents, and they have higher gas permeability than the polymers before desilylation. This discovery permits the preparation of high permeability, high selectivity, chemically stable, reverse-selective membranes.
[1] R. W. Baker, Membrane Technology and Applications, McGraw-Hill, New York, 2000.
[2] T. C. Merkel, Z. He, I. Pinnau, B. D. Freeman, A. J. Hill and P. Meakin, Effect of Nanoparticles on Gas Sorption and Transport in Poly(1-Trimethylsilyl-1-Propyne), Macromolecules, 36 (2003) 8406-8414.
[3] T. Masuda, E. Isobe and T. Higashimura, Polymerization of 1-(Trimethyl)-1-Propyne by Halides of Niobium(V) and Tantalum(V) and Polymer Properties, Macromolecules, 18 (1985) 841-845.
[4] K. Tsuchihara, T. Masuda and T. Higashimura, Polymerization of Silicon-Containing Diphenylacetylenes and High Gas Permeability of the Product Polymers, Macromolecules, 25 (1992) 5816-5820.
[5] T. C. Merkel, B. D. Freeman, R. J. Spontak, Z. He, I. Pinnau, P. Meakin and A. J. Hill, Sorption, Transport, and Structural Evidence for Enhanced Free Volume in Poly(4-Methyl-2-Pentyne)/ Fumed Silica Nanocomposite Membranes, Chemical Materials, 15 (2003) 109-123.
[6] J. C. W. Chien, G. E. Wnek, F. E. Karasz and J. A. Hirsch, Electrically Conducting Acetylene-Methylacetylene Copolymers. Synthesis and Properties, Macromolecules, 14 (1981) 479-485.
[7] A. Niki, T. Masuda and T. Higashimura, Effects of Organometallic Cocatalysts on the Polymerization of Distributed Acetylenes by Tantalum Chloride and Niobium Clhoride, Journal of Polymer Science Part A: Polymer Chemistry, 25 (1987) 1553-1562.
[8] M. Teraguchi and T. Masuda, Poly(Diphenylacetylene) Membranes with High Gas Permeability and Remarkable Chiral Memory, Macromolecules, 35 (2002) 1149-1151.