News Column

Patent Issued for High-Density Polydicyclopentadiene

July 30, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- University of Iowa Research Foundation (Iowa City, IA) has been issued patent number 8778186, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Bowden, Ned B. (Iowa City, IA); Gupta, Abhinaba (Iowa City, IA); Long, Tyler R. (Iowa City, IA).

This patent was filed on July 11, 2012 and was published online on July 15, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "Semipermeable membranes play an important part in industrial processing technology and other commercial and consumer applications. Examples of their applications include, among others, biosensors, transport membranes, drug delivery systems, water purification systems, optical absorbers, and selective separation systems for aqueous and organic liquids carrying dissolved or suspended components.

"Generally, semipermeable membranes operate in separation devices by allowing only certain components of a solution or dispersion to preferentially pass through the membrane. The fluid that is passed through the membrane is termed the permeate and comprises a solvent alone or in combination with one or more of the other agents in solution. The components that do not pass through the membrane are usually termed the retentate. The permeate and/or retentate may provide desired product.

"Membranes are one of the most common and economically efficient methods to purify active pharmaceutical ingredients (API) in industry and provide a critical alternative to distillations, recrystallizations, and column chromatography (B. Schmidt, et al., Org. Process Res. Dev. 2004, 8, 998-1008; and S. Muller, et al., Eur. J. Org. Chem. 2005, 1082-1096). Distillations require that an API be stable to elevated temperatures and require significant amounts of energy to complete. Recrystallizations often result in APIs with high purities, but not every molecule can be recrystallized and the recyrstallization conditions are often difficult to optimize and scale up to an appropriate level. In addition, the formation of multiple crystalline isomorphs is poorly understood and results in APIs with different delivery characteristics in the body. Column chromatography is often used in the early discovery and development of APIs due to its simplicity and success, but it is not widely used for large scale production of APIs due in part to the large volumes of solvents that are used which necessitate further purification.

"In contrast, the use of nanoporous membranes to purify APIs can be readily scaled up to purify large quantities of product, use little energy, and does not require large amounts of solvent (H. P. Dijkstra, et al., Acc. Chem. Res. 2002, 35, 798-810; M. F. J. Dijkstra, et al., J. Mem. Sci. 2006, 286, 60-68; J. Geens, et al., Sep. Sci. Technol. 2007, 42, 2435-2449; C. J. Pink, et al., Org. Proc. Res. Dev. 2008, 12, 589-595; and P. Silva, et al., Adv. Membr. Technol. Appl. 2008, 451-467). The use of nanoporous membranes in industry is common in aqueous separations or to purify gasses by pervaporation, but nanoporous membranes are used less commonly with organic solvents. A breakthrough was realized in 1990 when nanoporous membranes based on 'organic solvent nanofiltration' (OSN) membranes were used in an ExxonMobil refinery to separate oil from dewaxing solvents (R. M. Gould, et al., Environ. Prog. 2001, 20, 12-16). The next generation of OSN membranes based on cross-linked polyaniline, polyimides, and other polymers and sold as StarMem.TM., Duramem.TM., and PuraMem.TM. have been developed that function in a wide range of organic solvents and separate organic molecules dissolved in organic solvents (D. A. Patterson, et al., Desalination 2008, 218, 248-256; Y. H. See-Toh, et al., J. Mem. Sci. 2008, 324, 220-232; Y. H. S. Toh, et al., J. Mem. Sci. 2007, 291, 120-125; and L. G. Peeva, et al., In Comprehensive membrane science and engineering; Drioli, E., Giorno, L., Eds.; Elsevier: Boston, 2010; Vol. 2, p 91-111).

"All OSN membranes report values for the 'molecular weight cutoff' (MWCO) that correspond to the molecular weight where molecules transition from having high to low values of permeation (Y. H. S. Toh, et al., J. Mem. Sci. 2007, 291, 120-125; and L. G. Peeva, et al., In Comprehensive membrane science and engineering; Drioli, E., Giorno, L., Eds.; Elsevier: Boston, 2010; Vol. 2, p 91-111). Simply, molecules below the MWCO permeate the membranes but molecules above the MWCO have significantly reduced permeation and are retained. The use of membranes that feature a MWCO has limitations for the separation of catalysts from APIs because the ligands on a catalyst often have molecular weights that are similar to that of the product. Thus, ligands such as PPh.sub.3 (MW: 262 g mol.sup.-1), PCy.sub.3 (MW: 280 g mol.sup.-1), and binol (MW: 286 g mol.sup.-1) can be very challenging to separate from APIs with similar molecular weights or impossible to separate if an API has a higher molecular weight.

"The state-of-the-art membranes to separate catalysts from the products of reactions are based on highly cross-linked organic polymers that function in a range of organic solvents. For instance RuBINAP catalyst (molecular weight 795 g mol.sup.-1) was retained by OSN membranes at levels of approximately 98% for multiple cycles and was active for long periods of time (D. Nair, et al., Org. Proc. Res. Dev. 2009, 13, 863-869). The product was allowed to permeate the membranes and was isolated on the side of the membrane opposite of the catalyst. Part of the success of this project was the high molecular weight of the catalyst compared to the product (molecular weight 160 g mol.sup.-1) which allowed the catalyst to have a molecular weight significantly higher than the MWCO of the membrane (220 g mol.sup.-1).

"In other work, the flux of trialkylamines (i.e. NR.sub.3 where R is methyl, ethyl, propyl, etc) through commercially available OSN membranes (StarMem.TM. membranes) were studied (D. A. Patterson, et al., Desalination 2008, 218, 248-256). This study described perplexing results because even though the molecular weight cutoff was 220 g mol.sup.-1, only 19% of tridodecylamine (molecular weight 522 g mol.sup.-1) was retained (81% permeated the membrane). Also, when the system was studied using cross-flow, the rejection rate for all of the trialkylamines was much poorer than expected. The authors concluded that the use of a molecular weight cutoff for trialkylamines and the StarMem membranes was not useful and gave misleading predictions.

"OSN membranes have an important role in the chemical industry, but they have two limitations that hinder applications in many commercial syntheses of small molecules. First, to be effective there must be a large difference between the molecular weight of the catalyst and the organic product. The molecular weights of many common ligands range from a couple to several hundred grams per mole and would not provide enough difference in molecular weight to separate them from products with similar or higher molecular weights. Second, the MWCO of a membrane is defined as the molecular weight at which 90 to 98% of the solute is rejected; thus, significant amounts of a molecule may pass through these membranes even if the molecular weight is larger than the cutoff.

"Other membranes composed of nanopores etched in polycarbonate, zeolites, and metal-organic frameworks have been fabricated by others that can separate organic molecules. Zeolites are well known for distinguishing molecules based on size, but they are not used as membranes for molecules with the dimensions described in this proposal. Nanopores etched in polycarbonates have found some success, but the molecular size cutoffs are typically not sharp and the membranes suffer from low flux, fouling, and degradation with time (A. Asatekin and K. K. Gleason Nano Lett. 2011, 11, 677-686; K. B. Jirage, et al., Science 1997, 278, 655-658; C. R. Martin, et al., J. Phys. Chem. B 2005, 105, 1925-1934; and M. Wirtz, et al., Chem. Rec. 2002, 2, 112-117). Metal-organic frameworks have been developed that use porphyrins to define pores, but all of these examples require either water as the solvent or only separate gasses (J. T. Hupp, et al., Langmuir 2006, 22, 1804-1809; R. Q. Snurr, et al., AIChE Journal 2004, 50, 1090-1095, B. Chen, et al., Acc. Chem. Res. 2010, 43, 1115-1124; D.-H. Liu and C.-L. Zhong J. Mater. Chem. 2010, 20, 10308-10318; U. Mueller, et al., J. Mater. Chem. 2006, 16, 626-636; K. M. Thomas Dalton Tran. 2009, 1487-1505; D. Zhao, et al., Acc. Chem. Res. 2011, 44, 123-133; and R. Zou, et al., CrystEngComm 2010, 12, 1337-1353).

"PDCPD synthesized from the polymerization of commercially available dicyclopentadiene and the Grubbs catalyst is a relatively new material (M. Perring and N. B. Bowden Langmuir 2008, 24, 10480-10487; J. K. Lee, et al., J. Polym. Sci., Part B: Polym. Phys 2007, 45, 1771-1780; L. M. Bellan, et al., Macromol. Rap. Comm. 2006, 27, 511-515; A. D. Martina, et al., J. Appl. Polym. Sci. 2005, 96, 407-415; and J. D. Rule and J. S. Moore Macromolecules 2002, 35, 7878-7882). This polymer is cross-linked and forms a solid, hard material that, when synthesized by other catalysts, is used in the fabrication of the hoods of semitrucks and snowmobiles."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "Although PCPDCD is a hard polymer, it will readily swell in organic solvents and allow molecules to pass through it. Applicant has discovered a highly cross-linked PDCPD that can be used for liquid separations. It has been determined that molecules with a variety of polar functional groups and differing molecular weights permeate PDCPD membranes while other molecules do not. The difference in permeation is based on cross-sectional area of each molecule. Molecules that have cross-sectional areas larger than a critical value do not permeate the membranes while those below the critical value do permeate them (T. E. Balmer, et al., Langmuir 2005, 21, 622-632; M. R. Shah, et al., J. Mem. Sci. 2007, 287, 111-118; J. A. Cowen, et al., Rev. Sci. Instr. 2003, 74, 764-776; J. M. Watson, et al., J. Mem. Sci. 1992, 73, 55-71; S. Banerjee, et al., J. Appl. Polym. Sci. 1997, 65, 1789-1794; J. Du Pleiss, et al., Eur. J. Pharm. Sci. 2002, 15, 63-69; W. A. Philip, et al., ACS Appl. Mater. Inter. 2009, 1, 472-480; V. Sarveiya; J. F. Templeton and H. A. E. Benson Eur. J. Pharm. Sci. 2005, 26, 39-46; Y. Tamai, et al., Macromolecules 1994, 27, 4498-4508; Y. Tamai, et al., Macromolecules 1995, 28, 2544-2554; and J. Crank The mathematics of diffusion; Clarendon Press: Oxford, 1970).

"Both polar and apolar molecules permeate if their cross-sectional area is below the critical value. This criterion for separation is based on the highly cross-linked matrix of PDCPD that results in a set of pores that allow the polymer to have unique properties for molecules with molecular weights between 100-600 g mol.sup.-1.

"The highly cross-linked PDCPD described herein are the first membranes to separate organic molecules with these molecular weights based on cross-sectional areas. Molecules with a cross-sectional area of 0.50 nm.sup.2 or higher do not permeate the membranes and molecules with cross-sectional areas of 0.40 nm.sup.2 do permeate them. Notably, many common ligands for metals have cross-sectional areas above 0.50 nm.sup.2 and products of reactions with these ligands have cross-sectional areas 0.40 nm.sup.2 or lower.

"Accordingly, Applicant has discovered the first nanoporous membranes that separate many common ligands for metals from other molecules that possess molecular weights lower and higher than those of the ligands. The separation is due to the large cross-sectional area of ligands which hinders their diffusion through highly cross-linked PDCPD. In contrast to the ligands which do not permeate these membranes at any level, molecules with low to high molecular weights permeate them if their cross-sectional areas are below a critical threshold. Thus, the PDCPD materials of the invention retain key molecules that are common ligands for metals while allowing molecules with molecular weights over three times as high to permeate. Existing OSN membranes do not have this property for molecules with molecular weights of 100-600 g mol.sup.-1.

"In one embodiment the invention provides a method comprising, contacting a membrane comprising a highly cross-linked polydicyclopentyldiene matrix with a feed solution comprising a) a first component having a molecular weight in the range of from about 100 g mol.sup.-1 to about 600 g mol.sup.-1 and a cross-sectional area of less than about 0.40 nm.sup.2 and b) a second component having a molecular weight in the range of from about 100 to about 600 g mol.sup.-1 and a cross-sectional area of greater than about 0.50 nm.sup.2 so that the feed solution is fractionated into a permeate comprising the first component and a retentate enriched in the second component.

"In another embodiment the invention provides a method for preparing a highly cross-linked polydicyclopentdiene matrix comprising polymerizing cyclopentadiene in the presence of a catalyst to provide the highly cross-linked polydicyclopentdiene matrix.

"In another embodiment the invention provides a method for preparing a highly cross-linked polydicyclopentdiene matrix comprising, contacting a starting cyclopentadiene matrix wherein the ratio of crosslinked double bonds to uncrosslinked double bonds is less than about 3:2 with an organic solvent under conditions which yield the highly cross-linked polydicyclopentdiene matrix wherein the ratio of crosslinked double bonds to uncrosslinked double bonds increases to at least about 3:2.

"In another embodiment the invention provides a method for preparing a highly cross-linked polydicyclopentdiene matrix comprising, a) polymerizing cyclopentadiene in the presence of a catalyst to provide an intermediate polydicyclopentdiene matrix, and b) contacting the intermediate cyclopentadiene matrix with an organic solvent under conditions which yield the highly cross-linked polydicyclopentdiene matrix wherein the ratio of crosslinked double bonds to uncrosslinked double bonds increases to at least about 3:2.

"In another embodiment the invention provides a method comprising contacting a membrane comprising a highly cross-linked polydicyclopentyldiene matrix of the invention with a feed solution comprising a) a first component having a molecular weight in the range of from about 100 to about 600 g mol.sup.-1 and a cross-sectional area of less than about 0.40 nm.sup.2 and b) a second component having a molecular weight in the range of from about 100 to about 600 g mol.sup.-1 and a cross-sectional area of greater than about 0.50 nm.sup.2 so that the feed solution is fractionated into a permeate comprising the first component and a retentate enriched in the second component.

"In another embodiment the invention provides a highly cross-linked polydicyclopentdiene matrix prepared according to a method of the invention."

For the URL and additional information on this patent, see: Bowden, Ned B.; Gupta, Abhinaba; Long, Tyler R.. High-Density Polydicyclopentadiene. U.S. Patent Number 8778186, filed July 11, 2012, and published online on July 15, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8778186.PN.&OS=PN/8778186RS=PN/8778186

Keywords for this news article include: Science And Engineering, University of Iowa Research Foundation.

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Source: Journal of Engineering


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