Microporous polymeric composition

Abstract

A microporous polymeric composition including a matrix polymer having a fractional free volume of at least 0.1 and dispersed particles having a hypercrosslinked polymer.

Claims

1. A microporous polymeric composition comprising 60% to 90% by weight of a matrix polymer selected from at least one of substituted polyacetylenes and polymers of intrinsic microporosity (PIMs) and having a fractional free volume of at least 0.1 and dispersed particles comprising 5% to 25% by weight of the microporous polymeric composition of hypercrosslinked polymer comprising optionally substituted aryl groups (Ar) covalently linked by methylene bridging groups (CH.sub.2) providing a link with repeating units (ArCH.sub.2ArCH.sub.2)n- wherein n is the number of repeating units.

2. A microporous polymeric composition according to claim 1, wherein the methylene bridging groups form covalent links between two adjacent aryl groups to form a six membered carbocyclic ring that is attached to the aryl rings.

3. A microporous polymeric composition according to claim 1, wherein the hypercrosslinked polymer is prepared by polymerization of a substituted aryl monomer comprising at least two chloromethylene groups by Friedel Crafts catalysed polymerisation.

4. A microporous polymeric composition according to claim 1, wherein the hypercrosslinked polymer is prepared by polymerization of an optionally substituted aryl monomer with an external crosslinker.

5. A microporous polymeric composition according to claim 4, wherein the hypercrosslinked polymer is formed by Friedel Crafts catalysed polymerisation.

6. A microporous polymeric composition according to claim 1, wherein the hypercrosslinked polymer is formed by post polymerisation crosslinking of polymers containing aryl monomers selected from optionally substituted vinylbenzyl chloride, vinylbenzyl chloride-co-divinylbenzene copolymers, vinylbenzylchloride copolymers having at least two reactive groups to provide a rigid covalent link between two aryl groups.

7. A microporous polymeric composition according to claim 1, wherein the hypercrosslinked polymer is formed by post polymerisation crosslinking using an external cross-linker of polymers containing aryl monomers.

8. A microporous polymeric composition according to claim 4, wherein the optionally substituted aryl groups comprise an aryl selected from the group consisting of carbocyclic aryl selected from the group consisting of benzene, biphenyl, naphthylene, tetrahydronaphthylene, idene, azulene, anthracene and heterocyclic aryl selected from the group consisting of furanyl, thiophenyl, 2Hpyrrolyl, pyrrolinyl, oxazolinyl, thiazolinyl, indolinyl, imidazolidinyl, imidazolinyl, pyrazolyl, pyrazolinyl, isoxazolidinyl, isothiazolinyl, oxadiazolinyl, triazolinyl, thiadiazolinyl, tetrazolinyl, pyridinyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazenyl, indolyl, isoindolinyl, benzimidazolyl, benzoxazolyl, quinolinyl and isoquinolinyl and optional substituents are selected from the group consisting of C.sub.1 to C.sub.4 alkyl, C.sub.2 to C.sub.4 alkenyl, halo-C.sub.1 to C.sub.4 alkyl, amino, C.sub.1 to C.sub.4 alkylamino, di-(C.sub.1 to C.sub.4 alkyl)amino and sulfonate.

9. A microporous polymeric composition according to claim 1, wherein the repeating unit of the link comprises formula I or formula II: ##STR00008## wherein n represent the number of repeating units.

10. A microporous polymeric composition according to claim 1, wherein the hypercrosslinked polymer has a Brunauer-Emmett-Teller (BET) surface area in the range of from 500 m2/g to 2500 m2/g.

11. A microporous polymeric composition according to claim 1, wherein the weight ratio of matrix polymer to hypercrosslinked polymer is at least 4:1.

12. A microporous polymeric composition according to claim 1, wherein the matrix polymer is soluble in chlorinated hydrocarbon.

13. A microporous polymeric composition according to claim 1, wherein the matrix polymer having a free volume of at least 0.1 is selected from substituted polyacetylenes.

14. A microporous polymeric composition according to claim 1, wherein the matrix polymer is a substituted polyacetylene polymer comprising at least one selected from the group consisting of poly(1-(trimethylsilyl)-1-propyne) (PTMSP), poly(1-(dimethyl-n-propylsilyl)-1-propyne), poly(1-(dimethyl-n-butylsilyl)-1propyne), poly(1-phenyl-1-propyne)poly (diphenylacetylene), poly (t-butylacetylene), poly(1-phenyl-2-p-trimethylsilylphenyl-acetylene), poly(1-phenyl-2-p-hydroxyphenylacetylene), poly(4-methyl-2pentyne) and copolymers of two or more thereof.

15. A microporous polymeric composition according to claim 14, wherein the substituted polyacetylene polymer is poly-1-(trimethylsilyl)-1propyne.

16. A microporous polymeric composition according to claim 1, in the form of a membrane.

17. A microporous polymeric composition according to claim 16, for use in gas separations, liquid separations or separation of solids from liquids.

18. A microporous polymeric composition according to claim 16, wherein the gas permeability of the membrane is more than 80% after 100 days.

19. A microporous polymeric composition according to claim 16, wherein the gas permeability of the membrane does not decrease by more than 10% over a period of 50 days.

20. A method of preparing microporous polymeric composition according to claim 1 comprising the steps of: (a) dissolving a matrix polymer in a liquid to form a polymer solution, (b) introducing porous particles of the hypercrosslinked polymer to the polymer solution, and (c) subsequently removing at least a portion of the liquid to thereby form the microporous material.

21. A method of performing size-selective separation of a component in a mixture selected from a mixture of fluids or a mixture of a solid and a fluid, the method comprising the steps of: providing the mixture comprising a fluid component; contacting the mixture with one surface of a membrane comprising a microporous polymeric composition according to claim 1; applying a pressure difference across the membrane; and isolating a filtered composition from the opposite surface of the membrane to provide a filtered composition enriched in one component of the mixture.

22. A method for separation of liquids by pervaporation comprising the steps of: (a) providing a membrane having a feed side and a permeate side, the membrane comprising a separating layer of a microporous polymeric composition according to claim 1; (b) passing a liquid mixture containing a component to be separated across the feed side; (c) providing a driving force for transmembrane permeation; and (d) withdrawing from the permeate side a mixture comprising a gas or vapour enriched in the component compared with the liquid mixture.

23. A method of separation according to claim 22 wherein the mixture of liquids is an aqueous alcohol mixture and the alcohol is enriched on the permeate side.

24. A microporous polymeric composition comprising a matrix polymer having a fractional free volume of at least 0.1 and dispersed particles comprising hypercrosslinked polymer comprising optionally substituted aryl groups covalently linked by methylene bridging groups (CH.sub.2) wherein the hypercrosslinked copolymer is obtained by a friedel crafts catalysed polymerisation of either: (a) a substituted aryl monomer comprising at least two chloromethylene groups; or (b) an optionally substituted aryl monomer with an external cross-linker.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The Example is described with reference to the drawing.

(2) In the drawings:

(3) FIG. 1 is a column chart comparing the change in gas permeability with time (as a measure of ageing) of the matrix polymer alone and with different dispersed polymer particles including PAF-1 and a composition according to the invention comprising hypercrosslinked polymer particles.

(4) FIG. 2. The schematic of the pervaporation unit in this work.

(5) FIGS. 3A-D comprise a series of 4 charts showing the effects of (A) ethanol concentration (FIGS. 3A-B) and (B) temperature on the total flux and EtOH/water selectivity of membranes (FIGS. 3C-D). In each Chart the top dot relates to the PTMSP/p-DCX membrane; the middle dot relates to the PTMSP/PAF-1 membrane and the bottom dot relates to the PTMSP control membrane. The upper percentages show the percentage change in PTMSP/p-DCX for the PTMSP and the lower percentage is the change in the PTMSP/PAF-1 membrane from the PTMSP control.

(6) FIG. 4 is a graph providing a comparison of PV separation performances of the PTMSP membrane of the invention with other silicon based pervaporation membranes for EtOH/water separations.

(7) FIGS. 5A-C are a series of graphs showing (A) the intensity of various pore sizes for PTMSP/PAF-1; PTMSP; and the PTMSP/p-DCX membrane of the invention (b) the relative loss in percent of the membranes and (C) the ethanol uptake of the aged membranes.

(8) FIG. 6 is a graph showing the pore size distribution of PAF-1 (blue) and p-DCX (red) nanoparticles obtained from nitrogen adsorption isotherms performed at 77 K.

(9) FIGS. 7A-F shows a series of six graphs the first three showing solvent permeation of methanol, ethanol and isopropanol of as-cast (solid square) and aged (empty square) 1 um thin (A) PTMSP, (B) PTMSP/PAF-1 and (C) PTMSP/p-DCX membranes supported on polycarbonate substrates. The second series of three show Rose Bengal (orange), Thiazole Yellow (green), and Safranine O (purple) dyes rejection rates from ethanol of (D) PTMSP, (E) PTMSP/PAF-1 and (F) PTMSP/p-DCX membranes.

(10) FIGS. 8A-B are 2 graphs showing: (A) the effects of physical aging (after 500 hours of continuous operation at 5 bar of solvent pressure and 25 C.) on ethanol transport in PTMSP (black), PTMSP/PAF-1 (blue), and PTMSP/p-DCX (red) where membranes were cast using 0.5 wt. % of doping concentration; and (B) dye rejection rates of as-cast (solid) and aged (empty) membranes studied here.

(11) FIGS. 9A-H include three graphs showing the bimodal pore size distribution of (A) as-cast vs aged, PTMSP, PTMSP/PAF-1 and PTMSP/p-DCX membrane of the invention; (B) aged wet vs aged dry PTMSP, PTMSP/PAF-1, and PTMSP/p-DCX membranes determined using PALS; (C) The relationship between relative EtOH permeances of PTMSP, PTMSP/PAF-1 and PTMSP/p-DCX membranes and FFV content losses due to physical aging; and D the influence of additives on the EtOH adsorption in PTMSP, PTMSP/PAF-1 and PTMSP/p-DCX membrane.

EXAMPLES

Example 1Polycondensation of Bis(chloromethyl) Monomers (dichloroxylene) to Synthesis pDCX

(12) To a solution of monomer in anhydrous dichloroethane (DCE, 10 mL), a DCE solution of FeCl3 was added under nitrogen. The resulting mixture was heated while stirring at 80 C. The resulting brown precipitate was washed once with water, three times with methanol (until the filtrate was clear), and with diethyl ether followed by drying for 24 h at 60 C. Suitable p-DCX hypercrosslinked polymer particles may be prepared by the method of Wood et al., Chem. Mater. 2007, 19, 2034-2048.

(13) PTMSP is dissolved in solvents that may include chloroform, or tetrahydrofuran, or cyclohexane, followed by the dispersion of pDCX in this polymer solution. The mixture is allowed to stir for 12-24 hours to achieve a homogenous dispersion. This mixture is then casted on a glass petri dish, or Teflon petri dish, or porous substrate. Upon solvent evaporation, a polymer film forms, and is ready for characterisation. The pure gas permeabilities of the membrane are then tested using a simple time lag apparatus.

(14) 300 mg of PTMSP was mixed with 30 mg of hypercrosslinked resin (pDCX) in 10 mL CHCl.sub.3. After mixing the solution was stirred for 24 hours, after which the insoluble pDCX was well dispersed throughout the solution. A membrane was cast in a Teflon dish (47 mm). The resulting membrane was homogeneous and the polymer was well dispersed throughout the PTMSP.

(15) Permeability Measurement

(16) Single gas permeability measurements. Pure H.sub.2, N.sub.2, CH.sub.4, and CO.sub.2 permeabilities were determined using a constant volume, variable pressure method and primarily used for characterizing polymer aging. Gas permeabilities at 2 atm and room temperature were determined from the rate of downstream pressure build-up rate (dp/dt) obtained when permeation reached a steady state according to the following equation:

(17) $\begin{array}{cc}P=DS=\frac{273{10}^{10}}{760}\frac{\mathrm{VL}}{\mathrm{AT}\left[\frac{p276}{14.7}\right]}(\frac{\mathrm{dp}}{\mathrm{dt}})& \mathrm{Equation}1\end{array}$

(18) P refers to the permeability of a membrane to a gas and its unit is in Barrer (1 Barrer=110.sup.10 cm.sup.3 (STP)-cm/cm.sup.2 sec cmHg), D is the average effective diffusivity (cm.sup.2/s), S is the apparent sorption coefficient/solubility (cm.sup.3 (STP)/cm.sup.3 polymer cmHg), V is the volume of the downstream chamber (cm.sup.3), L is the film thickness (cm). A refers to the effective area of the membrane (cm.sup.2), T is the experimental temperature (K) and the pressure of the feed gas in the upstream chamber is given by p2 (psia).

(19) A PTMSP solution containing 10 wt. % of pDCX (p-dichloroxylene hypercrosslinked polymer) particles in chloroform was cast on a Teflon-lined glass petri dish. A 20 m film was formed over slow evaporation at 90 C. Subsequently, the free-standing films were thermally treated at 120 C. for 4 hours, 150 C. for 4 hours, and 200 C. under vacuum for 24 hours. These steps are required to fully evacuate the solvent from the films. The gas permeabilities of this nanocomposite are shown in FIG. 1.

(20) System 1 (FIG. 1) shows the performance of PTMSP, as can be seen the membrane has high permeability to gases. However, the membrane ages quickly and after 365 days the permeability has decreased by 90%. Previous work by the team has shown that this aging can be dramatically reduced by including a porous aromatic framework (PAF, system 2) and a number of modified PAFs (systems 3-6). The PAF is also a nanoporous organic polymer, like the hypercrosslinked polymer used in this invention, however, the surface area of the PAF is higher. The limitation of the PAF is large scale synthesis and cost. Hypercrosslinked polymers can be synthesized on a large scale using inexpensive reagents. When pDCX was incorporated into a PTMSP membrane the resulting materials have increased permeability to hydrogen, nitrogen, and carbon dioxide. The results are in line with the best of the optimized PAF systems with only system 6 outperforming the pDCX in terms of permeability. System 6 used a PAF that contains a lithiated fullerene so the pDCX is easier to access. Initial aging studies (Table 1) have demonstrated the pDCX membrane maintains permeability to hydrogen and carbon dioxide which shows the same anti-aging effect for the PAFs.

(21) TABLE-US-00001 TABLE 1 Initial Aging Results of PTMSP/p-DCX nanocomposite membranes (barrer units). Days of aging H.sub.2 N.sub.2 CH.sub.4 CO.sub.2 0 19673 6093 43538 7 19564 4287 42887 14 19336 4130 42402 28

Example 2Liquid Purification

(22) This example describes preparation of membranes of the invention comprising a matrix of PTMSP and dispersed particles of p-DCX (referred to as PTMSP/p-DCX) and compares their performance in pervaporation with membranes of PTMSP membranes comprising dispersed particles of PAF-1 (PTMSP/PAF-1) and PTMSP without dispersed particles (PTMFP). In some instances comparison is also made with commercially available polymer membranes used in pervaporation.

(23) S1. Chemicals and Materials

(24) Analytical grade methanol (MeOH), ethanol (EtOH), isopropanol (IPA), cyclohexane (EMD Millipore Corporation), Poly-trimethyl-silylpropyne (PTMSP) was purchased from Gelest Inc. (Morrisville Pa., USA) and used without purification. Chloroform, dichloro-methane (DCM), and hydrochloric acid (HCl) were used as received. 1,4, dichloroxylene (DCX) 98%, Iron (III) chloride, reagent grade, anhydrous 97%, 1,2 Dichloroethane (DCE) was supplied by Chem-Supply.

(25) S2. PAF-1 Synthesis

(26) PAF-1 was synthesised according to Ben, T. et al. [Targeted Synthesis of a Porous Aromatic Framework with High Stability and Exceptionally High Surface Area. Angew. Chem. 121, 9621-9624, doi:10.1002/ange.200904637 (2009)] to yield an off-white powder with a BET surface area of 3760 m.sup.2/g). 1,5-cyclooctadiene (dried over CaH.sub.2) was added into a solution of bis(1,5-cyclooctadiene) nickel and 2,2-bipyridyl in dehydrated DMF, and heated at 80 C. to form a purple solution. Tetrakis(4-bromophenyl)methane was added to the mixture and stirred overnight at 80 C. The mixture was allowed to cool to room temperature and concentrated HCl was added. The solids were collected and washed with chloroform, THF, and deionized water. The particle size was typically in the range of 100-200 nm.

(27) S3. p-DCX Synthesis

(28) To a solution of DCX monomer (0.171 mol, 30 g) in anhydrous DCE (388 mL), a DCE solution (388 mL) of FeCl.sub.3 (0.173 mol, 28 g) was added. The resulting mixture was stirred in an open vessel at room temperature. The precipitated p-DCX was washed once with water, three times with methanol (until the filtrate was clear), and with diethyl ether followed by drying for 24 h at 60 C.

(29) S4. Preparation of Membranes

(30) 2 wt. % PTMSP was dissolved in chloroform. The doping solution was poured into a polyfluortetraethylene (PTFE) dish. After the evaporation of chloroform, a 100 m thick membrane for PV was obtained. For the p-DCX and PAF-1 incorporated membranes, 10 wt. % of nanoparticles (compared with PTMSP) was added in the doping solution before the formation of uniform PTMSP solution. After that, all of the procedures are same with the pristine PTMSP PV membranes. The thickness of the final membranes was determined by a digital micrometer.

(31) S5. Pervaporation Experiments

(32) For the bulk of PV membrane characterisation, experiments were performed on 100 m thick unsupported PTMSP based membranes. Each PV run was conducted for 3 hours and each condition was repeated for 2-3 times. Total experimental time for unsupported PTMSP based membrane PV characterisation was 96 hours. Experiments performed on unsupported membranes were non-continuous i.e. there were start-up and shut-down periods between each run. The pervaporation experiments were carried out using a pervaporation unit with a heater, peristaltic pump, vacuum pump, as schematically shown in FIG. 2. The membrane was placed in the middle of a pervaporation cell and the effective surface area of the membrane was 12.57 cm.sup.2. Different concentration aqueous ethanol solutions 3-10 wt. % ethanol were used as feed solution. During the experiment, the feed solution was preheated between 20 to 60 C. using a water bath and circulated through the membrane cell using a Maserflex peristaltic pump. The permeate was collected using a liquid nitrogen cold trap. The vacuum at the permeate side of membranes was maintained at 5 and 15 Torr for unsupported and supported PTMSP based membranes, respectively.

(33) Total flux (J) is calculated as

(34) $J=\frac{W}{A}$

(35) where W is the weight of permeate collected, A is the effective membrane area, and t is the time that permeate was collected in the trap.

(36) The process separation factor 3 is defined as

(37) $=\frac{Y_e\text{/}{Y}_w}{X_e\text{/}{X}_w}$

(38) where X.sub.e and X.sub.w are mole fraction of ethanol and water in the feed, respectively. Y.sub.e and Y.sub.w are mole fractions of ethanol and water in the permeate, respectively. Ethanol concentration is determined using NMR analysis a Bruker Av400 NMR spectrometer. 1H NMR spectra were recorded in dimethyl sulfoxide (DMSO)-D6.

(39) FIG. 2 shows a schematic of the pervaporation unit in this work.

(40) FIGS. 3A-D show the effects of (A) ethanol concentration (FIGS. 3A-B) and (B) temperature on the total flux and EtOH/water selectivity of membranes (FIGS. 3C-D).

(41) FIG. 4 provides a comparison of PV separation performances of our membranes with other silicon based pervaporation membranes for EtOH/water separations; [a] and [e] are reported in reference J. A. Gonzlez-Marcos, C. Lpez-Dehesa, J. R. Gonzlez-Velasco, J. Appl. Polym. Sci. 2004, 94, 1395-1403; [b] and [c] are reported in reference S. B. Teli, G. S. Gokavi, M. Sairam, T. M. Aminabhavi, Sep. Purif. Technol. 2007, 54, 178-186; and [d] is reported in reference N. Petzetakis, C. M. Doherty, A. W. Thornton, X. C. Chen, P. Cotanda, A. J. Hill, N. P. Balsara, Nat Commun 2015, 6.

(42) PAF-1 and p-DCX additives were found to simultaneously enhanced both the total flux and EtOH/water selectivity of 100 m thick PTMSP PV membranes. PV experiments were performed at 40 C., with upstream and downstream pressures of 760 and 5 Torr, over 96 hours of continuous operation. From solution NMR experiments, we observed that the EtOH/water selectivities of PTMSP membranes increased by 52% and 65% with the inclusion of PAF-1, and p-DCX, respectively. EtOH adsorption over water in PTMSP membranes was drastically enhanced by p-DCX and PAF-1, leading to the higher EtOH/water selectivities. More importantly, the enhanced PV performances of aged PTMSP/p-DCX were 50% higher than as-cast pure PTMSP membranes.

(43) 10 wt. % of PAF-1 and p-DCX enhanced the total (water and ethanol) fluxes of unsupported 100 m thick PTMSP membranes by 31% and 79% respectively. The EtOH/water selectivities were increased by 52% and 64%). More importantly, the anti-aging effects of PAF-1 and p-DCX nanoparticles on PTMSP gas separation membranes were also observed here when the same membranes were deployed for continuous PV operations. PTMSP PV membranes studied here lost 51% of the total flux in nearly 100 hours of continuous operation, while the total fluxes of PTMSP/PAF-1 and PTMSP/p-DCX PV membranes were only reduced by 34% and 25%, respectively. The total flux of aged PTMSP/p-DCX membranes remained 30% higher than that of as-cast PTMSP membranes; indicating the applicability of these membranes for long term PV operation in the industry. Upon physical aging, the EtOH/water selectivity of PTMSP/p-DCX membranes increased by 10% while the selectivities of PTMSP and PTMSP/PAF-1 membranes remained the same. The simultaneous enhancements in total flux and EtOH/water selectivity of both PTMSP/PAF-1 and PTMSP/p-DCX membranes are atypical of most other PTMSP/additive membranes. Most PTMSP/additive membranes display a trade-off relationship between total flux and selectivity (similar to that described by Robeson's plots for pure gas permeability), where increments in total flux are reflected by a decrease or no changes in molecular selectivity, and vice versa. However low contents of high molecular weight polymer particles increased both the flux and EtOH/water selectivity of PTMSP PV membranes, but aging data of such membranes were not reported. The high porosities of hydrophobic PAF-1 and p-DCX nanoparticles provided additional channels for molecular diffusion, thus improving the total flux of our PTMSP/additive membranes. Meanwhile the exceptional surface areas of these hydrophobic particulate additives provide more adsorption sites that favoured alcohol adsorption over water; thus improving the EtOH/water selectivity. The combination of enhanced molecular adsorption and additional porosity for molecular diffusion accounted for drasticenhancements in both total flux and EtOH/water selectivity.

(44) p-DCX nanoparticles reduced the impact of physical aging on solvent flux losses. Through intimate non-bonding interactions with PTMSP chains, the mobilities of these polymer chains were drastically reduced, hence minimizing losses in free volume size and content. Non-compatible additives create nanogaps (as wide as 8 ) between additives and polymer chains that reduced EtOH/water selectivity by allowing both water (2.8 ) and EtOH (4.5 ) molecules to permeate across membranes. However, from PALS analysis, it was clear that such nanogaps were absent in free-standing 1 m thin PTMSP/p-DCX films. Coupled with a negligible reduction in pore sizes (0.8 ). The absence of nanogaps in PTMSP/PAF-1 membranes accounted for the unchanged EtOH/water selectivity over time. The unchanged EtOH/water selectivity in aged PTMSP/PAF-1 membranes implied that the permeation of EtOH and water across these membranes were uniformly reduced by physical aging. Interestingly, the EtOH/water selectivity of aged PTMSP/p-DCX membranes increased by nearly 10%. Upon physical aging in PTMSP/p-DCX films, the concentration of smaller pores (5.8 ) increased from 4.2 to 5.1% (within 0.3% error), while the concentration of the larger pores (14 ) were reduced by 2%. The total flux of aged PTMSP/p-DCX membranes remained higher than any membranes studied because of higher solvent solubility coefficients. The reduced pore size distributions contributed to the increase in EtOH/water selectivity of aged PTMSP/p-DCX membranes.

(45) FIGS. 5A-C include figures which show Pore sizes and concentration of 100 m thick as-cast (solid) and aged (dash) (A) PTMSP, (B) PTMSP/PAF-1, and (C) PTMSP/p-DCX films.

(46) In conclusion, the total flux of our aged PTMSP/p-DCX membranes remained superior to as-cast pristine PTMSP, polydimethylsiloxane (PDMS) mixed matrix membranes, commercial pervaporation membranes, and current-state-of-the-art PDMS membrane. The main concern of deteriorating solvent flux to extremely low values, especially in thin films of PTMSP over time is resolved through the intimate interactions between p-DCX nanoparticles and PTMSP. The performance of the PTMSP/p-DCX membranes.

(47) S6. Nitrogen Adsorption Isotherms

(48) Gas adsorption isotherms between the range of 0-700 mmHg were measured by a volumetric approach using a Micrometrics ASAP 2420 instrument. All the samples were transferred to pre-dried analysis tubes, sealed with Transeal stoppers, evacuated and activated at 120 C. under a 10.sup.6 dynamic vacuum for 24 hours. Ultra-high purity N.sub.2 gases were used for these experiments. N.sub.2 adsorption measurements were conducted at 77 K.

(49) FIG. 6 is a graph showing the pore size distribution of PAF-1 (blue) and p-DCX (red) nanoparticles obtained from nitrogen adsorption isotherms performed at 77 K.

(50) S7. Positron Annihilation Lifetime Spectroscopy (PALS)

(51) Bulk PALS experiments that were used to characterize aging in the material bulk were performed at CSIRO using an EG&G Ortec fast-fast coincidence system with fast plastic scintillators and a resolution function of 260 ps FWHM (.sup.60Co source with the energy windows set to .sup.22Na events). Due to the long lifetimes, and the low counting rate, the coincidence unit was removed and the range of the TAC extended to 200 ns. The film samples were stacked to a thickness of 2 mm, and powdered samples were packed (>1.5 mm depth), on either side of a 30 Ci .sup.22NaCl source sealed in a 2.54 m thick Mylar envelope (source correction 1.605 ns and 2.969%) and measured at 510.sup.7 Torr. At least five spectra of 4.5 million integrated counts were collected with each spectrum taking about 4.6 h to collect. Data analysis was performed using LT9. The spectra were best fitted with five components with the shortest lifetime fixed to 125 ps, characteristic of p-Ps annihilation. For the long lifetimes obtained, the Tao-Eldrup model.sup.2,3 traditionally used for calculating mean pore sizes from mean o-Ps lifetimes is not valid; therefore, the mean free path (nm) of the pores was calculated using the Rectangular Tao Eldrup (RTE) model.

(52) S8. Membrane Characterisation

(53) The cross-section and surface morphologies of the cryo-fractured membranes were characterised by FESEM (MERLIN Compact, Zeiss Company). A contact angle measuring system (G10 Kruss, Germany) was used to measure the static water contact angle of membranes. A deionized water droplet was placed on a dry flat membrane surface and the contact angle was obtained. The reported contact angle value was calculated by averaging over more than five contact angle values at different sites and are shown in Table 2.

(54) TABLE-US-00002 TABLE 2 Contact angles of PTMSP and PTMSP/PAF-1 membranes. Sample Name Water Contact Angle () PTMSP 117 PTMSP/PAF-1 127 PTMSP/p-DCX 122

Example 3Alcohol Purification

(55) This Example compares the performance of PTMFP/p-DCX membranes of the invention with corresponding PTMFP/PAF-1 membranes not of the invention and a cotrol membrane of PTMFP containing no dispersed particles as well as some commercially available membranes.

(56) Organic solvent nanofiltration (OSN) membranes are characterized by their nominal molecular weight cut-off for a reference compound where small molecules such as pharmaceuticals, and dyes are removed from organic liquids. The permeance enhancements in polymer membranes loaded with the hypercrosslinked porous particles was accompanied by higher alcohol selectivities over solutes such as dyes (which were used as a proxy for pharmaceutics), overcoming the trade-off relationship between permeance and selectivity. The separation performance of the membranes was found outperform commercially available polymer membranes. These membranes are optimal for transforming batch processes like alcohol purification into continuous operations; streamlining current industrial practices.

(57) Polymer physical aging is a process where the convergence of glassy polymer chains collapses the inter-chain free volume, also known as fractional free volume (FFV) content, required for molecular transport via diffusion and adsorption. Other than physical aging, separation performances of ultrathin polymer membranes can also deteriorate due to membrane compaction, where high pressures compress polymer chains and collapse molecular transportation pathways. In a commercial setting, membranes on polymeric substrates are generally allowed to age and compact to achieve steady-state permeance for continuous operation. This approach sacrifices the initial tantalising membrane performance for stability.

(58) S1. Chemicals and Materials

(59) Analytical grade methanol, ethanol, isopropanol, Rose Bengal (RB), Crystal Violet (CV), and Thiazole Yellow (TY) (Sigma-Aldrich) were purchased and used without further purification. PTMSP was purchased from Gelest Inc (SSP070-10GM, Lot 41-23599, Mw 210 kDa, 95% purity) and used without purification. Chloroform, dichloromethane (DCM), and hydrochloric acid (HCl) were used as received. 1,4, dichloroxylene (DCX) 98%, Iron (III) chloride, reagent grade, anhydrous 97%, Tetraphenylmethane, bis(1,5-cyclooctadiene) nickel, and 2,2-bipyridyl were purchased from Sigma Aldrich, and used without further purification. 1,2 Dichloroethane (DCE) was supplied by Chem-Supply.

(60) S2. PAF-1 and p-DCX Synthesis

(61) PAF-1 and p-DCX were prepared as describe in Example 2 (S2 and S3)

(62) S4. Preparation of Membranes

(63) The polymer dope solution was prepared by dissolving 2 wt. % of PTMSP (Gelest Inc.) in cyclohexane. 10 wt. % (with respect to PTMSP concentration) of porous additives, PAF-1 or p-DCX, were added to the polymer dope solution and stirred for 24 hours. This mixture was then poured onto a glass plate. Doctor blades with thickness 30, 50, 80, 100, 150 um were used to knife-cast thin membranes. Upon solvent evaporation, the glass plate with a thin layer of membrane was lowered into a water bath. This enabled the flotation of the thin polymer membrane film onto the surface of the water. A polycarbonate porous substrate was lowered into the water bath, and came into contact with the PTMSP-based membrane. Water was then drained out, and a free-standing PTMSP-based membrane supported on a polycarbonate substrate was obtained.

(64) S5. Scanning Electron Microscopy (SEM)

(65) All membrane films were cryo-fractured, to achieve a clean break, and then mounted on cross-section SEM sample stubs. These sample stubs were then coated with iridium for elemental analysis through energy dispersive spectroscopy (EDS) during imaging.

(66) TABLE-US-00003 TABLE 3 FFV content of free-standing as-cast, aged and wet (EtOH soaked) PTMSP, PTMSP/PAF-1, and PTMSP/p-DCX membranes. Aged FFV Aged FFV (%) Sample Name (%) dry wet PTMSP 20 11 PTMSP/PAF-1 21 14 PTMSP/p-DCX 30 12

(67) S8. Organic Solvent Nanofiltration Experiments

(68) The permeances or fluxes of OSN membranes were measured using a self-made, stainless steel dead-end pressure cell with a membrane area of 21.2 cm.sup.2. The feed solution was pressurised with nitrogen to 5 bar at room temperature. During filtration, the feed solution was stirred at 11.66 Hz (700 rpm) to avoid concentration polarization. Permeate samples were collected in cooled flasks as a function of time, weighed and analysed. The solvent flux and solvent permeance were calculated using the following equations:

(69) $\begin{array}{cc}F=\frac{V}{At}& \left(1\right)\\ \mathrm{Permeance}=\frac{F}{P}& \left(2\right)\end{array}$
where F represents the solvent flux (L m.sup.2 h.sup.1), V (L) is the volume of the solvent (or solution) passing through the membrane, A is the effective membrane area (m.sup.2), t is the operation time (h); and P is trans-membrane pressure (bar). Solvent permeances were tested in the order of MeOH>EtOH>i-PrOH.

(70) The solute rejections of NF membranes were calculated using Eq.3

(71) $\begin{array}{cc}R=\left(1-\frac{C_p}{C_f}\right).Math.100\%& \left(3\right)\end{array}$
where C.sub.p and C.sub.f are the solute concentrations in the permeate and the feed solution, respectively. Dye concentrations in IPA were measured with a UV-VIS CINTRA20-GBC apparatus (.sub.max of RB=548 nm). Each data point is an average of three repetitions of each test, with +5% standard deviation.

(72) FIGS. 7A-F include figures which show the methanol (black), ethanol (red) and isopropanol (blue) permeances of as-cast (solid) and aged (empty) 1 um thin (A) PTMSP, (B) PTMSP/PAF-1 and (C) PTMSP/p-DCX membranes supported on polycarbonate substrates. The Rose Bengal (orange), Thiazole Yellow (green), and Safranine O (purple) dyes rejection rates from ethanol of (D) PTMSP, (E) PTMSP/PAF-1 and (F) PTMSP/p-DCX membranes.

(73) PTMSP membranes (1 m thin) comprising PAF-1 and p-DCX nanoparticles supported on porous polycarbonate substrates were prepared for for OSN, and voided the need to sacrifice initial membrane performances for stability (FIG. 1). These membranes were used to recover alcohol from dye mixtures, mimicking industrial pharmaceutical recovery from alcohol. PAF-1 and p-DCX drastically enhanced the alcohol permeances of OSN membranes by 90%; whilst improving dye rejections. PAF-1 and p-DCX also prevented compaction impact on these OSN membranes. Continuous long term membrane operation in OSN conditions (5 bar, 25 C., stirring speed of 700 rpm) revealed a drastic lowering in physical aging in 1 m thin membrane films when the additives were incorporated. More importantly, p-DCX additives stabilised the drastically enhanced alcohol permeances of PTMSP mixed matrix membranes. Overall the membranes are locked in their initial state which allows effective use of the polymer membranes for high speed alcohol purification at low operating pressures.

(74) The incorporation of PAF-1 and p-DCX into PTMSP drastically enhanced ethanol permeation by 42% and 90%, respectively; whilst improving dye rejection.

(75) FIGS. 8A-B are 2 graphs showing: (A) the effects of physical aging (after 500 hours of continuous operation at 5 bar of solvent pressure and 25 C.) on ethanol transport in PTMSP (black), PTMSP/PAF-1 (blue), and PTMSP/p-DCX (red) where membranes were cast using 0.5 wt. % of doping concentration; and (B) dye rejection rates of as-cast (solid) and aged (empty) membranes studied here. The molecular weights of Rose Bengal, Thiazol Yellow, and Safranine O are 1017.64 g mol1, 695.74 g mol1, and 350.13 g mol1, respectively.

(76) The increment in EtOH permeance was attributed to the intrinsic pores of PAF-1 and p-DCX nanoparticles that provided additional molecular transportation pathways, the hydrophobicity of additives, and pore size enlargements in PTMSP membranes. Highly hydrophobic 5 pores in PAF-1 nanoparticles optimize alcohol diffusion. There are two pore size distributions centered at 5.9 and 13.5 in p-DCX nanoparticles, while there are three overlapping pore size distributions in PAF-1 in the region between 11.8 to 17.2 . The pore size distribution centered at 5.9 in p-DCX is optimal for alcohol diffusion; hence contributing to the 90% enhancement in EtOH permeance. The smaller pores of p-DCX nanoparticles also accounted for the 15% improvement in rejecting Safranine O, the smallest dye studied here (Mw 350.13 g mol.sup.1). PAF-1 and p-DCX nanoparticles slightly improved the 90% rejection rate of PTMSP membranes for both the larger Rose Bengal (Mw 1017.64 g mol.sup.1) and Thiazol Yellow (Mw 695.74 g mol.sup.1) dyes.

(77) Unlike other mixed matrix membranes, the incorporation of porous nanoparticles did not reduce dye rejection rates; indicating an absence of large nanogaps between the porous additives and polymer chains. The dye rejection rates of present PTMSP/additive membranes are comparable to commercial membranes.

(78) Physical aging was investigated using OSN membranes operated continuously for 500 hours at 5 bar. A lower operating pressure was chosen here to demonstrate that our ultrapermeable membranes can achieve alcohol permeances that are higher than commercial membranes without a large driving force. The EtOH permeance in PTMSP control membranes was reduced by 45%, and stabilized within the first 100 hours of aging. Physical aging reduced the pore sizes and concentration in PTMSP, hence impeding ethanol transport in aged PTMSP membranes. PAF-1 and p-DCX inhibited or abated the shrinkage and loss of such pores in anti-aging, and selective-aging gas separation PTMSP membranes. Here we report that this was also valid for alcohol transport across 1 m thin PTMSP membranes. The enhanced EtOH permeances of PTMSP membranes loaded with PAF-1 and p-DCX were only reduced by 20 and 12%, respectively, and stabilized within 13 hours of testing. The anti-aging effect is more pronounced with p-DCX nanoparticles. Different from gas separation membranes where only the permeation of large molecules like nitrogen (kinetic diameter 3.64 ) were affected by physical aging, we observed that the permeation of even larger molecules like ethanol (kinetic diameter 4.5 ), and i-PrOH (kinetic diameter 4.7 ) were not affected in our PTMSP/additive OSN membranes. Clearly, there is a different anti-aging mechanism for OSN.

(79) Positron annihilation lifetime spectroscopy (PALS) was used to track changes in pore size and concentration, and FFV content within 1 m thin free-standing PTMSP-based films in the wet (pre-soaked in EtOH) and dry states. There is a bimodal pore size distribution centred at 5.5 (d.sub.3) and 11 (d.sub.4) in PTMSP (FIGS. 9A-C). Physical aging reduced the d.sub.3 and d.sub.4 pore sizes in PTMSP by 0.5 and 2 , respectively. The incorporation of PAF-1 and p-DCX nanoparticles did not alter pore sizes and concentration in as-cast PTMSP, indicating the good compatibility between PTMSP and our porous additives. With PAF-1 and p-DCX, the d.sub.4 pores in aged PTMSP films were only reduced by 1 , while the d.sub.3 pore size and the d.sub.3 and d.sub.4 pore concentrations remain unchanged. Aged 1 m thin PTMSP, PTMSP/PAF-1, PTMSP/p-DCX membranes lost 48, 40, and 20% of FFV content (FIG. 9D). Higher FFV content i.e. porosity in aged PTMSP/additive membranes lowered transmembrane resistance and enhanced total flux. The relative losses in FFV content were smaller than relative losses in EtOH permeances in aged PTMSP/additive membranes. The impact of lost FFV content on EtOH transport could be mitigated by alcohol adsorption. This view is reinforced by the fact that PTMSP/PAF-1 membranes with higher FFV content had lower EtOH permeances when compared to PTMSP/p-DCX membranes with lower FFV content.

(80) We also observed changes in pore sizes and concentrations in aged dry and wet (soaked in EtOH) PTMSP-based films (FIGS. 9E-G). Polymer films were soaked in EtOH for 24 hours, dried with tissue paper, prior characterisation. In the presence of EtOH, the pore sizes in aged PTMSP remained the same, while the concentration of d.sub.3 and d.sub.4 pores increased and decreased, respectively. This indicated that d.sub.4 pores were filled up with EtOH molecules. The filling of pores with EtOH molecules was also observed across both d.sub.3 and d.sub.4 pores in both aged PTMSP/PAF-1 and PTMSP/p-DCX membranes. The filling of d.sub.3 pores in PTMSP/additive films could be attributed to film hydrophobicity. PAF-1 and p-DCX nanoparticles increased the hydrophobicity of PTMSP films, that improved alcohol adsorption. This accounted for the highest EtOH adsorption of 6.4 cm.sup.3/g in PTMSP/p-DCX membranes, 17% higher than PAF-1 loaded membranes (FIG. 9H). Higher EtOH adsorption did not swell PTMSP/additive membranes, but filled up the pores present in these membranes. The lack of swelling due to EtOH adsorption in our PTMSP/additive membranes indicated that the rigidification of PTMSP polymer chains by porous nanoparticles. This was further demonstrated through alcohol regeneration and membrane compaction tests.

(81) FIGS. 9A-H include figures which show the bimodal pore size distribution of (A) as-cast vs aged (FIGS. 9A-9C), and (B) aged wet vs aged dry PTMSP, PTMSP/PAF-1(FIG. 9D), and PTMSP/p-DCX membranes determined using PALS. The pore size distribution is expressed as a probability density function. The pore concentration is expressed as intensity %. (C) The relationship between relative EtOH permeances of PTMSP, PTMSP/PAF-1 and PTMSP/p-DCX membranes and FFV content losses due to physical aging. (FIGS. 9E-G). (D) The influence of additives on the EtOH adsorption in PTMSP membranes studied here (FIG. 9H).

(82) Alcohol regeneration is used to rejuvenate the collapsed FFV content between mobile polymer chains. Here we used this technique to reveal the rigidification of PTMSP chains by PAF-1 and p-DCX nanoparticles. Membranes were first exposed to 5 bar EtOH for 100 hours, and regenerated by a 100 hour EtOH soak. EtOH permeance in PTMSP membranes was reduced by 45% after 100 hours of physical aging. Alcohol regeneration of aged PTMSP membranes recovered 12% of EtOH permeances, while minimizing recovery impact on PTMSP/PAF-1 and PTMSP/p-DCX membranes. Even without alcohol regeneration, the EtOH permeances of PTMSP/PAF-1 and PTMSP/p-DCX membranes remained stable, and significantly higher than regenerated PTMSP. Without PAF-1 or p-DCX nanoparticles, PTMSP chains possessed more freedom and mobility. Through alcohol regeneration, alcohol molecules occupied and recovered the free spaces between these mobile polymers chains. As PTMSP chains were immobilized by PAF-1 or p-DCX nanoparticles, alcohol regeneration was subdued. This also minimized membrane compaction effects.

(83) Compaction effects were determined from OSN membranes that were off-line for 1 hour after exposure to 5 bar of EtOH for 100 hours. The 1 hour rest period allowed the membranes to depressurize. EtOH permeances of PTMSP, PTMSP/PAF-1, and PTMSP/p-DCX membranes were 45%, 10% and 5% higher than membranes that were characterized immediately after 100 hours, respectively. Mobile PTMSP chains relaxed upon depressurization and regained some free volume content that contributed to the recovery of molecular transportation rates; hence accounting for the significant recovery of EtOH permeance in pure PTMSP membranes. It is important to highlight that the recovered PTMSP EtOH permeances through alcohol regeneration or decompaction remained lower than the initial EtOH permeance of as-cast PTMSP membranes; highlighting that the inefficiencies of such techniques. Evidently, the incorporation of PAF-1 and p-DCX nanoparticles removed the need for membrane revitalization techniques, as the EtOH permeances of these nanocomposite membranes remained comparable to their initial EtOH permeances throughout all experiments.

(84) In the preceding, the unique interactions between porous additives such as p-DCX, and the super glassy polymer PTMSP has been utilised to enable longevity in high performing OSN membranes, reduce membrane compaction effects thus nullifying the need to stabilize membrane performance prior actual operation. This also ensures that the initial tantalising separation properties of the membranes are captured and immortalized. Addition of p-DCX reduced physical aging rates by 12%, whilst also doubling the permeance rates of EtOH through the fresh membrane. Careful experiments simulating applied settings delivered over 500 hours of continuous operation with stabilised performance, at as much as 90% higher permeance than aged controls. Detailed studies of various alcohols demonstrated the potential use of this system across a platform of low energy liquids purification applications. The permeabilites of our PTMSP/porous additive membranes stabilized to values that were higher than the initial permeances of as-cast PTMSP membranes, outperforming current state-of-the-art membrane. Unique threading of the polymer side chains into the additive pores was found to underpin this performance. Taken together, these findings enable further use of ageless, compaction-free OSN membranes as low energy separation alternatives, and further empower the highest performing polymers to be included in these membranes by imbuing them with longevity.