Polyimide Matrimid Research Articles

Fabrication of new proton conducting membrane for fuel cell applications based on porous polyimide Matrimid® and hydrophobic protic ionic liquid

AbstractA new proton conducting membrane has been developed by impregnation of porous polyimide Matrimid® (PI) with hydrophobic protic ionic liquid triethylammonium bis(trifluoromethylsulfonyl)imide (TEA‐TFSI). According to the results of dynamic mechanical analysis (DMA), PI/TEA‐TFSI membrane has satisfactory viscoelastic properties in the temperature range 25–100°C. However, the sharp drop in storage modulus (E') occurs at higher temperatures that is probably caused by the plasticizing effect of ionic liquid. To improve the mechanical properties of PI matrix, it was impregnated with the solution of polyetheramine Jeffamine® D‐400 in the TEA‐TFSI. This approach allowed to obtain a partially cross‐linked PI which is more resistant to deformation at elevated temperatures. Thus, DMA study revealed a storage modulus around 400 MPa for PI/Jeffamine/TEA‐TFSI membrane up to 150°C, like neat porous Matrimid®. Thermogravimetric analysis results indicate high thermal stability of PI/Jeffamine/TEA‐TFSI composite with thermal degradation point of 343°C. The ionic conductivity of the composite membrane is 4·10−3 S/cm at room temperature and reaches the level of 10−2 S/cm above 100°C. Overall, the results of this study indicate that partially cross‐linked porous PI impregnated with hydrophobic protic ionic liquid is a promising polymer electrolyte membrane for fuel cells operating at elevated temperatures in water‐free conditions.

Fabrication of proton exchange membrane for non-humidified fuel cells based on polyimide Matrimid® and hydrophobic protic ionic liquid

New proton exchange membrane based on polyimide Matrimid® (PI) and hydrophobic protic ionic liquid, 1-methylimidazolium bis(trifluoromethylsulfonyl)imide (MIM-TFSI), has been prepared by casting from methylene chloride/dimethylformamide solution. Infrared analysis revealed physicochemical interactions between 1-methylimidazolium cations and imide groups of PI. The results of mechanical testing indicate significantly reduced tensile strength of PI/MIM-TFSI composite membrane compared to neat polymer. Moreover, the dynamical mechanical analysis results revealed sharp drop in storage modulus (E´) of the polymer film above 60 °C. To improve the elastic properties of the membrane, PI was successively cross-linked with polyetheramine Jeffamine® D-2000 (10 mol. %) in methylene chloride/dimethylformamide solution, as well as in solid film at 100 °C. This approach allowed to prepare PI/Jeffamine/MIM-TFSI (70 wt. %) composite film which has an acceptable E' value of 210 MPa at 140 °C. According to thermal gravimetric analysis data, PI/Jeffamine/MIM-TFSI composite has a thermal degradation point (i.e. 5 % weight loss) of 286 °C. The ionic conductivity of PI/Jeffamine/MIM-TFSI composite membrane is around 10–4 S/cm at room temperature and reaches the minimal level of 10–3 S/cm, required for fuel cell applications, above 100 °C. Overall, the results of this study indicate that the cross-linking of polyimide Matrimid with flexible polyetheramine Jeffamine is an efficient approach for preparing dense composite membrane with high content of the protic ionic liquid. Such polymer-electrolyte membrane has the reasonable combination of good stiffness, thermal stability, and ionic conductivity and therefore is a promising candidate for use in fuel cells operating at elevated temperatures in water-free conditions.

Thin Film Composite Membranes Based on the Polymer of Intrinsic Microporosity PIM-EA(Me2)-TB Blended with Matrimid®5218.

In this work, thin film composite (TFC) membranes were fabricated with the selective layer based on a blend of polyimide Matrimid®5218 and polymer of intrinsic microporosity (PIM) composed of Tröger’s base, TB, and dimethylethanoanthracene units, PIM-EA(Me2)-TB. The TFCs were prepared with different ratios of the two polymers and the effect of the PIM content in the blend of the gas transport properties was studied for pure He, H2, O2, N2, CH4, and CO2 using the well-known time lag method. The prepared TFC membranes were further characterized by IR spectroscopy and scanning electron microscopy (SEM). The role of the support properties for the TFC membrane preparation was analysed for four different commercial porous supports (Nanostone Water PV 350, Vladipor Fluoroplast 50, Synder PAN 30 kDa, and Sulzer PAN UF). The Sulzer PAN UF support with a relatively small pore size favoured the formation of a defect-free dense layer. All the TFC membranes supported on Sulzer PAN UF presented a synergistic enhancement in CO2 permeance, and CO2/CH4 and CO2/N2 ideal selectivity. The permeance increased about two orders of magnitude with respect to neat Matrimid, up to ca. 100 GPU, the ideal CO2/CH4 selectivity increased from approximately 10 to 14, and the CO2/N2 selectivity from approximately 20 to 26 compared to the thick dense reference membrane of PIM-EA(Me2)-TB. The TFC membranes exhibited lower CO2 permeances than expected on the basis of their thickness—most likely due to enhanced aging of thin films and to the low surface porosity of the support membrane, but a higher selectivity for the gas pairs CO2/N2, CO2/CH4, O2/N2, and H2/N2.

Novel Ionic Conducting Composite Membrane Based on Polymerizable Ionic Liquids.

In this work, the design and characterization of new supported ionic liquid membranes, as medium-temperature polymer electrolyte membranes for fuel-cell application, are described. These membranes were elaborated by the impregnation of porous polyimide Matrimid® with different synthesized protic ionic liquids containing polymerizable vinyl, allyl, or methacrylate groups. The ionic liquid polymerization was optimized in terms of the nature of the used (photo)initiator, its quantity, and reaction duration. The mechanical and thermal properties, as well as the proton conductivities of the supported ionic liquid membranes were analyzed in dynamic and static modes, as a function of the chemical structure of the protic ionic liquid. The obtained membranes were found to be flexible with Young’s modulus and elongation at break values were equal to 1371 MPa and 271%, respectively. Besides, these membranes exhibited high thermal stability with initial decomposition temperatures > 300 °C. In addition, the resulting supported membranes possessed good proton conductivity over a wide temperature range (from 30 to 150 °C). For example, the three-component Matrimid®/vinylimidazolium/polyvinylimidazolium trifluoromethane sulfonate membrane showed the highest proton conductivity—~5 × 10−2 mS/cm and ~0.1 mS/cm at 100 °C and 150 °C, respectively. This result makes the obtained membranes attractive for medium-temperature fuel-cell application.

Biphenyl-Based Covalent Triazine Framework/Matrimid® Mixed-Matrix Membranes for CO2/CH4 Separation.

Processes, such as biogas upgrading and natural gas sweetening, make CO2/CH4 separation an environmentally relevant and current topic. One way to overcome this separation issue is the application of membranes. An increase in separation efficiency can be achieved by applying mixed-matrix membranes, in which filler materials are introduced into polymer matrices. In this work, we report the covalent triazine framework CTF-biphenyl as filler material in a matrix of the glassy polyimide Matrimid®. MMMs with 8, 16, and 24 wt% of the filler material are applied for CO2/CH4 mixed-gas separation measurements. With a CTF-biphenyl loading of only 16 wt%, the CO2 permeability is more than doubled compared to the pure polymer membrane, while maintaining the high CO2/CH4 selectivity of Matrimid®.

New polymer electrolyte membrane for medium-temperature fuel cell applications based on cross-linked polyimide Matrimid and hydrophobic protic ionic liquid

New hydrophobic protic ionic liquid, 2-butylaminoimidazolinium bis(trifluoromethylsulfonyl)imide (BAIM-TFSI), has been synthesized. The ionic liquid showed good thermal stability to at least 350 °C. The conductivity of BAIM-TFSI determined by electrochemical impedance method was found to be 5.6 × 10−2 S/cm at 140 °C. Homogeneous composite films based on commercial polyimide (PI) Matrimid and BAIM-TFSI containing 30–60 wt% of ionic liquid were prepared by casting from methylene chloride solutions. Thermogravimetric analysis data indicated an excellent thermal stability of PI/BAIM-TFSI composites and thermal degradation points in the temperature range 377 °C–397 °C. The addition of ionic liquid up to 50 wt% in PI films does not lead to any significant deterioration of the tensile strength of the polymer. The dynamic mechanical analysis results indicated both an increase of storage modulus E′ of PI/BAIM-TFSI composites at room temperature and a significant E′ decrease with temperature compared with the neat polymer. The cross-linking of the PI with polyetheramine Jeffamine D-400 allowed to prepare PI/Jeffamine/BAIM-TFSI (50%) membrane with E′ value of 300 MPa at 130 °C. The ionic conductivity of this cross-linked composite membrane reached the level of 10−2 S/cm at 130 °C, suggesting, therefore, its potential use in medium-temperature fuel cells operating in water-free conditions.

Aqueous One-Step Modulation for Synthesizing Monodispersed ZIF-8 Nanocrystals for Mixed-Matrix Membrane.

Enhancing the monodispersity and surface properties of nanoporous zeolitic imidazolate frameworks (ZIFs) are crucial for maximizing their performance in advanced nanocomposites for separations. Herein, we developed an in situ method to synthesize monodispersed ZIF-8 nanocrystals with unique dopamine (DA) surface decoration layer (ZIF-8-DA) in an aqueous solution at room temperature. Interestingly, the in situ formation of the monodispersed ZIF-8-DA nanocrystals experiences a triple-stage crystallization process, resulting in a rhombic dodecahedron architecture, which is greatly different from the synthesis of conventional ZIF-8. The crystallinity and abundant microporosity of ZIF-8-DA nanocrystals is well maintained even with the DA surface decoration. Owing to the advanced surface compatibility and pore properties of ZIF-8-DA, ZIF-8-DA/Matrimid mixed-matrix membranes exhibit both higher gas permeability and selectivity than the pristine Matrimid polyimide membrane, which breaks out the traditional "trade-off" phenomena between permeability and selectivity.

CO2 plasticization effect on glassy polymeric membranes

The effect of CO2 on the mechanical properties of three different glassy polymeric materials, polystyrene (PS), polymethylmethacrylate (PMMA) and Matrimid polyimide (PI), has been investigated by dedicated Dynamic Mechanical Analysis (DMA) at 35 °C on samples equilibrated at different penetrant pressures (0–30 bar). The experimental campaign has been designed to inspect the mechanical properties associated to the so-called plasticization phenomenon, which has been invoked as responsible for the increase of gas permeability versus feed pressure in glassy polymeric membranes. The main aim of the work is to find if any correlation holds between the effects induced on polymer mechanical properties and on gas permeability by the presence of different amounts of penetrant gas.The DMA analysis revealed that CO2 produces a decrease of polymer storage modulus E′ and an enhancement of tan δ factor. Experimental data for both E’ and tan δ vary regularly and monotonically with CO2 content in the membrane, with no indication of the onset of other new phenomena at pressures higher than the “plasticization pressure” associated to permeability data. The mechanical properties show very similar behaviors with CO2 content for all polymers analyzed, notwithstanding their CO2 permeability behaviors are different: decreasing with upstream pressure for PS, increasing for PMMA and nonmonotonous for Matrimid. The results obtained indicate that there is no direct correlation between gas permeation dependence on CO2 content and the changes in the polymer mechanical properties induced by the same CO2 content.

The gas separation performance adjustment of carbon molecular sieve membrane depending on the chain rigidity and free volume characteristic of the polymeric precursor

Carbon molecular sieve membranes (CMSMs) are regarded as promising membranes for gas separation due to its high gas separation performance. Polyimide (ODPA-FDA) precursor films were prepared and characterized for the formation of carbon molecular sieve membranes. This was compared to a commercial polyimide Matrimid. The precursor membranes were characterized with dynamic mechanical analysis, thermogravimetric analysis, X-ray diffraction, FTIR spectroscopy, positron annihilation lifetime spectroscopy in order to determine the effect of the polyimide structure on its permeation properties. The carbonized membranes were characterized by determining its pore size distribution and sorption isotherms. Results showed that ODPA-FDA polyimide has a higher Tg and d-spacing than that of Matrimid. The permeability and selectivity of ODPA-FDA precursor and carbonized films were higher or similar than that of Matrimid precursor and carbonized films due to the addition of a bulky aromatic group in the ODPA-FDA amine moiety which causes narrow free volume distribution. The unique structure of ODPA-FDA polyimide makes it an attractive candidate for the precursor of CMSM.

POLYMER-ELECTROLYTE MEMBRANE FOR FUEL CELLS BASED ON CROSS-LINKED POLYIMIDE AND PROTIC IONIC LIQUID

The aim of this research was to develop polymer-electrolyte membrane on the base of commercial polyimide Matrimid which has high proton conductivity at elevated temperatures above 100 °C. Hydrophobic ionic liquid 1-butylimidazolium bis(trifluoromethylsulfonyl)imide (BIM-TFSI) has been synthesized and used as proton conducting electrolyte. The electrical conductivity of the ionic liquid determined by electrochemical impedance method was found to have a value of 10–3 S/cm in the temperature range from 100 to 180 °С. The composite film based on Matrimid polyimide containing 70 wt % of protic ionic liquid has been prepared by casting from methylene chloride solution. Polyetheramine Jeffamine® D-2000 was used as a cross-linking agent for polyimide. According to mechanical and thermal analysis data, Matrimid/BIM-TFSI composite has tensile strength of 18 MPa and thermal degradation point of 306 °С. Electrophysical properties of polyimide film impregnated with ionic liquid was studied by two-probe technique at the frequencies of 0.1, 1.0 and 10 kHz by using immitance meter in the temperature range from 25 to 180 °С. The electrical conductivity was found to be 2.7∙10–4 S/cm at room temperature and reached the value of 1.5∙10–3 S/cm at 180 °С. Thus, in this work proton conducting membrane based on commercial polyimide has been obtained for the first time by simple method without additional sulfonation stage. Matrimid/BIM-TFSI composite membrane is promising for applications in fuel cells operating at elevated temperature without external humidification.

Investigation and comparison of mixed matrix membranes composed of polyimide matrimid with ZIF – 8, silicalite, and SAPO – 34

Mixed Matrix type membranes (MMMs) containing 10wt% of either silicalite, SAPO – 34, and ZIF – 8 in polyimide Matrimid were fabricated and tested for their suitability to separate a number of gas mixtures by conducting single gas permeation experiments using H2, CO2, N2, and CH4 gases. The transport of these gases through the polymeric and inorganic membrane phases, as well as their interfacial voids, have additionally been distinguished from each other by fabricating MMMs containing non-calcined fillers of silicalite and SAPO-34. The ideal selectivities that have been calculated using the experimentally determined permeabilities can be attributed to the relative pore size and volume of the fillers in each membrane, as well as changes to the mobility of polymer chains in the vicinity of fillers. Due to its large pore volume as well as simultaneous reductions of interfacial voids and polymer chain mobility, ideal selectivities and gas permeabilities that are higher than those achieved by a neat Matrimid membrane have been achieved using ZIF – 8 containing MMMs. For the ZIF – 8 containing membranes, the largest permeabilities for H2, CO2, N2, and CH4 were found to be 51.1, 15.5, 0.64, and 0.54 barrer, respectively. This H2 permeability in particular was found to be the most outstanding out of all of the membranes that have been tested, and ideal selectivities for the separation of H2/N2, and H2/CH4, were found to be 80.3 and 102, respectively. The performance of the membranes that were fabricated using uncalcined silicalite and SAPO-34 also suggest that the structure of the Matrimid phase is altered by the addition of these fillers as greater selectivities at the expense of permeability were also achieved using these MMMs in comparison to a neat Matrimid membrane.

Enhanced gas transport properties of mixed matrix membranes consisting of Matrimid and RHO type ZIF-12 particles

Zeolitic imidazolate frameworks (ZIF) have been showed as potential active inorganic fillers in high-performance gas separation membranes. Among them, zeolitic imidazolate framework-12 crystals were synthesized as a porous filler material by alcohol-based solution method using benzimidazole–toluene interactions and they were incorporated into a commercial glassy polyimide Matrimid 5218 with various ZIF-12 loadings (0, 10, 20, 30, 40wt.%), as the continuous phase. As-synthesized ZIF-12 was characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), multipoint Brunauer–Emmett–Teller (BET) surface analysis, Fourier Transform Infrared Spectroscopy (FT-IR) and Thermogravimetric Analysis (TGA). SEM images of ZIF-12 particles assert regular external surfaces with a rhombic dodecahedron structure. Matrimid mixed matrix membranes (MMMs) loaded with different amounts of ZIF-12 were prepared by solution casting method and characterized by XRD, FT-IR, TGA and SEM analyses. Our findings showed that there was a good dispersion and wetting of ZIF-12 particles in the continuous phase. Gas transport properties of the membranes were investigated by single gas permeation experiments of H2, CO2 and CH4 at 4bar feed pressure and 35°C. The permeability values increased as the ZIF-12 loading increased up to 20wt.%. However, at higher loadings, 30 and 40wt.%, the permeability decreased for all gases and the CO2/CH4 and H2/CH4 selectivities increased depending on the influence of the ZIF-12 filler. The maximum ideal separation factor for CO2/CH4 and H2/CH4 were found about 66.70 and 212.00, significantly higher than the pure polymer ideal separation factor.

Polyimides cross‐linked with amino group‐containing compounds

The commercially available linear polyimide Matrimid® 9725 was crosslinked with amino groups containing both high‐molecular‐weight and low‐molecular‐weight compounds. The multi‐functional amine‐terminated hyperbranched polyimide precursor (hyperbranched polyamic acid), based on 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride and 4,4′,4″‐triaminotriphenylmethane, and its fully imidized form (amine‐terminated hyperbranched polyimide), bifunctional amine, 4,4′‐diaminodiphenylamine and trifunctional amine, 4,4′,4″‐triaminotriphenylamine, were used as the crosslinkers. Theoretically, 10% or 20% of the Matrimid imide groups was reacted with the amino groups of the crosslinking agent during the formation of the amide groups. The insoluble content (gel) in the final materials was very low at the crosslinking temperature of 80°C and was in the 55–90% range at the crosslinking temperature of 200°. The permeability coefficients of hydrogen, carbon dioxide and methane in the self‐standing, mechanically tough film (membrane) based on the combination of Matrimid and hyperbranched polyimide were approximately 30–45% higher compared with those in the membrane made of pure Matrimid at a comparable separating ability (selectivity). POLYM. ENG. SCI., 57:1367–1373, 2017. © 2017 Society of Plastics Engineers

Polymer–Metal Organic Framework Composite Films as Affinity Layer for Capacitive Sensor Devices

We report a simple method for sensor development using polymer-MOF composite films. Nanoparticles of NH2-MIL-53(Al) dispersed in a Matrimid polyimide were applied as a thin film on top of capacitive sensor devices with planar electrodes. These drop-cast films act as an affinity layer. Sensing studies carried out with methanol vapor using impedance spectroscopy demonstrate that the presence of MOF enhances the overall response and lowers the detection limit compared to MOF-free polymer films and bare devices. This can be understood by additional changes of the local polarity of the composite films due to higher adsorption of methanol by the porous MOF particles. We expect that this work will stimulate the design of composite polymeric affinity layers for a range of analytes by a proper choice of dispersed MOF particles.

Olefin–paraffin separation performance of polyimide Matrimid®/silica nanocomposite membranes

In this study, the performance of polyimide Matrimid® membranes in the separation of ethylene/ethane and propylene/propane was improved by silica nanoparticles.

Metal-organic framework MIL-101(Cr) based mixed matrix membranes for esterification of ethanol and acetic acid in a membrane reactor

Mixed matrix membranes (MMMs) based on the polyimide Matrimid® (PI) with metal-organic framework (MOF) MIL-101(Cr) as porous nanostructured filler were synthesized and applied as separation element in a membrane reactor to carry out the esterification of acetic acid with ethanol. The MMMs were characterized by techniques including X-ray diffraction, IR spectroscopy and scanning electron microscopy. In order to compare the performance of MIL-101(Cr)-PI MMMs in the membrane reactor, pure PI and HKUST-1-PI membranes were also used. MMMs provided a better reactor performance than the bare PI membrane because of the increase in permeability associated to the presence of MOF as filler. The PI membrane reactor barely achieved the same conversion as a fixed bed reactor, while the MIL-101(Cr)-PI membrane showed a reactor performance similar to that of the HKUST-1-PI membrane with higher stability, as confirmed by membrane characterization after the reaction experiments.

Fabrication of ultrathin films containing the metal organic framework Fe-MIL-88B-NH 2 by the Langmuir–Blodgett technique

Abstract In this work, the fabrication of ultrathin films containing the metal organic framework (MOF) Fe-MIL-88B-NH 2 by the Langmuir–Blodgett (LB) technique has been explored. MOF crystals of two different sizes (1.5 ± 0.3 and 0.07 ± 0.01 μm) have been synthesized and assembled at the air–liquid interface by the LB method. The effect of the subphase pH and particle size on the film formation process has been studied. Moreover, for the first time, mixed MOF + polymer (the commercial soluble polyimide Matrimid ® ) LB films containing different MOF loadings have been fabricated. These experiments show that it is possible to obtain ultrathin MOF + polymer films with a controlled MOF density. Furthermore, MOF particles are homogeneously distributed in the polymer matrix, even with very large amounts of MOF (up to 95 wt%). LB films have been incorporated into materials of different nature, including glass and mica substrates and also polymeric membranes based on polysulfone Udel ® and PIM-1 (polymer of intrinsic microporosity), and the modification of water contact angle after LB film deposition has been analyzed.

Pervaporation and membrane reactor performance of polyimide based mixed matrix membranes containing MOF HKUST-1

Mixed matrix membranes (MMM) containing MOF Cu3(BTC)2 (HKUST-1) at 20–40wt% loading have been prepared using commercial polyimide (PI) Matrimid® 5218 as polymer matrix. With the addition of this hydrophilic MOF, the water/ethanol separation via pervaporation was improved by increasing the water flux from 0.24kgm−2h−1 for bare PI up to 0.43kgm−2h−1 with 40wt% Cu3(BTC)2 MMM without significant changes in the separation factor (>200). Due to their selective water permeation, these MMMs have been used to displace equilibrium in the esterification of acetic acid with ethanol. By coupling separation by membrane and the reaction in the same device, the conversion obtained at the same feed rate and catalyst loading was higher than that achieved without any membrane. At 70°C the membrane reactor reached a conversion of 70%, higher than the equilibrium value (66%).

Gas Permeation Properties and Characterization of Polymer Based Carbon Membrane

Membrane gas separation is a forthcoming technology that advertised a great commercial potential in diverse industrial applications. Consequently, membrane-based natural gas processing has been among the fastest growing segments of the economic growth. The turbostratic structure of carbon membranes has been affirmed to accommodate with good separation selectivity for permanent gases. With that, the most auspicious technique acquired is by controlling the carbonization temperature during the carbon membrane fabrication. In this study, polymer-based carbon tubular membranes have been fabricated and characterized in terms of its structural morphology and gas permeation properties. Polyimide (Matrimid 5218) was used as a precursor for carbon tubular membrane preparation to produce high quality of carbon membrane via carbonization process. The polymer solution was coated on TiO2 –ZrO2 tubular tubes (Tami) by using dip-coating method. The polymer tubular membrane was then carbonized under Nitrogen atmosphere at 600, 750, and 850 ◦C. The structural morphology of the resultant carbon membranes was analyzed by means of scanning electron microscope (SEM). Pure gas permeation tests were performed using CO2 and N2 gases at 8 bars and room temperature. Based on the results, the highest CO2/ N2 selectivity of 79.53 was obtained for carbon membrane prepared at 850 oC.

Pervaporation of water/ethanol mixtures through polyimide based mixed matrix membranes containing ZIF‐8, ordered mesoporous silica and ZIF‐8‐silica core‐shell spheres

AbstractBACKGROUNDPervaporation (PV) is a prospective industrial process for the separation of liquid mixtures such as azeotropic and close‐boiling point. PV efficiency depends mainly on the properties of the membrane used. Hence, designing a membrane structure with high permeation rate and separation factor is an important issue.RESULTSMixed matrix membranes (MMMs) containing a number of molecular sieves, i.e. metal organic framework ZIF‐8, ordered mesoporous MCM‐41 silica spheres of two sizes, 3.1 µm (MSS‐1) and 0.53 µm (MSS‐2), and ordered mesoporous silica‐(ZIF‐8) core‐shell spheres (MSS‐Z8), were prepared at different filler loadings using polyimide (PI) Matrimid® 5218 as polymeric matrix and applied in the dehydration of ethanol via PV. With MSS‐2 MMMs the PV flux was improved from 0.24 to 0.44 kg m−2 h−1 without significant changes in the separation factor compared with the bare PI membrane.CONCLUSIONSPV performance of the PI membrane was improved by adding different fillers to the polymer matrix, and the effect of porosity, hydrophilicity and particle size of the filler on the PV results was analyzed. The best result in terms of PV performance was obtained with 12 wt% MSS‐2 MMM, where the use of smaller particles yielded a superior particle–polymer interfacial area and provided better accessibility to the hydrophilic silica pores. © 2014 Society of Chemical Industry