Influence of the Polymer Surface Charge on the Synthesis and

Oct 26, 2015 - Technology, 405 Fayette Pike, Montgomery, West Virginia 25136, United States. ABSTRACT: Silica−polymer composites using positively ...
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Influence of the Polymer Surface Charge on the Synthesis and Properties of Polymer−Silica Composites Gifty Osei-Prempeh,*,† James Ingles,† Megan Keffer,† David Dunlap,† Garth Thomas,† and Asad Davari‡ †

Department of Chemical Engineering, ‡Department of Electrical and Computer Engineering, West Virginia University Institute of Technology, 405 Fayette Pike, Montgomery, West Virginia 25136, United States ABSTRACT: Silica−polymer composites using positively charged polystyrene and Amberlite beads and neutral Amberlite beads as seeds were prepared in an acidic silica synthesis medium. The potential for functionalization of the composites for specific applications depends on the inorganic (silica) phase present. The synthesized composites were characterized by determining the percentage of organic content, particle size, surface area, and pore size and volume and the percentage of CO2 adsorbed to investigate the potential for specific application. The use of positively charged polymers resulted in a higher content of silica incorporated, leading to an increase in the composite particle size and a higher incorporation of the amine functional group. Application of the composites for CO2 adsorption shows higher sorption rates in the composites made with positively charged polymer seeds. The highest amount of CO2 adsorbed is seen in the amine-functionalized composite made from Amberlite IRA900 Cl, positively charged polymer beads with relatively large pores.

1. INTRODUCTION Materials such as cellulosic fibers, glass fibers, carbon fibers, organic fibers, ceramic fibers, and particles are used as reinforcements in matrixes such as polymer, metal, ceramic, and carbon.1 Composites of polymers and inorganic materials play important roles in everyday living. Inorganic materials in the form of fibers (fiber-reinforced composites) and particles such as spheres (particle-reinforced composites) are incorporated into polymer matrixes to increase the functionality of the polymer. The right combination of polymer and inorganic materials can improve the performance of different properties.2 Functionality in both the organic and inorganic phases can be accessed for specific applications. Composites are used in areas such as structural, electronic, electrochemical, thermal, environmental, and medical applications.3 Ceramics such as nanoporous silica (NS) are used as reinforcements in polymer composites.4−6 NS can be obtained by using a structure-directing agent (e.g., surfactant template) during the sol−gel synthesis process in an acidic or a basic medium.7,8 These materials can be pre- or postfunctionalized for specific applications.9,10 The incorporation of surfacemodified NS into polymers generates nanosized or micronsized silica−polymer composite materials with improved thermal properties in addition to increased surface area and pore volume, properties that are necessary in separation applications. Recently, researchers are looking at enhancing the performance of polymers in addition to making use of novel behaviors such as functionality that the nanoparticles introduce into the polymer.11 These composites are obtained by techniques such as blending (a traditional and simple method), sol−gel processing, and in situ polymerization. The use of in situ polymerization provides great control of the polymer architecture and the final structure of the nanocomposite.12 Recently, colloidal nanocomposites are taking the forefront with the advantage of generating materials with defined morphology and properties.13−17 There are four possible nanocomposite morphologies (Figure 1); raspberry, currant © 2015 American Chemical Society

Figure 1. Schematic of the four possible nanocomposite morphologies: (A) raspberry; (B) currant bun; (C) nanoparticle core−polymer shell; (D) polymer core−nanoparticle shell.

bun, a latex core with a nanoparticle shell (core−shell), or a nanoparticle core with a polymer shell (core−shell)18 depending on the distribution of the nanoparticle in the polymer matrix. In this paper, the preparation and characterization of micronsized polystyrene−silica (D morphology) and Amberlite−silica composites (A or D morphology) are presented in view of the surface charge of the polymer matrix. Additionally, the potential of tailoring the surface properties of these composites for applications such as CO2 capture is also shown. The underlying objective of this work is to generate larger particles than standard as-synthesized mesoporous silica with the potential of incorporating functional groups for applications where the size of the silica particles will pose transport limitations. The properties of the composites are compared to those of standard mesoporous silica.

2. METHOD Three different polymer−silica composites were synthesized: a polystyrene−silica composite (PSS) and two Amberlite−silica composites (ABXS and ABIS). Positively charged polystyrene (PS) particles were synthesized using 2,2-azobis(2-methylproReceived: Revised: Accepted: Published: 11295

July 6, 2015 October 18, 2015 October 26, 2015 October 26, 2015 DOI: 10.1021/acs.iecr.5b02450 Ind. Eng. Chem. Res. 2015, 54, 11295−11301

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Industrial & Engineering Chemistry Research

Figure 2. FTIR spectra of polymers (PS, ABX, and ABI), surfactant unextracted and extracted silica or PS−silica composites (NS and PSS), Amberlite−silica composites (ABXS and ABIS), and amine-functionalized silica or silica−polymer composites (AP-NS, AP-PSS, AP-ABXS, and APABIS): (A) mesoporous silica; (B) polystyrene−silica; (C) Amberlite (ABX)−silica; (D) Amberlite (ABI)−silica.

Figure 3. Electron microscopy images of the polymer−silica composites (A) PSS, (B) ABXS, and (C) ABIS.

of CTAB in an aqueous HCl solution was used for the PSS synthesis, with the addition of 5 g of the synthesized PS powder. A total of 3 mL of tetramethoxysilane (TMOS) was then added to the NS and PSS synthesis media and the solution allowed to stir for 48 h. The samples were then vacuum-filtered and allowed to dry for 24 h. After the drying period, the surfactant is removed by washing the sample in an acidic ethanol solution (150 mL of ethanol plus 3 mL of 12.1 N HCl) for 24 h. The samples were vacuum-filtered and washed again with 150 mL of a fresh acidic ethanol solution for 24 h. Samples were then vacuum-filtered and allowed to dry for 24 h. No surfactant template was used for the synthesis of ABXS and ABIS. A total of 3 g of Amberlite particles, ABX and ABI, were added to 3 mL of TMOS in separate beakers and covered for 24 h to allow the polymer to swell based on the method used by Kierys et al.19 The swollen polymer was then added to 50 mL of an aqueous 0.02 M HCl solution and stirred for 24 h. The samples were vacuum-filtered, washed with a copious amount of water, and allowed to dry for 24 h. 3-Aminopropyl-functionalized samples (AP-NS, AP-PSS, APABXS, and AP-ABIS) were synthesized by adding the silica and

pionamidine) dihydrochloride (AAPH) as the initiator. Initially, 9 g of styrene monomer was added to 180 mL of distilled water and the mixture stirred for 15 min. While that solution was being mixed, a second solution was prepared by adding 0.18 g of AAPH to 15 g of distilled water and stirred for 15 min. The two mixtures were heated to 60 °C, and then the initiator solution was added to the monomer solution. The final mixture was then heated to 70 °C and allowed to stir for 24 h, resulting in a white milky product. The milky product solution was poured into a Petri dish and allowed to dry at room temperature for 72 h. The completely dried hardened powder was ground into small particles. Amberlite XAD7HP (ABX, an aliphatic acrylic polymer) and Amberlite IRA 900 Cl (ABI, copolymer with a styrene−divinylbenzene backbone) were purchased from Sigma-Aldrich. The polymer particles were used as seeds in the silica synthesis medium. Nanoporous silica (NS) and the polymer− silica composites (PSS, ABXS, and ABIS) were synthesized in an acidic, aqueous 0.02 M HCl, solution. NS was synthesized by adding 4 g of cetyltrimethylammonium bromide (CTAB) to 50 mL of an aqueous 0.02 M HCl solution. The same amount 11296

DOI: 10.1021/acs.iecr.5b02450 Ind. Eng. Chem. Res. 2015, 54, 11295−11301

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Industrial & Engineering Chemistry Research polymer−silica composites to a solution of 3 mL of (3aminopropyl)triethoxysilane in 30 mL of ethanol in separate beakers. The mixtures were allowed to stir at 30 °C for 24 h, vacuum-filtered, and washed with a copious amount of ethanol. The samples were dried for 24 h before analysis.

Table 1. SEM/EDX Composition Information element (wt %)

3. RESULTS AND DISCUSSION 3.1. Functional Group Identification by Fourier Transform Infrared (FTIR) Spectroscopy. FTIR was used to determine the incorporation of silica into the polymer matrix and to confirm complete removal of the CTAB surfactant template. Three peaks, 1070 cm−1 with a shoulder at 1130 cm−1 and 950 and 787 cm−1 (Figure 2), present in the silica material (NS) and also in all of the composite samples indicate the presence of silica. These peaks are due to the −Si−O−Si− and −Si−OH vibrations in the silica phase.10 In Figure 2A, the peaks observed at 2800, 1500, and 900 cm−1 for unextracted NS are due to the C−C and C−H vibrations in the CTAB template. The peaks are also observed in the unextracted PSS samples (Figure 2B). These peaks completely disappear after surfactant extraction, except for PSS, where the residuals from these peaks are due to the C−C and C−H vibrations in PS. The presence of the polymer in the composite is confirmed by the presence of prominent peaks seen in the spectra for the polymers still showing up in the spectra for the composite materials. For PS (Figure 2B), these peaks are observed at wavenumbers of 690, 1440, and 1430 cm−1. In the composite materials from ABX peaks at 1373 cm−1, 1450, 1628, and 1720 cm−1 (Figure 2C) are still present. These peaks signify the presence of the ABX polymer after composite formation. The signature peaks from ABI that are still observed in the composite samples (Figure 2D) can be seen at wavenumbers 1470 and 1620 cm−1. 3.2. Confirming Composite Formation by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) Imaging. To understand the structure of the particles and how the silica is incorporated into the polymer matrix, SEM and TEM images of the samples were taken using JEOL JSM-7600F and JEOL JEM 2100 microscopes, respectively. Samples for TEM analysis were embedded in a resin and sectioned into 100 nm sizes with an ultramicrotome. Figure 3 shows sample images for the three polymer−silica composites PSS, ABXS, and ABIS. From these images, PSS (Figure 3A1,A2) and ABXS (Figure 3B1) show two distinct phase systems. but ABIS (Figure 3C1) shows a uniform phase of composite particles. The distinct two-phase systems in PSS and ABXS show some kind of phase separation of the silica and polymer phases. The PS composite (PSS) is seen as small spherical beads imbedded in a large irregular silica phase. However, TEM analysis of the spherical beads (Figure 3A3) shows an inner core (possibly PS) and an outer shell (most probably silica). The ABXS composite materials show an irregular silica phase between the spherical particles, which exhibit polymer core−silica shell morphology (Figure 3B2). The silica shell is observed to be unstable and highly susceptible to separation from the polymer core (Figure 3B3). Further analysis of these phases by SEM/energy-dispersive X-ray spectroscopy (EDX; Table 1) shows that the spherical particles for PSS, ABXS, and ABIS are definitely polymer−silica composites possessing both carbon, silicon, and oxygen atoms, while the irregular phase between the spherical particles in ABXS is pure silica (mostly silicon and oxygen atoms). The irregular phase in the PSS materials shows the presence of

sample type

C

O

Si

Cl

PSS, spherical PSS, irregular ABXS, spherical ABXS, irregular ABIS, spherical

47.56 42.21 40.08

35.18 40.63 47.81 61.76 22.49

17.27 17.16 11.39 38.24 10.46

13.05

54.00

carbon, silicon, and oxygen atoms due to the fact that the very small composite particles are distributed within the irregular phase. EDX analysis of ABIS (Table 1) confirms the presence of silicon, carbon, and oxygen atoms, implying that the material is a polymer−silica composite. The chlorine atom found in ABIS is from the counterion of the polymer seed. Composites made with the positively charged polymer matrixes (PS and ABI) show the stability of the incorporated silica, a property that is not observed for ABX samples. The PS particles and CTAB were first added to the 0.02 M HCl acidic synthesis medium (pH = 1.69) before the silica precursor was added. A pH of 1.69 is below the aqueous isoelectric point of silica.20 PS has a Cl− counterion (X−), and CTAB has a Br− counterion (X−). In an acidic medium, the cationic surfactant (S+) and cationic polymer (S+) interact with the positively charged silicate (I +) surface by counterion mediation (S+X−I+).21 The counterions catalyze the silica condensation. These ionic interactions are strong, hence leading to a stable PS core−silica shell composite. The presence of irregular-shaped silica is characteristic of the CTAB-templated silica due to Br− mediation.21 ABI, an Amberlite polymer, has a Cl− counterion. This polymer is added to the silica precursor and allowed to swell, permitting the precursor to fill up the large pores in the polymer. When the swollen polymer is added to the acidic synthesis medium, a counterion-mediated interaction (S+X−I+) could result within the pores, leading to silica beads imbedded in the pores of the polymer. The addition of a swollen neutral Amberlite polymer (ABX) to the acidic synthesis medium could lead to a hydronium ion (H3O+) interaction with the neutral polymer, resulting in hydrogen bonding with the Cl− ion in solution, which interacts with the positively charged silicate, producing an (S0H+)(X−I+) interaction.20 The hydrogen bonding could lead to the unstable silica phase on the ABX polymer in the ABXS composite. 3.3. Particle Size Analysis. Using polymer as a seed in the silica synthesis medium should result in increased particle size after composite formation and possibly after amine functionalization. The number-average particle size of the materials was measured using a Microtrac S3500 particle size analyzer to investigate the particle size change after composite formation. The PS and PSS samples were sonicated in the instrument sample chamber before analysis was performed. From Table 2, an increase in the particle size can be observed for all of the composites formed from PS (0.45 μm) to PSS (0.77 μm), from ABX (543 μm) to ABXS (603 μm), and from ABI (582 μm) to ABIS (779 μm). This increase in the particle size is due to the incorporation of silica into the organic (polymeric) phase and, in the case of PSS, the presence of a pure irregular silica phase in addition to the PS−silica composite particles (Figure 3A2). The pure silica particles, which are larger, may have contributed to the 71% increases in the size of the PS particle after composite formation. The size increase observed in ABX (about 11%) is due to a core−shell composite formation 11297

DOI: 10.1021/acs.iecr.5b02450 Ind. Eng. Chem. Res. 2015, 54, 11295−11301

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Industrial & Engineering Chemistry Research Table 2. Material Textural Properties, Particle Size, Organic Content, and Amount of CO2 Adsorbed at 50 °C material NS AP-NS PS PSS AP-PSS ABX ABXS AP-ABXS ABI ABIS AP-ABIS a

BJH average pore size, nm

single-point pore volume, cm3/g at P/P0 = 0.99

BET surface area, m2/g

3.47 2.69

0.60 0.42

718 363

3.61 2.62 30−40a 6.09 9.56

0.40 0.30 0.47a 0.51 0.43

472 262 380a 373 254

60.7 76.0

0.14 0.03

number-average particle size, μm

% organic content

mmol of amine/g

± ± ± ± ± ± ± ± ± ± ±

3.73 ± 0.46 9.96 ± 0.08

1.07

25.7 ± 2.88 34.8 ± 4.24

1.56

64.6 ± 2.25 70.3 ± 0.98

0.98

45.8 ± 4.94 54.0 ± 2.61

1.41

4.15 1.57 0.45 0.77 1.09 543 603 623 582 779 853

12.4 7.6

1.81 0.38 0.25 0.08 0.22 86 122 115 117 138 126

% CO2 adsorbed

mmol of CO2/g

± ± ± ± ±

0.27 0.37 0.03 0.20 0.31 0.08 0.27 0.26 0.15 0.85 0.92

1.19 1.63 0.14 0.88 1.35 0.36 1.17 1.16 0.66 3.74 4.05

0.27 0.12 0.02 0.07 0.20

± 0.26 ± 0.63 ± 0.94 ± 0.81

Data obtained from manufacturer’s fact sheet.22

Figure 4. Nitrogen adsorption−desorption isotherms for all samples.

(Figure 3B). The ABI material 34% size increase after composite formation is mainly due to silica imbedding in the pores of the starting polymer (Figure 3C). It can be observed that the polymeric materials with positively charged surfaces

show greater particle size increases, probably because of a high incorporation of the silica phase as a result of favorable interaction between the polymer and silica. In a 0.02 M HCl synthesis medium (pH = 1.69), the greater size increase 11298

DOI: 10.1021/acs.iecr.5b02450 Ind. Eng. Chem. Res. 2015, 54, 11295−11301

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Industrial & Engineering Chemistry Research

Figure 5. Sample TGA weight change profiles as a function of the temperature for all samples.

show type IV isotherms with H3 hysteresis loops, suggesting that these materials could have slitlike pores (Figure 4).23 This is expected because these materials were synthesized with no pore structure-directing agent and the pores in the starting polymers did not have any order. All materials show broad pore-size distributions (Figure 4) and a shift toward smaller pore sizes for the NS and PSS samples after amine functionalization. The ABXS and ABIS samples, on the other hand, show a shift to larger pore sizes after amine functionalization. AP-NS and AP-ABXS exhibit respectively pore doublet and triplet peaks that show the nonuniformity of the pores in the samples. The aim is to compare the surface areas and pore characteristics of the composites and the changes after amine functionalization, and the BET surface area, BJH pore size, and pore volume at a relative pressure of 0.99 are used (Table 2). The surface area, average pore size, and pore volume all decrease after grafting aminopropyl functional groups in the NS material (AP-NS). The inorganic silica phase of the PS composite was also synthesized with a CTAB template; hence, the average pore sizes of the PSS composite and amine-functionalized composite (AP-PSS) are comparable to that of the nanoporous materials. The surface areas and pore volumes of the PS composites, however, decreased by about 30% compared to the NS materials. The inorganic phase in the Amberlite composites was synthesized without a surfactant template (structure-directing agent); hence, the pores in the silica phase do not have any order. However, the composites from the ABX polymer matrix show fairly high surface areas and pore volumes (Table 2). This observation could be a result of the fairly high surface area and pore volume of the starting polymer matrix and large silica phase separated from the polymer shown by the SEM. The average pore sizes of ABXS and AP-ABXS are about 70−80% smaller than that of the starting polymer, confirming the incorporation of the inorganic silica phase within the pores of the polymer matrix and a silica

observed with the PS particles may be the result of the presence of large irregular silica particles; however, the TEM image (Figure 3A3) shows a stable shell layer around a core compared to the ABIS sample, where the silica phase grew mostly within the pores of the polymer in a “raspberry” fashion (Figure 3C3). A further particle size increase is observed after postsynthesis functionalization with 3-aminopropyl groups. The PS composite (PSS) shows a 41% increase, while ABXS increases by 3.3% and ABIS by 9.5%. There could be several possibilities for the smaller increase in size in the Amberlite samples after functionalization. The percentages of the silica phase in those materials are smaller compared to the PSS sample, hence a lower amount of surface −Si−OH that could undergo further reaction with the functionalized precursor. Additionally, the surface area, pore size, and pore volume in these materials will play a major role in the availability of reaction sites for the functionalized precursor. The increase in the particle size observed for the composite materials was not seen for NS to AP-NS. This is because the NS materials were initially agglomerated but could have been effectively separated during the functionalization process in ethanol. 3.4. Analysis of the Textural Properties. NS materials usually have very high surface areas, on the order of hundreds of meters squared per gram, as a result of using a structuredirecting agent during their synthesis. The surfactant template acts as a structure-directing agent, leading to pores that could have long-range order.7,10 Nitrogen adsorption analyses were performed using a Micromeritics ASAP 2020 system. The NS materials synthesized exhibit a type IV nitrogen adsorption isotherm (Figure 4) with an H2 hysteresis loop.23 The steep desorption at relative pressure higher than 0.4 suggests materials with poor pore connectivity.23 After amine functionalization, AP-NS show a type IV isotherm with an H4 hysteresis loop. Similar isotherms and hysteresis loops are observed for PSS (type IV, H2) and AP-PSS (type IV, H4). Composites ABXS and ABIS and their amine-functionalized counterparts all 11299

DOI: 10.1021/acs.iecr.5b02450 Ind. Eng. Chem. Res. 2015, 54, 11295−11301

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analyzer. The analysis began by loading a certain mass of the sample into the thermogravimetric analyzer, which was run with nitrogen (N2) purge gas. The temperature was ramped to 100 °C, maintained there for 5 min, and ramped down to 50 °C. The gas is then switched to pure CO2 and the system allowed to run for 20 min more. The percentages of pure CO2 adsorbed on all of the samples ranging from 0.14% in PS to 4.05% in AP-ABIS are given in Table 2. CO2 adsorption on the nonfunctionalized materials (NS, PSS, ABXS, and ABIS) is possible. It has been observed that such adsorption usually occurs by physical adsorption, where the adsorbate (CO2) binds to active sites on the adsorbent.25,26 The amine-functionalized materials of each set gave the highest amount of CO2 adsorbed except for AP-ABXS, which is an outlier. The increase in the amount of CO2 adsorbed by the functionalized composites is expected because CO2 molecules interact with amine groups, as shown in Scheme 1. PSS and ABIS composites synthesized using positively

phase with no apparent pore order. Composites from the ABI matrix possess much lower surface areas and pore volumes and surprisingly very large pore sizes. These composites have a much higher inorganic silica phase content compared to the ABXS composites but are distributed within the very large pores of the polymer matrix. The large pores could play a part in producing the very small surface areas and pore volumes of these composites. The increase in the pore size observed for AP-ABXS and AP-ABIS compared to their starting composites ABXS and ABIS could be the result of washing away some of the silica particles within the pores of the polymer during postsynthesis amine functionalization in ethanol. 3.5. Fraction of Organics in the Composite Materials by TGA. Thermogravimetric analysis (TGA) was used to determine the amount of organics in the composite materials. These data provide information on the degree of silica incorporation in the polymer matrix during composite formation. The organic content analysis was performed by loading a weighted sample of the composite in the thermogravimetric analyzer, ramping from room temperature to 900 °C, and holding at 900 °C for 10 min in an air environment (Figure 5). The percentage of weight loss of the sample is due to the evaporation of moisture and the combustion of the organic groups in the composites. The organic content was calculated using the change in the sample weight (arrow range on Figure 5) after the first transition, which occurred between 100 and 200 °C. This first transition is due to the evaporation of moisture. For the NS sample, the organic content in NS is due to possible residual surfactant that remained after the surfactant extraction process and/or condensation of surface silanol groups.24 This material ideally should not contain any organic group because it is not a composite. The composites PSS, ABXS, and ABIS show mean percent organic contents of 25.7, 64.6, and 45.8 wt %, respectively. This result shows a lower organic content in the composites synthesized with the positively charged polymer matrix, matching the trend observed in the particle size increase. The PS composite shows the lowest organic content, meaning that, on average, 74.3 wt % of the composite is from the incorporated silica, while ABIS shows 54.2 wt % of the incorporated silica compared to 35.4 wt % in ABXS (neutral polymer matrix). The organic content in the 3-aminopropyl-functionalized materials is due to the presence of both the polymer and amine group in the composite samples. The difference between the percentage organics in the amine-functionalized samples and that of the nonfunctionalized one is used to determine the percentage of functional group incorporation. This percentage is then converted to mmol/(g of sample), Table 2. The aminefunctionalized composites made from the positively charged polymer matrix show higher incorporation of the amine group, 1.56 mmol/g in AP-PSS and 1.41 mmol/g in AP-ABIS, 31− 46% higher than the amount incorporated in AP-NS and 43− 59% higher than that in AP-ABXS. The functional group incorporation results for the composite materials are in line with the percentage of silica phase present. A higher amount of silica content results in a higher amine functionalization and vice versa. 3.6. CO2 Sorption Analysis. The composite materials were used as adsorbents to determine how much CO2 can be captured per unit mass of sample. This is done to determine the degree of accessibility to the functional groups. The CO2 sorption analysis was performed in a thermogravimetric

Scheme 1. CO2 Reaction with Primary Amines

charged polymer matrixes have high amounts of CO2 adsorbed compared to ABX (neutral) composites. This could be due to the relatively high amount of silica content and amine group incorporation in the PS and ABI composites compared to the ABX composites. However, the samples NS and AP-NS had higher CO2 sorption content than their respective PS and ABX counterparts. This is because the NS samples have a higher content of inorganic phase per gram of material. Overall, the ABI composites adsorbed the highest amount of CO2. The amount of CO2 adsorbed in ABIS is about 3.1 times that in NS, and the amount adsorbed in AP-ABIS is about 2.5 times that in AP-NS. This suggests that the large pores promote better access to the adsorption sites and the amine functional groups on the surface of the ABI composites, although these samples have the lowest surface areas.

4. CONCLUSIONS Polymer particles used as seeds in the silica synthesis medium resulted in the generation of silica−polymer composites, where the silica has been incorporated into the polymer phase. Polymer particles with positively charged surfaces incorporated the highest amount of silica into the matrix, resulting in composites with a high percentage of inorganic phase and an increase in the particle size. The composites can be targeted for applications such as CO2 capture when the inorganic phase is functionalized with the right functional group. The success of the particular application, such as CO2 capture analysis performed in this work, not only depends on the amount of functional group incorporated but also depends on easy access to the functional groups. Thus, the positively charged polymer matrix with large pores shows the best accessibility to the incorporated functional groups.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Phone: 304-4423163. 11300

DOI: 10.1021/acs.iecr.5b02450 Ind. Eng. Chem. Res. 2015, 54, 11295−11301

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Industrial & Engineering Chemistry Research Notes

(20) Zhao, D.; Huo, Q.; Feng, J.; Chmelka, B. F.; Stucky, G. D. Nonionic Triblock and Star Diblock Copolymer and Oligomeric Surfactant Syntheses of Highly Ordered, Hydrothermally Stable, Mesoporous Silica Structures. J. Am. Chem. Soc. 1998, 120, 6024. (21) Cassiers, K.; Van Der Voort, P.; Linssen, T.; Vansant, E. F.; Lebedev, O.; Van Landuyt, J. A Counterion-Catalyzed (S0H+)(X-I+) Pathway toward Heat- and Steam-Stable Mesostructured Silica Assembled from Amines in Acidic Conditions. J. Phys. Chem. B 2003, 107, 3690. (22) Rohm and Haas. Amberlite XAD7HP Industrial Grade Polymeric Adsorbent. http://www.dow.com/assets/attachments/ business/process_chemicals/amberlite_xad/amberlite_xad7_hp/tds/ amberlite_xad7hp.pdf, 2006. (23) Kruk, M.; Jaroniec, M. Gas Adsorption Characterization of Ordered Organic-Inorganic Nanocomposite Materials. Chem. Mater. 2001, 13, 3169. (24) Glinka, Y. D.; Jaroniec, C. P.; Jaroniec, M. Studies of Surface Properties of Disperse Silica and Alumina by Luminescence Measurements and Nitrogen Adsorption. J. Colloid Interface Sci. 1998, 201, 210. (25) Delaney, W.; Knowles, G. P.; Chaffee, A. L. Hybrid Mesoporous Materials for Carbon Dioxide Separation. Fuel Chemistry Division Preprints 2002, 47, 65. (26) Qi, G.; Wang, Y.; Estevez, L.; Duan, X.; Anako, N.; Park, A.-H. A.; Li, W.; Jones, C. W.; Giannelis, E. P. High efficiency nanocomposite sorbents for CO2 capture based on amine-functionalized mesoporous capsules. Energy Environ. Sci. 2011, 4, 444.

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Funding was received from the West Virginia Division of Energy, “WVU Tech Projects with Industry” (Grant 11-220), and West Virginia Higher Education Policy, Research Proposal Mini Grant program (Award HEPC.dsr.14.27).

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DOI: 10.1021/acs.iecr.5b02450 Ind. Eng. Chem. Res. 2015, 54, 11295−11301