Tailored synthesis of polymer-brush-grafted mesoporous silicas with N-halamine and quaternary ammonium groups for antimicrobial applications

Accepted Manuscript Tailored synthesis of polymer-brush-grafted mesoporous silicas with N-halamine and quaternary ammonium groups for antimicrobial applications Yingfeng Wang, Maoli Yin, Xinhuan Lin, Lin Li, Zhiguang Li, Xuehong Ren, Yuyu Sun PII: DOI: Reference:

S0021-9797(18)30990-1 https://doi.org/10.1016/j.jcis.2018.08.080 YJCIS 24013

To appear in:

Journal of Colloid and Interface Science

Received Date: Revised Date: Accepted Date:

2 July 2018 21 August 2018 22 August 2018

Please cite this article as: Y. Wang, M. Yin, X. Lin, L. Li, Z. Li, X. Ren, Y. Sun, Tailored synthesis of polymerbrush-grafted mesoporous silicas with N-halamine and quaternary ammonium groups for antimicrobial applications, Journal of Colloid and Interface Science (2018), doi: https://doi.org/10.1016/j.jcis.2018.08.080

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Tailored synthesis of polymer-brush-grafted mesoporous silicas with N-halamine and quaternary ammonium groups for antimicrobial applications Yingfeng Wang a, Maoli Yin a, Xinhuan Lin a, Lin Li a, Zhiguang Li a, Xuehong Ren*, Yuyu Sun b a

Key Laboratory of Eco-textiles of Ministry of Education, College of Textiles and

Clothing, Jiangnan University, Wuxi, Jiangsu214122, China b

Department of Chemistry, University of Massachusetts Lowell, Lowell, MA 01854,

USA

*

Corresponding author: E-mail: [email protected] (X.H. Ren)

Abstract Antimicrobial mesoporous materials with polymer brushes on the surface were prepared, and their structure and antimicrobial performance investigated. Poly ((3-acrylamidopropyl)

trimethylammonium

chloride)

(PAPTMAC)

modified

mesoporous silica was prepared by a polymer-brush-grafted method through treatment with the initiator 4,4’-azobis (4-cyanovaleric acid) (ACVA) and polymerized with (3-acrylamidopropyl) trimethylammonium chloride (APTMAC). A covalent bond was formed between mesoporous silica and N-halamine precursor; N-H bonds were successfully transformed to N-Cl bonds after chlorination. Morphology and structure of mesoporous silica were affected to some extent after modification. The surface area of the polymerized sample decreased, but was sufficient for further applications. Compare to the original sample, antimicrobial properties of the polymerized samples with quaternary ammonium groups (QAS) increased slightly.

After exposure to dilute household bleach, the chlorinated samples showed excellent antimicrobial properties against 100% of S. aureus (ATCC 6538) (7.63 log) and E. coli O157:H7 (ATCC 43895) (7.52 log) within 10 min. The prepared mesoporous silicas with effective antimicrobial properties could be very useful for potential application in water filtration.

Keywords N-halamines, antimicrobial, Mesoporous silica, polymer brushes

1. Introduction In recent years, there has been considerable interest, driven by the health concern and increasing living standard, to develop efficient functional antimicrobial materials since infections caused by the bacteria are affecting millions of people worldwide [1]. Research towards new approaches led to surface modified antimicrobial materials which can have a significant effect to preventing the growth of pathogenic microbes and inhibiting the spread of microorganisms [2]. Antimicrobial agents, such as metal ions [3, 4], quaternary ammonium salts [5, 6] and N-halamines [7] have been widely investigated and applied for antibacterial materials. Particularly, the N-halamine compounds which contain one or more nitrogen-halogen covalent bonds have great importance due to their properties as broad-spectrum agents against bacteria. Further, they are eco-friendly, low cost, rechargeability and have low toxicity. The biocidal property of N-halamines is due to the oxidation state of halide atoms in chloramine (N-Cl) or bromamine (N-Br) groups [7]. For chloramine-containing compounds, the

antimicrobial efficacies follow the order of amine > amide > imide, whereas the stability of the structures is just in the reverse order [8]. To further enhance the biocidal property of antibacterial agents, combined organic-inorganic antibacterial materials have been prepared [9, 10]. The chloramine or bromamine compound was transformed to nitrogen-hydrogen bonds when inhibiting the microbes. The chloramine can be recharged with house bleach solution and the biocidal property restored [11]. The antimicrobial mechanism of N-halamines was reported by direct transfer of oxidative halogen from N-halamines to the microbial cell membrane and participation the ionic reactions in the bacteria which caused inhibition or destruction of metabolic process of bacteria [12, 13]. As another effective biocide, the quaternary ammonium salts (QAS), have also been widely researched and applied. The antimicrobial mechanism of QAS is well-known [14, 15]. Here, QAS is penetrating the cell membrane, disrupting the membrane integrity, and inducing cell lysis [16]. The different charges between QAS and bacteria promote the biocidal process. The different organic structure linked to the nitrogen of QAS affect the biocidal property of the compounds [13, 17]. Considering the advantages of each antimicrobial mechanism, it might be possible to achieve further improvement of the biocidal properties by combining QAS with N-halamines [14, 15]. Surface modification of mesoporous silica with a wide variety of chemical groups could yield excellent candidates for these materials for various applications in catalysis, separation, and hemostatic, etc [18-20]. Among them, SBA-15 is obtained special interest by researchers because of its high uniform pore size, highly ordered

hexagonal arrays of cylindrical channels, high surface area and large number of silanol groups on its surface and channels [21]. The advantages of SBA-15 with high surface area, excellent thermal stability and nanometer-size make it have potential application in antibacterial materials. To improve the interaction between SBA-15 and N-halamine/QAS structures, organic/inorganic hybrid materials were prepared through post-polymerization. The grafting of polymers is mainly completed by one of three methods: grafting from, grafting through and grafting to. Polymer brushes can be formed via a “grafting from” approach, which can generate a high degree of control over grafting thickness and density of polymers in comparison with other methods [22]. In our previous research, mesoporous silica was functionalized with N-halamine which showed good efficacy against S. aureus (ATCC 6538) and E. coli O157:H7 (ATCC 43895) [23, 24]. The initiator molecule coupled to the nanocrystal surface first and allowed the growth of polymer chain, until a covalently bound polymer layer was formed on the surface [25]. This method has been widely used for grafting onto various nanoparticles carriers including gold, quantum dots, and silica [26-28]. Reversible addition-fragmentation chain transfer polymerization (RAFT) becomes the most effective method to form the polymer chains and reduce stringent experimental conditions [29, 30]. In order to extend the application of mesoporous silica, graft polymer brushes with different properties on mesoporous silica is preferred through this versatile method. The ordered polymer chain growing on the surface of mesoporous silica can retain the surface area and reduce the blockage of

pores. To our knowledge, this study is the only example of the use of the RAFT method to prepare N-halamine modified mesoporous silica with the purpose of improving antimicrobial properties. In this paper, we described the development of surface initiated radical polymerization to prepare N-halamine/QAS functionalized mesoporous silica particles. The initiator was attached on the surface of mesoporous silica particles, then the N-halamine/QAS monomer was polymerized and formed polymer brushes. The process of modification and polymerization of SBA-15 were showed in Figure 1. S. aureus (ATCC 6538) and E. coli O157:H7 (ATCC 43895) were used to test the antimicrobial property of the prepared samples.

Figure 1. Schematic illustration of the modification and polymerization process of SBA-15

2. Experimental 2.1 Materials Mesoporous molecular sieves (SBA-15) were purchased from Nanjing XFNANO Materials Tech Co., Ltd. 4,4’-Azobis (4-cyanovaleric acid) (ACVA, purity: 98%) was provide by Shanghai Macklin Biochemical Co., Ltd. (3-acrylamidopropyl) Trimethylammonium chloride (APTMAC, 72% solution in H2O) was supplied by J&K scientific Co., Ltd. Pyridine, ethanol, potassium persulfate and other chemicals were obtained from Sinopham Chemical Reagent Co., Ltd (Analytical Reagent). All

chemicals were used without further purification.

2.2 Pretreatment of SBA-15 SBA-15 was pretreated according to procedure as bellow: 0.5 g of SBA-15 was dispersed in 100 mL of hydrochloric acid (0.1N), followed with ultrasonic process in the ice bath for 30 min. The acidified sample was centrifuged (10,000 rpm, 15 min), washed with deionized water several times, and dried in a vacuum oven at 110℃ for 24 h.

2.3 Synthesis of SBA-15 macro-initiator (SBA-15-ACVA) To form the macroinitator, 0.6 g ACVA was dissolved in 50 mL of deionized water, and 60 μg pyridine was added and stirred for several minutes. Then 0.3 g SBA-15 was added to the mixture and stirred at room temperature for 48 h. After the reaction was completed, the mixture was centrifuged (10,000 rpm, 5 min) and washed several times with deionized water and ethanol, then dried at 45℃ overnight.

2.4 Graft polymerization of APTMAC from SBA-15 macro-initiator The graft polymerization of SBA-15-ACVA was performed in an oil bath. 0.5 g SBA-15-ACVA was suspended in 60 mL of deionized water and degassed with nitrogen. After aeration for 10 min, 2 g monomer APTMAC was added in the mixture under nitrogen atmosphere and the mixture degassed for another 10 min. The temperature of the reaction mixture was increased to 60℃ and the suspension stirred

for 8 h. After polymerization, the obtained product was centrifuged (10,000 rpm, 10 min) and washed several times with the deionized water. The polymer-brush-grafted mesoporous silica (SBA-15-PAPTMAC) was obtained after drying under reduced pressure at 60℃.

2.5 Preparation of SBA-15-PAPTMAC-Cl and titration To transform the amide into N-halamines, SBA-15-PAPTMAC was suspended in the 10% sodium hypochlorite solution at pH 7 (adjusted with 1 N H2SO4), stirred and reacted at room temperature for 2 h. After chlorination, the sample was centrifuged (10,000 rpm, 15 min) and washed three times with deionized water. The SBA-15-PAPTMAC-Cl was dried in the oven at 45℃ for 2 h. The non-bonded free chlorine in the sample can be removed under the drying process. The active chlorine content of the chlorinated sample was determined by iodimetric/thiosulfate titration. Briefly, a known weight of sample was dispersed in deionized water. 0.5 g potassium iodide and several drops of starch solution (1 wt%) were added, and the mixture was stirred at room temperature for half an hour. The released iodine was titrated with 0.01 mol/L sodium thiosulfate aqueous solution. The same process was applied for unchlorinated controls. The weight percentage of chlorine was calculated by the following equation (Eq. 1):

where VCl and V0 are the volumes of sodium thiosulfate solutions (mL) after and before the titration of the samples, respectively. W is the weight of the sample (g). The

titration was repeated with three independent samples and the obtained results were averaged.

2.6 Biocidal efficacy test Antimicrobial property evaluation of each sample was performed by exposure to Gram-positive S. aureus (ATCC 6538) and Gram-negative E. coli O157:H7 (ATCC 43895). Briefly, 0.1 g sample was suspended in 10 mL PBS solution with ultrasonication. Then 0.1 mL of bacteria suspension was added into the above PBS solution. The mixture was incubated in shaking incubator at 37℃. After 1, 5, 10, 30 min, 500 μL of suspension was taken out and added into 4.5 mL of 0.11 wt% sodium thiosulfate aqueous PBS solution to quench the residual oxidative chlorine [31]. The solution was serially diluted and 100 µL of each dilution was dispersed on trypticase agar plates. The colony-forming units (CFU) of bacteria on the agar plates were counted after incubation at 37℃ for 24 h. The amount of CFU was directly related to the antimicrobial property. The test was repeated three times and the obtained results were averaged.

2.7. Characterization Scanning electron microscope (SEM) images were obtained by SU1510 (Hitachi, Japan), scanning electron voltage is 5 KV. Transmission electron microscope (TEM) images were taken by JEM-2100 (HR) Transmission Electron Microscope (JEOL Ltd., Japan) at 200 kV. Fourier-transform infrared spectroscopy (FTIR) spectra were

recorded via the KBr pellet method with Thermo Is5 (Nicolet Instrument Corporation, USA) at room temperature, at a spectral width ranging from 400 to 4000 cm-1 with 4 cm-1/s. X-ray photoelectron spectroscopy (XPS) was carried out with an ESCLAB 250Xi (Thermo Scientic, USA) with Al K radiation (energy step size was 0.05 eV). X-ray diffraction patterns (XRD) were collected with D8 Advance X-ray diffractometer (Brucker, Germany) at 3 kW with Cu Kα radiation (λ=0.154 nm) in the range 2θ=0.5-70o with step of 0.02o. Brunauer-Emmett-Teller (BET) data were taken on Tristar II 3020 (Micromeritics Instrument Corporation, USA) surface area analyzer with liquid nitrogen.

3. Results and discussion 3.1. Characterization of SBA-15, SBA-15-ACVA and SBA-15-PAPTMAC The FTIR spectra of each sample were recorded and confirmed that SBA-15 was successfully functionalized with ACVA and APTMAC. The results are shown in Figure 2. The typical band of stretching vibration of Si-O-Si group in the silica structure appears at 1082 cm-1 [32]. After modified with ACVA, a new peak appeared at 1714 cm-1, which belongs to the stretching vibration of carboxyl group in ACVA. The

characteristic

vibrational

bands

of

SBA-15-PAPTMAC

and

SBA-15-PAPTMAC-Cl at 1479 cm-1 and 1553 cm-1 (Figure 2) correspond to the methyl vibrational modes and amide Ⅱ region of N-halamine [33, 34], respectively. New peaks appeared near 2923 cm-1 and 2966 cm-1 were ascribed to the asymmetric and symmetric stretching vibrations of methylene and methyl in N-halamine precursor

[22]. These peaks were not found in SBA-15 or SBA-15-ACVA, which indicates that the N-halamine precursor has been grafted on the materials successfully. The broad absorption band at 1650 cm-1 is due to the absorbed water molecules in the sample, and belongs to the bending vibrations of H-O-H [35, 36]. The amide Ⅰ band of the polymerized sample was partly overlapped with the band of H-O-H bending vibrations at 1650 cm-1 [37].

Figure 2. FTIR spectra of SBA-15, SBA-15-ACVA, SBA-15-PAPTMAC and SBA-15-PAPTMAC-Cl

Additionally, the XPS analysis was performed in Figure 3. After modified with ACVA, the new signals appeared at 392.88 eV and 280.88 eV (Figure 3a), which corresponding to N and C elements on the surface of the modified sample with ACVA. After polymerized with APTMAC, both of the two peaks, especially the peak of carbon, became stronger than the modified sample with ACVA. This result indicates that the APTMAC had been polymerized on the surface of the modified mesoporous materials.

Moreover,

the

chlorine

peaks

can

also

be

observed

from

SBA-15-PAPTMAC due to the quaternary ammonium salt (R4N+-Cl-). The Cl 2p has been fitted with two contributions, and Cl 2p1/2 (200.08 eV) and Cl 2p3/2 (198.28 eV) appeared in the spectrum (Figure 3c). These two chlorine peaks also indicate the APTMAC had been successfully polymerized on the surface of the modified mesoporous materials. The peak of Si 2p was resolved into two peaks at 103.38 eV

and 102.47 eV. These two binding energy ranges of the chemical species Si-O-Si and Si-O-C were 103-104 eV and 101-102 eV, respectively [38], which indicates that the new chemical bond (Si-O-C) was formed on the surface of SBA-15-ACVA. According to our previous work, the chlorine peak of N-Cl in N-halamine structure is around 200 eV, which also can be fitted with two peaks of Cl 2p1/2 (201.52 eV) and Cl 2p3/2 (199.72 eV), respectively [22, 39, 40]. The peak of chlorine in SBA-15-PAPTMAC-Cl can split into four peaks. The peaks of 198.58 eV and 200.38 eV belong to Cl 2p3/2 and Cl 2p1/2 of quaternary ammonium salt (R4N +-Cl-), and the peaks of 199.28 eV and 201.18 eV belong to Cl 2p3/2 and Cl 2p1/2 of N-halamine. The results suggest that APTMAC was polymerized on the surface of the modified mesoporous materials, and the N-halamine precursor had been transformed into N-halamine structure after chlorination.

Figure 3. XPS spectra of sample (a), Cl 2p peak of SBA-15-PAPTMAC (b), Si 2p peak of SBA-15-ACVA (c) and Cl 2p peak of SBA-15-PAPTMAC-Cl

3.2 Morphologies and structure analysis of mesoporous samples The

SEM

and

TEM

images

for

SBA-15,

SBA-15-ACVA

and

SBA-15-PAPTMAC are shown in Figure 4. As can be seen in the SEM micrographs, the samples consist of relatively uniform rod-like particles similar to conventional SBA-15[41]. The particles are aggregated because of nano-size. There was no significant change in surface morphology after modification and polymerization. The

particle size of SBA-15 averages to 374 nm × 921 nm (standard deviation: 35 nm × 97 nm). The particle size of SBA-15-ACVA and SBA-15-PAPTMAC were 382 nm × 974 nm (standard deviation: 30 nm × 98 nm) and 417 nm × 982 nm (standard deviation: 40 nm × 98 nm), respectively. It can therefore be concluded that the functionalization did not significantly change the particle size. Figure 4a, 4b and 4c illustrate the TEM images of each sample in order to confirm the mesoporous structure of the materials [42]. All samples showed symmetric straight channels and typical honeycomb appearance resembling that of SBA-15, which illustrates that the meso-structure of SBA-15 has not been altered after modification and polymerization.

Figure 4. TEM images of SBA-15 (a), SBA-15-ACVA (b), SBA-15-PAPTMAC (c) and SEM images of SBA-15 (d), SBA-15-ACVA (e), SBA-15-PAPTMAC (f)

The powder XRD patterns (large-angle and small-angle) of each sample are presented in Figure 5. The large-angle XRD patterns (Figure 5b) with 2θ from 10 to 70o display the typically non-crystalline phase structure. After modification and polymerization, the non-crystalline phase structure of samples does not show any significant changes compared to the original sample. As can be seen in Figure 5a, all samples show three characteristic peaks at the 2θ values around 1.0, 1.6 and 1.8, which corresponded to the (100), (110) and (200) lattice planes, respectively. These three peaks belong to the two-dimensional ordered hexagonal pore with p6mm space structure [43, 44]. These three peaks shifted slightly to the high-angle region,

indicating the shrinkage of meso-structure after modification and polymerization, which means the pore structure was affected slightly. This phenomenon has also been reported by other research groups [45, 46]. The main reflectance peaks of the small-angle XRD pattern maintained their original shape, corresponding to the remained ordered hexagonal mesoporous structure of the sample. A slight shift of the three peaks could be caused by formation of functional organic molecule layer through the modification and polymerization. Overall, the distinct (100), (110) and (200) diffractions in the XRD pattern of SBA-15-ACVA and SBA-15-PAPTMAC confirm that the ordered mesoporous structure of the composite has not been altered by the functionalization.

Figure 5. Small-angle XRD patterns (a) and large-angle XRD patterns (b) of SBA-15, SBA-15-ACVA and SBA-15-PAPTMAC

The BET surface area, pore volume and pore size of the modified SBA-15 are listed in Table 1. The pore volume, pore size and BET area of the original SBA-15 decrease slightly after the modification of ACVA. However, after polymerization with APTMAC, the BET area, pore volume and pore size decreased by 56.11%, 65.20% and 9.97% compared to original sample, respectively. The big decrease in pore volume of and the small decrease in the pore size of SBA-15-PAPTMAC indicate that most of polymerization occurred in the channels, instead of blocked the pores of mesoporous silica. The absorption-desorption isotherms of samples were carried out

in order to characterize the permanent porosity (Figure 6a). All three samples show reversible type IV isotherms, which is the main characteristic of mesoporous materials. The hysteresis loops appear in the range 0.7 < P/P 0 < 0.8 and are the typical H1 hysteresis loops, which also attributed to the ordered mesoporous pore of the materials [47]. As shown in Figure 6a, the type of the isotherm of the modified samples is still type IV and the hysteresis loops also indicate no change, which means that the overall structure and ordered mesoporous pores were not affected by the modification and polymerization. The pore size distributions are exhibited in Figure 6b. SBA-15 showed a pore size distribution in the range of 6-10 nm. After modification with ACVA and polymerization with APTMAC, the pore size distribution changed significantly. However, all these three samples still exhibited significantly mesoporous pore size. The BET analysis results are consistent with the TEM images and small-angle XRD data and imply that the modification and polymerization only slightly changed the mesoporous structure and pore size of mesoporous silica.

Table 1. Textural parameter of SBA-15 and the modified samples

Figure 6. (a) Brunauer-Emmett-Teller analysis and (b) pore size distribution from BJH of SBA-15, SBA-15-ACVA and SBA-15-PAPTMAC

3.3 Biocidal efficacy testing

Chlorinated and unchlorinated samples modified and polymerized with ACVA and PAPTMAC were challenged with S. aureus and E. coli O157:H7, respectively. The concentrations of S. aureus and E. coli O157:H7 were 7.63 logs and 7.52 logs. The results are shown in Table 2. Unchlorinated samples were used as control; the chlorine loading of the chlorinated sample was 1.62%. The result reveal that SBA-15 and SBA-15-ACVA have small log reductions for each bacterial within 10 min, mainly due to the adhesion of bacteria to the surfaces of mesoporous materials. After polymerization with APTMAC, SBA-15-PAPTMAC showed higher log reduction than the unpolymerized sample (0.09 log reduction of S. aureus and 0.12 log reduction of E. coli O157:H7) with 10 min of contact time due to the quaternary ammonium groups in the PAPTMAC. It is well-known that the bacteria cell surface is negatively charged, while the QAS group is positively charged. Thus, the electrostatic interaction caused by the different charges between QAS and bacteria can disrupt the cell membrane and inactive the growth of bacteria [48]. The chlorinated sample could inactivate 100% of both S. aureus (7.63 log reduction) and E. coli O157:H7 (7.52 log reduction) within 10 min. The biocidal efficacy of the samples improved significantly after the introduction of the N-halamine structure. The transfer of oxidative chlorine from N-halamine to bacteria membrane caused the inhibition of cells. It is interesting that N-halamine is capable of inactivating the inoculated bacteria much faster than QAS groups. However, even after the loss of the oxidative chlorine during application, the materials still have a certain biocidal property against S. aureus and E. coli O157:H7.

Table 2. Biocidal efficacy of samples against S. aureus and E. coli O157:H7

4. Conclusion In summary, we successfully grafted the initiator (ACVA) and polymerized the N-halamine/QAS monomer onto the surface of mesoporous silica by means of a polymer-brush-grafted method. SEM and TEM images showed that the structure and morphology mesoporous silica have slightly affected by modification and polymerization. According XPS analysis, the covalent bond (Si-O-C) was formed between SBA-15 and initiator, and N-halamine materials obtained after household bleach treatment. Compared with original sample, the functionalized mesoporous silica still shows mesoporous structures and high surface area in XRD and BET analysis. After chlorination, the chlorinated mesoporous sample enhance antimicrobial property significantly, and could inactive both of S. aureus (7.63 log) and E. coli O157:H7 (7.52 log) within 10 min. With the good antimicrobial property and high surface area, the prepared materials may have a great potential for practical application in water treatment and filtration areas.

Notes: The authors declare no competing financial interest.

Acknowledgements

The authors thank the research funds from Postgraduate Research & Practice Innovation Program of Jiangsu Provence (KYCX17_1444), the fundamental Research Funds for the Central Universities (No. JUSRP51722B, JUSRP11702), the scholarship for the Jiangnan University Scholarship Fund, the Project of Jiangsu Science and Technological Innovation Team, national first-class discipline program of Light Industry Technology and Engineering (LITE2018-2), and 111 Projects (B17021).

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Table 1. Textural parameter of SBA-15 and the modified samples Surface area (m2/g)

Pore volume (cm3/g) b

Pore size (nm) c

Sample a

SBA-15

674.84

1.54

7.70

SBA-15-ACVA

536.41

1.23

7.36

SBA-15-PAPTMAC

296.19

0.69

7.01

a

b

Surface area was calculated by BET methods. Pore volume was from BJH absorption cumulative volume of pores between 1.70 and

300.00 nm. c

Pore size was estimated using BJH absorption average pore width (4V/A).

Table 2. Biocidal efficacy of samples against S. aureus and E. coli O157:H7 log reduction sample

SBA-15 SBA-15-ACVA SBA-15-PAPTMAC SBA-15-PAPTMAC-Cl

a

Contact time

10min 10min 10min 30s 1min 5min 10min

inoculum population was 7.63 logs. inoculum population was 7.52 logs. c Cl+ loaded on samples was 1.62%±0.01wt%. b

S. aureusa

E. coli O157:H7b

0.02± 0.01 0.06± 0.02 0.09± 0.01 0.14± 0.02 0.25± 0.02 1.33± 0.01 7.63

0.01± 0.01 0.01± 0.01 0.12± 0.03 0.27± 0.04 1.01± 0.03 2.29± 0.02 7.52

Figure captions: Figure 1. Schematic illustration of the modification and polymerization process of SBA-15 Figure 2. FTIR spectra of SBA-15, SBA-15-ACVA, SBA-15-PAPTMAC and SBA-15-PAPTMAC-Cl Figure 3. XPS spectra of sample (a), Cl 2p peak of SBA-15-PAPTMAC (b), Si 2p peak of SBA-15-ACVA (c) and Cl 2p peak of SBA-15-PAPTMAC-Cl Figure 4. TEM images of SBA-15 (a), SBA-15-ACVA (b), SBA-15-PAPTMAC (c) and SEM images of SBA-15 (d), SBA-15-ACVA (e), SBA-15-PAPTMAC (f) Figure 5. Small-angle XRD patterns (a) and large-angle XRD patterns (b) of SBA-15, SBA-15-ACVA and SBA-15-PAPTMAC Figure 6. (a) Brunauer-Emmett-Teller analysis and (b) pore size distribution from BJH of SBA-15, SBA-15-ACVA and SBA-15-PAPTMAC

Figure 1. Schematic illustration of the modification and polymerization process of SBA-15

Figure 2. FTIR spectra of SBA-15, SBA-15-ACVA, SBA-15-PAPTMAC and SBA-15-PAPTMAC-Cl

Figure 3. XPS spectra of sample (a), Cl 2p peak of SBA-15-PAPTMAC (b), Si 2p peak of SBA-15-ACVA (c) and Cl 2p peak of SBA-15-PAPTMAC-Cl

Figure 4. TEM images of SBA-15 (a), SBA-15-ACVA (b), SBA-15-PAPTMAC (c) and SEM images of SBA-15 (d), SBA-15-ACVA (e), SBA-15-PAPTMAC (f)

Figure 5. Small-angle XRD patterns (a) and large-angle XRD patterns (b) of SBA-15, SBA-15-ACVA and SBA-15-PAPTMAC

Figure 6. (a) Brunauer-Emmett-Teller analysis and (b) pore size distribution from BJH of SBA-15, SBA-15-ACVA and SBA-15-PAPTMAC

Graphical Abstracts

Graphical abstract