ARTICLE pubs.acs.org/Langmuir
Directed Deposition of Functional Polymers onto Porous Substrates Using Metal Salt Inhibitors Philip Kwong, Cristofer A. Flowers, and Malancha Gupta* Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089, United States
bS Supporting Information ABSTRACT: This paper demonstrates the ability to control the location of polymer deposition onto porous substrates using vapor phase polymerization in combination with metal salt inhibitors. Functional polymers such as hydrophobic poly(1H,1H,2H,2H-perfluorodecyl acrylate), click-active poly(pentafluorophenyl methacrylate), and light-responsive poly(ortho-nitrobenzyl methacrylate) were patterned onto porous hydrophilic substrates using metal salts. A combinatorial screening approach was used to determine the effects of different transition metal salts and reaction parameters on the patterning process. It was found that CuCl2 and Cu(NO3)2 were effective at uniformly inhibiting the deposition of all three polymers through the depth of the porous substrate and along the entire cross section. This study offers a new and convenient method to selectively deposit a wide variety of functional polymers onto porous materials and will enable the production of next-generation multifunctional paper-based microfluidic devices, polymeric photonic crystals, and filtration membranes.
’ INTRODUCTION The development of next-generation microfluidic devices,1,2 biological sensors,2,3 and photonic devices4,5 requires the ability to selectively deposit functional polymers onto porous materials. For example, deposition of temperature-responsive and clickactive polymers onto filtration membranes and paper-based microfluidic devices will enhance their current capabilities. Patterning nonplanar surfaces is much more challenging than patterning flat surfaces. Current patterning techniques often involve top-down processing techniques such as photolithography which requires specific light-sensitive chemical moieties1 and reactive etching which requires multiple processing steps.4,5 In this paper, we introduce a novel and versatile bottom-up patterning technique that uses solventless initiated chemical vapor deposition (iCVD) in combination with transition metal salt inhibitors. The iCVD process is a one-step, solventless, substrate-independent process that can be used to deposit a wide variety of organic polymer coatings. In the iCVD process, vapors of monomer and initiator are flown into a vacuum reactor where a heated filament array decomposes the initiator into free-radicals. The free-radicals and monomer molecules adsorb onto the surface of a cooled substrate where polymerization occurs via a free-radical mechanism. The advantages of using iCVD over liquid phase polymerization are (i) iCVD is an environmentally benign process because it does not require the use of organic solvents; (ii) iCVD does not suffer from surface tension problems such as dewetting and clogging6 8 and therefore can be used to coat r 2011 American Chemical Society
complex structures such as carbon nanotubes,9 membranes,10 and electrospun fiber mats;7,11 (iii) iCVD can be used to deposit a wide range of polymers that exhibit functionalities such as hydrophobicity,12 chemical reactivity,13 and photoresponsiveness;14 and (iv) iCVD can be scaled up for large-scale roll-to-roll processing. 15 Although the iCVD technique has been used to pattern polymers onto flat surfaces using colloidal lithography,16 electron-beam lithography,17,18 and capillary force lithography,19 these techniques are not amenable to nonplanar substrates and a general technique to pattern polymers onto porous materials has not yet been demonstrated. Unlike other vapor deposition techniques, the iCVD process is not a line-of-sight process and deposition occurs in all directions. Figure 1 shows our attempt to pattern the deposition of hydrophobic poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA) onto porous chromatography paper using a physical mask. The PPFDA deposited onto the entire sheet, indicating that we could not restrict the deposition to regions directly exposed to the vapor. The monomer precursor and initiator radicals diffuse isotropically throughout the porous paper due to their large mean free path. Since physical masking did not work to pattern deposition onto porous materials, we developed an alternative method that involved photolithographic patterning.14 We used iCVD to deposit light-sensitive Received: April 26, 2011 Revised: July 20, 2011 Published: August 12, 2011 10634
dx.doi.org/10.1021/la201532s | Langmuir 2011, 27, 10634–10641
Langmuir
ARTICLE
reversibly complexes to the quinonoid intermediate; this causes deactivation of the intermediate and thereby prevents it from participating in initiation or propagation reactions. In this paper, we demonstrate that transition metal salt inhibitors can be used in conjunction with the iCVD process to pattern functional acrylate-based polymers onto porous substrates. Specifically, we show that we can pattern PPFDA, PoNBMA, and poly(pentafluorophenyl methacrylate) (PPFM) onto porous chromatography paper. Furthermore, we use a combinatorial screening process for high-throughput examination of the effect of the cation and the anion of the metal salt, the monomer, the concentration of the transition metal salt, the monomer flow rate, and the deposition time on the inhibition process. The polymers patterned herein are useful in a broad range of applications as they have very diverse functionalities. The hydrophobic nature of PPFDA can be exploited to make water-repellent and selfcleaning surfaces.27,28 The highly reactive ester group of PPFM can be used to covalently attach biological molecules such as immunoglobulin G29 and biotin ligands.30
’ EXPERIMENTAL PROCEDURE
Figure 1. (A) A physical mask with holes was placed on top of porous chromatography paper and placed into the iCVD chamber. (B) After iCVD deposition of PPFDA, dyed water was repelled over the entire surface of the paper, indicating that the physical mask cannot be used to control the location of growth onto porous substrates. Scale bars represent 1 cm.
poly(ortho-nitrobenzyl methacrylate) (PoNBMA) onto porous chromatography paper and then selectively removed the PoNBMA by cleaving the nitrobenzyl moieties using ultraviolet light and dissolving the exposed polymer in pH 8 buffer. This topdown patterning method can only be used with light-sensitive polymers such as PoNBMA. In this paper, we introduce a bottom-up patterning method that can be used to control the location of deposition of a wide variety of acrylate-based polymers irrespective of their chemical composition. Metal compounds have been known to inhibit polymerization in a wide range of systems. In a 1952 patent, Taylor demonstrated that nitrites of alkali and alkaline earth metals inhibited the polymerization of viscous monomer and polymer mixtures of both methyl methacrylate and styrene.20 Inskip and Patane inhibited the solution phase polymerization of a variety of unsaturated hydrocarbons, hydrocarbyl acids, and hydrocarbyl esters using cobalt(III), nickel(II), and manganese(II) N-nitrosophenylhydroxylamine compounds.21 More recently, Jensen and co-workers used transition metals and transition metal salts to inhibit the vapor phase deposition of parylene-based polymers to produce spatially controlled two-dimensional polymer coatings on flat surfaces.22 25 The vapor phase deposition of parylene occurs via pyrolytic polymerization where di-p-xylylene precursors are cleaved at high temperatures to form reactive quinonoid intermediates, which self-react to form parylene.26 Jensen and coworkers proposed a mechanism in which the inhibiting metal
Iron(III) chloride (FeCl3) (Aldrich, 97%), iron(III) nitrate (Fe(NO3)3) nonahydrate (Aldrich, >98%), copper(II) chloride (CuCl2) dihydrate (Aldrich, reagent grade), copper(II) nitrate (Cu(NO3)2) hydrate (Aldrich, 99.999%), ruthenium(III) chloride (RuCl3) hydrate (Aldrich, reagent grade), cobalt(II) chloride (CoCl2) (Aldrich, 97%), 1H, 1H,2H,2H-perfluorodecyl acrylate (PFDA) (Aldrich, 97%), ortho-nitrobenzyl methacrylate (oNBMA) (Polysciences, 95%), pentafluorophenyl methacrylate (PFM) (Synquest, 97%), and tert-butyl peroxide (TBPO) (Aldrich, 98%) were used as received without further purification. Aqueous solutions of FeCl3, Fe(NO3)3, CuCl2, Cu(NO3)2, RuCl3, and CoCl2 were prepared by dissolving the metal salts in deionized water. A commercially available wax printer (Xerox Phaser 8560N color printer) was used to print 1.45 cm 1.45 cm squares onto Whatman No. 1 chromatography paper (VWR) as described by Lu et al.31 and Carrilho et al.32 The printed lines had a width of 0.56 ( 0.01 mm. In order to generate individual compartments, the paper was heated for 10 min at approximately 160 °C using a hot plate (VWR). The wax melted through the depth of the paper (approximately 180 μm) and spread isotropically. The width of the line increased to 1.74 ( 0.06 mm and 1.57 ( 0.07 mm on the top and bottom of the paper, respectively. The final inner dimensions of the melted square compartments on the top measured 1.34 cm 1.34 cm. A volume of 25 μL of metal salt solution was applied to each square compartment to ensure complete liquid coverage. The solutions were applied by placing one 5 μL droplet in the center of the square and one 5 μL droplet at each corner of the square. This method generated a more uniform salt distribution compared to placing 25 μL of solution directly in the center of the square. Samples were allowed to dry for a minimum of 1 h under ambient conditions prior to placement into the iCVD chamber. The paper samples were taped onto the inside stage of a custom designed pancake-shaped reaction chamber (GVD Corporation, 25.0 cm in diameter, 4.8 cm in height). The pressure in the reaction chamber was maintained using a rotary vane vacuum pump (Edwards E2M40) and controlled using a throttle valve (MKS 153D). The pressure in the reaction chamber was monitored using a capacitance manometer (Baratron 622A01TDE). The reactor stage was kept at a constant temperature using a back-side recirculating heat exchanger. The top of the reaction chamber was composed of removable quartz glass that allowed for sample loading and visual inspection during deposition. The quartz top was covered with aluminum foil during the deposition of PoNBMA to prevent ambient light from entering the 10635
dx.doi.org/10.1021/la201532s |Langmuir 2011, 27, 10634–10641
Langmuir
ARTICLE
Table 1. Reaction Conditions stage polymer
temp (°C)
monomer source
Metal Screening Series monomer flow rate (sccm)
temp (°C)
initiator flow rate (sccm)
total pressure (mTorr)
deposition time (min)
1a
PPFDA
40.0
50.0
0.7
1.0
110
1b
PPFM
30.0
23.0
1.7
1.0
200
15
1c
PoNBMA
22.0
85.0
0.05
1.0
120
120
total pressure
deposition
stage polymer
temp (°C)
Monomer Flow Rate Series monomer source monomer flow temp (°C)
rate (sccm)
initiator flow rate (sccm)
(mTorr)
15
time (min)
2a
PPFDA
40.0
42.5
0.4
1.0
110
15
2b
PPFDA
40.0
50.0
0.7
1.0
110
15
2c
PPFDA
40.0
60.0
0.9
1.0
110
15
stage
monomer source
Deposition Time Series monomer flow
initiator flow
total pressure
deposition
rate (sccm)
rate (sccm)
polymer
temp (°C)
temp (°C)
(mTorr)
time (min)
3a
PPFDA
40.0
50.0
0.7
1.0
110
30
3b
PPFDA
40.0
50.0
0.7
1.0
110
45
3c
PPFDA
40.0
50.0
0.7
1.0
110
60
Figure 2. Contact angles of water on untreated paper and paper treated with a 2.0 M solution of FeCl3 after iCVD deposition of PPFDA, PPFM, and PoNMBA. Without the use of the salt, polymerization occurs on the untreated paper and the surface becomes hydrophobic. When the inhibiting salt is used, polymerization does not occur and the paper remains hydrophilic and wets. reactor. A stainless steel monomer source jar was located 23.5 cm from the edge of the reaction chamber and was opposite to the vacuum pump. The monomer source jar was maintained at a constant temperature using an external electrical heating jacket (Watlow 0903C-14) and was fed into the reaction chamber through externally heated (Watlow 0934C-57) stainless steel piping (12.7 mm diameter). A bellows sealed valve (12.7 mm diameter) was used to isolate the monomer source jar from the reaction chamber. The monomer flow rate was controlled by varying the source temperature and was determined based on the rate of the increase in pressure in the chamber. The TBPO source jar was located 42.0 cm from the edge of the reaction chamber and was opposite
to the vacuum pump. For all depositions, TBPO was kept at room temperature and fed into the reaction chamber through stainless steel piping (6.35 mm diameter). The TBPO flow rate was controlled using a mass flow controller (MKS 1479A) to achieve a flow rate of approximately 1.0 sccm. A nichrome filament array (Omega Engineering, 80%/ 20% Ni/Cr) was resistively heated between 200 and 225 °C as measured by a thermocouple (Omega Engineering, K-type) to decompose the TBPO initiator into radicals. The distance between the filament array and the substrate was kept constant at 32 mm. The specific reactor conditions for the experiments are summarized in Table 1. Contact angle goniometry (Rame-Hart model 290-F1) was used to study the surface properties of the substrates. High resolution images of the chromatography paper were taken using a JEOL-6610 low vacuum scanning electron microscope. X-ray photoelectron spectroscopy (XPS) was performed using a Surface Science Instruments M-Probe spectrometer with a monochromatic Al KR X-ray source. Low resolution survey spectra for analysis of PoNBMA on paper were acquired between binding energies of 1 and 1000 eV with a resolution of 1 eV. High resolution spectra for analysis of the metal salts were acquired with a resolution of 0.065 eV. Data analysis was performed using the ESCA25 Analysis Application (V5.01.04) software. Metal salts were drop-casted onto silicon wafers for XPS analysis of the inhibition mechanism. Circular patterns were drawn onto silicon wafers using a permanent marker (black Sharpie) in order to prevent the solution from spreading. Twenty microliters of 250 mM aqueous metal salt solutions were pipetted onto the center of the circular patterns. The substrate was heated to 75 °C to evaporate the water, resulting in dried adhered salt. PPFM was deposited onto the substrate using the reactor condition 1b in Table 1 with the deposition time increased to 50 min.
’ RESULTS AND DISCUSSION We examined the deposition of poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA), poly(pentafluorophenyl methacrylate) (PPFM), and poly(ortho-nitrobenzyl methacrylate) (PoNBMA) onto porous chromatography paper. Chromatography paper is 10636
dx.doi.org/10.1021/la201532s |Langmuir 2011, 27, 10634–10641
Langmuir naturally hydrophilic; however, the paper becomes hydrophobic when PPFDA, PPFM, or PoNBMA is uniformly deposited over the entire surface. We can therefore use visual analysis of the contact angle of water to determine if polymerization has occurred or been inhibited. Figure 2 shows an example of our analysis method using the reaction conditions described in Table 1 (conditions 1a 1c) and a 2.0 M aqueous solution of FeCl3 as the inhibiting transition metal salt. Without the use of the inhibiting salt, polymerization occurs on the chromatography
Figure 3. (A) Schematic of the experimental setup. The inhibition capability of different transition metal salts was combinatorially screened by dividing the porous chromatography paper into individual square compartments. (B) Chemical structures of the monomer precursors used in this study.
ARTICLE
paper and the surface becomes hydrophobic. If the inhibiting salt is used, polymerization does not occur and the paper remains hydrophilic and wets. The inhibition capability of different transition metal salts was combinatorially screened by dividing the porous chromatography paper into individual square compartments and treating each compartment with 2.0 M aqueous solutions of FeCl3, Fe(NO3)3, CuCl2, Cu(NO3)2, RuCl3 and CoCl2. The individual compartments were fabricated by melting wax barriers through the depth of the paper as described in detail in the experimental section. Figure 3 shows a schematic of the setup and the structure of the monomer precursors. Our combinatorial approach ensured that the reaction conditions were identical when comparing the effects of different transition metal salts. We compared the wetting behavior through the depth of the paper and along the edges in order to test the uniformity of the inhibition process. Table 2 shows the inhibiting behavior of each metal salt at the center and along the edges on both the top and the bottom of the paper with respect to PPFDA, PPFM, and PoNBMA. An entry of “I” indicates that the deposition of polymer was inhibited and an entry of “P” indicates that deposition occurred. When deposition occurred, water did not penetrate into the paper. An entry of “I” was given when water penetrated into the paper irrespective of the rate of penetration. The rate of penetration was generally faster for squares that exhibited uniform inhibition. The shaded regions in Table 2 indicate uniform inhibition through the depth of the paper and along the edges. CuCl2 and Cu(NO3)2 were able to uniformly inhibit the deposition of all three polymers. Figure 4 shows the wetting behavior at the top center of the square after deposition of PPFM. CuCl2, Cu(NO3)2, and CoCl2 were able to uniformly inhibit polymerization, whereas Fe(NO3)3 and RuCl3 did not. Although FeCl3 was able to inhibit polymerization at the top center of the square, the inhibition was not uniform. The cation appears to affect the ability of a metal compound to inhibit polymer deposition since metal compounds with similar oxidation states and anions did not behave similarly. For example, CuCl2 uniformly inhibited the deposition of PPFDA while polymer growth occurred in the presence of CoCl2, and FeCl3 uniformly inhibited the deposition of PoNBMA while polymer growth occurred in the presence of RuCl3. Of the salts tested, RuCl3 was the least effective at uniformly inhibiting polymerization. Some salts were effective at uniformly inhibiting polymerization of only certain polymers. For example,
Table 2. Summary of the Effects of the Metal Salts on the Inhibition through the Depth of the Paper and along the Edges for PPFDA, PPFM, and PoNBMAa
“I” indicates that polymerization was inhibited, while “P” indicates that polymerization occurred; “T” indicates the top of the paper, and “B” indicates the bottom of the paper. The shaded regions indicate uniform inhibition through the depth and along the edges.
a
10637
dx.doi.org/10.1021/la201532s |Langmuir 2011, 27, 10634–10641
Langmuir Fe(NO3)3 was able to uniformly inhibit the deposition of PPFDA and PoNBMA but not PPFM, whereas CoCl2 was only able to inhibit the deposition of PPFM. These results suggest that specific combinations of cation and monomer result in inhibition which is consistent with the inhibition of parylene-based polymers in which there are strong effects depending on the metal cation and precursor molecule.24,33 For example, Lahann and coworkers found that the deposition of reactive vinyl-containing parylene-based polymers could be inhibited, while the deposition of parylene-based polymers that contain oxygen and nitrogen could not be inhibited.33 It is important to note that several salts such as CuCl2 and Cu(NO3)2 could uniformly inhibit the deposition of all three of our polymers which indicates that we have found a general technique to pattern iCVD polymers irrespective of their chemical functionality.
Figure 4. Wetting behavior after deposition of PPFM using 2.0 M salt solutions. The square compartments measure 1.34 cm 1.34 cm, and the dotted gray circles indicate the location of beaded water droplets. Polymerization occurs on the untreated paper surrounding the square compartments.
ARTICLE
XPS was used to examine the chemical composition on the chromatography paper in order to confirm inhibition. Figure 5A and B shows the XPS survey scans of the top and the bottom of chromatography paper after PoNBMA deposition. The atomic percentages calculated from the XPS scans are 70.6% carbon, 5.0% nitrogen, and 24.4% oxygen on the top and 68.4% carbon, 4.0% nitrogen, and 27.6% oxygen on the bottom. These values are in close agreement to the theoretical atomic percentages calculated from the chemical formula of the oNBMA monomer (68.75% carbon, 6.25% nitrogen, and 25.00% oxygen), confirming that the PoNBMA coating is uniform through the depth of the paper. Figure 5C and D shows the XPS survey scans of the top and the bottom of chromatography paper treated with a 2.0 M solution of FeCl3 after PoNBMA deposition. The lack of a nitrogen peak in both spectra verifies that inhibition occurs uniformly through the depth of the paper. Figure 6 shows the scanning electron microscopy images of plain chromatography paper, paper after deposition of PoNBMA, paper treated with a 2.0 M solution of FeCl3, and paper treated with a 2.0 M solution of FeCl3 after PoNBMA inhibition. There is no variation among the images; hence, the addition of polymer and salt does not change the porosity or morphology of the paper. We chose to use CuCl2 to further study the effect of the concentration of the inhibiting salt and the reactor conditions on the inhibition process because of the ability of CuCl2 to uniformly inhibit the deposition of all three polymers through the depth of the paper and across the cross section. The individual compartments of the paper substrate were treated with different concentrations of CuCl2 solutions, and the inhibition of PPFDA was studied as a function of the monomer flow rate and the deposition time. In the iCVD process, it has been established that the rate of polymer deposition is dependent on the concentration of monomer at the surface of the substrate.34,35 The monomer surface concentration is monotonically related to the
Figure 5. (A,B) XPS survey scans of the top and bottom of chromatography paper after PoNBMA deposition, respectively. The presence of the nitrogen 1s peak indicates PoNBMA deposition. (C,D) XPS survey scans of the top and bottom of paper treated with a 2.0 M solution of FeCl3 after PoNBMA deposition, respectively. The lack of a nitrogen peak in both spectra verifies that inhibition occurs uniformly through the depth of the paper. 10638
dx.doi.org/10.1021/la201532s |Langmuir 2011, 27, 10634–10641
Langmuir ratio of the monomer partial pressure, Pm, to the saturation pressure, Psat. In order to determine whether increasing the monomer surface concentration can lead to a loss of inhibition due to
Figure 6. SEM images of (A,B) plain chromatography paper, (C,D) paper after deposition of PoNBMA, (E,F) paper treated with a 2.0 M solution of FeCl3, and (G,H) paper treated with a 2.0 M solution of FeCl3 after PoNBMA inhibition. The addition of polymer and salt does not change the porosity or morphology of the paper.
ARTICLE
passivation of the CuCl2 molecules, the monomer source temperature was varied between 42.5 and 60.0 °C (experiments 2a 2c in Table 3), which varied the value of Pm/Psat from 0.19 to 0.31. For a 15 min deposition, it was found that the minimum concentration of CuCl2 required to uniformly inhibit the deposition of PPFDA was 2.0 M for all values of Pm/Psat. The inability of compartments with lower concentrations of CuCl2 to inhibit polymer deposition is likely due to rapid passivation of the small number of CuCl2 molecules. For parylene-based polymers, it was found that the deposition of polymer could not be inhibited indefinitely and extended deposition times led to polymer growth.24 In the proposed parylene mechanism, loss of inhibition resulted from secondary adsorption on top of the deactivated precursor species that occupied available metal sites. It was hypothesized that a layer of deactivated precursor molecules effectively shielded additional quinonoid intermediates from the inhibiting metal. We studied the mechanism associated with inhibition in the iCVD process by using XPS to examine the chemical composition of the salts before and after deposition. If inhibition occurs though chemical reactions with the metal salts, we would expect a shift in the location or a change in the shape of the peaks associated with the metal cation or anion. Figure S-1 in the Supporting Information shows examples of high resolution scans of the Cu 2p and Cl 2s peaks of CuCl2 and Cu 2p and N 1s peaks of Cu(NO3)2 before and after PPFM deposition. There is no significant change in the location or shape of the peaks before and after deposition indicating that inhibition most likely occurs through physical means and not covalent interactions. The monomer most likely forms a reversible complex with the salt. Since the
Table 3. Summary of the Inhibition of PPFDA Deposition through the Depth of the Paper and along the Edges with Varying Monomer Source Temperature (2a 2c) and Deposition Time (3a 3c)a
“I” indicates that deposition was inhibited, “P” indicates polymer deposition occurred, “T” indicates the top of the paper, and “B” indicates the bottom of the paper. The shaded regions indicate uniform inhibition through the depth and along the edges.
a
10639
dx.doi.org/10.1021/la201532s |Langmuir 2011, 27, 10634–10641
Langmuir
ARTICLE
Cu(NO3)2 before and after PPFM deposition. This material is available free of charge via the Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION Corresponding Author
*E-mail:
[email protected].
’ ACKNOWLEDGMENT This work was supported by the National Science Foundation Division of Civil, Mechanical, and Manufacturing Innovation Award Number 1069328 and the National Sciences and Engineering Research Council of Canada Scholarship (P.K.). We thank the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology for use of their XPS. Figure 7. Inhibition through the depth of the paper and along the edges varies with deposition time as shown by PPFDA deposited on paper treated with different concentrations of CuCl2 solutions after (A,B) 15 min of deposition and (C,D) 60 min of deposition.
polymerization of all three acrylates can be inhibited, the complex is likely formed between the metal salt and the acrylate moiety as opposed to the pendant side group. To test if extended deposition times affected inhibition in the iCVD process, the deposition time was increased from 15 to 60 min (experiments 3a 3c in Table 3). As the duration of deposition increased, higher concentrations of CuCl2 were required to uniformly inhibit polymer deposition. Figure 7 shows that solutions of at least 2.0 M CuCl2 were required to uniformly inhibit the deposition of PPFDA during a deposition of 15 min, whereas even CuCl2 solutions as high as 2.5 M were unable to uniformly inhibit deposition after 60 min as shown by polymerization along the edges of the squares. The loss of uniform inhibition after extended deposition times is likely due to the passivation of CuCl2 by accumulation of deactivated species which shield additional precursor molecules from the inhibiting metal salt.
’ CONCLUSION We have demonstrated a general method to control the location of polymer deposition onto three-dimensional porous substrates using metal salt inhibitors. The generality of our process was confirmed by demonstrating that the deposition of PPFDA, PPFM, and PoNBMA could be inhibited by several transition metal salts such as CuCl2 and Cu(NO3)2. The inhibition process lost uniformity after extended deposition times likely due to the passivation of the salt by accumulation of deactivated precursor molecules. Our study offers a new and convenient method to deposit hydrophobic, click-active, and light-responsive polymers onto specific regions of porous materials. In our study, the inhibiting metal salt was contained within compartments in order to combinatorially screen the impact of reaction conditions; however, inkjet printing will be used to print the transition metal salts for future applications.36,37 Future work involves using our patterning process to develop multifunctional paper-based microfluidic devices and filtration membranes. ’ ASSOCIATED CONTENT
bS
Supporting Information. High resolution XPS scans of the Cu 2p and Cl 2s peaks of CuCl2 and Cu 2p and N 1s peaks of
’ REFERENCES (1) Lee, J.-T.; George, M. C.; Moore, J. S.; Braun, P. V. J. Am. Chem. Soc. 2009, 131, 11294–11295. (2) Martinez, A. W.; Phillips, S. T.; Butte, M. J.; Whitesides, G. M. Angew. Chem., Int. Ed. 2007, 46, 1318–1320. (3) Dungchai, W.; Chailapakul, O.; Henry, C. S. Anal. Chem. 2009, 81, 5821–5826. (4) Arsenault, A. C.; Clark, T. J.; von Freymann, G.; Cademartiri, L.; Sapienza, R.; Bertolotti, J.; Vekris, E.; Wong, S.; Kitaev, V.; Manners, I.; Wang, R. Z.; John, S.; Wiersma, D.; Ozin, G. A. Nat. Mater. 2006, 5, 179–184. (5) Li, Y. Y.; Kollengode, V. S.; Sailor, M. J. Adv. Mater. 2005, 17, 1249–1251. (6) Tenhaeff, W. E.; Gleason, K. K. Adv. Funct. Mater. 2008, 18, 979–992. (7) Ma, M.; Mao, Y.; Gupta, M.; Gleason, K. K.; Rutledge, G. C. Macromolecules 2005, 38, 9742–9748. (8) Gupta, M.; Kapur, V.; Pinkerton, N. M.; Gleason, K. K. Chem. Mater. 2008, 20, 1646–1651. (9) Lau, K. K. S.; Bico, J.; Teo, K. B. K; Chhowalla, M.; Amaratunga, G. A. J.; Milne, W. I.; McKinley, G. H.; Gleason, K. K. Nano Lett. 2003, 3, 1701–1705. (10) Gupta, M.; Gleason, K. K. Thin Solid Films 2009, 517 3547–3550. (11) Ma., M.; Gupta, M.; Li, Z.; Zhai, L.; Gleason, K. K.; Cohen, R. E.; Rubner, M. F.; Rutledge, G. C. Adv. Mater. 2007, 19, 255–259. (12) Gupta, M.; Gleason, K. K. Langmuir 2006, 22, 10047–10052. (13) O’Shaughnessy, W. S.; Marí-Buye, N.; Borros, S.; Gleason, K. K. Macromol. Rapid Commun. 2007, 28, 1877–1882. (14) Haller, P. D.; Flowers, C. A.; Gupta, M. Soft Matter 2011, 7, 2428–2432. (15) Gupta, M.; Gleason, K. K. Thin Solid Films 2006, 515, 1579– 1584. (16) Trujillo, N. J.; Baxamusa, S.; Gleason, K. K. Thin Solid Films 2009, 517, 3615–3618. (17) Im, S. G.; Kim, B. S.; Lee, L. H.; Tenhaeff, W. E.; Hammond, P. T.; Gleason, K. K. Macromol. Rapid Commun. 2008, 29, 1648–1654. (18) Mao, Y.; Felix, N. M.; Nguyen, P. T.; Ober, C. K; Gleason, K. K. J. Vac. Sci. Technol., B 2004, 22, 2473–2478. (19) Im, S. G.; Bong, K. W.; Kim, B.-S.; Baxamusa, S. H.; Hammond, P. T.; Doyle, P. S.; Gleason, K. K. J. Am. Chem. Soc. 2008, 130, 14424–14425. (20) Taylor, R. S. U.S. Patent 2,607,081, August 19, 1952. (21) Inskip, E. B.; Patane, J. M. U.S. Patent 4,638,079, January 20, 1987. (22) Vaeth, K. M.; Jensen, K. F. U.S. Patent 5,869,135, February 9, 1999. (23) Vaeth, K. M.; Jensen, K. F. Adv. Mater. 1999, 11, 814–820. (24) Vaeth, K. M.; Jensen, K. F. Chem. Mater. 2000, 12, 1305–1313. (25) Vaeth, K. M.; Jackman, R. J.; Black, A. J.; Whitesides, G. M.; Jensen, K. F. Langmuir 2000, 16, 8495–8500. 10640
dx.doi.org/10.1021/la201532s |Langmuir 2011, 27, 10634–10641
Langmuir
ARTICLE
(26) Gorham, W. F. J. Polym. Sci., Part A-1: Polym. Chem. 1966, 4, 3027–3039. (27) Churchley, D.; Rees, G. D.; Barbu, E.; Nevell, T. G.; Tsibouklis, J. Int. J. Pharm. 2008, 352, 44–49. (28) Kumar, V.; Pulpytel, J.; Rauscher, H.; Mannelli, I.; Rossi, F.; Arefi-Khonsari, F. Plasma Processes Polym. 2010, 7, 926–938. (29) Francesch, L.; Borros, S.; Knoll, W.; F€orch, R. Langmuir 2007, 23, 3927–3931. (30) Francesch, L.; Garreta, E.; Balcells, M.; Edelman, E. R.; Borros, S. Plasma Processes Polym. 2005, 2, 605–611. (31) Lu, Y.; Shi, W.; Jiang, L.; Qin, J.; Lin, B. Electrophoresis 2009, 30, 1497–1500. (32) Carrilho, E.; Martinez, A. W.; Whitesides, G. M. Anal. Chem. 2009, 81, 7091–7095. (33) Chen, H.-Y.; Lai, J. H.; Jiang, X.; Lahann, J. Adv. Mater. 2008, 20, 3474–3480. (34) Lau, K. K. S.; Gleason, K. K. Macromolecules 2006, 39, 3688– 3694. (35) Lau, K. K. S.; Gleason, K. K. Macromolecules 2006, 39, 3695– 3703. (36) Reddington, E.; Sapienza, A.; Gurau, B.; Viswanathan, R.; Sarangapani, S.; Smotkin, E. S.; Mallouk, T. E. Science 1998, 280, 1735–1737. (37) Thomas, S. W., III; Chiechi, R. C.; LaFratta, C. N.; Webb, M. R.; Lee, A.; Wiley, B. J.; Zakin, M. R.; Walt, D. R.; Whitesides, G. M. Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 9147–9150.
10641
dx.doi.org/10.1021/la201532s |Langmuir 2011, 27, 10634–10641
