Enhanced Surface Wetting of Pigment Coated Paper by UVC Irradiation

Ind. Eng. Chem. Res. 2010, 49, 11351–11356

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Enhanced Surface Wetting of Pigment Coated Paper by UVC Irradiation Anni Ma¨a¨tta¨nen, Petri Ihalainen,* Roger Bollstro¨m, Shaoxia Wang, Martti Toivakka, and Jouko Peltonen Centre of Excellence for Functional Materials, Laboratory of Paper Coating and ConVerting, Åbo Akademi UniVersity, Porthaninkatu 3-5, FI-20500 Turku, Finland

The effect of UVC (λmax ) 254 nm) treatment on wettability of pigment-coated papers was examined. The paper samples were coated with conventional pigments including ground calcium carbonate (GCC), precipitated calcium carbonate aragonite (PCC), and Kaolin. The coating formulation also included poly(styrene-butadiene) (SB) latex binder and a dispersing agent, sodium polyacrylate (NaPA), for formation of a colloidally stable pigment slurry at a relatively high solids content. A significant decrease of contact angle of water on the studied pigment-coated papers was observed as a result of UVC treatment. The effect was most pronounced for carbonate-based coatings. In addition, the UVC treatment showed long-term stability. A detailed analysis of the surface chemical composition of the PCC-based coatings indicated that the UVC treatment leads to photooxidation and photodegradation, and eventual desorption of a thin NaPA overlayer from the pigment surface. This in turn increases the polarity of the surface and enhances its wettability. 1. Introduction The control of wettability and adhesion of coated paper and plastic films is an important issue contributing to the print quality both in conventional graphic printing1-4 and in functional printing applications.5 Corona and plasma treatments have been shown to enhance surface wettability of coated and surfacesized papers and paperboards.6,7 In addition, UV treatment has been shown to increase surface wettability and adhesion of polymer and rubber surfaces.8-12 When compared to other methods, the attractiveness of the UV treatment lies in its economical and environmental friendliness as well as ease of applicability without the need of a vacuum atmosphere or chemical agents. Several types of UV radiation sources have been examined and described previously.12,13 In general, two principal UV wavelength ranges are used for different photochemical treatments; the wavelength range at ca. 220-300 nm (UVC, λmax ) 254 nm) and ca. 320-400 nm (UVA, λmax ) 365 nm).14-18 The former breaks down chemical bonds (i.e., photolysis),14-17 whereas the latter is used to generate electron-hole pairs and free radicals (i.e., photocatalysis).15,18 In addition, shortwave (∼180-220 nm) UV energy can be generated by specially designed UV lamps to produce ozone.13 Low-pressure mercury lamps with radiation composed mainly (∼90%) of two narrow intense lines at wavelengths 185 and 254 nm are most often used for increasing surface wettability in polymer and rubber films.8,10-12 The UV radiation produced at 185 nm generates ozone and ground-state oxygen atoms from oxygen in air. In addition, UV radiation at 254 nm is absorbed by the ozone molecules, resulting in decomposition of ozone to molecular oxygen and a very reactive form of atomic oxygen. The latter is able to effectively oxidize a polymer, creating polar moieties (e.g., hydroxyl and carboxylic groups) and increasing the wettability. The extent of improvement in wettability due to the photooxidation depends on the surface composition.8 The UV-ozone treatment has been shown to be reversible.19 Here, the effect of UVC (λmax ) 254 nm) treatment on the wettability of pigment-coated papers was examined. The paper * To whom correspondence should be addressed. Tel.: +358-2-2154859. Fax: +358-2-215-3226. E-mail: [email protected].

samples were coated using three different pigments, ground calcium carbonate (GCC), precipitated calcium carbonate aragonite (PCC), and Kaolin (main chemical composition, Al2O3 · 2SiO2 · H2O). The coating formulation also included a dispersing agent, sodium polyacrylate (NaPA), and poly(styrenebutadiene) (SB) latex binder. Changes in water contact angle were measured before and after UVC radiation. In addition, the effect of UVC treatment on topography and microroughness as well as surface chemistry was studied. 2. Materials and Methods 2.1. Sample Preparation. The substrates were prepared by applying a 15 g/m2 coating layer on a base paper (75 g/m2, Kangas) with a laboratory blade coater (DT Paper Science Oy Ab). The coated sheets were dried with an IR drier for 4 s and then calendered with a laboratory calender (DT Paper Science Oy Ab) using 37 °C roll temperature, a nip-pressure of 87 kN m-1, and a speed of 2 m/min. Pigments used in the coating color formulations were as follows: ground calcium carbonate (HydroCarb 90 FO, Omya AG, Malvern Mastersizer S median particle size 0.9 µm, in powder form), precipitated calcium carbonate aragonite (OPACARB A40, Specialty Minerals Nordic Oy, Sedigraph 5100 median particle size 0.4 µm, form factor ∼ 5:1, in slurry),20 and Kaolin (Capim SP, Imerys Performance Minerals, Sedigraph 5100 median particle size 0.6 µm, form factor ∼ 25:1, in slurry).21 The PCC and GCC suspensions also included sodium polyacrylate as a dispersant (5 min) resulted in yellowing of the sample surface. Similar yellowing of SB rubber surfaces has been reported after long UVC-ozone exposures.10 This is attributed to styrene oxidation and the formation of conjugated CdC moieties and unsaturated ketones. 3.2. Topography and Roughness. Figure 3A shows a typical AFM topograph of a PCC coated structure with pigments randomly oriented at the surface. The relative surface area

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fraction of PCC pigment is approximately 85% (calculated from AFM topographs by grain analysis), with the remainder composed of pores and SB latex binder. No visible topographical changes were detected on the PCC coating surface after UVC radiation (Figure 3B). Similar results were also obtained for the other pigment-coated samples (data not shown). The unchanged topography shows that ablation of the latex surface has not occurred, as has been observed for long-term UV-ozone-treated rubber surfaces.10 Furthermore, Figure 4 shows σ as a function of T throughout the available length scale of AFM (limited by tip geometry and maximal image size) for each sample before and after UVC treatment. In all cases, both the untreated and UVC treated surfaces show identical σ-T behavior. This implies that UVC enhanced surface wetting arises from the changes in chemical properties rather than changes in topography. 3.3. Surface Chemistry. Surface chemistry of the untreated and UVC treated PCC based coatings was examined by XPS and surface energy determination. Table 2 lists the elemental composition from XPS spectra before and after UVC treatment. The values are an average of three parallel measurements with a standard deviation of less than 3%. Also included in Table 2 are the values for the pure PCC layer (i.e., without dispersant and latex). This was used as a reference to distinguish the effect of contaminants in the analysis. In addition, Figure 5 shows high-resolution XPS C1s spectra of (A) pure PCC layer, (B) untreated PCC coating, and (C) UVC treated (60 s) PCC coating including the deconvoluted C1s peaks. The surface energy data for the PCC samples are compiled in Table 3.

Figure 2. Static water contact angle (θw,s) values as a function of UVC irradiation time for (A) Kaolin and (B) PCC coated samples.

Figure 3. AFM topography images of the PCC coated sample (A) before and (B) after UVC treatment (60 s). The images are captured at exactly the same spot. The image size is 20 × 20 µm2 and height scale 700 nm.

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Figure 4. rms roughness (σ) as a function of correlation length (T) before and after UVC treatment (60 s) for (A) the Kaolin, (B) the PCC, and (C) the GCC coated paper samples. Table 2. Binding Energies (BE) and Atomic Percentages (at. %) of Elements for Pure PCC Layer as well as Untreated and UVC Treated PCC Pigment Coatingsa pure PCC layer

untreated coating

element

EB (eV)

at. %

EB (eV)

at. %

EB (eV)

at. %

C1s O1s Ca2p3/2

285.0 532.2 348.0

30.9 54.4 14.3

285.0 532.2 348.0

59.2 32.1 8.6

285.0 532.2 348.0

52.3 39.2 8.2

284.6

58.9

286.1 288.1 289.6

15.0 4.0 22.1

531.6

89.9

533.1

10.1

C1 C2 C3 C4 C5 O1 O2 O3

285.0 286.4 287.9 289.6 531.3 532.4

Composition of the 284.4 40.0 285.1 4.1 2.5 53.4 289.7

C1s Peak 63.9 19.0 16.7

Composition of the O1s Peak 94.0 531.6 98.7 6.0 533.3 1.3

UVC treated coating

Figure 5. High-resolution XPS C1s spectra of (A) pure PCC layer, (B) untreated PCC coating, and (C) UVC treated (60 s) PCC based coating. Also shown are the deconvoluted C1s peaks. Table 3. Total and Compositional Surface Energy Values for PCC Samples before and after UVC Treatment (60 s) surface energy component

untreated sample (mN/m)

UVC treated sample (mN/m)

nonpolar polar total

46.5 0.01 46.7

38.9 13.9 52.8

a

Also shown are results from the curve fitting of the C1s and O1s peaks.

The main component on the surface of the reference sample is oxygen (Table 2). The carbon content was found to be slightly higher than the O/C stoichiometric ratio in the reference sample, which was taken as an indication of surface contamination, most

probably resulting from the production and storage of the samples. The C1s peak fit reveals four bands. The band at 285.0 eV (C2) is assigned to C-C and C-H bonds.28-32 The bands at 286.4 (C3) and 287.9 eV (C4) are assigned to oxidized species (e.g., C-O, CdO, and O-C-O).28-32 All of these are believed to originate from organic surface contaminants. The band at the highest energy

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level (C5) is assigned to inorganic carbon in a calcite matrix. The O1s peak fit reveals two bands. The peak at the lower energy level (O1) originates from carbonate groups and the peak at 532.4 eV from organic contaminants. XPS analysis for the untreated pigment-coated sample shows an increased content of carbon and a decreased amount of oxygen and calcium on the surface in comparison to the reference sample (pure PCC layer). This can be attributed to the presence of NaPA dispersant and SB latex binder on the surface. The former forms a thin layer on the surface of pigments, while the latter remains mostly in the interstices between the pigments (Figure 3). The curve fitting of C1s shows three bands (Table 2). The bands at 284.4 (C1) and 285.1 eV (C2) are assigned to unoxidized carbon moieties. The former (not present in the pure PCC sample) is assigned to unsaturated CdC bonds and the latter to C-C and C-H bonds.28-32 The CdC bonds originate from SB latex (-[(CH2-CHd CH-CH2)n-(CH(C6H5)-CH2)m]z-), as the chemical structure of NaPA (repeating unit -[CH2-CH(COONa)]n-) does not contain unsaturated carbon bonds. The C-C and C-H bonds are assigned to latex, dispersant, and possible surface contaminants. For typical pigment-coated papers which contain latex binder and polymeric dispersant, 90% of surface carbon has been shown to originate from the latex binder and the remaining 10% from a thin dispersant overlay on the pigment surface.33 The third band (C5) is assigned to carbonate groups but also includes carboxyl moieties of NaPA. However, compared to the reference surface no other oxidized species (e.g., C-O or CdO) were detected. This indicates a negligible atmospheric oxidation of the untreated pigment-coated surface. The curve fitting of O1s also shows that the origin of oxygen belonging to organic species is different as the band is clearly at a higher energy level compared to the pure PCC sample. Different reaction mechanisms have been suggested for the binding of poly(acrylic acid) (PAA) to CaCO3.32,34 According to Fantinel et al., PAA forms a bidentate chelating complex with a Ca2+ ion; i.e. both oxygen atoms in the polyacrylate carboxylate group bond to a single Ca2+ ion.34 In addition, the complexation process goes through different intermediate states, including a unidentate complex where only one oxygen atom is bound to calcium.34 On the other hand, Shui proposed a reaction mechanism involving the hydrolytic degradation of carbonate ions and formation of hydrogen bonding between CaOH and the carboxylic group of polyacrylate.32 The lack of C-O (C3) and O-C-O (C4) moieties on the surface of the untreated sample argues against bidentate complex formation, whereas the presence of organic (O3) oxygen arising from carboxylic moieties supports a reaction mechanism involving the binding of only one oxygen to calcium (Table 2). The total surface energy value of untreated PCC coating was found to be close to 47 mN/m (Table 3). In addition, the compositional surface energy values show that the surface is practically nonpolar. The surface tension (or surface energy) of pure CaCO3 is reported to be 200 mN/m.35 By adding polymeric dispersants with low surface energy, the surface energy of mineral pigments can be lowered to more closely match that of binder latex, enabling a more homogeneous mixture.35 For example, the surface energy of CaCO3 can be lowered to 40 mN/m by coating the pigments with stearic acid.35 The monolayer thickness of PAA on CaCO3 has been estimated to be about 0.5 nm.32 In the case of monolayer thickness, the carboxylic side groups of PAA are preferentially oriented toward the mineral pigment interface, while leaving the apolar carbohydrate chains toward the air.32 Thus, the nonpolar nature of

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the surface indicates that PCC particles are effectively fully covered by NaPA, although for the coating formulations used here, the amount of NaPA is less than what is required for a full monolayer coverage (∼3 wt % concentration in solution versus CaCO3).32 The presence of oxygen as well as the C1s carbonate and carboxyl peaks in XPS spectra can be explained by a higher probing depth (∼5-10 nm) of the XPS technique compared to the contact angle measurements. The UVC treatment decreased the C/O ratio of the PCC pigment coated surface (Table 2). The relative amount of calcium remained the same. The C1s peak fit reveals four bands, two of which were not observed for the untreated sample. The band at 286.1 eV (C3) arises from C-O moieties, and 288.1 eV (C4) is assigned to the higher oxidation states (e.g., O-C-O and CdO moieties). Furthermore, the relative ratio of the band assigned to CdC (C1) was slightly decreased while the ratio of the C5 (carbonate + carboxyl) peak had increased. The most prominent difference between the untreated and UVC treated samples was the lack of the C2 band in the latter. In the untreated sample, the band was assigned to C-C and C-H moieties arising from both the SB latex and NaPA. The decreased C/O ratio and the increased presence of oxidized carbon moieties in XPS spectra (Table 2) are consistent with the increased surface energy value of the polar component (Table 3). In addition, the surface energy value of the nonpolar component decreased (Table 3). However, this was not enough to offset the considerably increased polarity, and thus the total surface energy of the PCC based coating was found to increase. The disappearance of the C2 band in the XPS spectrum as well as the increased polarity of the PCC based coating can be partly explained by the photooxidation of the SB latex surface. This is also reflected by a small decrease in the relative ratio of CdC moieties (C1). The UV-ozone treatment has been shown to increase the polarity of SB rubber surfaces by photooxidization, enhancing the surface wettability considerably.8,10 The UVC treatment did not have a significant effect on the surface wettability of the SB binder latex used in the coating formulations (Table 1). Furthermore, the SB latex is a minority component on the surface (Figure 2). Therefore, the possible photooxidation of the SB binder by UVC is not believed to be the dominant mechanism for the enhanced surface wetting in PCC based coatings.8,10 This conclusion is also supported by the fact that polymer films oxidized by UV treatment have been shown to have reversible wetting behavior; the contact angle value returns to about 80% of its original value after a week.19 On the other hand, the effect of ozone-free UVC irradiation used here was confirmed to be irreversible after 7 days (Figure 1). A possible mechanism behind the enhanced surface wetting of pigment-coated paper is the photodegradation and photooxodation and eventual desorption of NaPA from the pigment surface. The UVC irradiation has been shown to etch the PAA film surface, changing the surface wettability.36 The relative amount of carboxylic groups desorbed has been shown to be dependent on the irradiation time.16 The influence of the UVC exposure time on the wetting was demonstrated in Figure 2. Different photoreactions take place upon UVC irradiation of PAA, including cross-linking, chain scission, and the destruction and abstraction of side carboxyl groups.16,36 In addition, PAA is also oxidized in air atmosphere during UVC treatment.16 The lack of the C2 band and appearance of oxidized moieties (C3 and C4) in the UVC treated sample (Table 2) indicates photooxidation of the nonpolar carbohydrate chains of NaPA. This is supported by the decreased surface energy value of the nonpolar component and the increased polarity after UVC treatment (Table 3). Furthermore, the relative ratio of the band (C5)

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assigned to carbonate and carboxyl moieties was increased (Table 2). The increase can be attributed to the greater content of carbonate groups on the surface, as the removal of side carboxyl groups from NaPA would decrease the ratio (Table 2). This indicates etching of NaPA due to abstraction of the side carboxyl groups which leads in exposure of the highly polar pigment surface. This is further supported by the changes in the nonpolar and polar surface energy values as a result of UVC treatment (Table 3). 4. Conclusions The wettability of pigment coated paper substrates was enhanced by the UVC (λmax ) 254 nm) treatment. This was demonstrated by a significant decrease in static contact angle of water. The efficiency of the UVC treatment was dependent on the type of coating pigment used, as well as the irradiation time. The topography and roughness of the pigment coated paper samples was however not affected by the UVC treatment. A detailed analysis of surface chemistry of the PCC based coatings showed that UVC irradiation mainly affected the thin overlay of NaPA on the PCC pigment surface. Two mechanisms contribute to the enhanced surface wettability and polarity of the studied PCC pigment coatings. First, the oxidation of nonpolar hydrocarbon backbone of NaPA increases the polarity of the surface. Second, the destruction or abstraction of the side carboxylic groups and eventual removal of NaPA from the pigment surface which exposes the high surface energy (and highly polar) pigment surface. The increased polarity, in turn, enhanced the surface wettability of the coated paper surface by, e.g., water. However, etching of the very thin polymer overlayer from the pigment surface showed no visible change in AFM topographs nor had it any influence on the roughness of the relatively rough coated paper surface. The possibility of tuning surface wettability of paper after production without affecting the topography of the coating layer could be an advantage in, e.g., both conventional and functional printing performed by inkjet. For example, droplet spreading in inkjet is known to be dependent on the porosity and surface chemistry of the print substrate. Use of UVC could improve printability and runnability as well as offer cost savings in the form of a reduced requirement for additives in the coating color preparation. Acknowledgment The Academy of Finland under Grant 118650 is acknowledged for financial support. Literature Cited (1) Kipphan, H. Handbook of Print Media Technologies and Production Methods; Springer: New York, 2001. (2) Keunings, R.; Bousfield, D. W. Analysis of Surface Tension Driven Leveling in Viscoelastic Films. J. Non-Newtonian Fluid Mech. 1987, 22, 219. (3) Gane, P. A. C.; Schoelkopf, J.; Spielmann, D. C.; Matthews, G. P.; Ridgway, C. J. Fluid Transport into Porous Coating Structures: Some Novel Findings. TAPPI J. 2000, 83, 77. (4) Donigian, D. A New Mechanism for the Setting and Gloss Development of Offset Ink. J. Pulp Pap. Sci. 2006, 32, 163. (5) Bollstro¨m, R.; Ma¨a¨tta¨nen, A.; Tobjo¨rk, D.; Ihalainen, P.; Kaihovirta, N.; ¨ sterbacka, R.; Peltonen, J.; Toivakka, M. A Multilayer Coated Fiber-Based O Substrate Suitable for Printed Functionality. Org. Electron. 2009, 10, 1020. (6) Schuman, T.; Adolfsson, B.; Wikstro¨m, M.; Rigdahl, M. Surface Treatment and Printing Properties of Dispersion-Coated Paperboard. Prog. Org. Coat. 2005, 54, 188. (7) Pyko¨nen, M.; Sundqvist, H.; Ja¨rnstro¨m, J.; Kaukoniemi, O.-V.; Tuominen, M.; Lahti, J.; Peltonen, J.; Fardim, P.; Toivakka, M. Effects of Atmospheric Plasma Activation on Surface Properites of Pigment-Coated and Surface-Sized papers. Appl. Surf. Sci. 2008, 255, 3217.

(8) Romero-Sa´nchez, M. D.; Martin-Martı´nez, J. M. Influence of Additives in Adhesion of UV Radiation Surface-Treated SBS Rubber. J. Adhes. 2006, 82, 753. (9) Gotoh, K.; Kikuchi, S. Improvement of Wettability and Detergency of Polymeric Materials by Excimer UV treatment. Colloid Polym. Sci. 2005, 3, 1356. (10) Romero-Sa´nchez, D.; Mercedes Pastor-Blas, M.; Martin-Martı´nez, J. M.; Walzak, M. J. UV Treatment of Synthetic Styrene-Butadiene-Styrene Rubber. J. Adhes. Sci. Technol. 2003, 17, 25. (11) Bradley, R. H.; Mathieson, I. Chemical Interactions of Ultraviolet Light with Wool Fiber Surfaces. J. Colloid Interface Sci. 1997, 194, 338. (12) Ranby, B.; Rabek, J. F. Photodegeneration, Photo-oxidation and Photostabilization of Polymers; John Wiley and Sons: New York, 1975. (13) Koller, L. R. UltraViolet Radiation; John Wiley and Sons: New York, 1965. (14) Wang, B.; Wu, F.; Li, P.; Deng, N. UV-Light Induced Photodegradation of Bisphenol A in Water: Kinetics and Influencing Factors. React. Kinet. Catal. Lett. 2007, 92, 3. (15) Ravichandran, L.; Selvam, K.; Muruganandham, M.; Swaminathan, M. Photocatalytic Cleavage of C-F Bond in Pentafluorobenzoic Acid with Titanium Dioxide-P25. J. Flourine Chem. 2006, 127, 1204. (16) Kaczmarek, H.; Szalla, A. Photochemical Transformation in Poly(acrylic acid)/Poly(ethylene oxide) Complexes. J. Photochem. Photobiol., A 2006, 180, 46. (17) Masuda, S.; Sertova, N.; Petkov, I. Photochemical Behavior of Poly(ethylacryloylacetate) and Poly(acryloylacetone) Films. J. Polym. Sci., Part A: Polym. Chem. 1997, 35, 3683. (18) Twesme, T. M.; Tompkins, D. T.; Anderson, M. A.; Root, T. W. Photocatalytic Oxidation of Low Molecular Weight Alkanes: Observations with ZrO2-TiO2Supported Thin Films. Appl. Catal., B 2006, 64, 153. (19) Gotoh, K.; Nakata, Y.; Tagawa, M.; Tagawa, M. Wettability of Ultraviolet Excimer-Exposed PE, PI and PTFE Films Determined by the Contact Angle Measurements. Colloids Surf., A 2003, 224, 165. (20) Ja¨rnstro¨m, J.; Peltonen, J.; Sinervo, L.; Toivakka, M. Topography and Gloss of Precipitated Calcium Carbonate Coating Layers on a Model Substrate. TAPPI J. 2007, 6, 23. (21) Lemstro¨m, A. Inverkan av pigmentets partikelform pa˚ egenskaperna hos bestruket papper. M.Sc. thesis, Åbo Akademi University, Turku, Finland, 2008. (22) Fowkes, F. M. Attractive Forces at Interfaces. Ind. Eng. Chem. 1965, 56, 40. (23) Owens, D. K.; Wendt, R. C. Estimation of the Surface Free Energy of Polymers. J. Appl. Polym. Sci. 1969, 13, 1741. (24) Kaelble, D. H. Dispersion-Polar Surface Tension Properties of Organic Solid. J. Adhes. 1970, 2, 66. (25) van Oss, C. J.; Chadhury, M. J.; Good, R. J. Monopolar Surfaces. AdV. Colloid Interface Sci. 1987, 28, 35. (26) van Oss, C. J.; Chadhury, M. J.; Good, R. J. Interfacial Lifshitzvan der Waals and Polar Interactions in Macroscopic Systems. Chem. ReV. (Washington, DC, U. S.) 1988, 88, 927. (27) Ja¨rnstro¨m, J.; Ihalainen, P.; Backfolk, K.; Peltonen, J. Roughness of Pigment Coatings and Its Influence on Gloss. Appl. Surf. Sci. 2008, 254, 5. (28) Beamson, G.; Briggs, D. High Resolution of XPS of Organic Polymers; John Wiley & Sons: New York, 1992. (29) Stevens, J. S.; Schroeder, S. L. M. Quantitative Analysis of Saccharides by X-ray Photoelectron Spectroscopy. Surf. Interface Anal. 2009, 41, 453. (30) Conners, T. E.; Banerjee, S. Surface Analysis of Paper;: CRC Press: Boca Raton, FL, 1995. (31) Moulder, J. F.; Stickle, W. F.; Sobol, P. E.; Bomben, K. D. Handbook of X-ray Photoelectron Spectroscopy; Physical Electronics: Eden Prairie, MN, 1995. (32) Shui, M. Polymer Surface Modification and Characterization of Particulate Calcium Carbonate Fillers. Appl. Surf. Sci. 2003, 220, 359. (33) Stro¨m, G.; Carlsson, G. Chemical Composition of Coated Paper Surfaces Determined by Means of ESCA. Nord. Pulp Pap. Res. J. 1993, 1, 105. (34) Fantinel, F.; Rieger, J.; Molnar, F.; Hubler, P. Complexation of Polyacrylates by Ca2+ Ions. Time-Resolved Studies Using Attenuated Total Reflectance Fourier Transform Infrared Dialysis Spectroscopy. Langmuir 2004, 20, 2539. (35) Tegelhoff, F. W.; Rohleder, J.; Kroker, E. Calcium Carbonate: From the Cretaceous Period into the 21st Century; Birkha¨user: Berlin, 2001. (36) Kaczmarek, H.; Szalla, A.; Chaberska, H.; Kowalonek, J. Changes of Surface Morphology in UV-Irradiated Poly(acrylic acid)/Poly(ethylene oxide) Blends. Surf. Sci. 2004, 566 (568), 560.

ReceiVed for reView February 17, 2010 ReVised manuscript receiVed September 16, 2010 Accepted October 1, 2010 IE100367K