Controlling the Processing of Mesoporous Titania Films by in Situ

(3) Phase equilibrium diagrams of a triblock copolymer, such as Pluronic .... and a closed cabinet was mounted around the microscope to control the RH...
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Controlling the Processing of Mesoporous Titania Films by in Situ FTIR Spectroscopy: Getting Crystalline Micelles into the Mesopores Plinio Innocenzi,*,† Luca Malfatti,† Tongjit Kidchob,† and David Grosso‡ Laboratorio di Scienza dei Materiali e Nanotecnologie, D.A.P., UniVersita` di Sassari, and CR-INSTM, Palazzo del Pou Salid, Piazza Duomo 6, 07041 Alghero (Sassari), Italy, and Laboratory. Chim. Mat. Condensee Paris, UniVersity of Paris 06, College de France, CNRS, UPMC, UMR 7574, F-75231 Paris 05, France ReceiVed: October 18, 2009; ReVised Manuscript ReceiVed: May 4, 2010

Processing of mesoporous films is a critical step that needs a careful control and comprehension of the chemical-physical phenomena that governs evaporation induced self-assembly. We have used time-resolved infrared spectroscopy to study two of the main stages of self-assembly in titania films: evaporation and postdeposition drying. Mesostructured titania cast films have been prepared by using a triblock copolymer (Pluronic F127) and TiCl4 as the titania precursor. A droplet of the precursor titania sol has been cast, and the unimer to micelle evolution has been observed. The drying stage, in the 25-165 °C temperature range, has been studied in situ by infrared spectroscopy. We have observed that upon drying, with complete removal of water, the block copolymer crystallizes; this process is reversible and can be reproduced several times. The infrared data have also given some additional information about the nature of hybrid surfactant-titania oxo-clusters interface, which appears formed by a complex chemical environment which is dependent on the drying conditions. Introduction Triblock copolymers PEOn-PPOm-PEOn are one of the surfactants that are commonly employed as templating agent for self-assembly mesostructured films.1,2 The copolymer undergoes different chemical-physical changes and complex interactions at the hybrid organic-inorganic interface during evaporation-induced self-assembly (EISA) of thin films.3 Phase equilibrium diagrams of a triblock copolymer, such as Pluronic F127, show that the surfactant forms micelles of different types as a function of the concentration and temperature.4 Besides this temperature-concentration dependent property, Pluronic F127 if heated at temperatures high enough to remove the solvent shows gelation and eventually crystallization.5 This behavior has been well studied, especially by small-angle X-ray scattering (SAXS) and by Fourier transform infrared (FTIR) spectroscopy. FTIR, in particular, appears as a well-suitable technique because is highly sensitive, and the infrared spectra of Pluronic F127 in the amorphous and crystalline states have well distinctive features. Infrared time-resolved spectroscopy is, more in general, a very good experimental tool to follow evaporation processes; we have developed and widely applied this technique to study evaporation phenomena of different systems.6 The main advantage of this technique is the possibility of following a time-dependent phenomenon, such as evaporation, with a good temporal resolution, at least in a time scale that is fast enough to study several processes such as EISA.7 The technique can be used for developing simultaneous analytical methods, such as combined in situ time-resolved FTIR and small-angle X-ray scattering.8 Achieving organization in template-assisted self-assembly requires controlling EISA processing parameters and postprocessing, which means postdeposition thermal treatment. Self* To whom correspondence should be addressed. † Universita` di Sassari. ‡ University of Paris 06.

assembly of titania films is particularly interesting because organization is highly correlated with a strict control of chemical-physical conditions during and after film deposition.9 Several detailed studies have pointed out that order is finally obtained only if the system has the capability of responding to external conditions, such as relative humidity. Processing of titania films after deposition is very important, and it has been well understood that for obtaining high optical quality and excellent organization the film has to be deposited at low RH (generally lower than 45% to avoid the absorption of water from external environment), and a postprocessing at high RH has to follow.10 The further step is drying and firing that have to be carefully done to avoid a fast condensation of the titania framework; a set of aging treatments under controlled relative humidity followed by progressive thermal treatments (from 60 to 130 °C) is necessary to stabilize the mesophase.11 Calcination at temperatures higher than 200 °C is performed to remove the block copolymer via thermal degradation; the temperature of thermal treatment affects the dehydration of the PEO and PPO blocks: PPO dehydrates between 20 and 50 °C, PEO at higher temperatures (around 80 °C).12 Drying of titania films is, therefore, a very critical step that simultaneously involves changes into the physical-chemical state of the micelle, micelle-inorganic interface, and inorganic network. We have observed in a previous work that during the evaporation of an aqueous solution of Pluronic F127 the surfactant crystallizes as soon as the water evaporation has gone to completion; there is a direct correlation between these two phenomena. Keeping in mind this finding, we have posed the question if eventually during drying of mesoporous films, before thermal degradation, the same phenomenon could be observed in self-assembled mesostructures. This is quite difficult to observe and not yet reported up to now because of the need for a specific in situ analysis to be performed. We have therefore used FTIR spectroscopy to investigate the EISA and drying process in titania mesostructured cast films; we have been able to observe

10.1021/jp9099732  2010 American Chemical Society Published on Web 06/01/2010

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in detail the different chemical-physical changes which include also the surfactant crystallization. Experimental Section Titanium tetrachloride (TiCl4), Pluronic F127 (EO106PO70EO106, EO ) ethylene oxide and PO ) propylene oxide), and ethanol (EtOH) were purchased by Aldrich and used as received; bidistilled water was used for the preparation. (100) oriented, P-type/boron-doped silicon wafers were purchased by Jocam and used as the substrates. Titania sols were prepared using TiCl4, EtOH, H2O, and Pluronic F127, with the following molar ratios: TiCl4:EtOH: F127:H2O ) 1:40:0.005:10. The precursor sol was obtained by slow addition of TiCl4 into a mixture of EtOH and surfactant; water was added, drop by drop, after 5 min of stirring. Titania films were deposited by dip-coating in a controlled chamber, at 25 °C and 25% relative humidity (RH), at a withdrawal rate of 15 cm min-1. Time-resolved in situ infrared (IR) analysis was performed using a Bruker Vertex 70 interferometer equipped with a Globar source. The IR measurements were done in the 600-7000 cm-1 range with a resolution of 8 cm-1. A MCT detector (250 × 250 µm size) cooled to the liquid nitrogen temperature and a KBr beamsplitter were used. To study the evaporation of a cast droplet of titania sol, rapid-scan time-resolved (RSTR) measurements were performed by averaging four interferograms per spectrum in an acquisition time of 0.8 s and a time interval of 2 s between the beginning of the acquisition of consecutive spectra. We have selected the scan time to optimize the signalto-noise ratio and resolution as a function of the experimental conditions. The relative humidity (RH, %) during the experiment was carefully monitored and a closed cabinet was mounted around the microscope to control the RH, which was kept constant at 45%; the measurements were performed at 25 °C and at ambient pressure. In situ FTIR measurements in temperature were performed in transmission using a water-cooled heating jacket by SPECAC. The measures were done in situ in air on as-deposited films on silicon at the selected temperature from 25 up to 200 °C; silicon wafer in air was used as background. The temperature was increased from 25 to 200 °C with steps of 10 °C, and the spectra were measured 10 min after the temperature was stabilized. Reference FTIR spectra of Pluronic F127 in water and in the solid state were recorded using a 5 wt % aqueous solution and the powder for preparing KBr pellets. A Bruker Hyperion 3000 IR microscope working in transmission mode and a one side polished silicon wafer as substrate were used; the background spectrum of the Si substrate was recorded as the average of 128 interferograms. The EISA experiment was realized casting a small drop of titania-Pluronic F127 precursor (∼1 µL) on the silicon substrate; the measurement was started immediately afterward. We followed the evaporation of the droplet during several runs to ensure the reproducibility of the experimental conditions. Reference spectra of Pluronic F127 in solid state have been obtained using a KBr pellet; the results were analyzed by Bruker Opus 6.5 software. Results and Discussion Pluronic F127 Physical-Chemical Changes during EISA. Figure 1 shows the FTIR absorption spectra in the 1225-1000 cm-1 range of Pluronic F127 in an amorphous state in aqueous solution (red line) and in the crystalline state in powder (black line); these spectra are used as reference for the discussion of results. The two spectra in the C-O-C stretching region

Figure 1. FTIR absorption spectra in the 1225-1000 cm-1 of Pluronic F127 in aqueous solution (red line) and in the crystalline state (black line). The positions of the Pluronic F127 crystalline bands are indicated by arrows.

(∼1200-1000 cm-1) show a significant difference that allows discriminating between the amorphous and crystalline states. The spectrum of crystalline Pluronic F12713 shows a typical triplet of overlapped bands at 1060 (νs(COC) + Fs(CH2)), 1111 (νs(COC) or νas(COC)), and 1150 cm-1 (ν(CC) - νas(COC)). This triplet transforms into a broad intense band peaking around 1090 cm-1 with a shoulder around 1130 cm-1, which is the characteristic spectrum of the surfactant dispersed in water, while the peak at 1063 cm-1, which is distinctive of the helical structure of PEO in the crystalline state,14 disappears. The C-O-C stretching mode at 1090 cm-1 is quite sensitive to hydrogen bonding between water and the oxygens in the block copolymer,15 and when Pluronic F127 is dissolved in water, this band shifts to lower wavenumbers and broadens. This indicates that the PEO-PPO-PEO molecules in the aqueous environment have a higher mobility and a disordered packing with respect to the solid state. Specific bands that are assigned to the amorphous and crystalline phase can be also detected in the CH2 twisting region (∼1200-1320 cm-1) and wagging region (∼1400-1320 cm-1), but we limit the analysis and the discussion to the C-O-C stretching region (∼1200-1000 cm-1). We have followed at first the change in the block copolymer state during the evaporation process of a titania-Pluronic F127 solution which is used to prepare mesostructured porous titania films. We have used a cast droplet of the solution to follow the last stages of evaporation, when ethanol is already evaporated to leave a water-rich solution. In a previous work we have already performed a similar experiment studying the evaporation of a titania sol from the beginning of the process and following the general aspects connected to self-assembly;16 in the present work we have observed in the detail only the last stage of evaporation. The titania-Pluronic F127 system is particular suitable to study the change in the state of the surfactant during evaporation because the bands of water, Pluronic F127, and titania species are well separated and can be specifically distinguished during the process. On the other hand, evaporation is the driving process for self-assembly which induces the surfactant to aggregate and forming the templating micelles. Figure 2 shows the time-resolved FTIR absorption spectra in the 1250-1025 cm-1 region; the spectra, with the proceeding of evaporation time, show a small decrease in intensity, a shift to higher wavenumbers, and a decrease in the full width at halfmaximum (fwhm). The direction of change of spectra with evaporation is indicated in Figure 2 by the arrows that are a guide for the eyes. The evaporation process has been monitored until we observed the water to end evaporating, which we have taken as the moment when no changes are detected in the spectra

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Figure 2. Time-resolved FTIR absorption spectra in the 1225-1040 cm-1 of Pluronic F127-titania during evaporation of a Pluronic F127-titania sol droplet in a time span from 0 to 400 s after casting. The time interval between the beginning of the acquisition of consecutive spectra was 2 s. The arrows indicate the direction of intensity change of the curves during evaporation.

with time; at the end of this process the system appears formed by a “soft” droplet of water-Pluronic F127-titania in which evaporation is compensated by absorption of water from the external environment. These data point out that the titania cast film at this stage is not yet condensed, and the surfactant is in a chemical environment that is still “liquid-like”. Another important question to address is if the surfactant at this stage is in the micellar state; an answer can be obtained by monitoring the band around 1376 cm-1 which is assigned to the CH3 deformation mode and is assumed to be sensitive to the chemical environment and to intermolecular interactions.17 An abrupt shift of this band from 1381 cm-1 to lower wavenumbers is indicative of micelle formation; this shift is due to a reduced interaction of the methyl groups with water molecules, which means that the chemical shell around CH3 groups has a lower polarity. The shift is also accompanied by a reduction of bandwidth which is due to a reduced mobility of the PO blocks in the micellar phase. We have observed that from the beginning of our measure the micelles are already formed because the CH3 deformation mode is found at 1376 cm-1, but a change in bandwidth is still observed. This fact can be explained by considering the cooling effect induced by the ethanol evaporation. During the drying of the droplet, in fact, the temperature of the sol is locally lowered and the critical micelle concentration is extremely sensitive to temperature changes; as already shown by Alexandridis et al.,18 the cmc of the Pluronic-type block copolymers decreases dramatically for small droplets with the temperature. This fact, in accordance with the previous considerations for the C-O-C stretching modes (Vide supra), indicates a reduced mobility of the micelles that are in a more constrained environment which is gradually formed by the condensation of titania species. Figure 3a shows the timeresolved FTIR absorption spectra in the 1390-1367 cm-1 region; the direction of change of spectra with evaporation is indicated by the arrows that are a guide for the eyes. Baseline has been corrected by concave rubberband algorithm using OPUS 6.5 software, 2 iterations, 64 baseline points, in the wavenumber figure range; no smoothing has been performed, but postzero filling of 4 points in the figure range has been done. With the proceeding of evaporation the spectra reveal a decrease of the bandwidth even if the maximum does not shift ((1 cm-1 which is within the resolution of the measure). This can be better visualized using a surface plot FTIR spectra time-wavenumberabsorbance in the same range of wavenumbers (Figure 3b); the data in the figure show that basically we can identify two distinct

Figure 3. (a) RSTR FTIR absorption spectra in the 1390-1367 cm-1 during evaporation of a cast droplet of Pluronic F127-titania sol. The arrows indicate the direction of intensity change of the curves during evaporation. (b) RSTR 3D time-wavenumber-absorbance FTIR spectra; the absorbance intensity is shown in a false colors scale. The time interval between the beginning of the acquisition of consecutive spectra was 2 s.

regimes whose boundary is at around half of the spectra recording time. In the first one (I) the spectra decrease in bandwidth while in the second one (II) they are stable and no significant changes are observed. The change in intensity is mostly attributed to the partial overlapping of a close band at lower wavenumbers whose effect has not been eliminated by data treatment. We explain the presence of these two distinctive regions by the reduced mobility of the micelles, but also with the final micellization of residual unimer block copolymers which are present in the aqueous environment. The broad infrared bands observed during the stage I are also indicative of the presence of absorption modes around 1381 cm-1, which are correlated to the partial presence of unimers. Clearly these data show that the micellization process is not a sharp event during evaporation, and from the formation of the first micelle to the completion of micellization there is always a time delay which depends on the specific evaporation conditions (temperature, surfactant concentration, RH, solvents, etc.). At stage II during evaporation the micelles are well formed and increasingly constrained by the evaporation of water and formation of a partially condensed titania network. The titania network at this stage is still highly flexible to allow modification of the micelles organization as widely demonstrated in the literature. Reversible Thermal Induced Crystallization of Pluronic F127. The in situ evaporation study has shown that the block copolymer at the end of film deposition is still in a kind a “liquid-like” state even if the presence of the titania species that start to condensate to form the inorganic network partially reduces the mobility of the micelles. We have done FTIR measures in situ at different temperatures on freshly deposited titania films to observe the effect of the processing on the templating micelles.

Processing of Mesoporous Titania Films

Figure 4. FTIR absorption spectra in the 1220-990 cm-1 range as a function of drying temperature of a titania mesostructured film. The spectra have been recorded during in situ measures from 25 up to 165 °C with steps of 10 °C.

Figure 4 shows the FTIR absorption spectra in the 1225-980 cm-1 range recorded from the titania films at temperatures from 25 up to 165 °C. The spectra show the transition from amorphous to crystalline state during the heating process, which is indicated by the transformation of the typical broad amorphous band into the triplet signature of the crystalline phase. The process can be directly visualized by a surface plot (Figure 5) which shows the evolution of the absorption intensity as a function of temperature and wavenumbers (Figure 5a). We have also shown in Figure 5b the surface plot of the absorption bending mode of water at 1640 cm-1 obtained during the same set of measures. Water evaporates completely from the films around 100 °C, at the same temperature the micelles crystallize; the dotted white line in the figure shows the end evaporation line which also marks the amorphous-crystalline boundary. An important effect of the drying thermal treatment is, therefore, the crystallization of PEO in the micelles, which is realized as soon as water evaporates. This effect has already been found in a previous experiment of controlled evaporation of an aqueous solution of Pluronic F127;19 at the end of water evaporation a semicrystalline block copolymer is observed. In the present case crystallization is also promoted by water evaporation, but this is a thermal induced effect and the micelles with the proceed of drying are in a chemical environment that is becoming more and more constrained, because of the titania condensation, with respect to a purely aqueous solution. This process remains, however, highly reversible, and after cooling to room temperature, the micelles in great part become again amorphous. Figure 6 shows the FTIR absorption spectra of the titania film as deposited at 25, 165, and 25 °C after cooling at the end of the thermal cycle. At 25 °C the film appears amorphous, at 165 °C is crystalline and after cooling again amorphous with likely a small residual crystalline part (revealed by the band at 1030 cm-1). After cooling to room temperature (25 °C) the system quickly absorbs water from the external environment, producing a swelling of the micelles and their return to the amorphous state; this dry crystalline-wet amorphous cycle can be repeated up to six times in a time span of around 5 min. Some additional information about the system properties upon drying are given by the wide O-H stretching band peaking around 3300 cm-1 which is due to absorbed water20 and Ti-OH surface groups; the O-H band is partially overlapped at lower wavenumbers to the CH2 stretching bands of Pluronic F127 (Figure 7a). The O-H band decreases in intensity with the thermal treatment temperature from 25 up to 165 °C; the first band is the most intense one in the series of spectra in Figure

J. Phys. Chem. C, Vol. 114, No. 24, 2010 10809 7a and has been recorded from the sample maintained at 25 °C in air. An important consideration can be done on the basis of results shown in Figure 7a and is that around 100-120 °C the OH band completely disappears, which means that the sample is dried because of completion of water evaporation but also that no Ti-OH groups should be present. The complete disappearance of the OH stretching band deserves a specific comment because this is an indication that (a) all the water has been removed and (b) the titania oxo-clusters have been condensed to form a titania network around the micelles. We have cross-checked the first point by the disappearance of the water band at 1640 cm-1 (not shown in figures), but on the other hand, the absence of Ti-OH species does not mean that the titania network is fully condensed. In Figure 7b are shown the FTIR absorption spectra of the as-deposited sample (25 °C), black line, and after cooling down at the end of thermal drying, blue line. The film after drying shows again the presence of the OH band, but the intensity is lower and the absorption peak shifts to higher wavenumbers. This band is formed by two different contributions: the absorbed water around 3200 cm-1 and the titanols around 3700 cm-1. This indicates that water is again adsorbed into the system and is responsible for the reversible behavior of the micelles but also that titania is not completely condensed. The shift of the O-H signal to higher wavenumber indicates, in fact, a partial condensation of titania. The question is why the FTIR measure in situ at temperatures higher than 110 °C shows no presence of OH species and therefore of Ti-OH bonds? Previous works have shown that the interaction of hydrophilic titania oxo-clusters with the micelle interface depends on the chemical environment, and the presence of water21 has a paramount importance to address the surfactant-metal interaction at the interface. The hydrophilic oxo-clusters can be covalently and directly attached to the surfactant via condensation of OH groups (anhydrous conditions) or loosely bonded via weaker H-bonding-type interactions (hydrolytic conditions); intermediate and mixed interactions are of course the most likely situation (see refs 10 and 21 for an extensive discussion of this point). Chlorine, however, does not evaporate all with water; previous works have shown, in fact, that there is always a certain residual amount of Cl in the film even after drying.10,22 Typically, just after drying it has been observed the presence of one Ti-Cl bond per Ti atom; this correlation decreases to 0.7 after 1 h of film aging, and it goes to 0.4 after 72 h; chlorine is totally removed only after a thermal treatment at 400 °C.10 The residual chlorine atoms at the hybrid interface play an important role; what can occur, in fact, is an exchange between chlorine and OH from H2O. Heating the film has the effect of removing H2O and hydroxyls, while chlorine ions that are in the hydrophilic PEO/H2O region bonds to Ti instead of OH; upon cooling water is reabsorbed, and the reverse substitution occurs because water has a dielectric constant strong enough to dissociate Ti-Cl bonds. This is not the only explanation of the reversible disappearance of OH groups upon heating-cooling cycle: another possibility is that the O-CH2-CH2-O units complex the Ti atoms at the surface of the oxo-clusters; this complexation forms coordination bonds that are relatively stable but are reversible.23 Removing water is also associated with loss of mobility for the PEO because water is located close to the EO polar units. The full removal of water during drying has therefore a strong influence on (a) micelles, (b) oxo-cluster species, and (c) organic-inorganic interface. (a) The PEO chains in the micelles crystallize as soon as the water is removed from the hydrophilic shell of the block copolymer; (b) the oxo-

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Figure 5. (a) Time-resolved surface plot time-wavenumber-absorbance FTIR absorption spectra in the 1220-990 cm-1 range (C-O-C stretching region) during drying at different temperatures of a titania mesostructured film. (b) Time-resolved surface plot time-wavenumber-absorbance FTIR spectra in the 1750-1550 cm-1 range (H2O bending stretching region) during drying at different temperatures of a titania mesostructured film. The absorbance intensity is shown in a false colors scale.

Figure 6. FTIR absorption spectra in the 1220-990 cm-1 range of a titania mesostructured film after drying at 25 (blue line) and 165 °C (violet line) and after cooling down at 25 °C (red line).

cluster species undergo a partial condensation; and (c) the PEO chains complex the Ti atoms at the surface of the oxoclusters while Cl atoms reversibly exchange with OH. At around 110 °C the titania film is dry, with a partially condensed oxide network and with partially crystalline micelles that are connected to the inorganic species at the interface through stable but secondary bonds. This situation is in part reversible; in fact, if we cool the film to room temperature at 45% RH, we observe immediately after that the system returns to almost the original state. We have also evaluated, applying a deconvolution method to the single infrared spectra, how the degree of crystallization changes from the beginning (25 °C) to the end of the evaporation process (165 °C). Figure 8a shows the deconvolution of the 25 °C infrared curve; the spectrum has been fitted using four Gian curves that have been attributed to crystalline (blue lines) and amorphous (red lines) components.19,17 The fitting curve is the cyan dashed line, which well fits the experimental spectrum; the quality of the fit has been evaluated by the residual mean square error. We have used only two curves for the crystalline components because the 1060 cm-1 band is not observed, and a good fit could not be achieved with five curves. Integration of the amorphous and crystalline bands areas has allowed to evaluate that at the begin of the process; before the sample is dried by a thermal treatment, the amorphous component is 73% and the crystalline one 27%. We have then compared these results with what happens at the end of the evaporation when the sample is in a dried state; we have therefore fitted the 165 °C spectrum with a similar procedure. Figure 8b shows the deconvolution of the 165 °C infrared curve; we have chosen three curves for the crystalline component (blue lines) and two

Figure 7. (a) FTIR absorption spectra in the 3800-2600 cm-1 range (O-H and CH2 stretching region) during drying at different temperatures of a titania mesostructured film. (b) FTIR absorption spectra of the as-deposited sample (25 °C), black line, and after cooling down at the end of thermal drying, blue line.

for the amorphous one (red lines), and the fitting curve is the cyan dashed line. Calculating the band areas, we observe that after drying the crystallization reaches 74% and 26% of the block copolymer remains amorphous. We have demonstrated, by the present experiments, that the micelles of the block copolymer crystallize during the drying stage; this phenomenon it is likely of general nature and should be present in most of self-assembling films of different compositions. In the case of titania films the evaporation phenomena can be directly observed by FTIR because there are no overlapping infrared signals between the oxide and the polymer, such as the case of silica. We have also to point out that a direct extension to dip-coated or spin-coated films has to be done with caution because all the order-disorder transitions

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J. Phys. Chem. C, Vol. 114, No. 24, 2010 10811 the form of micelles; the complete conversion of unimers to micelles is observed at the last stage of evaporation when the partial condensation of oxo species gives a more constrained environment. The drying process produces a removal of water, and at around 110 °C a crystallization of the Pluronic F127 is observed; the amorphous-crystal state is reversible, and several cycles can be performed. The hybrid organic (micelle)-inorganic (titania oxo -clusters) appears formed by a complex chemical environment which is dependent on the drying conditions. Acknowledgment. Dr. Massimo Piccinini is gratefully acknowledged for support during FTIR experiments. References and Notes

Figure 8. (a) Deconvolution of the 25 °C infrared curve; the spectrum has been fitted using four Gian curves that have been attributed to crystalline (blue lines) and amorphous (red lines) components. The fitting curve is the cyan dashed line, which well fits the experimental spectrum. (b) Deconvolution of the 165 °C infrared curve; the spectrum has been fitted using five Gian curves that have been attributed to crystalline (blue lines) and amorphous (red lines) components. The fitting curve is the cyan dashed line.

which are triggered by evaporation phenomena are strongly affected by kinetics of the process. Another question is about the role of micelle crystallization in self-assembly, while a direct observation of crystallization-mesophase formation is extremely complex because requires an in situ simultaneous observation by SAXS and FTIR during the drying stage; likely, we can suppose that the crystallization of the micelles can form a stronger scaffold for the formation through condensation of the oxide framework. Conclusions In situ time-resolved FTIR spectroscopy has allowed following the chemical-physical changes of a triblock copolymer, Pluronic F127, during the evaporation (EISA process) and during thermal drying of a micelle templated mesostructured titania film. The evaporation process leaves a “wet” titania film which is rich in water. At the end of evaporation Pluronic F127 is all in

(1) Soler-Illia, G. J. A. A.; Sanchez, C.; Lebeau, B.; Patarin, J. Chem. ReV. 2002, 102, 4093. (2) Lu, Y. F.; Ganguli, R.; Drewien, C. A.; Anderson, M. T.; Brinker, C. J.; Gong, W. L.; Guo, Y. X.; Soyez, H.; Dunn, B.; Huang, M. H.; Zink, J. I. Nature 1997, 389, 364. (3) Soler-Illia, G.; Innocenzi, P. Chem.sEur. J. 2006, 12, 4478. (4) Alexandridis, P.; Zhou, D.; Khan, A. Langmuir 1996, 12, 2690. (5) Alexandridis, P.; Hatton, T. A. Colloids Surf., A 1995, 96, 1. (6) (a) Innocenzi, P.; Malfatti, L.; Piccinini, M.; Marcelli, A.; Grosso, D. J. Phys. Chem. A 2009, 113, 2745. (b) Innocenzi, P.; Malfatti, L.; Costacurta, S.; Kidchob, T.; Piccinini, M.; Marcelli, A. J. Phys. Chem. A 2008, 112, 6512. (c) Innocenzi, P.; Malfatti, L.; Piccinini, M.; Grosso, D.; Marcelli, A. Anal. Chem. 2009, 81, 551. (7) Innocenzi, P.; Kidchob, T.; Malfatti, L.; Costacurta, S.; Takahashi, M.; Piccinini, M.; Marcelli, A. J. Sol-Gel Sci. Technol. 2008, 48, 253. (8) (a) Innocenzi, P.; Malfatti, L.; Kidchob, T.; Falcaro, P.; Costacurta, S.; Piccinini, M.; Marcelli, A.; Morini, P.; Sali, D.; Amenitsch, H. J. Phys. Chem. C 2007, 111, 5345. (b) Marcelli, A.; Hampai, D.; Xu, W.; Malfatti, L.; Innocenzi, P. Acta Phys. Pol. 2009, 115, 489. (9) (a) Grosso, D.; Soler-Illia, G. J. de A. A.; Babonneau, F.; Sanchez, C.; Albouy, P. A.; Brunet-Bruneau, A.; Balkenende, A. R. AdV. Mater. 2001, 13, 1085. (b) Soler-Illia, G. J. de A. A.; Scolan, E.; Louis, A.; Albouy, P. A.; Sanchez, C. New J. Chem. 2001, 25, 156. (10) Crepaldi, E.; Soler-Illia, G.; Grosso, D.; Cagnol, F.; Ribot, F.; Sanchez, C. J. Am. Chem. Soc. 2003, 125, 9770. (11) Crepaldi, E. L.; Soler-Illia, G. J. de A. A.; Grosso, D.; Sanchez, C. New J. Chem. 2003, 27, 9. (12) Fo¨rster, S.; Antonietti, M. AdV. Mater. 1998, 10, 195. (13) Dissanayaket, M.; Frech, R. Macromolecules 1995, 28, 5312. (14) Marcos, J. I.; Oriandi, E.; Zerbi, G. Polymer 1990, 31, 1899. (15) Cabana, A.; Aı¨t-Kadi, A.; Juha´sz, J. J. Colloid Interface Sci. 1997, 190, 307. (16) Innocenzi, P.; Kidchob, T.; Mio Bertolo, J.; Piccinini, M.; Cestelli Guidi, M.; Marcelli, A. J. Phys. Chem. B 2006, 110, 10837. (17) Zerbi, G.; Magni, R.; Gussoni, M.; Moritz, K. H.; Bigotto, A.; Dirlikov, S. J. Chem. Phys. 1981, 75, 3175. (18) Alexandridis, P.; Holzwarth, J.; Hatton, T. Macromolecules 1994, 27, 2414. (19) Innocenzi, P.; Malfatti, L.; Piccinini, M.; Marcelli, A. J. Phys. Chem. A 2010, 114, 304. (20) (a) Innocenzi, P. J. Non-Cryst. Solids 2003, 316, 309. (b) Falcaro, P.; Grosso, D.; Amenitsch, H.; Innocenzi, P. J. Phys. Chem. B 2004, 108, 10942. (21) Soler-Illia, G.; Sanchez, C. New J. Chem. 2000, 24, 493. (22) Yang, P.; Zhao, D.; Margolese, D. I.; Chmelka, B.; Stucky, G. Chem. Mater. 1999, 11, 2813. (23) (a) Ying, J. Y.; Mehnert, C. P.; Wong, M. S. Angew. Chem., Int. Ed. 1999, 38, 57. (b) Zhao, D.; Yang, P.; Huo, Q.; Chmelka, B.; Stucky, G. Curr. Opin. Solid State Mater. Sci. 1998, 3, 111. (c) Brinker, C. J.; Lu, Y.; Sellinger, A.; Fan, H. AdV. Mater. 1999, 11, 579;.

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