In situ and ex situ FTIR–ATR and Raman microscopic studies of organosilane hydrolysis and the effect of hydrolysis on silane diffusion through a polymeric film

In Situ and Ex Situ FTIR–ATR and Raman MicroscopicStudies of Organosilane Hydrolysis and the Effect ofHydrolysis on Silane Diffusion Through a Polymeric Film

PETER EATON,1 PAUL HOLMES,2 JACK YARWOOD3

1 School of Pharmacy and Biomedical Sciences, University of Portsmouth, St. Michaels Building, White Swan Road,Portsmouth, PO1 2DT, United Kingdom

2 Pilkington plc, Group Research, Pilkington Technology Centre, Hall Lane, Lathom, Ormskirk, L40 5UF, United Kingdom

3 Materials Research Institute, Sheffield Hallam University, Pond Street, Sheffield, S1 1WB, United Kingdom

Received 31 July 2000; accepted 19 February 2001Published online 11 September 2001; DOI 10.1002/app.2047

ABSTRACT: We report combined FTIR–ATR and Raman microscopic studies of thedistribution and redistribution of three different silane adhesion promoters in thin(10–20 mm) PVC films deposited on a Si/SiO2/SiOH substrate (a “model” glass surface).It has been shown that the different functionalized silanes diffuse at different ratesthrough the polymer (at 70°C) and therefore have different distributions at the poly-mer/glass interface. The differences in behavior have been rationalized in terms of theirrespective abilities to hydrolyze and condense, under the different humidity and tem-perature conditions used. As the level of humidity rises there is evidence that thediffusion rate (measured using a dual-mode sorption model) decreases as a result ofhydrolysis and condensation in the polymer films. The data are of importance as adirect measure of the relation between humidity levels and the adhesive action of asilane promoter at polymer/glass interfaces. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci82: 2016–2026, 2001

Key words: organosilanes; diffusion; polymeric film; hydrolysis; condensation; dual-mode sorption

INTRODUCTION

Organosilanes are a class of materials with a widerange of industrial applications.1 Most of theseapplications make use of the ability of silanes toform a covalent bond to inorganic materials. Ex-amples include the functionalization of silica foruse as a chromatographic material,2 as chemicalreagents,3 and as an adhesion promoter in poly-mer composites and laminates.4,5 In all these ap-

plications, silane must be hydrolyzed for conden-sation to take place. The reaction scheme(Scheme 1) shown emphasizes that silanes hy-drolyze in the presence of water to form a hy-droxylsilane, which is more reactive than the cor-responding alkoxysilane. The hydroxysilanesmay then undergo a condensation reaction at amineral surface (i.e., the surface to be functional-ized).

In reality, however, the reaction can be muchmore complicated than that shown because ofcompeting reactions. For example, two hydroxyl-silanes may condense to form a dimer. Indeed, themost common silanes have three alkoxy groups,

Correspondence to: J. Yarwood.Journal of Applied Polymer Science, Vol. 82, 2016–2026 (2001)© 2001 John Wiley & Sons, Inc.

2016

so each silane may be hydrolyzed to form a mono-,di-, or trihydroxyl form. Therefore it is entirelyfeasible for silanes to form polymeric chains (re-ferred to as condensation). The overall reactionthat will occur is highly dependent on variablessuch as the availability of water, the nature of thesurface to be grafted, the chemical functionality ofthe silane, and the pH of the original solution.Because of the usefulness of the products of hy-drolysis of organosilanes in both the scientific andcommercial worlds, the reaction has been verywidely studied, and a full survey of the availableliterature is beyond the scope of this study. How-ever, the study of the hydrolysis of silanes in thiscontext has mainly been ex situ (i.e., in solution),although the use of silanes in commercial appli-cations is not usually from solution. Hydrolysis isperformed in situ, using water in the ambientatmosphere.

The object of the work described in this studywas to combine the use of confocal Raman micros-copy and FTIR–ATR spectroscopy to study theeffects, both in situ and ex situ, of the hydrolysisof organosilanes on the way in which they areable to diffuse and redistribute themselves withina polymeric/glass laminate. We attempted to usethe techniques to monitor the effect of hydrolysison the rate of diffusion within a PVC film castonto a silicon ATR crystal (which comprises sili-con/silicon oxide) at the polymer/substrate inter-face. Measurements were performed as a functionof the humidity conditions to which the polymer

film is exposed and depending on whether thesilane was prehydrolyzed.

Both infrared and Raman spectroscopy werepreviously used to study the hydrolysis of silanes.For example, Raman techniques were used tostudy the hydrolysis of silanes in aqueous solu-tion.6,7 The technique is highly suitable for suchstudies because it has the same ability to distin-guish chemicals by their groups as constituentinfrared spectroscopy, but can be applied moreeasily to aqueous solutions. The changes in Ra-man band intensity of vinylsilane and methacrylsilane6 were used to follow the hydrolysis of suchmaterials in aqueous solutions including the con-densation to siloxane oligomers. However, suchstudies depend on the rate of hydrolysis, as indi-cated in a study of aminosilanes,7 for which theprocess proceeded so quickly to condensation thatthe hydrolysis reaction could not be followed. Thecatalytic effect of the amine group in this contextwas also described elsewhere.6,7 Raman spectros-copy was also previously used by Bertelsen andBoerio8 to study the rate of g-glycidoxypropyltri-methoxy-silane (GPS), which was strongly depen-dent on the water concentration in solution. After2 h in aqueous solution, the species present (con-firmed using 29Si–NMR7,9,10) was the condensate.The correlation of the concentration of oligomerswith durability tests on the specimens showedthat a high concentration of silane oligomers wasdetrimental to sample durability. It was foundthat Raman spectroscopy could not be used tostudy condensation directly but that a measure ofcondensation was possible by measuring the de-crease in the concentration of the SiOOOSigroups.

Other techniques were also used to follow si-loxane hydrolysis, including FTIR spectrosco-py11–15 and the measurement of isotherms on theLangmuir trough.15,16 Several silanes showed in-frared bands near 1030 cm21 that were assignedto the SiOOOSi stretching bands of oligomerizedsilanes.17 However, the infrared hydrolysis stud-ies with which we are familiar were carried out onthin films of silanes on mineral surfaces ratherthan in situ in a polymer/glass laminate.

In situ studies investigations of silane hydroly-sis in composite systems are even more limited.However, a laminate system used in the manu-facture of circuit boards was examined using neu-tron reflection depth profiling.18 The silane layer(; 80 Å thick) was sandwiched between a siliconwafer and an epoxy polymeric layer (; 2 mmthick). It was found that, after humidity condi-

Scheme 1

ORGANOSILANE HYDROLYSIS AND SILANE DIFFUSION 2017

tioning, the thin interfacial layer of water waspresent at the silicon/silane interface. In lami-nates without silane this layer was found to beabsent. This was a surprising result, given that ithas been found19 that such silanes increase thelaminate resistance to weakening by water. It isclear that a water-based reaction was occurring atthe interface and the authors assumed that thisreaction was hydrolysis. However, because theadhesive bond between the epoxy and silicon wasnot degraded by this process, it is clear that, ifhydrolysis occurred, it was not complete. Somewater was also found throughout the epoxy poly-mer layer but at a low concentration. The tech-nique allowed depth profiling to be performed andit was found that there appeared to be a high levelof penetration of epoxy into the silane layer. Con-versely, no evidence of diffusion of silane into theepoxy layer was found.

However, in contrast to this work a systemconsisting of glass fibers treated with an aminosi-lane, mounted in an epoxy resin, was analyzed byFTIR microscopy. In this case the intensity of theOH band of water appeared to show the lowestintensity at the fiber surface. The apparent con-tradiction between the neutron and FTIR results,as far as we know, has not yet been explained.However, some evidence of in situ hydrolysis wasalso seen by Dibenedetto and Scola.20 In a glass/silane/epoxy system the silane and epoxy werecast in the same solution to form a mixed layer.Using SIMS spectroscopy they discovered that,upon curing, the polymer appeared to form threedistinct layers: a polymerized siloxane at the air/epoxy surface, oligomers at the center of the film,and again a polymeric siloxane structure at theglass epoxy interface. This is thought to be attrib-uted to hydrolysis and condensation with theavailable water at the air/glass interface but littleor no condensation was observed in the center ofthe laminate.

EXPERIMENTAL

The silanes studied were [3-(phenylamino)-propyl]trimethoxysilane, known as Y9669 (.95%);[3-(amino)propyl]trimethoxysilane, known asA1110 (97%); and [3-(mercapto)propyl]triethox-ysilane, known as A1891 (.80%), all obtainedfrom Fluka Chemicals (Buchs, Switzerland). Thestructures are shown below.

Y9669: C6H5NH(CH2)3Si(OMe)3

A1110: H2N(CH2)3Si(OMe)3

A1891: HS(CH2)3Si(OEt)3

The silanes were handled only in a dry nitro-gen environment to prevent hydrolysis prior tothe start of the experiments. In the case of exper-iments using prehydrolyzed silanes, the silaneswere removed from their containers and exposedto the atmosphere for 24 h prior to use.

The polymer used was poly(vinyl chloride)(PVC), secondary standard, molecular weight80,000, from the Aldrich Chemical Company (Mil-waukee, WI). In plasticized films, the plasticizerwas dihexyladipate (DHA) provided by Pilkingtonplc (Ormskirk, UK). The plasticized films wereproduced by mixing 15% w/w of DHA with PVCbefore casting from dimethylformamide. The sub-strates for film casting were polished silicon wa-fers. These wafers also functioned as micro-ATRcrystals for FTIR–ATR experiments. These micro-ATR crystals produced approximately 40 reflec-tions in the ATR experiment, and were thereforeconsiderably more sensitive than standard ATRcrystals.21 The crystals were also found to be suit-able for use as substrates in Raman microscopybecause of the lack of fluorescence, commonlyseen with glass microscope slides. For infraredexperiments, PVC films were cast from N,N-dim-ethylformamide to produce films of 10 mm thick-ness. To study diffusion, a large amount of silanewas bushed onto the outside of the PVC film. ForRaman microscopy experiments, similar lami-nates were constructed, but with 20 mm PVCfilms. In the Raman experiments, the silane wascovered with a very thin (20 mm) coverslip toprotect the microscope objective from silane ad-sorption. Because of the low signal-to-noise ratioand background absorption in some of the Ramanexperiments, the Raman data were analyzed bycurve-fitting a Gaussian function to the peak ofinterest, and a second-order curve to the back-ground. The area of the Gaussian function wasused to estimate the integrated intensity of theRaman band. This was found to give more reliableresults than those by simple integration, and alsoremoved the possibility of interference from ad-joining peaks.

Infrared measurements were made using aMattson Polaris FTIR spectrometer, with 4 cm21

resolution. Spectra were collected by coadding120 to 520 scans. Reference spectra were obtainedin transmission on a KBr disc and diffusion mea-surements were made using micro-ATR accesso-

2018 EATON, HOLMES, AND YARWOOD

ries (see above). Raman measurements weremade using a Renishaw Ramanscope 2000 fittedwith a helium neon laser (633 nm) and a CCDdetector. The spatial resolution in the z direction,achieved in confocal mode, was found to be ap-proximately 1.8 mm. The measurement of thisfigure was previously described22 and involvesmeasuring the full width at half height FWHH ofthe response of the microscope at the surface of asilicon reference sample.

RESULTS AND DISCUSSION

To follow diffusion of silanes into PVC films, FTI-R–ATR spectroscopy was previously used.22 If thesilane diffuses through the PVC film, the spec-trum of the silane is measured in the FTIR–ATRexperiment, and grows in intensity as the silaneapproaches the ATR crystal, until an equilibriumis reached. First, reference spectra of the threesilanes were measured in transmission (Fig. 1).

Ex Situ Hydrolysis

To determine the kinetics of hydrolysis under am-bient conditions, silanes were exposed to air byspraying neat silane onto potassium bromideplates. Changes in the infrared spectra of thesilanes were then monitored over approximately1 week. The spectra obtained for Y9669 are shownin Figure 2. In the case of Y9669, a band at 992cm21 decreased in intensity with time, whereas ashoulder on the band at 1080 cm21 (at about 1020

cm21) increased in intensity. The band at 992cm21, which was assigned to the SiOOOEtstretching mode for an ethoxy silane,2,23 wastherefore assigned to the SiOOOMe stretchingmode in this case. The loss of this band confirmshydrolysis of the methoxy silane. A similar silaneshowed a shoulder at 1038 cm21 upon condensa-tion, and therefore we assigned the increase inthe shoulder at 1020 cm21 in the spectra of Y9669to condensation of the silane to siloxane oligomers(see Scheme 1). The rate of hydrolysis of thesilane may thus be followed by monitoring theintensity of the 992 cm21 peak. It was found thatthe other silanes, A1110 and A1891, had similarbands that also showed very similar sensitivity tohydrolysis (not shown). In the case of A1110, theband was at 930 cm21, and in A1891 it was at 958cm21.

The intensities of the bands used were plottedagainst time to determine the rate of hydrolysis ofeach of the silanes (see Fig. 3). It may be seen thatY9669 underwent rapid hydrolysis over the first24 h in air, followed by much more gradual hy-drolysis over the next week. A1110 also under-went immediate hydrolysis, but seemed to con-tinue significantly to hydrolyze over the nextweek. On the other hand, A1891 initially under-went little change, even after 2 days. However,after 5 days there was a decrease in intensity,showing that hydrolysis had begun, and the reac-tion appeared to be still under way after 9 days.The relatively rapid hydrolysis of A1110 andY9669 (i.e., the aminosilanes) may have been be-

Figure 1 Reference FTIR spectra of silanes (unhydrolyzed).


cause the amino silanes were able to autocatalyzetheir hydrolysis.

Diffusion with Prehydrolyzed Silanes

Using the reference infrared spectra, one non-overlapping peak was selected for each silane touse as a marker for diffusion. The intensity ofthis peak was used to show how far towards thecrystal the silane had diffused. It should benoted, however, that the relationship betweenFTIR–ATR band intensity and diffusion dis-tance is nonlinear.24 The bands used to showdiffusion are summarized in Table I. Diffusionof these silanes through plasticized PVC filmswas previously observed22; however, this wasfor plasticized PVC films. It was found that inunplasticized (pure) PVC films, diffusion didnot occur unless the films were heated to nearthe Tg of the PVC (i.e., 70°C). Raising the tem-perature to the Tg and plasticizing the polymerboth induce enhanced flexibility of the polymerchains, thus presumably facilitating the diffu-sion of the silanes. To observe the rates of dif-fusion of the silanes, the films were periodicallyheated to 70°C and cooled before a measure-ment was made. Silanes were used as receivedand were exposed to atmospheric humidity for24 h. From the previous section, it can be seenthat, after 24 h of such exposure Y9669 under-

went considerable hydrolysis, A1110 showedsome change, and A1891 showed very little re-action. The results are shown for both unhydro-lyzed and prehydrolyzed silanes in Figures 4and 5 for Y9669 and A1891, respectively. Thetimes shown in the figures refer to the treat-ment times at 70°C (followed by cooling). Nodiffusion was observed in the case of A1110.Figure 4 shows that hydrolyzed Y9669 took con-siderably longer to diffuse through the PVCfilm. Figure 5, on the other hand, shows verylittle change between the hydrolyzed and unhy-drolyzed A1891.

The previous results (Fig. 3) showed that,whereas Y9669 underwent considerable hydroly-sis after 24 h, A1891 did not. It was concludedthat silanes that have undergone hydrolysis (andprobably subsequent condensation) tend to dif-fuse more slowly through PVC films at 70°C. Thereason that no diffusion was detected in the caseof A1110 is not known. It seems possible thatexposure to the atmospheric humidity causedsuch rapid hydrolysis that no diffusion could oc-cur in that experiment. Another possibility is thatan amine bicarbonate may be formed upon heat-ing in the presence of CO2. The product of thisreaction would be evident in the FTIR spectra.25

However, because no diffusion occurred, no spec-tra were observed. There was no indication ofbicarbonate formation in the spectra of the other

Figure 2 The SiOO stretching region of spectra obtained in transmission of Y9669undergoing hydrolysis with atmospheric water.


aminosilane, Y9669, after heating. It is worthnoting, however, that diffusion of A1110 throughplasticized PVC was previously observed.22

In Situ Hydrolysis Under Controlled Conditions

The work described in the previous section ap-peared to show that humidity could slow the dif-fusion of the silane Y9669, probably by hydrolysisand/or condensation of the silane. However, theuse of atmospheric humidity to affect hydrolysishas the disadvantage of an uncontrolled level ofwater. It was decided, therefore, to treat thesilanes at a known level of humidity, to assesshow differing the amount of moisture would affect

Figure 3 Intensities of peaks assigned to SiOOOCstretching versus time exposed to atmospheric humid-ity for each silane.

Table I Infrared Bands Used for DiffusionMeasurements

SilaneFrequency

(cm21) Assignment

Y9669 1602 CAC ring stretch and NOHbend

Y9669 3408 NOH stretchA1110 1600 NOH bendA1891 2565 SOH stretch

Figure 4 The integrated intensity of the 1602 cm21

band of hydrolyzed (M) and unhydrolyzed (‚) Y9669versus time, during diffusion in PVC at 70°C.

Figure 5 The integrated intensity of the n(SH)stretching band of hydrolyzed (M) and unhydrolyzed(‚) A1891 versus time, during diffusion in unplasti-cized PVC at 70°C.


the diffusion. At the same time Raman micros-copy was used to determine whether hydrolysiscould be affected by moisture in the PVC/siliconlaminate. It was thought that this might be animportant effect because direct incorporation ofthe silane into the polymer laminate, without pre-hydrolysis, is sufficient to induce adhesion in theindustrial lamination process. Given that somehydrolysis is thought to be necessary for adhesionto occur, it seems reasonable to assume that hy-drolysis would occur inside a polymer laminate.

Figure 6 shows the results of an experimentused to explore the diffusion of Y9669 in a PVCfilm that had no prior special treatment (i.e., ithad been exposed to atmospheric humidity). In anexperiment similar to the infrared experimentsdescribed earlier, the intensity of the 1600 cm21

Raman band of the silane was measured near thepolymer/silicon interface after the silane had beenapplied to the top of the laminate. If the silanediffused through the PVC film, one would expectto see an increase in the intensity of the Ramanband over time. However, as discussed below, thespatial sensitivity of the two experiments (FTIR–ATR and Raman) was different, so direct compar-ison of the results is difficult. The microscope wasfocused, in confocal mode, a distance of 6 mm fromthe PVC/silicon interface of a laminate. The focalpoint was therefore 18 mm from the applicationpoint of the silane. In each experiment, the inten-sity was then monitored over a number of hours.

The results (Fig. 6) show that the silane Y9669did indeed diffuse through the PVC film. The

Raman intensity of the silane did not reach anequilibrium value during the experiment, indicat-ing that diffusion was ongoing after 8 h. However,the diffusion did appear to have been slowingdown by the end of the experiment. A Ramandepth profile of the laminate was obtained after-ward, which is shown in Figure 7. This shows thatthe silane had diffused throughout the PVC film.As was noted previously,22 a depth-profile distri-bution such as that in Figure 7 is thought to beindicative of an even distribution of the silane,with a small excess of silane remaining at the

Figure 6 Integrated intensity of the 1600 cm21 Raman band of Y9669 versus time,during diffusion. The laminate was exposed to atmospheric conditions.


Raman band of Y9669 versus distance after diffusionwas complete. The laminate was exposed to atmo-spheric conditions.


air/PVC interface. The reduction in intensitythroughout the depth of the PVC film is attrib-uted to scattering of the laser light by the polymerfilm. An ATR infrared diffusion experiment wasalso performed on this sample (exposed to atmo-spheric humidity), the results of which are shownin Figure 8, along with the fitting to a dual-sorp-tion model, obtained as previously described.22 Itcan clearly be seen that the diffusion appeared tooccur much more rapidly in the infrared experi-ment than in the Raman diffusion experiment

(Fig. 6). This was because of the thinner film usedin the infrared experiments.

With the results (Figs. 6–8) of hydrolysis anddiffusion in mind we then proceeded to explorewhat happened for a PVC film prepared in thesame way but then exposed to a relative humidityof 44% for 48 h. This level of humidity was ob-tained by allowing the air to come into equilib-rium with a saturated solution of K2CO3(aq) (andchecked with a hygrometer). The results of theRaman experiment are shown in Figure 9. Eventhough the experiment was performed for alonger time than that described earlier, the diffu-sion did not seem to have reached the inflectionpoint at which it started to slow, and diffusionappeared to be slower than that seen in the pre-vious experiment (Fig. 6). In fact, some laser-induced degradation led to an increase in back-ground fluorescence. This meant that a depth pro-file in the same spot afterward was not possible.However, an infrared diffusion experiment wasperformed with a film treated in the same way.The results are shown in Figure 10, along with afitting to the dual-sorption model. A comparisonof Figure 10 with Figure 8 shows that two infra-red diffusion experiments led to similar overalldiffusion rates, although to different proportions(and hence different shapes) of the overall diffu-sion rates of mobile and partially mobile solutespecies26 (and hence different shapes).


infrared band of Y9669 versus time, during diffusion.The laminate was exposed to atmospheric conditions.

Figure 9 The integrated intensity of the 1602 cm21 Raman band of Y9669 versustime, during diffusion. The laminate was exposed to K2CO3 (relative humidity 50%).


The third set of conditions used involved expo-sure of the film to a humidity of 90% for 48 h usinga saturated solution of NH4Cl(aq). For this exper-iment, the laser intensity was reduced and longeracquisition times were used, in an attempt toavoid thermal degradation of the PVC. The re-sults of the Raman diffusion experiment areshown in Figure 11, from which we may deducethat the diffusion was considerably slower afterthe film had been treated at 90% humidity than atlower humidities. The depth profile shown in Fig-

ure 12 has a very similar profile to that in Figure7, indicating complete diffusion through the film,with a small excess at the surface of the film. Theresults of an infrared diffusion experiment on afilm treated with 90% humidity are shown in Fig-ure 13. Comparison of Figure 13 with Figures 8and 10 clearly shows that the diffusion rate wasconsiderably slower than the diffusion in filmswith lower water levels. Table II confirms thistrend and demonstrates that at the highest hu-midities there is a movement toward a single


infrared band of Y9669 versus time, during diffusion.The laminate was exposed to K2CO3(aq) (relative hu-midity 50%).

Figure 11 The integrated intensity of the 1602 cm21 Raman band of Y9669 versustime, during diffusion. The laminate was exposed to NH4Cl (relative humidity 90%).


band of Y9669 versus distance after diffusion into alaminate exposed to NH4Cl(aq) vapor (relative humid-ity 90%).


Fickian diffusion process. It is thought that thistrend is the result of hydrolysis and subsequentcondensation, slowing the diffusion of the silanes,ascribed to steric effects. This is therefore indirectevidence of in situ hydrolysis of the silanes insidethe PVC films.

The Raman data were analyzed by measuringhow much the intensity of the Raman band in-creased over its initial value during a set period of9 h. The results are shown in Table III. It can beseen that by this measurement, the Raman re-sults show that there was a clear trend towardslower diffusion, from atmospheric conditions,through 44% humidity, to 90% humidity. Thisslower diffusion process with increased film hu-midity is thought to result from in situ hydrolysisand condensation of the silane.

Although the results from the two techniquesshould not be directly compared, one would expectthe overall trend to be the same. The fact that the

Raman experiments showed a larger decrease indiffusion rates with humidity level may be be-cause of the way that the experiments were per-formed. In the Raman experiments, the laminatewas covered with a glass coverslip after the silanewas applied and taped in place on the sampleholder. This may have prevented the PVC filmfrom losing its internal humidity and coming intoequilibrium with the atmosphere, whereas theinfrared samples were exposed to the atmosphereduring the course of the experiment, so one mightexpect humidity levels to decrease gradually tothose in the atmosphere.

CONCLUSIONS

It was shown that all three silanes may be hydro-lyzed by exposure to atmospheric conditions. Inthe case of Y9669, such hydrolysis leads to signif-icantly slower diffusion through unplasticizedPVC. Because of a lower propensity to hydrolysis,A1891 did not show slower diffusion after a 24-hexposure. Hydrolysis may also occur inside a poly-mer laminate. The level of humidity in a PVC filmaffects not only the distribution of a silane in apolymer laminate but also the extent of hydroly-sis and condensation in that laminate. This inturn results in both a diffusion rate change to theinterface and in the mechanism of diffusion (therelevant curves becoming more single Fickian asthe level of humidity in the film increases). Ourdata confirm that the use of silane promoters toinduce adhesion at polymer/glass laminate inter-faces must take account of the water content ofthe polymer component and water levels in thesubstrate surface.

REFERENCES

1. Plueddemann, E. P. Silane Coupling Agents, 2nded.; Plenum Press: New York, 1990.

Table II Diffusion Coefficients Obtained fromDual-Mode Sorption Fitting of Infrared Datafrom Three Different Humidity Treatments

AtmosphericConditions

K2CO3(aq)(44%)

NH4Cl(aq)(90%)

D1 9.92 3 1029 9.12 3 1029 4.31 3 1029

D2 4.62 3 1029 4.25 3 1029 2.93 3 1029

X1 0.51 0.77 0.90

Table III Increase in Intensity of the 1602cm21 Raman Band of Y9669 After 9 hfor All Three Film Treatments

Condition1602 cm21 Band Area After

9 h/Initial Area

Atmospheric conditions 10.6K2CO3(aq) 5.4NH4Cl(aq) 1.2


infrared band of Y9669 versus time, during diffusion.The laminate was exposed to NH4Cl (relative humidity90%).


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In situ and ex situ FTIR–ATR and Raman microscopic studies of organosilane hydrolysis and the effect of hydrolysis on silane diffusion through a polymeric film