Research Article Two-Dimensional FTIR as a Tool to Study...

Research ArticleTwo-Dimensional FTIR as a Tool to Study the ChemicalInteractions within Cellulose-Ionic Liquid Solutions

Kalyani Kathirgamanathan1 Warren J Grigsby23

Jafar Al-Hakkak34 and Neil R Edmonds1

1University of Auckland Auckland 1072 New Zealand2Scion Rotorua 3010 New Zealand3Biopolymer Network Ltd Rotorua 3040 New Zealand4Plant amp Food Research Auckland 1142 New Zealand

Correspondence should be addressed to Warren J Grigsby warrengrigsbyscionresearchcom

Received 30 September 2014 Accepted 11 December 2014

Academic Editor Long Yu

Copyright copy 2015 Kalyani Kathirgamanathan et al This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

In this study two-dimensional FTIR analysis was applied to understand the temperature effects on processing cellulose solutionsin imidazolium-based ionic liquids Analysis of the imidazolium ion ]C2ndashH peak revealed hydrogen bonding within cellulosesolutions to be dynamic on heating and cooling The extent of hydrogen bonding was stronger on heating consistent with greaterionmobility at higher temperaturewhen the ionic liquid network structure is broken At ambient temperatures a blue shifted ]C2ndashHpeakwas indicative of greater cation-anion interactions consistent with the ionic liquid network structure Both cellulose andwaterfurther impact the extent of hydrogen bonding in these solutions The FTIR spectral changes appeared gradual with temperatureand contrast shear induced rheology changes which were observed on heating above 70∘C and cooling below 40∘C The influenceof cellulose on solution viscosity was not distinguished on initial heating as the ionic liquid network structure dominates rheologybehaviour On cooling the quantity of cellulose has a greater influence on solution rheology Outcomes suggest processing cellulosein ionic liquids above 40∘C and to reduce the impacts of cation-anion effects and enhance solubilisation processing should be doneat 70∘C

This paper is dedicated to the late Professor Allan Easteal who was PhD supervisor colleague and contributor to the researchpresented in this paper

1 Introduction

The use of ionic liquids for cellulose solubilisation and mediafor cellulose chemical modification emerged over a decadeago [1] Since this time a range of ionic liquids have been eval-uated to dissolve cellulosic precursors and prepare cellulosefractions gels and various regenerated cellulose materialsMore recently the application of ionic liquids to dissolvecellulose has progressed to use in pretreatment and isolationof lignocellulosic fractions and feedstocks [2] Alongsidethe extensive work on cellulose solubilisation and regener-ation studies have evaluated the processing of ionic liquidscontaining cellulose typically undertaken as solutions or

on gel formation This has included the rheological prop-erties of the celluloseionic liquid solutions which havepractical applications for equipment design and processing[3 4] There are many considerations for celluloseionicliquid solution properties including viscosity and chemicalstability Celluloseionic liquid solution rheology propertiesare dependent on cellulose concentration and degree ofpolymerization together with the frequency and shear rate[5 6] Typically studies have revealed cellulose solutions tobe shearing thinning and dependent on temperature [5 7ndash9]However cosolvents or water content can also influencecellulose solution rheology behaviours [10 11]

Hindawi Publishing CorporationInternational Journal of Polymer ScienceVolume 2015 Article ID 958653 9 pageshttpdxdoiorg1011552015958653

2 International Journal of Polymer Science

The chemistry of cellulose dissolution and processing inionic liquids has been subject to significant investigation [1]Hydrogen bonding determines the structures and proper-ties of room-temperature ionic liquids where connectionsbetween hydrogen bonds form a network within the liquid[12 13] Hydrogen bonding within the ionic liquid is impor-tant to cellulose dissolution as well as the structure and result-ing physical properties of the solution or gel Interactionsbetween the anion and cellulose play an important role incellulose solvation [1 14] Furthermore hydrogen bondingand solvation efficiency can determine chemical interactionsin ionic liquids and cellulose solutions [15] We have becomeinterested in processing cellulose in ionic liquids to generatenovel nanoscale architectures which require control of cellu-lose solution properties [16]Thepurpose of the current paperis to relate the practical aspects of processing celluloseionicliquid solutions to the chemistry and hydrogen bondingnetworks within these solutions Primarily we investigate theinfluence of temperature on solution chemistry and rheologybehaviours Through the use of two-dimensional infraredcorrelations we relate how the presence of cellulose andwater sorption impact these properties Ultimately the goalis to establish preferred conditions to dissolve and processcellulose in ionic liquids as well as outcomes potentiallycontributing to understandings of cellulose dissolution byionic liquids

2 Methodology

21 Materials The ionic liquids 1-butyl-3-methylimida-zolium chloride (BMIMCl) and 1-ethyl-3-methylimida-zolium acetate (EMIMOAc) were obtained from SigmaAldrich Each was dried and distilled under vacuum priorto use Allyl chloride and N-methylimidazole were obtainedfrom Aldrich and freshly distilled prior to their use Thecellulose used was a Whatman high purity microcrystallinecellulose powder which was poly-dispersed with a molarmass distribution range between 1 times 104 and 3 times 106 andfurther defined elsewhere [16] Postprocessing molecularweight analysis was not undertaken given differing condi-tions were employed (N

2 air)

211 1-Allyl-3-methylimidazolium Chloride (AMIMCl) Syn-thesis Allyl chloride (200mL) was added to N-methylimid-azole (100mL) in a round bottomed flask as described byZhang et al [14] The mixture was then refluxed undernitrogen for 24 h with stirring After cooling any unreactedmaterials were removed by extraction with ethyl acetateThe residual product was vacuum distilled to give pureAMIMCl as an amber liquid (yield 62) mz calculated1585 found 15805 Refractive index 1547 lit value 154651HNMR120575 363 (NndashCH3) 489 (NndashCH2ndashCH) 528 (NndashCH

2ndash

CH=CH2) 601 (NndashCH2ndashCH=CH

2) 78-77 (C4H C5H)

940 (C2H) ppm 13C NMR 120575 360 (NndashCH3) 509 (Nndash

CH2CH) 1205 (NndashCH

2CH=CH

2) 1224 (C5) 1239 (C4)

1320 (NndashCH2ndashCH=CH

2) 1368 (C2)

22 Cellulose Dissolution Prior to cellulose dissolution cel-lulose and each ionic liquid were further dried in a vacuum

oven at 65ndash70∘C overnight Cellulose (2ndash10 ww) was thenweighted into a flask containing ionic liquid Dissolution ofeach solution was then carried out by stirring in a sealed flaskat elevated temperature (70ndash90∘C)using an oil bath Cellulosedissolution was monitored by light microscopy until nomorefibrous material was observed Cellulose solutions were thenstored at 35∘C in a vacuum oven prior to use

23 Rheology Oscillatory and steady shear measurementswere carried out using aUniversalDynamicRheometer (UDS200 Paar-Physica Germany) equipped with an air cooledpeltier heating element using a parallel plate geometry (MP30 25mm 0∘) with a gap distance of 05mm Temperaturesweep studies employed a strain of 1 and an angularfrequency of 10Hz Heating or cooling was undertaken at arate of 1∘Cmin

24 Fourier Transform Infrared Spectroscopy (FTIR) FTIRspectra were acquired employing a Thermo Electron Nicolet8700 FTIR spectrometer A total of 32 scans were collectedin the 650 cmminus1 to 4000 cmminus1 range with a resolution of4 cmminus1 Variable temperature spectra were collected usinga Spectra-Tech Thermal ARK accessory fitted with a ZnSecrystal trough plate which was flushed with dry air Forheating or cooling spectra the sample was heated at a rateof 5∘Cmin and allowed to equilibrate at the set temperaturefor 5 minutes prior to spectra acquisition

241 Two-Dimensional Correlation Analysis A baseline cor-rection was performed for all spectra in defined wavenumberranges before calculation of the 2D correlation A referencespectrum was chosen as the average spectrum of all thespectra selected for correlation analysis A generalised two-dimensional correlation analysis was performed using the 2Dspectral correlation analysis solution of the OMNIC spectro-scopic software (version 110 Thermo Electron CooperationSpectra Corr) In the 2D contour maps the red colouredregions are defined as the positive correlation intensities withblue-coloured region the corresponding negative correlationintensities

3 Results and Discussion

In this study cellulose was dissolved in ionic liquids withconcentrations varying from 1 to 10 ww Of the threeionic liquids used cellulose solutions prepared with 1-butyl-3-methylimidazolium chloride (BMIMCl) tendedto have relatively higher viscosity than using 1-allyl-3-methylimidazolium chloride (AMIMCl) with 1-ethyl-3-methylimidazolium acetate (EMIMOAc) solutions provingto be the least viscous Cellulose concentrations up to 7were used in rheology assessments but practically lowerconcentration cellulose solutions were easier to handle andprocess as noted by others [5 17 18] The cellulose solutionswere also prepared to avoid moisture sorption but rheologyand infrared evaluations were conducted in ambientconditions to mimic typical processing environments

International Journal of Polymer Science 3

20 40 60 80 100

2 cell4 cell

7 cell0 cell

Temperature (∘C)

10E + 05

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Cooling

(a)

20 40 60 80 100Temperature (∘C)

10E + 05

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Heating

2 cell4 cell

7 cell0 cell

(b)

Figure 1 Effect of cellulose concentration of storage modulus with temperature for AMIMCl solutions on cooling (a) and heating (b) PureAMIMCl (black) 2 cellulose (green) 4 cellulose (red) and 7 cellulose (blue) solutions

This led to the hygroscopic cellulose solutions and respectiveionic liquids readily adsorbing moisture during analyses

31 Rheology of Ionic Liquids and Cellulose Solutions Rhe-ological behaviours of ionic liquids and cellulose solu-tions were assessed by oscillatory shear experiments Shearbehaviour profiles of AMIMCl solutions with varying cellu-lose content are given in Figure 1 In these profiles samplesolutions were analysed by initially cooling from 100∘C tominimise any effects of solution hygroscopicity on rheologyAnalysis revealed the 2 cellulose solution had very low stor-age modulus (G1015840) at 100∘C which was observed to increase atca 40∘C followed by aminor G1015840 increase with further coolingto 20∘C On cooling the 4 cellulose solution two transitionswere observed with the first at ca 65∘C followed by a secondat ca 45∘C At 7 cellulose content the solution has greaterstorage modulus at high temperatures and on cooling anincrease was observed at 50∘C with the profile being similarto both 2 and 4 solutions on further cooling to 20∘C Onheating all samples have relatively similar G1015840 profiles to ca60∘C where each exhibited a transition onset with significantloss in G1015840 between 70 and 100∘CThis transitionwas observedat 77∘C 86∘C and 96∘C for the 2 4 and 7 cellulose solu-tions respectively Pure AMIMCl did not show these shearbehaviours on cooling or heating Interestingly a 2 cel-lulose solution prepared with 1-butyl-3-methylimidazoliumchloride (BMIMCl) showed comparable shear behaviour asthat observed with AMIMCl (see Supplementary Materialavailable online at httpdxdoiorg1011552015958653)

A dependency of cellulose content in AMIMCl solutionshear behaviour was also evident in viscosity profiles of thesesolutions (Figure 2) Unsurprisingly higher cellulose contentgave greater viscosity [5 17 18] with this more distinguishedat higher temperature On cooling from 100 to 20∘C samplesshow a steady consistent viscosity increase However on

heating samples initially have comparable viscosities butabove 50∘C viscosity was distinguished by higher cellulosecontent This shear thinning viscosity behaviour is consistentwith reportedly pseudoplastic AMIMCl solutions at 10ndash25cellulose content [17] However discontinuities in viscosityprofiles are also evident in Figure 2 which can be relatedto temperature transitions observed in rheology profiles(Figure 1) On cooling below 50∘C the discontinuity was asso-ciated with an increase in viscosity evident across the threecellulose solutions but not with pure AMIMCl Similarly onheating above 50∘C each solution showed an abrupt increasein viscosity compared to pure AMIMCl This discontinuitywas at 55∘C for the 2 cellulose solution compared to 70∘Cfor 7 cellulose content consistent with the observed onsetof the transition and shear behaviours on heating (Figure 1)

Rheology evaluation of EMIMOAc cellulose solutionsalso revealed shear behaviour dependencieswith temperatureand cellulose content (Figure 3) On cooling 4 and 7cellulose solutions there appeared minimal effect on rhe-ological behaviours above 50∘C Cooling below 40∘C gavean increase in G1015840 with transitions observed at 25∘C and35∘C for the 4 and 7 solutions respectively On heatingboth solutions show a decrease in G1015840 above ca 40∘C with asignificant loss inG1015840 between 55∘C (4) and 70∘C (7)whichwas comparable to that observed for AMIMCl solutions(Figure 1) In contrast the 2 cellulose EMIMOAc solutionmaintained a relatively static G1015840 profile on cooling to 20∘Cbeing similar to the behaviour of pure EMIMOAc This wassimilarly the case on heating both pure EMIMOAc and the2 cellulose solution Also perhaps an emerging influenceof moisture on rheology profiles is evident in Figure 3Cooling EMIMOAc solutions revealed decreases in G1015840 valuesconsistent with ionic liquid hygroscopicity with water knownto impact EMIMOAc rheological properties [11]


0 cell7 cell

4 cell2 cell

20 40 60 80 100Temperature (∘C)

10E + 02

10E + 01

10E + 00

10E minus 01

10E minus 02

Visc

osity

(Pamiddot

s)

Cooling

(a)

20 40 60 80 100Temperature (∘C)

10E + 02

10E + 01

10E + 00

10E minus 01

10E minus 02

Visc

osity

(Pamiddot

s)

Heating

0 cell7 cell

4 cell2 cell

(b)

Figure 2 Viscosity profiles for cellulose in AMIMCl solution on cooling (a) and heating (b) Pure AMIMCl (black) 2 cellulose (green) 4cellulose (red) and 7 cellulose (blue) solutions

2 cell4 cell

7 cell0 cell

20 40 60 80 100Temperature (∘C)

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Cooling

(a)

20 40 60 80 100Temperature (∘C)

10E + 05

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Heating

2 cell4 cell

7 cell0 cell

(b)

Figure 3 Effect of cellulose concentration of storage modulus with temperature for EMIMOAc solutions on cooling (a) and heating (b) PureEMIMOAc (black) 2 cellulose (green) 4 cellulose (red) and 7 cellulose (blue) solutions

32 FTIR Spectroscopy Analysis To assess the effect of tem-perature on ionic liquid networks and observed rheologicalproperties infrared analysis was used to gain insights intothe extent of hydrogen bonding FTIR spectra were acquiredfor cellulose solutions at key temperatures between 20 and100∘C on first heating and then cooling samples (Figure 4)Generally for each cellulose solution the spectra wererelatively similar to that obtained for the respective pureionic liquid (Supplementary Material) The spectrum of 2cellulose in AMIMCl solution shows key peaks at 3050 29651570 and 1165 cmminus1 attributable to ]C2ndashH ]CndashHmethyl ]CndashN and 120575CndashH respectively [15] These peaks representative

of the imidazolium ion were also common to BMIMCland EMIMOAc solutions Other relevant identifying peaksinclude 3100 (]CndashH) 1645 (]C=C) and 1420 cmminus1 (120575CH)Peaks attributable to cellulose such as the key cellulose ]CndashOndashC peak at 1020 cmminus1 were difficult to determine perhapsreflective of the low concentration in the ionic liquid [19]

Analysis of cellulose in AMIMCl spectra revealed the]C2ndashH (3050 cmminus1) and alkyl (]CndashH 2980 cmminus1) peakswere dynamic on both heating and cooling (Figure 4) Eachtemperature step in Figure 4 was selected to encompasstemperatures incorporating rheological transitions evident inFigure 1With the ]C2ndashHpeak sensitive to hydrogen bonding


000

004

008

012

016

020

6001000140018002200260030003400

Rela

tive a

bsor

banc

e

Wavenumber (cmminus1)

25∘C

40∘C

70∘C

100∘C

25∘C

40∘C

70∘C

(a)

000

009

018

027

036

Rela

tive a

bsor

banc

e

6001000140018002200260030003400Wavenumber (cmminus1)

25∘C

40∘C

70∘C

100∘C

25∘C

40∘C

70∘C

(b)

Figure 4 FTIR spectra of 2 cellulose solutions in AMIMCl (a) and EMIMOAc (b) solutions Spectra obtained on heating (mdash) from 25∘Cto 100∘C and then on cooling (- - -) to 25∘C 25∘C (black) 40∘C (blue) 70∘C (green) and 100∘C (red)

[15] Figure 4 provides evidence for changes in the extent ofimidazolium ion hydrogen bonding with temperature Anincrease in hydrogen bonding causes the lengthening of theC2ndashH bond with the ]C2ndashH stretching peakmoving to lowerwavenumbers (red shift) In contrast other AMIMCl (cellu-lose solution) peaks between 700 and 1700 cmminus1 including theallyl group (1645 and 1420 cmminus1) remain relatively unaffectedon heating or cooling In comparing the relative intensitychanges of imidazolium ion peaks to that observed withthe pure ionic liquid (Supplementary material) these appearrelatively less than observed for the cellulose solutionDespiteattempts to excludemoisture evident in Figure 4were spectrashowing the strong ]OndashH stretching band (3500ndash3200 cmminus1)to be dynamic on both heating and cooling This reflectssample hygroscopicity where the ]OndashH peak was indicat-ing water loss on heating with water sorption evident oncooling A comparison of FTIR obtained with pure AMIMClalso revealed similar hygroscopicity with water sorptionalso evident on both heating and cooling Analysis of theBMIMCl cellulose solution revealed spectral changes of theimidazolium ion peaks were similar to AMIMCl but the ]OndashH absorption was observed to increase both on heating andcooling (Supplementary Material)

Infrared spectroscopic evaluation of the EMIMOAc cel-lulose solution revealed spectral changes were relativelymore responsive to heating and cooling than AMIMClsolution (Figure 4) Imidazolium ion ]CndashH peaks at 2990and 2970 cmminus1 decrease in intensity with higher temperatureFurthermore this change in peak intensity was relativelygreater with the cellulose solution than for pure EMIMOAc(Supplementary Material) Dynamic EMIMOAc peaks werealso observed between 700 and 1650 cmminus1 attributable to theacetate anion (1590 and 1380 cmminus1) Analysis of the broad ]OndashH peak revealed the presence of water to remain relativelystatic onheating but increase in intensity upon coolingwhich

was similarly the case for pure EMIMOAc (SupplementaryMaterial)

Infrared analysis revealed imidazolium ion peaks inboth AMIMCl and EMIMOAc cellulose solutions to bedynamic on heating and cooling There were changes toboth peak shifts and intensities indicating that temperaturewas influencing the hydrogen bonding networks within bothionic liquids Furthermore when compared with pure ionicliquids the presence of cellulose appeared to also impact therelative intensity of these changes However the presenceof water also proved to complicate this interpretation withwater known to influence hydrogen bonding and cellulosedissolution in ionic liquids [11] To further distinguish tem-perature andwater influences on ionic liquid hydrogen bond-ing two-dimensional correlation spectroscopy (2D FTIR)analysis was undertaken Synchronous and asynchronousspectra generated from simulated spectra gave positive (red)and negative (blue) correlation squares for FTIR peak (band)shift and intensity changes (Figures 5 to 7 and SupplementaryMaterial) Typically both heating and cooling spectra of pureionic liquids and cellulose solutions by 2D FTIR show strongcross peaks associated with ]OndashH and ]C2ndashH peaks evidentas correlation squares (Figure 5)

Two-dimensional correlation FTIR analysis revealed thesynchronous spectrum of the cellulose solution in AMIMClduring heating (Figure 6) was similar to the synchronousspectrum of pure AMIMCl during cooling (SupplementaryMaterial) On heating the cellulose solution has a broad in-phase autopeak for ]OndashH (3600 to 3200 cmminus1) and ]C2ndashHpeaks The autocorrelation peak (]C2ndashH) was at 3072 cmminus1for the cellulose solution whereas in the pure AMIMClcooling spectrum it was at 3093 cmminus1 This indicated waterand potentially cellulose even at 2 concentration wasinfluencing hydrogen bonding of the imidazolium ion withinthe solutionMoreover other ]CndashHpeakswere also impacted



Wav

enum

ber (

cmminus1)

3500

3500

3600

3400

3400

3300

3300

3200

3200

3100

3100

3000

3000

2900

2900

2800

2800

2700

2700

Figure 5 Two-dimensional FTIR correlation analysis for 2 cel-lulose in AMIMCl solution Asynchronous spectrum on heatingSpectral range from 2700 to 3600 cmminus1

in the cellulose solution whereas for pure AMIMCl only the]CndashH at 2937 cmminus1 peak was affected (Supplementary Mate-rial) In the case of spectra obtained on cooling (Figure 5) thesynchronous spectrum of this cellulose solution was similarto that for heating perhaps reflective of temperature effectsand similar water content observed on heating and cooling(Figure 4) However any alkyl ]CndashH cross peaks with the]OndashH region (3500 to 3100 cmminus1) were not developed for thissolution during cooling

In the corresponding asynchronous heating spectrumfor the cellulose AMIMCl solution (Figure 5) out of phasecross peaks were developed for the ]CndashH alkyl vibrationsand imidazolium ]C4ndashH and ]C5ndashH peaks with ]OndashHThisindicated the intensities of two spectral features change outof phase with each other and that these differing functionalgroups were experiencing different effects from heating Noasynchronous cross peaks were observed between ]OndashHand ]C2ndashH peaks This contrasts the asynchronous spec-trum of pure AMIMCl which showed cross peaks between]OndashH and ]C2ndashH (Supplementary Material) In this lattercase the cross peaks observed between ]OndashH and ]C2ndashH were observed in both the pure AMIMCl synchronousand asynchronous spectrums indicating these two changeswere not occurring simultaneously but were either delayed oraccelerated These results were suggestive of both water andtemperature influencing imidazolium ion hydrogen bondingwith the asynchronous correlations suggesting the presenceof cellulose may also impact hydrogen bonding networksgiven emergence of C4ndashH and C5ndashH cross peaks

Two-dimensional correlation spectroscopy of the EMI-MOAc cellulose solution revealed positive cross peaks at3089 and 2981 cmminus1 and a relative absence of interactionwith the ]OndashH region in the synchronous spectrum onheating (Figure 7 Supplementary Materials) No cross peakswere observed in the asynchronous spectrum of the heatingspectra in this region This suggests water was not contribut-ing to any imidazolium ion hydrogen bonding differencesin EMIMOAc solution on heating In contrast on coolingautopeaks were observed for 3080 cmminus1 and the ]OndashH regionwith an absence of any correlation peak at 2981 cmminus1Thiswas

also the case for pure EMIMOAc in which there was a strongautopeak at 3070 cmminus1 and the ]OndashH region compared toa reduced prominence of the 2978 cmminus1 peak Unlike thecellulose solution the asynchronous cooling spectrum ofpure EMIMOAc (SupplementaryMaterial) has cross peaks at3030 cmminus1 and 2960 cmminus1 with the 3330 cmminus1 band indicativeof water interactions Collectively this shows on coolingthat water also had an effect on hydrogen bonding withinEMIMOAc solution Moreover this was consistent withthe increasing presence of water in this sample on cooling(Figure 4)

With the presence of an acetate anion the carbonylabsorption of EMIMOAc was also analysed by 2D FTIR todetermine the extent of any cation-anion hydrogen bondingin EMIMOAc solution (Figure 7) Analysis of the cellulosesolution revealed cross peaks of the anion (1500ndash1600 cmminus1)with ]CndashH and ]OndashH peaks which increase on heatingand lessen during cooling Similarly for pure EMIMOActhe band at 1602 cmminus1 was correlated with the ]OndashH peakbut was decreasing with both the ]C2ndashH (3030 cmminus1) and]CndashH (2960 cmminus1 alkyl) peaks (Supplementary Material)These results suggest that the anion is interacting with thecation C2H and methyl group during heating but only withthe C2H on cooling Figure 7 shows contrasting behaviourof this carbonyl absorption during cooling together with across peak between the ]OndashH and ]C2ndashH at 3086 cmminus1 Thisprovides evidence that the acetate carbonyl (1602 cmminus1) ishydrogen-bonded with water and also involved in hydrogenbonding with the imidazolium ]C2ndashH particularly at lowertemperatures consistent with network structure formation[20] In comparing 2DFTIR analysis for the cellulose solutionand pure EMIMOAc their similarity suggests at 2 the cel-lulose content may not impact hydrogen bonding networkswithin the ionic liquid This finding was also consistent withthe 2 cellulose content having no impact on the rheologyprofile (Figure 3)

33 Discussion It was evident in FTIR analysis that tem-perature together with water sorption due to ionic liquidhygroscopicity was influencing the interactions and hydro-gen bonding of the imidazolium cation Water can play asignificant role in cellulose dissolution in ionic liquids inaddition to impacting hydrogen bonding networks in theionic liquid [11 21] In this study 2D FTIR has revealedtemperature can also influence hydrogen bonding networkswithin the ionic liquids which may manifest in observedrheology profiles A shift in the ]C2ndashH peak is an indicationto the extent of hydrogen bonding [15] with C2ndashH bondlengthening contributing a red shift to lower wavenumbersFor cellulose in AMIMCl solution the ]C2ndashH absorption wasat 3072 cmminus1 during heating but increased to 3093 cmminus1 oncooling (Figure 4) This was similarly the case in BMIMClsolution with the ]C2ndashH absorption at 3040 cmminus1 on heatingand increasing to 3087 cmminus1 on cooling (SupplementaryMaterial) This indicated hydrogen bonding of imidazoliumion C2ndashH was stronger on heating consistent with greater


Wavenumber (cmminus1)3500 3400 3300 3200 3100 3000 2900 2800 2700

(a)

Wavenumber (cmminus1)3500 3400 3300 3200 3100 3000 2900 2800

(b)

Figure 6 Two-dimensional FTIR correlation analysis of cellulose in AMIMCl solution Synchronous spectrum on heating (a) and cooling(b) Spectral range 2700 to 3600 cmminus1


Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(a)


Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(b)

Figure 7 Two-dimensional FTIR correlation analysis of cellulose in EMIMOAc solution Full spectrum range (400 to 4000 cmminus1)synchronous spectra on heating (a) and cooling (b)

ion mobility at higher temperature At ambient temperaturethere were more cation-anion interactions with the ]C2ndashH frequency blue shifted Also consistent with heating andcooling effects were other ]CndashH peak changes indicating thealkyl groups have greater rotational and vibrational freedomat higher temperature when the ionic liquid network struc-ture is broken FTIR results suggest the higher water contentson cooling enabled water to interact more contributing toa weaker imidazolium-anion interaction and ]C2ndashH peakshift Furthermore the presence of cellulose in AMIMClsolution also induced changes in the imidazolium ]CndashHabsorptions which were not observed in the pure ionic liquid2D FTIR suggests cellulose may have minimised the waterinfluence on hydrogen bonding given differences observedbetween out of phase cross peaks on heating and cooling(Figure 6)

WithEMIMOAc the ]C2ndashHpeak of pure EMIMOAcwasat 3030 cmminus1 during heating and blue shifted to 3070 cmminus1during cooling suggesting temperature similarly influencedthe extent of imidazolium cation hydrogen bonding asestablished for AMIMCl However cellulose in EMIMOAc

solution contributed to a narrower range in the ]C2ndashHpeak shift (3080ndash3089 cmminus1) indicating a relatively minimalinfluence on ]C2ndashH hydrogen bonding due to temperatureMoreover results show the anion to be interacting with C2Htogether with other imidazolium CndashH and methyl groupsPotentially this indicates differences in the extent of interac-tions between the imidazolium ion and acetate and chlorideanions in cellulose solutions with EMIMOAc and AMIMClrespectively The ]OH peak also contributed a dominantinfluence on hydrogen bonding due to water sorption oncooling

FTIR spectra show a gradual change in imidazolium ionhydrogen bonding between 25 and 100∘C on both heatingand cooling At lower temperatures there were closer inter-actions between cations and anions indicative of a networkstructure in the ionic liquids The shear applied to the ionicliquid solutions was sufficient to break this network withthis observed as transitions under shear at key temperaturesin Figures 1 and 3 These transitions resulted in significantinflexions in rheology storagemodulus values whichwere notdistinguished by FTIR at these temperature steps perhaps as


FTIR was undertaken without solution shear Furthermorethere was a rheological hysteresis evident between heatingand cooling With decreasing temperature there is apparentsuper cooling and gel formation [1] leading to slower networkorganisation within the liquid observed below 40∘C How-ever on heating initially the ionic liquid network structureis greater and the effect of shear not evident until a highertemperature (50ndash70∘C) being common to both ionic liquids(Figures 1 and 3) The presence of cellulose increases theionic liquid viscosity (Figure 2) but has minimal effect oninitial heating (Figures 1 and 3) as the ionic liquid networkstructure is dominant Only on cooling and gel formationwas the presence and quantity of cellulose observed to impactrheologyMoreover given the impact of cellulose observed by2D FTIR it can be expected cellulose plays an increasing rolein hydrogen bonding in AMIMCl at higher concentrationswhereas in EMIMOAc any impact of cellulose was observedat ge4 concentration

4 Conclusion

Oscillatory shear experiments reveal a dependency of tem-perature and cellulose content on rheology profiles ofAMIMCl BMIMCl and EMIMOAc cellulose solutions whichalsomanifest in viscosity profiles on heating and cooling Useof two-dimensional FTIR shows dynamic hydrogen bondingbetween the imidazolium cation and anion on heating andcooling which was also impacted by the presence of celluloseand moisture sorption A red shift of the imidazolium ]C2ndashH peak on heating indicated hydrogen bonding of the cationwas stronger consistent with greater ion mobility and lossof the ionic network structure with temperature TheseFTIR spectral changes appeared gradual with temperatureand contrast shear induced rheology changes which wereobserved on heating above 70∘C and cooling below 40∘CThepresence of cellulose increases ionic liquid solution viscositybut this was not distinguished in solution rheology on initialheating as the ionic liquid network structure dominates Oncooling the quantity of cellulose has a greater influence onsolution rheology with this also expected to influence theprocessing of cellulose solutions at temperature Practicallythe results of this study suggest the processing of cellulosein ionic liquids to be undertaken above 40∘C and to reducethe impacts of cation-anion effects and enhance ionic liquidsolubilisation processing should be done at 70∘C

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

Kalyani Kathirgamanathan would like to thank the Biopoly-mer Network Ltd for financial support and scholarshipstipend The work presented in this study was supportedthrough funding provided through the New Zealand Min-istry of Business Innovation and Employment

References

[1] H Wang G Gurau and R D Rogers ldquoIonic liquid processingof celluloserdquo Chemical Society Reviews vol 41 no 4 pp 1519ndash1537 2012

[2] M Mora-Pale L Meli T V Doherty R J Linhardt and J SDordick ldquoRoom temperature ionic liquids as emerging solventsfor the pretreatment of lignocellulosic biomassrdquo Biotechnologyand Bioengineering vol 108 no 6 pp 1229ndash1245 2011

[3] J Dupont ldquoOn the solid liquid and solution structural orga-nization of imidazolium ionic liquidsrdquo Journal of the BrazilianChemical Society vol 15 no 3 pp 341ndash350 2004

[4] M Gericke K Schlufter T Liebert T Heinze and T BudtovaldquoRheological properties of celluloseionic liquid solutions fromdilute to concentrated statesrdquo Biomacromolecules vol 10 no 5pp 1188ndash1194 2009

[5] X Chen Y Zhang L Cheng and H Wang ldquoRheology of con-centrated cellulose solutions in 1-butyl-3-methylimidazoliumchloriderdquo Journal of Polymers and the Environment vol 17 no4 pp 273ndash279 2009

[6] F Lu J Song B-W Cheng X-J Ji and L-J Wang ldquoViscoelas-ticity and rheology in the regimes from dilute to concentratedin cellulose 1-ethyl-3-methylimidazolium acetate solutionsrdquoCellulose vol 20 no 3 pp 1343ndash1352 2013

[7] Z LiuHWang Z Li et al ldquoCharacterization of the regeneratedcellulose films in ionic liquids and rheological properties of thesolutionsrdquoMaterials Chemistry and Physics vol 128 no 1-2 pp220ndash227 2011

[8] Z Liu H Wang Z Li et al ldquoRheological properties of cottonpulp cellulose dissolved in 1-butyl-3-methylimidazolium chlo-ride solutionsrdquo Polymer Engineering and Science vol 51 no 12pp 2381ndash2386 2011

[9] F Lu LWang X Ji B Cheng J Song andXGou ldquoFlowbehav-ior and linear viscoelasticity of cellulose 1-allyl-3- methylimida-zolium formate solutionsrdquo Carbohydrate Polymers vol 99 pp132ndash139 2014

[10] R Arin M Brodin A Boldizar and G Westman ldquoThermaland viscoelastic properties of cellulosic gels with different ionicliquids and coagulation agentsrdquo BioResources vol 8 no 2 pp2209ndash2221 2013

[11] C Olsson A Idstrom L Nordstierna and GWestman ldquoInflu-ence of water on swelling and dissolution of cellulose in 1-ethyl-3-methylimidazolium acetaterdquo Carbohydrate Polymers vol 99pp 438ndash446 2014

[12] B D Rabideau A Agarwal and A E Ismail ldquoThe role of thecation in the solvation of cellulose by imidazolium-based ionicliquidsrdquo Journal of Physical Chemistry B vol 118 no 6 pp 1621ndash1629 2014

[13] Z Xiong J Gao D Zhang and C Liu ldquoHydrogen bondnetwork of 1-alkyl-3-methylimidazolium ionic liquids a net-work theory analysisrdquo Journal ofTheoretical and ComputationalChemistry vol 11 no 3 pp 587ndash598 2012

[14] H Zhang J Wu J Zhang and J He ldquo1-Allyl-3-methylimida-zolium chloride room temperature ionic liquid a new and pow-erful nonderivatizing solvent for celluloserdquoMacromolecules vol38 no 20 pp 8272ndash8277 2005

[15] H He H Chen Y Zheng et al ldquoThe hydrogen-bondinginteractions between 1-ethyl-3-methylimidazolium lactate ionicliquid andmethanollowastrdquoAustralian Journal of Chemistry vol 66no 1 pp 50ndash59 2013

[16] K Kathirgamanathan Modification of cellulose using ionic liq-uids [Doctoral thesis] University of Auckland 2010


[17] F Lu B Cheng J Song andY Liang ldquoRheological characteriza-tion of concentrated cellulose solutions in 1-allyl-3-methylimid-azolium chloriderdquo Journal of Applied Polymer Science vol 124no 4 pp 3419ndash3425 2012

[18] H Song J Zhang Y Niu and Z Wang ldquoPhase transition andrheological behaviors of concentrated celluloseionic liquidsolutionsrdquo Journal of Physical Chemistry B vol 114 no 18 pp6006ndash6013 2010

[19] M Fitzpatrick P Champagne and M F Cunningham ldquoQuan-titative determination of cellulose dissolved in 1-ethyl-3-meth-ylimidazolium acetate using partial least squares regression onFTIR spectrardquo Carbohydrate Polymers vol 87 no 2 pp 1124ndash1130 2012

[20] B Fazio A Triolo and G di Marco ldquoLocal organization ofwater and its effect on the structural heterogeneities in room-temperature ionic liquidH

2

O mixturesrdquo Journal of RamanSpectroscopy vol 39 no 2 pp 233ndash237 2008

[21] L K J Hauru M Hummel A W T King I Kilpelainen andH Sixta ldquoRole of solvent parameters in the regeneration ofcellulose from ionic liquid solutionsrdquo Biomacromolecules vol13 no 9 pp 2896ndash2905 2012

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


The chemistry of cellulose dissolution and processing inionic liquids has been subject to significant investigation [1]Hydrogen bonding determines the structures and proper-ties of room-temperature ionic liquids where connectionsbetween hydrogen bonds form a network within the liquid[12 13] Hydrogen bonding within the ionic liquid is impor-tant to cellulose dissolution as well as the structure and result-ing physical properties of the solution or gel Interactionsbetween the anion and cellulose play an important role incellulose solvation [1 14] Furthermore hydrogen bondingand solvation efficiency can determine chemical interactionsin ionic liquids and cellulose solutions [15] We have becomeinterested in processing cellulose in ionic liquids to generatenovel nanoscale architectures which require control of cellu-lose solution properties [16]Thepurpose of the current paperis to relate the practical aspects of processing celluloseionicliquid solutions to the chemistry and hydrogen bondingnetworks within these solutions Primarily we investigate theinfluence of temperature on solution chemistry and rheologybehaviours Through the use of two-dimensional infraredcorrelations we relate how the presence of cellulose andwater sorption impact these properties Ultimately the goalis to establish preferred conditions to dissolve and processcellulose in ionic liquids as well as outcomes potentiallycontributing to understandings of cellulose dissolution byionic liquids

2 Methodology

21 Materials The ionic liquids 1-butyl-3-methylimida-zolium chloride (BMIMCl) and 1-ethyl-3-methylimida-zolium acetate (EMIMOAc) were obtained from SigmaAldrich Each was dried and distilled under vacuum priorto use Allyl chloride and N-methylimidazole were obtainedfrom Aldrich and freshly distilled prior to their use Thecellulose used was a Whatman high purity microcrystallinecellulose powder which was poly-dispersed with a molarmass distribution range between 1 times 104 and 3 times 106 andfurther defined elsewhere [16] Postprocessing molecularweight analysis was not undertaken given differing condi-tions were employed (N

2 air)

211 1-Allyl-3-methylimidazolium Chloride (AMIMCl) Syn-thesis Allyl chloride (200mL) was added to N-methylimid-azole (100mL) in a round bottomed flask as described byZhang et al [14] The mixture was then refluxed undernitrogen for 24 h with stirring After cooling any unreactedmaterials were removed by extraction with ethyl acetateThe residual product was vacuum distilled to give pureAMIMCl as an amber liquid (yield 62) mz calculated1585 found 15805 Refractive index 1547 lit value 154651HNMR120575 363 (NndashCH3) 489 (NndashCH2ndashCH) 528 (NndashCH

2ndash

CH=CH2) 601 (NndashCH2ndashCH=CH

2) 78-77 (C4H C5H)

940 (C2H) ppm 13C NMR 120575 360 (NndashCH3) 509 (Nndash

CH2CH) 1205 (NndashCH

2CH=CH

2) 1224 (C5) 1239 (C4)

1320 (NndashCH2ndashCH=CH

2) 1368 (C2)

22 Cellulose Dissolution Prior to cellulose dissolution cel-lulose and each ionic liquid were further dried in a vacuum

oven at 65ndash70∘C overnight Cellulose (2ndash10 ww) was thenweighted into a flask containing ionic liquid Dissolution ofeach solution was then carried out by stirring in a sealed flaskat elevated temperature (70ndash90∘C)using an oil bath Cellulosedissolution was monitored by light microscopy until nomorefibrous material was observed Cellulose solutions were thenstored at 35∘C in a vacuum oven prior to use

23 Rheology Oscillatory and steady shear measurementswere carried out using aUniversalDynamicRheometer (UDS200 Paar-Physica Germany) equipped with an air cooledpeltier heating element using a parallel plate geometry (MP30 25mm 0∘) with a gap distance of 05mm Temperaturesweep studies employed a strain of 1 and an angularfrequency of 10Hz Heating or cooling was undertaken at arate of 1∘Cmin

24 Fourier Transform Infrared Spectroscopy (FTIR) FTIRspectra were acquired employing a Thermo Electron Nicolet8700 FTIR spectrometer A total of 32 scans were collectedin the 650 cmminus1 to 4000 cmminus1 range with a resolution of4 cmminus1 Variable temperature spectra were collected usinga Spectra-Tech Thermal ARK accessory fitted with a ZnSecrystal trough plate which was flushed with dry air Forheating or cooling spectra the sample was heated at a rateof 5∘Cmin and allowed to equilibrate at the set temperaturefor 5 minutes prior to spectra acquisition

241 Two-Dimensional Correlation Analysis A baseline cor-rection was performed for all spectra in defined wavenumberranges before calculation of the 2D correlation A referencespectrum was chosen as the average spectrum of all thespectra selected for correlation analysis A generalised two-dimensional correlation analysis was performed using the 2Dspectral correlation analysis solution of the OMNIC spectro-scopic software (version 110 Thermo Electron CooperationSpectra Corr) In the 2D contour maps the red colouredregions are defined as the positive correlation intensities withblue-coloured region the corresponding negative correlationintensities

3 Results and Discussion

In this study cellulose was dissolved in ionic liquids withconcentrations varying from 1 to 10 ww Of the threeionic liquids used cellulose solutions prepared with 1-butyl-3-methylimidazolium chloride (BMIMCl) tendedto have relatively higher viscosity than using 1-allyl-3-methylimidazolium chloride (AMIMCl) with 1-ethyl-3-methylimidazolium acetate (EMIMOAc) solutions provingto be the least viscous Cellulose concentrations up to 7were used in rheology assessments but practically lowerconcentration cellulose solutions were easier to handle andprocess as noted by others [5 17 18] The cellulose solutionswere also prepared to avoid moisture sorption but rheologyand infrared evaluations were conducted in ambientconditions to mimic typical processing environments


20 40 60 80 100

2 cell4 cell

7 cell0 cell

Temperature (∘C)

10E + 05

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Cooling

(a)

20 40 60 80 100Temperature (∘C)

10E + 05

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Heating

2 cell4 cell

7 cell0 cell

(b)








0 cell7 cell

4 cell2 cell

20 40 60 80 100Temperature (∘C)

10E + 02

10E + 01

10E + 00

10E minus 01

10E minus 02

Visc

osity

(Pamiddot

s)

Cooling

(a)

20 40 60 80 100Temperature (∘C)

10E + 02

10E + 01

10E + 00

10E minus 01

10E minus 02

Visc

osity

(Pamiddot

s)

Heating

0 cell7 cell

4 cell2 cell

(b)


2 cell4 cell

7 cell0 cell

20 40 60 80 100Temperature (∘C)

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Cooling

(a)

20 40 60 80 100Temperature (∘C)

10E + 05

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Heating

2 cell4 cell

7 cell0 cell

(b)






000

004

008

012

016

020

6001000140018002200260030003400

Rela

tive a

bsor

banc

e


25∘C

40∘C

70∘C

100∘C

25∘C

40∘C

70∘C

(a)

000

009

018

027

036

Rela

tive a

bsor

banc

e


25∘C

40∘C

70∘C

100∘C

25∘C

40∘C

70∘C

(b)









Wav

enum

ber (

cmminus1)

3500

3500

3600

3400

3400

3300

3300

3200

3200

3100

3100

3000

3000

2900

2900

2800

2800

2700

2700










(a)


(b)



Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(a)


Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(b)








4 Conclusion




Acknowledgments


References






















2










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




20 40 60 80 100

2 cell4 cell

7 cell0 cell

Temperature (∘C)

10E + 05

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Cooling

(a)

20 40 60 80 100Temperature (∘C)

10E + 05

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Heating

2 cell4 cell

7 cell0 cell

(b)








0 cell7 cell

4 cell2 cell

20 40 60 80 100Temperature (∘C)

10E + 02

10E + 01

10E + 00

10E minus 01

10E minus 02

Visc

osity

(Pamiddot

s)

Cooling

(a)

20 40 60 80 100Temperature (∘C)

10E + 02

10E + 01

10E + 00

10E minus 01

10E minus 02

Visc

osity

(Pamiddot

s)

Heating

0 cell7 cell

4 cell2 cell

(b)


2 cell4 cell

7 cell0 cell

20 40 60 80 100Temperature (∘C)

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Cooling

(a)

20 40 60 80 100Temperature (∘C)

10E + 05

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Heating

2 cell4 cell

7 cell0 cell

(b)






000

004

008

012

016

020

6001000140018002200260030003400

Rela

tive a

bsor

banc

e


25∘C

40∘C

70∘C

100∘C

25∘C

40∘C

70∘C

(a)

000

009

018

027

036

Rela

tive a

bsor

banc

e


25∘C

40∘C

70∘C

100∘C

25∘C

40∘C

70∘C

(b)









Wav

enum

ber (

cmminus1)

3500

3500

3600

3400

3400

3300

3300

3200

3200

3100

3100

3000

3000

2900

2900

2800

2800

2700

2700










(a)


(b)



Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(a)


Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(b)








4 Conclusion




Acknowledgments


References






















2










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 cell7 cell

4 cell2 cell

20 40 60 80 100Temperature (∘C)

10E + 02

10E + 01

10E + 00

10E minus 01

10E minus 02

Visc

osity

(Pamiddot

s)

Cooling

(a)

20 40 60 80 100Temperature (∘C)

10E + 02

10E + 01

10E + 00

10E minus 01

10E minus 02

Visc

osity

(Pamiddot

s)

Heating

0 cell7 cell

4 cell2 cell

(b)


2 cell4 cell

7 cell0 cell

20 40 60 80 100Temperature (∘C)

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Cooling

(a)

20 40 60 80 100Temperature (∘C)

10E + 05

10E + 03

10E + 01

10E minus 01

10E minus 03

10E minus 05

10E minus 07

Stor

age m

odul

us (G

998400 P

a)

Heating

2 cell4 cell

7 cell0 cell

(b)






000

004

008

012

016

020

6001000140018002200260030003400

Rela

tive a

bsor

banc

e


25∘C

40∘C

70∘C

100∘C

25∘C

40∘C

70∘C

(a)

000

009

018

027

036

Rela

tive a

bsor

banc

e


25∘C

40∘C

70∘C

100∘C

25∘C

40∘C

70∘C

(b)









Wav

enum

ber (

cmminus1)

3500

3500

3600

3400

3400

3300

3300

3200

3200

3100

3100

3000

3000

2900

2900

2800

2800

2700

2700










(a)


(b)



Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(a)


Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(b)








4 Conclusion




Acknowledgments


References






















2










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




000

004

008

012

016

020

6001000140018002200260030003400

Rela

tive a

bsor

banc

e


25∘C

40∘C

70∘C

100∘C

25∘C

40∘C

70∘C

(a)

000

009

018

027

036

Rela

tive a

bsor

banc

e


25∘C

40∘C

70∘C

100∘C

25∘C

40∘C

70∘C

(b)









Wav

enum

ber (

cmminus1)

3500

3500

3600

3400

3400

3300

3300

3200

3200

3100

3100

3000

3000

2900

2900

2800

2800

2700

2700










(a)


(b)



Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(a)


Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(b)








4 Conclusion




Acknowledgments


References






















2










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





Wav

enum

ber (

cmminus1)

3500

3500

3600

3400

3400

3300

3300

3200

3200

3100

3100

3000

3000

2900

2900

2800

2800

2700

2700










(a)


(b)



Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(a)


Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(b)








4 Conclusion




Acknowledgments


References






















2










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





(a)


(b)



Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(a)


Wav

enum

ber (

cmminus1)

3000

3000

3500

2000

2000

2500

1000

1000

1500

(b)








4 Conclusion




Acknowledgments


References






















2










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





4 Conclusion




Acknowledgments


References






















2










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials








2










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Research Article Two-Dimensional FTIR as a Tool to Study...

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Transcript of Research Article Two-Dimensional FTIR as a Tool to Study...