Inverse gas chromatographic characterization of functionalized polysiloxanes. Relevance to sensors technology

Sensors and Actuators B 62 Ž2000. 1–7 www.elsevier.nlrlocatersensorb

Inverse gas chromatographic characterization of functionalized polysiloxanes. Relevance to sensors technology Caroline Demathieu a , Mohamed M. Chehimi a

a,)

, Jean-Franc¸ois Lipskier

b

Institut de Topologie et de Dynamique des Systemes, UniÕersite´ Paris 7, Denis Diderot, associe´ au CNRS (UPRESA 7086), 1 rue Guy de la Brosse, ` 75005 Paris, France b Thomson-CSF, Laboratoire Central de Recherches, Domaine de CorbeÕille, 91404 Orsay, France Received 1 December 1998; received in revised form 22 March 1999; accepted 24 March 1999

Abstract Inverse gas chromatography ŽIGC. was used to determine partition coefficients between reference solutes and a series of five polysiloxanes: polymethylhydrosiloxane ŽPMHS., polyŽmethyl 3,3,3-trifluoropropylsiloxane. ŽPMTFPS., polyŽcyanopropylsiloxane. ŽPCPMS. and a linear and branched functionalized polysiloxanes with hexafluorodimethylcarbinol groups ŽPLF and PBF.. These partition coefficients, combined with the solvation energy relationship ŽLSER. allowed us to determine physicochemical parameters describing dispersive, polar and acid–base properties of polysiloxanes. The strong acidic character of PLF and PBF on the one hand, and the basic character of PCPMS on the other hand are firmly demonstrated. q 2000 Elsevier Science S.A. All rights reserved. Keywords: Polysiloxanes; Inverse gas chromatography; Surface acoustic waves sensors; Molecular probes; Sorption; Dispersive interactions; Polar interactions; Acid–base interactions

1. Introduction In the recent years, chemical sensors were the subject of numerous academic and applied researches for they are relevant to various fields such as motor car industry, medicine, environment, food industry or civil protection. These devices are expected to be of small size, autonomous, robust and easy to use. Depending on the target application, a given chemical sensor will be subject to sensitivity, selectivity, time constant and long term use constraints. Among the variously available chemical sensors w1,2x, there is a potential interest in the development of surface acoustic wave ŽSAW. sensors w2x. The use of a SAW sensor to detect chemical vapors Žpentane, hexane, octane, dodecane, chlorotoluene. was first reported in 1979 w3x and has since been widely studied. Numerous polymer-coated SAW sensors were proposed w4x, for example to detect NH 3 , H 2 S w5,6x, chlorinated hydrocarbons w7x, nitrobenzene derivatives w8x or H 2 O w9–11x.

Polysiloxanes constitute an interesting class of polymers which are used in various applications such as cosmetics, textiles, plastics, resins, medicine, lubricants, electricity, electronic, paints, adhesives or papers w12,13x. These polymers can be easily synthesized andror chemically modified with various functional pendent groups. They exhibit a very good thermal stability due to the Si–C bonds and a low glass transition temperature ŽTg . due to the large Si–O–Si angle and Si–O bond length. A low Tg is an interesting property when sorption and diffusion phenomena are concerned. Indeed, a low-Tg polymer will promote diffusion and sorption of molecules and this is the main reason for the potential use of polysiloxanes in the SAW sensor technology. In SAW sensors, the detection is based on the partition of the analytes between the environment surrounding the sensor and the active sensing layer. The partition coefficient of a solute between the stationary phase Žpolymer coating. and the gas phase is defined by: Ks

)

Corresponding author. Tel.: q33-1-44-27-68-09; fax: q33-1-44-2768-14; e-mail: [email protected]

CS CV

Ž 1.

where CS is the solute concentration in the stationary phase and C V the solute concentration in the gas phase. K

0925-4005r00r$ - see front matter q 2000 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 5 - 4 0 0 5 Ž 9 9 . 0 0 3 5 7 - 3

C. Demathieu et al.r Sensors and Actuators B 62 (2000) 1–7

2

is related to the experimental data measured in SAW sensors by w14x: D f V s D fSCV

K

r

Ž 2.

where D f S is the frequency shift of the sensor due to the active layer, D f V the frequency shift due to the sorbed volatile species, and r the density of the active layer. Since K can be determined by inverse gas chromatography ŽIGC., there is thus a close relationship between IGC and the detection of volatile species by a SAW sensor. For this reason, several publications were devoted to the characterization of the sensing material by IGC at infinite dilution w15–18x, with the sensing material acting as a stationary phase. As part of an R & D programme on SAW sensors, we wished to investigate on the physicochemical properties of a series of polysiloxanes by IGC. This technique has indeed come of age in the characterization of the surface and the bulk of polymers w19–23x. IGC permits to evaluate the van der Waals and acid–base interactions of polymers and other materials. The use of solutes of known physicochemical constants permit to evaluate constants for the polymer under test. The combination of physicochemical constants describing the ability of a polymer and a solute to undergo van der Waals and acid–base interactions is a key for the prediction of the interaction strength between the host polymer and the volatile solute w24,25x. This paper aims at characterizing a series of polysiloxanes by IGC with a view of determining physicochemical constants related to the polarizability, polarity, dispersive and acid–base interactions. These constants will be evaluated using the experimental values of partition coefficients derived from IGC and the well known linear solvation energy relationship ŽLSER. w24,25x.

2. Experimental sections 2.1. Materials Poly Žmethylhydrosiloxane. ŽPMHS ., poly Žmethyl 3 ,3 ,3 -triflu o ro p ro p y lsilo x an e . Ž P M T F P S . an d polyŽcyanopropylsiloxane. ŽPCPMS. were provided by ABCR ŽLauterbourg, France.. We synthesised the linear and branched polymers functionalized with hexafluorodimethylcarbinol groups ŽPLF and PBF.. The full details concerning these syntheses will be described in a forthcoming paper w26x. The structures of these polysiloxanes are illustrated in Fig. 1. The density of PLF, PBF and PCPMS were determined by weighing and those of PMHS and PMTFPS were obtained from ABCR. The density values are reported in Table 1.

Fig. 1. Chemical structure of polysiloxanes under test: Ža. polymethylhydrosiloxane ŽPMHS.; Žb. polyŽmethyl 3,3,3-trifluoropropylsiloxane. ŽPMTFPS.; Žc. polyŽcyanopropylsiloxane. ŽPCPMS.; Žd. linear functionalized polymer ŽPLF.; Že. branched functionalized polymer ŽPBF..

2.2. InÕerse gas chromatography 2.2.1. Stationnary phases The polysiloxanes were coated on acid-washed silanized Chromosorb PAW-DMCS Ž80–100 mesh, Chrompack product. according to the soaking method of Al-Saıgh ¨ and Munk w27x. For each of the five polymers, three loadings were prepared: 2.5, 5, and 10% wrw. The amount of polymer deposited was systematically controlled by thermogravimetric analysis and found to correspond to the initial amount before polymer deposition. This gives full credit to the method of Ref. w27x. 2.2.2. Apparatus and measurements A gas chromatograph ŽHewlett Packard HP 6890. fitted with a flame ionization detector and a flow rate electronic regulator was used. Methane ŽAlphagaz. was the noninteracting marker and a high purity-grade helium ŽAir Liquide. was the carrier gas. The flow rate was set at 25 mlrmin. The injector and detector temperatures were 358C and 2008C, respectively. All columns were conditioned at 1008C under a stream of helium for 90 min prior to chromatographic measurements. During the experiment, the column temperature was set at 358C. Probe vapours were injected manually at least in triplicate by a Hamilton gastight syringe. To achieve extreme dilution we injected between 0.5 and 40 ml of air–vapor mixture. The retention data were collected with a Borwin JMBS ŽLe Fontanil, France. chromatographic data acquisition system, and the retention times were determined at the peak maxima. Retention time error bars did not exceed 1–2%. Two columns were packed for each polymer and each loading: a short one Ž30 cm. for the strongly sorbed probes and a longer one Ž1 m. for the fast eluted probes. Twenty-

C. Demathieu et al.r Sensors and Actuators B 62 (2000) 1–7 Table 1 Density of polysiloxanes under test

3

3. Results and discussion

Polymer

PMHS

PLF

PBF

PMTFPS

PCPMS

Density Žgrml.

0.99

1.43

1.30

1.30

1.08

three solutes of known physico-chemical properties ŽTable 2. were used to probe the bulk properties of polysiloxanes. They were of high-purity grade and used as received. For more details concerning the solvation energy parameters see text below. 2.3. Data analysis In IGC, probes are injected at infinite dilution and behave independently; thus lateral probe–probe interactions are negligible. Therefore, retention is governed only by stationary phase–probe interactions. The net retention volume VN w19x is defined as the volume of carrier gas required to sweep out an injected probe from the chromatographic column. V N is related to t N , the net retention time, by V N s jFt N

Ž 3.

where j is the compression correction factor and F the corrected carrier gas flow rate.

3.1. Determination of partition coefficients K There are three major retention mechanisms of an injected probe: interaction with the bulk and surface of the polymer Žor any other coating. under test and also the chromatographic support surface. Therefore, the net retention volume corresponds to the sum of the three contributions w19x: VN s K I A I q K S AS q K L VL

Ž 4.

where A I , A S , VL are the polymer surface area, the surface area of the support and the volume of polymer. K I , K S and K L are the partition coefficients for the following corresponding interactions: solute–polymer surface solute–support surface solute–polymer bulk Dividing Eq. Ž4. by V L , one obtains VN VL

sKL q

K I AI VL

q

K S AS

Ž 5.

VL

A plot of the VN rVL ratio vs. 1rVL leads to a curve of which intercept corresponds to the partition coefficient K L Žsee Fig. 2.. It should be noted that an accurate determina-

Table 2 Solutes under study and their physicochemical properties

n-alkanes

Acids

Bases

Aromatics

Solutes

Symbol

T eb Ž8C.

R2

p U2

a 2H

b 2H

log L16

Supplier

Non-specific solutes hexane heptane octane nonane decane

C6 C7 C8 C9 C10

69 98.5 125.5 149 172.5

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

0 0 0 0 0

2.688 3.173 3.677 4.182 4.686

Prolabo normapur min 95.0 Prolabo normapur min 99.0 Fluka) 99% Fluka) 99% Fluka) 98%

Specific solutes chloroform carbon tetrachloride 1,2 dichloroethane ethanol butanol tertbutanol acetonitrile heptene ethyl sulfide tetrahydrofuran methyl acetate methyl ethyl ketone benzene toluene ethylbenzene o-xylene m-xylene p-xylene

CHCl 3 CCl 4 1,2 DCE EtOH BuOH TBA ACN p7 DES THF MA MEC – – EtBenz – – –

60 76.5 83 78.5 117.5 83 81.8 94 91 67 57.4 79.6 80.1 110.6 136.25 144 139 138

0.425 0.458 0.416 0.246 0.224 0.180 0.237 0.092 0.373 0.289 0.142 0.166 0.610 0.601 0.613 0.663 0.623 0.613

0.58 0.28 0.81 0.40 0.40 0.40 0.75 0.08 0.36 0.58 0.60 0.67 0.59 0.55 0.53 0.51 0.51 0.51

0.20 0 0.10 0.33 0.33 0.32 0.09 0 0 0 0 0 0 0 0 0 0 0

0.02 0 0.05 0.44 0.45 0.49 0.44 0.07 0.29 0.55 0.40 0.48 0.14 0.14 0.15 0.17 0.17 0.17

2.480 2.823 2.573 1.485 2.601 2.018 1.560 3.063 3.104 2.534 1.960 2.287 2.803 3.344 3.765 3.937 3.864 3.858

Aldrich 99.8% Prolabo normapur min 99.8 Aldrich 99 q % Prolabo min 99.8 Prolabo normapur min 99.5 Aldrich 99.5% Janssen 99 q % Aldrich 99 q % Aldrich 98 q % Prolabo rectapur 99% Janssen 99% Prolabo Prolabo normapur min 99.8 Prolabo normapur min 99.5 Prolabo Prolabo Prolabo Prolabo

4

C. Demathieu et al.r Sensors and Actuators B 62 (2000) 1–7 Table 3 K L values for each solute–polymer pair. For each solute, the highest K L values are in italics

Fig. 2. Plot of VN r V L vs. 1r VL : determination of K L .

tion of VL is a pre-requisite for the assessment of K L . V L is derived from the density and the mass of stationary phase Žpolymer. contained in each column as determined by weighing Žor TGA in our case.. The experimental determination of K L for some solute–PCPMS pairs is depicted in Fig. 3. The actual V N rVL vs. 1rVL plots for the determination of K L are fitted with a straight line corresponding to the portion of the parabola in Fig. 2 where 1rVL has small values. Indeed, in our case we used polymer loadings up to 2.5% wrw which is fairly high. Therefore, given our mass loadings, there is strong supporting evidence that a straight line is a good approximation of the portion of parabola. A fit with a parabola would have required more experimental data points. The K L values obtained for each solute–polymer pair are reported in Table 3. For each solute we have underlined the highest partition coefficient. PMHS appears as the material which develops the most important dispersive

Fig. 3. Determination of K L for each PCPMS–solute pair: Ža. C6, C7, C8, C9, C10 and p7; Žb. p7, CHCl 3 , CCl 4 , 1,2DCE, benzene and toluene.

C6 C7 C8 C9 C10 P7 CHCl 3 CCl 4 1,2 DCE Benzene Toluene Ethylbenzene o-Xylene m-Xylene p-Xylene DES MEC MA TBA ACN EtOH BuOH THF

PMHS

PLF

PBF

PMTFPS

PCPMS

158 412 1062 2733 6938 379 189 281 254 289 776 1850 2456 1981 2010 414 117 29 y54 y20 y118 272 45

34 73 160 336 722 98 76 92 260 175 456 910 1472 1184 1133 1788 15 372 5620 6401 3834 3637 19 192 27 794

77 186 453 1097 2619 211 117 164 248 246 679 1459 2262 1806 1775 1553 11 274 3740 5367 486 2930 20 372 21 768

43 96 218 499 1080 104 95 100 192 181 435 795 1209 925 926 202 521 242 100 339 y250 545 424

34 78 173 358 737 115 450 202 780 418 995 2075 3116 2265 2215 420 485 169 341 520 239 1705 288

interactions as judged from the interaction strength with n-alkanes Že.g., K L ŽC10–PMHS. s 6938.. It is to note that P7 has almost the same K L with PMHS as for the PMHS–C7 interaction. This is fairly the same trend as for the other polymer–P7 systems. This shows that P7 develops relatively weak specific interactions with the functionalized polysiloxanes. CHCl 3 Žacidic. has the strongest interaction with PCPMS mostly due to the basic character of the cyano group. This is the same trend for the Lewis acidic species 1,2 DCE. As far as CCl 4 is concerned, the highest value of K L is obtained for the sorption in PMHS interaction. However, this interaction is most probably due to dispersive interactions as K L value is intermediate between those of C6 and C7, a trend that is reported for the boiling points of these two n-alkanes and CCl 4 . In contrast, the interaction of CCl 4 with PCPMS appears to be dominated by specific interactions since it is far strongest than the interactions of C6 and C7 with PCPMS. We shall now consider the interaction of aromatic species with the five polysiloxanes. Table 3 shows that all aromatic species interact more favourably with PCPMS. This can be attributed to the interaction of the nitrogen doublet of this polymer with solute aromatic rings. One can also note that PMHS and PBF have a significant affinity for aromatic solutes Ž K L Žethylbenzene–PMHS. s 1850; K L Žethylbenzene–PBF. s 1459.. It is worth noticing the difference of K L values obtained on the one hand with o-xylene on PCPMS Ž K L Ž o-xylene–

C. Demathieu et al.r Sensors and Actuators B 62 (2000) 1–7

PCPMS. s 3116. and on the other hand with m-xylene and p-xylene Ž K L Ž m-xylene–PCPMS. s 2265; K L Ž pxylene–PCPMS. s 2215.. Therefore, steric effects can be suspected. In the case of the alkyl benzene–PCPMS pairs, K L decreases in the order ethylbenzene ) toluene ) benzene which is actually the same trend of the molecular masses. PLF and PBF appear to be the most acidic polymers under study as judged from the K L values obtained with all reference Lewis bases and amphoteric species Žsee Table 3 from DES to THF.. These K L values are at least one order of magnitude higher than those obtained with the other polymers. However, it is quite surprising that K L for the ACN–PLF interaction is one order of magnitude higher than that obtained for ACN–PBF pair. As far as the polymer-mobile phase interface is concerned, one can determine K I by dividing Eq. Ž4. by A I . The polymer surface A I varies with the loading of polymer and was determined by BET. Plotting V N rA I ratio vs. 1rA I , we obtained K I value for each solute–polymer pair. Generally, the K I A I contributions were negligibly small. The chromatographic support contribution was determined in two ways. In the first method, K S A S was obtained from the slope of the plot of VN rVL vs. 1rVL and by subtracting the K I A I contribution. Alternatively, we studied the retention of solutes on a column containing uncoated Chromosorb Žsecond method.. In this case Eq. Ž4. becomes VN s K S AS Ž 6. The support surface was assessed by BET. Whatever the method used, the K S A S contribution was found to be several orders of magnitude smaller than that of K L V L . 3.2. Determination of physicochemical properties of polymers by the linear solÕation energy relationship (LSER) The LSER permits to connect a measured data Žthe partition coefficient. to the physicochemical parameters of the solute and the solvent Žhere polymers.. According to Abraham et al. w25x: DG ( log K L s c q rR 2 q sp U2 q a a 2H q bb 2H q 1 log L16 Ž 7. where R 2 , p U2 , a 2H , b 2H and log L16 parameters refer to the solute whereas r, s, a, b and l are relative to the

5

polymer. R 2 w28x is a calculated excess molar refraction parameter, p U2 w29–32x measures solute dipolarityr polarizability, a 2H w33,34x and b 2H w35,36x are acidity and basicity parameters, respectively, and L16 w37,38x is the gasrliquid partition coefficient of the solute on hexadecane at 258C. L16 is a measure of the dispersive interactions of the solute. Solute solvation parameters were determined for numerous compounds w25,28,37,39–41x, those related to the solutes used in this work are reported in Table 2. The partition coefficients K reported in Table 3 and a fiveparameter multiple regression permitted to determine the physicochemical parameters r, s, a, b and l relative to the stationary phase. These coefficients obtained for PMHS, PMTFPS, PCPMS, PLF and PBF are reported in Table 4. Because of its chemical structure, PMHS develops weak specific interactions except a slight acidity due to the oxygen atoms. It should be noted that polyŽdimethyl siloxane., PDMS, was found to be slightly acidic w42x. On the other hand, the dispersive interactions are important Ž l s 0.846.. The fluor atoms of PMTFPS are polar Ž s s 1.443. and poorly basic Ž a s 0.112.. For the same polymer, Abraham et al. w43x has reported similar values for the s and a parameters Ž1.298 and 0.441, respectively.. Kersten et al. w44x determined a s value of 1.10 which is weaker than the values cited above. Nevertheless, the experiments were carried out at temperature of 1218C instead of 258C in the case of Abraham and 358C in our case. PCPMS is polar Ž s s 1.48. and basic Ž a s 1.997.. This is due to the CN group. These values are weak in comparison with the polyŽbis-cyanopropyl.siloxane of which s and a values are 2.3 and 3.1 at 258C w4,18,43x. The higher s and a values for the cyanopropylsiloxane compared to those of PCPMS are due to the existence of two cyano groups per repeat unit in the former polymer. PLF and PBF behave as very strong acidic species. Their b coefficients are 4.785 and 4.269, respectively. This acidity is due to the presence of hydroxyl groups, acidity strengthened by the very electron attractor fluor atoms. It is to note that the r values of fluorinated polymers are negative as it has been shown elsewhere w28,45x. Returning to the acid–base properties, it is well known that hexafluroisopropanol ŽHFIP. is a very strong, corrosive, reference acid w46x. In addition, Kwei et al. w47x reported on the acidity of a polyŽstyrene-covinylphenyl hexafluoro dimethyl carbinol.. This copolymer

Table 4 Dispersion Ž l ., polarity Ž s ., polarisability Ž r ., basicity Ž a. and acidity Ž b . solvation parameters for the polysiloxanes at 358C

PMHS PLF PBF PMTFPS PCPMS

c

Polarisability Ž r .

Polarity Ž s .

Basicity Ž a.

Acidity Ž b .

Dispersion Ž l .

y0.077 y0.296 y0.331 y0.328 y0.258

0.139 y1.161 y0.979 y0.757 0.167

0.203 1.325 0.744 1.443 1.480

1.025 0.971 1.324 0.112 1.997

y 0.469 4.785 4.269 1.221 0.694

0.846 0.674 0.810 0.721 0.674

6

C. Demathieu et al.r Sensors and Actuators B 62 (2000) 1–7

contained 95% of styrene repeat units and its HFIP-modified styrene moieties had an OH stretching frequency shifts similar to those of HFIP. In our case, it is therefore clear that HFIP confers to polysiloxanes a sharp increase of the acidic behaviour. Fluoropolyol, widely studied in the literature devoted to SAW sensors to detect basic pollutes is less acidic than PLG and PBG with a, b coefficient value of 4.09 at 258C w4,43,48,49x. In the same manner, the b parameters of SFXA 1 and ZDOL 2 are 4.250 and 3.668, respectively w43,48,49x. On the other hand, P4V 3 is more acidic than the PLG with a,b parameter of 5.877 for a temperature of 258C w43,48,49x.

4. Conclusion Polymethyl hydrosiloxane ŽPMHS. and a series of modified polysiloxanes derived from PMHS were characterized by IGC at infinite dilution at 358C. Partition coefficients for the solute–polymer bulk interactions Ž K L . were determined using three polymer mass loadings. These constants were subsequently combined with the well known linear solvation energy relationship ŽLSER. in order to derive physicochemical constants describing dispersive, polar and acid–base interactions. We have reached the following results: 1. PMHS develops few specific interactions. It interacts favourably with n-alkanes and aromatic species. 2. PCPMS appears to be the most basic, polar and polarisable polymer under study. 3. PLF and PBF retain Lewis bases solutes very strongly. This reflects a significantly strong acidic character of these polymers due to hexafluorodimethylcarbinol groups. 4. K L values and the LSER enabled us to derive solvation parameters which will be useful to predict the interaction strength of the polysiloxanes under test with other solutes of known solvation parameters. This work highlights the important role of functionalization of Si–H-terminated polysiloxanes. Our results suggest that PLF and PBF could be used as selective layers in chemical sensors specific for the detection of basic pollutants. The combination of IGC and the LSER appears to be a very powerful approach to characterize and perhaps to predict the interaction strength of polymers with volatile species.

1 SFXA: PolyŽoxymethylw4-hydroxy-4,4,bisŽtrifluoromethyl.but-1-en1-ylxsilylene4.. 2 ZDOL: a-Ž1,1-Difluoro-2-hydroxyethyl.-v-Žoxy-1,1-difluoro-2hydroxyethyl.-polywoxyŽdifluoromethylene.-co-oxyŽ1,1,2,2 - tetrafluoroethylene.x. 3 P4V: Poly  1- w4- Ž2-hydroxy-1,1,1,3,3,3-hexafluoroprop-2-yl . phenylxethylene4.

Acknowledgements The authors would like to thank ADEME for financial support. C.D. is indebted to the french ANRT and Thomson-CSF for 3-year scolarship.

References w1x J. Janata, M. Josowicz, D.M. DeVaney, Chemical sensors, Anal. Chem. 66 Ž1994. 207R–228R. w2x W. Gopel, J. Hesse, J.N. Zemel, Sensors, a comprehensive survey, ¨ in: W. Gopel, T.A. Jones, M. Kleitz, J. Lundstrom, ¨ ¨ T. Seiyama ŽEds.., Chemical and Biochemical Sensors Part I, Vol. 2, 1991. w3x H. Wohltjen, R. Dessy, Surface acoustic wave probe for chemical analysis: I. Introduction and instrument description, Anal. Chem. 51 Ž1979. 1458–1464. w4x G. Harsanyi, Polymer Films in Sensor Applications, Technomic, ´ 1995. w5x S.J. Vigmond, K.M.R. Kallury, V. Ghaemmaghami, M. Thompson, Characterization of the polypyrrole film-piezoelectric sensor combination, Talanta 39 Ž1992. 449–456. w6x J.M. Slater, E.J. Watt, Piezoelectric and conductivity measurements of polyŽpyrrole. gas interactions, Anal. Proc. ŽLondon. 29 Ž1992. 53–56. w7x G.C. Frye, S.J. Martin, Solvent Substitution, Annu. Int. Workshop Solvent Substitution, 1990, p. 215. w8x L.V. Rajakovic, Selectivity of bulk acoustic wave sensor modified with Žaminopropyl.triethoxysilane to nitrobenzene derivatives, J. Serb. Chem. Soc. 56 Ž1991. 521–534. w9x D.W. Galipeau, J.F. Vetelino, R. Lec, C. Feger, The study of polyimide films and adhesion using a surface acoustic wave sensor, Sensors and Actuators B 5 Ž1991. 59–65. w10x D.W. Galipeau, J.F. Vetelino, C. Feger, The study of polyimide film properties and adhesion using a surface acoustic wave sensor, J. Plast. Film Sheeting 8 Ž1992. 258–272. w11x T. Nomura, K. Oobuchi, T. Yasuda, S. Furukawa, Measurement of humidity using surface acoustic wave device, Jpn. J. Appl. Phys. 31 Ž1992. 3070–3072. w12x S.J. Clarson, J.A. Semlyen, Polymer Science and Technology Series, Siloxane Polymers, PTR Prentice Hall, 1993. w13x H.F. Mark, N.M. Bikales, C.G. Overberger, G. Menges, Encyclopedia of Polymer, Science and Engineering, Vol. 15, 2nd edn., Wiley, New York, 1976, pp. 271–298. w14x H. Wohltjen, Mechanism of operation and design considerations for surface acoustic wave device vapor sensors, Sensors and Actuators 5 Ž1984. 307–325. w15x J.W. Grate, M.H. Abraham, Solubility interactions and the design of chemically selective sorbent coatings for chemical sensors and arrays, Sensors and Actuators B 3 Ž1991. 85–111. w16x J.W. Grate, A. Snow, D.S. Ballantine, H. Wohltjen, M.H. Abraham, R.A. Mc Gill, P. Sasson, Determination of partition coefficients from surface acoustic wave vapor sensor responses and correlation with gas–liquid chromatographic partition coefficients, Anal. Chem. 60 Ž1988. 869–875. w17x M.H. Abraham, I. Hamerton, J.B. Rose, J.W. Grate, Hydrogen bonding: XVIII. gas–liquid chromatographic measurements for the design and selection of some hydrogen bond acidic phases suitable for use as coatings on piezoelectric sorption detectors, J. Chem. Soc. Perkin Trans. II Ž1991. 1417–1423. w18x J.W. Grate, R.A. Mc Gill, M.H. Abraham, Chemically selective polymer coatings for acoustic vapor sensors and arrays, Proc. IEEE Ultrason. Symp., Ž1992. 275–279. w19x J.R. Conder, L.C. Young, Physicochemical Measurement by Gas Chromatography, Wiley, Chichester, 1979.

C. Demathieu et al.r Sensors and Actuators B 62 (2000) 1–7 w20x D.R. Lloyd, T.C. Ward, H.P. Schreiber, Inverse Gas Chromatography Characterization of Polymers and Other Materials, ACS Symposium Series no. 391, American Chemical Society, Washington, DC, 1989. w21x Z.Y. Al-Saıgh, ¨ Recent advances in the characterization of polymers and polymer blends using the inverse gas chromatography method, Polym. News 19 Ž1994. 269–279. w22x M.M. Chehimi, S.F. Lascelles, S.P. Armes, Characterization of surface thermodynamic properties of p-toluene sulfonate-doped polypyrrole by inverse gas chromatography, Chromatographia 41 Ž1995. 671–677. w23x M.M. Chehimi, M.-L. Abel, Z. Sahraoui, An inverse gas chromatographic study of the PMMA-conducting polypyrrole interface, J. Adhes. Sci. Technol. 10 Ž1996. 287–303. w24x P. Politzer, J.S. Murray ŽEds.., Quantitative Treatments of SoluterSolvent Interactions, Elsevier, 1994. w25x M.H. Abraham, Scales of solute hydrogen-bonding: their construction and application to physicochemical and biochemical processes, Chem. Soc. Rev. 22 Ž1993. 73–83. w26x C. Demathieu, M.M. Chehimi, J.-F. Lipskier, in preparation. w27x Z.Y. Al-Saıgh, P. Munk, Study of polymer–polymer interaction ¨ coefficients in polymer blends using inverse gas chromatography, Macromolecules 17 Ž1984. 803–809. w28x M.H. Abraham, G.S. Whiting, R.M. Doherty, W.J. Shuely, Hydrogen bonding: Part 13. A new method for the characterization of GLC stationnary phases, the Laffort data set, J. Chem. Soc. Perkin Trans. II Ž1990. 1451–1460. w29x M.H. Abraham, P.L. Grellier, I. Hamerton, R.A. Mc Gill, D.V. Prior, G.S. Whiting, Solvation of gaseous non-electrolytes, Faraday Discuss. Chem. Soc. 85 Ž1988. 107–115. w30x M.J. Kamlet, R.M. Doherty, J.L.M. Abboud, M.H. Abraham, R.W. Taft, Solubility, a new look, Chemtech 16 Ž1986. 566–576. w31x M.H. Abraham, R.M. Doherty, M.J. Kamlet, R.W. Taft, A new look at acids and bases, Chem. Br. 22 Ž1986. 551–553. w32x M.J. Kamlet, R.M. Doherty, M.H. Abraham, R.W. Taft, Quant. Struct.-Act. Relat. 7 Ž1988. 71. w33x M.H. Abraham, P.P. Duce, P.L. Grellier, D.V. Prior, J.J. Morris, P.J. Taylor, Hydrogen-bonding: Part 5. A thermodynamically-based scale of solute hydrogen-bond acidity, Tetrahedron Lett. 29 Ž1988. 1587– 1590. w34x M.H. Abraham, P.L. Grellier, D.V. Prior, P.P. Duce, J.J. Morris, P.J. Taylor, Hydrogen bonding: Part 7. a scale of solute hydrogen-bond acidity based on logK values for complexation in tetrachloromethane, J. Chem. Soc. Perkin Trans. II Ž1989. 699–711. w35x M.H. Abraham, P.L. Grellier, D.V. Prior, J.J. Morris, P.J. Taylor, C. Laurence, M. Berthelot, Hydrogen-bonding: Part 6. A thermodynamically-based scale of solute hydrogen-bond basicity, Tetrahedron Lett. 30 Ž1989. 2571–2574. w36x M.H. Abraham, P.L. Grellier, D.V. Prior, J.J. Morris, P.J. Taylor, Hydrogen bonding. Part 10: A scale of solute hydrogen-bond basicity using logK values for complexation in tetrachloromethane, J. Chem. Soc. Perkin Trans. II Ž1990. 521–529. w37x M.H. Abraham, P.L. Grellier, R.A. McGill, Determination of olive oil–gas hexadecane-gas partition coefficients, and calculation of the corresponding olive oil–water and hexadecane–water partition coefficients, J. Chem. Soc. Perkin Trans. II Ž1987. 797–803. w38x M.H. Abraham, R. Fuchs, Correlation and prediction of gas–liquid partition coefficients in hexadecane and olive oil, J. Chem. Soc. Perkin Trans. II Ž1988. 523–527. w39x M.H. Abraham, G.S. Whiting, R.M. Doherty, W.J. Shuely, Hydro-

w40x

w41x

w42x w43x

w44x w45x

w46x

w47x w48x w49x

7

gen bonding: XVI. A new solvation parameter p 2H from gas chromatographic data, J. Chromatogr. 587 Ž1991. 213–228. M.H. Abraham, G.S. Whiting, Hydrogen bonding: XXI. Solvation parameters for alkylaromatic hydrocarbons from gas–liquid chromatographic data, J. Chromatogr. 594 Ž1992. 229–241. M.H. Abraham, Hydrogen bonding: XXVII. Solvation parameters for functionally substituted aromatic compounds and heterocyclic compounds from gas–liquid chromatographic data, J. Chromatogr. 644 Ž1993. 95–139. S. Ross, N. Nguyen, Interactions of polyŽdimethylsiloxane. with Lewis bases, Langmuir 4 Ž1988. 1188–1193. M.H. Abraham, J. Adonian-Haftvan, C.M. Du, V. Diart, G.S. Whiting, J.W. Grate, R.A. McGill, Hydrogen bonding. Part 29: Characterization of 14 sorbent coatings for chemical microsensors using a new solvation equation, J. Chem. Soc. Perkin Trans. II Ž1995. 369–378. B.R. Kersten, S.K. Poole, C.F. Poole, J. Chromatogr. 411 Ž1989. 43. M.H. Abraham, G.S. Whiting, R.M. Doherty, W.J. Shuely, Hydrogen bonding: XV. A new characterization of the McReynolds 77stationnary phase set, J. Chromatogr. 518 Ž1990. 329–348. F.L. Riddle Jr., F.M. Fowkes, Spectral shifts in acid–base chemistry: 1. van der Waals contributions to acceptor numbers, J. Am. Chem. Soc. 112 Ž1990. 3259–3264. T.K. Kwei, E.M. Pearce, F. Ren, J.P. Chen, J. Polym. Sci. Polym. Phys. Ed. 24 Ž1986. 1597. R.A. McGill, M.H. Abraham, J.W. Grate, Choosing polymer coatings for chemical sensors, Chemtech 24 Ž1994. 27–37. J.W. Grate, S.J. Patrash, M.H. Abraham, Method for estimating polymer-coated acoustic wave vapor sensor responses, Anal. Chem. 67 Ž1995. 2162–2169.

Mohamed M. Chehimi Graduated in Physical Chemistry at Universite´ Paris 7 ŽUP7. in 1982. He obtained a Master of Physical Organic Chemistry in 1983 and PhD in 1988. He joined the CNRS ŽCentre National de la Recherche Scientifique. in 1989 as a permanent researcher and collaborated with the ESCA group at the University of Surrey ŽUK. as a visiting scientist in 1990. His main research topics concern the characterization of molecular interactions at interfaces. He is leader of the Surface Interface Adhesion group Ž «ESCA group». within ITODYS since 1997. Caroline Demathieu obtained the Maıtrise de Chimie-Physique Žgraduaˆ tion. and the Diplome ˆ d’Etudes Approfondies ŽMaster. in Spectrochimie from the University of Paris VII in 1994. She worked for 3 years both at ŽITODYS. of the Institut de Topologie et de Dynamique des Systemes ` the University of Paris VII and the Central Research Laboratory of Thomson-CSF, on the study of polymer–gas interactions to realize chemical sensors. She received her PhD in Spectrochimie in 1998. Jean-Franc¸ois Lipskier graduated as an Engineer from the Ecole Nationale Superieure de Chimie de Paris and hold a PhD in Physical ´ Chemistry from the University of Paris XI. Specializing in the Chemical Physics of organic materials, J.-F. Lipskier worked for 3 years both in France at the Centre d’Etudes de Saclay ŽCommissariat a` l’Energie Atomique. and in Canada at the Department of Nuclear Medicine and Radiology of the University of Sherbrooke, on the study of photoinduced electron and energy transfers in supramolecular assemblies by ultra-fast spectroscopy. In 1991 he joined the Central Research Laboratory of Thomson-CSF and soon started studying chemical sensors. He presently manages several research projects in this field.