Fundamentals and Applications of Chemical Sensors - American

18 Amidoxime-Functionalized Coatings for Surface Acoustic Wave Detection of Simulant Vapors 1

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Neldon L. Jarvis , John Lint , Arthur W. Snow , and Hank Wohltjen

Downloaded by CORNELL UNIV on September 2, 2016 | http://pubs.acs.org Publication Date: May 29, 1986 | doi: 10.1021/bk-1986-0309.ch018

Chemistry Division, U.S. Naval Research Laboratory, Washington, DC 20375-5000

The objective of the work was to prepare coatings for a surface acoustic wave (SAW) sensor that would have a chemical specificity and sensitivity toward phosphonate ester agent simulants. Butadiene-acrylonitrile-acryl amidoxime terpolymer coatings of varying composition were prepared and evaluated for chemical sensitivity toward methanesulfonyl fluoride (MSF) and dimethyl methylphosphonate (DMMP) simulants. Chemical reac tivity was monitored by infrared spectroscopy, and physical adsorption by SAW frequency measurements. The amidoxime functional group did not react rapidly and quantitatively with the MSF vapor. Both simulants were physically adsorbed by the coating the degree of which is correlated with solubility parameters, vapor pressures and glass transition temperatures. The preparation of thin film coatings with highly sensitive and specific absorption for particular vapors is a critical requirement for the development of chemical electronic microsensors as point detectors. In this work, coatings which have a specific interaction with simulants for nerve agents are being investigated using a SAW device. The SAW device detects extremely small gravimetric changes in a coating by registering a frequency shift in the resonance of the piezoelectric substrate. Previous work from this laboratory has employed a model reactive polymer-vapor system based on the DielsAlder reaction between poly(ethylene maleate) and cyclopentadiene to learn how the SAW sensor responds to reactive and non-reactive vapors Ο ) . In addition to discrimination between physisorption and 'Current address: Chemical Research and Development Center, U.S. Army, Aberdeen Proving Grounds, MD 21010 Current address: 5536 Fillmore Ave., Alexandria, VA 22311 Author to whom correspondence should be addressed. 'Current address: Microsensor Systems, Inc., P.O. Box 90, Fairfax, VA 22030

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This chapter not subject to U.S. copyright. Published 1986, American Chemical Society

Schuetzle and Hammerle; Fundamentals and Applications of Chemical Sensors ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

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FUNDAMENTALS AND APPLICATIONS OF CHEMICAL SENSORS


c h e m i s o r p t i o n , i t was a l s o l e a r n e d t h a t good s e n s i t i v i t y i s dependent on t h e p o l y m e r i c f i l m m a t r i x b e i n g above i t s g l a s s t r a n s i t i o n t e m p e r a t u r e f o r e f f i c i e n t permeation o f t h e vapor. I n t h i s work t h e o b j e c t i v e i s t o i n c o r p o r a t e a f u n c t i o n a l group, t h a t has s p e c i f i c r e a c t i v i t y toward nerve agent s i m u l a n t s , i n t h e t h i n f i l m c o a t i n g o f a SAW d e v i c e a n d t o e v a l u a t e t h e d e t e c t o r ' s response t o t h e simul a n t ' s v a p o r . The amidoxime was s e l e c t e d as t h e r e a c t i v e f u n c t i o n a l g r o u p a n d m e t h a n e s u l f o n y l f l u o r i d e (MSF) (MSF has been p a t e n t e d as a s i m u l a n t f o r t h e n e r v e agent GB ( 2 ) ) and d i m e t h y l methylphosphonate (DMMP) were s e l e c t e d a s r e a c t i v e and n o n - r e a c t i v e agent s i m u l a n t s . ( C a u t i o n : MSF i s t o x i c ( a n t i c h o l i n e s t e r a s e a c t i v i t y ) and s h o u l d be h a n d l e d w i t h g l o v e s a n d g a s - t i g h t s y r i n g e s i n an e f f i c i e n t hood.) The s y n t h e s i s , c h a r a c t e r i z a t i o n a n d SAW d e t e c t o r r e s p o n s e a r e described i n this report. Experimental A l l r e a g e n t s a n d s o l v e n t s were o f reagent grade q u a l i t y , purchased c o m m e r c i a l l y and used without f u r t h e r p u r i f i c a t i o n unless otherwise n o t e d . I n f r a r e d s p e c t r o s c o p i c d a t a were o b t a i n e d w i t h a P e r k i n - E l m e r 267. G l a s s t r a n s i t i o n temperatures were determined by d i f f e r e n t i a l s c a n n i n g c a l o r i m e t r y w i t h a Dupont 990 Thermal A n a l y z e r and a 910 D i f f e r e n t i a l Scanning Calorimeter. P o l y m e r s o l u b i l i t y parameters were d e t e r m i n e d b y measuring weight p e r c e n t s w e l l i n g i n s o l v e n t s o f v a r y i n g s o l u b i l i t y p a r a m e t e r ( w a t e r , 23.4 ( c a l / m l ) ^ ^ . methanol, 14.5; e t h a n o l , 1 2 . 7 ; 2 - p r o p a n o l , 1 1 . 5 ; t - b u t y l a l c o h o l , 1 0 . 6 ; a c e t o n e , 1 0 . 0 ; t e t r a h y d r o f u r a n , 9.5; e t h y l a c e t a t e , 9.5; c a r b o n t e t r a c h l o r i d e , 8.6; c y c l o h e x a n e , 8.2; d i e t h y l e t h e r , 7.4; benzene, 9.2; methylene c h l o r i d e , 9.7; n-pentane, 7.0) a f t e r 12 h r . immersion. SAW d e v i c e s were coated by s o l v e n t e v a p o r a t i o n from a d i l u t e polymer s o l u t i o n p l a c e d on t h e d e v i c e s u r f a c e . I n e r t atmosphere d i l u t i o n o f s i m u l a n t v a p o r s a n d SAW f r e q u e n c y measurements have been d e s c r i b e d previously.(3) The butadiene (80%)-acrylonitrile(17%)-acrylamidoxime(3%) t e r p o l y m e r was p r e p a r e d b y r e a c t i n g 2.5g b u t a d i e n e ( 8 0 % ) - a c r y l o n i t r i l e ( 2 0 % ) c o p o l y m e r ( A l d r i c h ) i n 150 ml x y l e n e w i t h 1.61g h y d r o x y l a m i n e h y d r o c h l o r i d e i n 12 ml n-butanol ( f r e e d o f HCl immediately b e f o r e a d d i t i o n by method o f H u r d ( 4 ) by d r o p w i s e a d d i t i o n under n i t r o g e n . R e a c t i o n time and temperature were 23 h r . and 90-95°C. The p o l y m e r p r o d u c t was worked up by s l o w l y adding t h e r e a c t i o n m i x t u r e t o 500 m l e t h e r w i t h r a p i d s t i r r i n g . The p r e c i p i t a t e d polymer was a l l o w e d t o s e t t l e , t h e supernate decanted and t h e polymer resuspended and washed w i t h two 100 m l p o r t i o n s o f e t h e r f o l l o w e d by vacuum drying. Y i e l d 2.04g ( 8 1 % ) . C o n v e r s i o n o f n i t r i l e f u n c t i o n a l groups t o amidoxime groups was 15% by i n f r a r e d a b s o r p t i o n . The b u t a d i e n e ( 5 5 % ) - a c r y l o n i t r i l e ( 3 8 % ) - a c y l a m i d o x i m e ( 7%) t e r p o l y m e r was p r e p a r e d by r e a c t i n g 2.00g b u t a d i e n e ( 5 5 % ) - a c r y l n i t r i l e ( 4 5 % ) c o p o l y m e r i n 50 m l t e t r a h y d r o f u r a n w i t h 1.46g h y d r o x y l a m i n e h y d r o g e n c h l o r i d e ( f r e e d o f H C l ( 5 ) ) i n 12 ml n-butanol a t 70°C f o r 18 h r s . u n d e r n i t r o g e n . The p r o d u c t was worked up a n a l o g o u s l y t o t h e 3% a m i d o x i m e t e r p o l y m e r . Y i e l d and conversion t o amidoxime were 2.02g (91%) and 15%, r e s p e c t i v e l y . The b u t a d i e n e ( 5 5 % ) - a c r y l a m i d o x i m e ( 4 5 % ) t e r p o l y m e r was prepared by r e a c t i n g 2.00g b u t a d i e n e ( 5 5 % ) - a c r y l o n i t r i l e ( 4 5 % ) copolymer i n 50 ml t e t r a h y d r o f u r a n w i t h 2.92g h y d r o x y l amine hydrogen c h l o r i d e ( f r e e d


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of H C l ( 5 ) ) i n 25 ml n - b u t a n o l a t 75-80°C f o r 24 h r s . under n i t r o g e n . The p r o d u c t was worked up a n a l o g o u s l y t o t h e 3% amidoxime t e r p o l y m e r . Y i e l d a n d c o n v e r s i o n t o amidoxime were 2.45g (96%) and 100%, respectively.


R e s u l t s and D i s c u s s i o n The s e l e c t i o n o f t h e amidoxime f u n c t i o n a l group was based on s e v e r a l c o n s i d e r a t i o n s . As a r e a s o n a b l y w e l l u n d e r s t o o d organophosphonate CW agent s p e c i f i c r e a c t i o n , t h e n u c l e o p h i l i c phosphorylation reaction was c h o s e n . I t was d e s i r e d t o employ a n e u t r a l , h i g h l y n u c l e o p h i l i c f u n c t i o n a l g r o u p t h a t c o u l d r e a d i l y be c o v a l e n t l y a t t a c h e d t o a u n i f o r m t h i n - f i l m - f o r m i n g p o l y m e r i c m a t r i x and undergo a p h o s p h o r y l a t i o n r e a c t i o n w i t h an a g e n t v a p o r . Of t h e common n u c l e o p h i l i c g r o u p s s t u d i e d ( 5 - 8 ) ( h y d r o x a m i c a c i d s , o x i m e s a n d p h e n o l s ) most r e q u i r e a b a s i c s o l u t i o n medium s i n c e t h e c o n j u g a t e a n i o n i s t h e reactive species. The a m i d o x i m e g r o u p a p p e a r e d t o be a p o s s i b l e exception. I n i t s n e u t r a l s t a t e t h e amidoxime i s r e p o r t e d t o have a s t r o n g e r n u c l e o p h i l i c i t y i n a c y l a t i o n ( 9 ) and p h o s p h o r y l a t i o n (10) r e a c t i o n s t h a n does t h e o x i m e . A t room temperature amidoximes a r e r e a d i l y a c y l a t e d b y a c i d h a l i d e s o r a n h y d r i d e s ( II) . Possible schemes f o r t h e c h e m i s t r y o f t h i s r e a c t i o n w i t h MSF a r e d e p i c t e d i n F i g u r e 1. I t i s a l s o worth n o t i n g t h a t t h e amidoxime i s a p o w e r f u l h y d r o g e n b o n d i n g g r o u p , and h y d r o g e n bonded complexes can a l s o be envisioned. T h a t t h e f u n c t i o n a l g r o u p be r e a c t i v e i n i t s n e u t r a l s t a t e i s n e c e s s a r y i f t h e p o l y m e r i c m a t r i x t o which i t i s a t t a c h e d i s t o m a i n t a i n a p e r m e a b l e rubbery c h a r a c t e r . From a c o n s i d e r a t i o n o f s y n t h e t i c a c c e s s i b i l i t y , t h e n i t r i l e group o f a b u t a d i e n e - a c r y l o n i t r i l e r u b b e r may be c o n v e r t e d t o an a m i d o x i m e b y r e a c t i o n w i t h hydroxylamine ( E q u a t i o n 1 ) .

NH QH 2

The r e l a t i v e i n i t i a l r a t i o o f a c r y l o n i t r i l e t o b u t a d i e n e and d e g r e e o f c o n v e r s i o n o f n i t r i l e t o amidoxime a r e d i r e c t l y r e l a t e d t o the r e s u l t a n t f i l m ' s s o l u b i l i t y parameter and g l a s s t r a n s i t i o n temperature. I d e a l l y , t h e c o n c e n t r a t i o n o f amidoxime f u n c t i o n a l groups would be maximized w h i l e t h e c o a t i n g ' s s o l u b i l i t y parameter i s matched t o t h e vapor t o be d e t e c t e d and t h e g l a s s t r a n s i t i o n temperat u r e i s k e p t b e l o w room t e m p e r a t u r e . I n p r a c t i c e , the conversion l i m i t a t i o n s a r e s e t b y t h e r e a c t i o n c o n d i t i o n s o f l i m i t e d polymer s o l u b i l i t y , r e a c t i o n temperature and time. Three terpolymers of v a r y i n g b u t a d i e n e , a c r y l o n i t r i l e a n d a m i d o x i m e c o m p o s i t i o n s were p r e p a r e d as i n d i c a t e d i n T a b l e 1. The i n f r a r e d s p e c t r a o f t h e b u t a d i e n e - a c r y l o n i t r i l e copolymer and b u t a d i e n e - a c r y l o n i t r i l e - a c r y l a m i d o x i m e t e r p o l y m e r s a r e p r e s e n t e d i n F i g u r e 2. The a m i d o x i m e s p e c i f i c bands appear a t 3480 and 3380 cm" (NH2 s t r e t c h i n g ) a n d a t 1660 cm" (C=N s t r e t c h i n g ) ( 12!). The g l a s s t r a n s i t i o n temperatures and s o l u b i l i t y parameters o f t h e c o r r e s p o n d i n g p o l y m e r s a r e a l s o p r e s e n t e d i n T a b l e 1. A s t h e a e r y l a m i d o x i m e c o n t e n t i n c r e a s e s from 3 t o 7 t o 45 mole p e r c e n t , t h e 1

1



312

Fig. 1


P o s s i b l e R e a c t i o n Schemes f o r Amidoxime w i t h M e t h a n e s u l f o n y l Fluoride.



Fig.

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IR S p e c t r a of B u t a d i e n e - A c r y l o n i t r i l e - A m i d o x i m e Copolymers. I n s e r t e d s t r u c t u r e s I n d i c a t e copolymer c o m p o s i t i o n s but not microstructures.


314


c o r r e s p o n d i n g Tg i n c r e a s e s f r o m -35 t o 19 t o 50°C, and s o l u b i l i t y parameter i n c r e a s e s from 9.3 t o 9.7 t o 16 ( c a l / c m ) . 3

1

TABLE 1 C o m p o s i t i o n , S o l u b i l i t y Parameter and G l a s s T r a n s i t i o n Temperature o f ( B u t a d i e n e ) - ( A c r y l o n i t r i l e ) - ( A c r y l a m i d o x i m e ) Terpolymers x


Terpolymer 1 2 3

v

x(%)

y(%)

z(%)

80 55 55

17 38 0

3 7 45

3

1

«(cal/cm ) / 9.3 9.7 16

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Tg(°C) -35 19 50

The i n t e r a c t i o n o f t h e acrylamidoxime polymer c o a t i n g s w i t h t h e MSF a n d DMMP s i m u l a n t vapors was i n v e s t i g a t e d by i n f r a r e d s p e c t r o s copy and by t h e SAW d e v i c e response. The i n f r a r e d e x p e r i m e n t c o n s i s t e d o f p l a c i n g a c o a t i n g on a s o d i u m c h l o r i d e d i s c by s o l v e n t e v a p o r a t i o n f r o m a t e r p o l y m e r s o l u t i o n a n d e x p o s i n g i t t o a s a t u r a t e d s i m u l a n t atmosphere i n a c l o s e d c o n t a i n e r f o r one hour. The NaCl d i s c supported f i l m was then i m m e d i a t e l y t r a n s f e r r e d t o an i n f r a r e d s p e c t r o m e t e r , and t h e t r a n s m i s s i o n spectrum obtained. The s p e c t r a o f t h e exposed 7% amidoxime t e r p o l y m e r t o g e t h e r w i t h t h e s p e c t r a o f t h e l i q u i d simulants are p r e s e n t e d i n F i g u r e 3. I n t h e c a s e w i t h MSF, t h e spectrum o f t h e exposed polymer i s m o s t l y an a d d i t i v e s u p e r p o s i t i o n i n g o f t h e s p e c t r a o f t h e u n e x p o s e d polymer and t h e l i q u i d s i m u l a n t . The shaded bands a t 1210 a n d 1400 cm"" , w h i c h correspond t o t h e 0*S«0 symmetric and a s y m m e t r i c s t r e t c h i n g (1^2), a r e p a r t i c u l a r l y p e r t i n e n t . I f t h e f l u o r i d e i o n were n u c l e o p h i l i c a l l y d i s p l a c e d , a 50 cm" s h i f t o f these bands s h o u l d r e s u l t ( 1 2 ) . T h i s indeed may be t h e source o f t h e weak new band a t 1178 cnT^T b u t t h e r e a c t i o n between t h e a c r y l a m i d oxime f u n c t i o n a l g r o u p a n d t h e MSF v a p o r i s n e i t h e r r a p i d n o r quantitative. I n t h e c a s e w i t h DMMP, a s i m i l a r predominant p h y s i s o r p t i o n i s a l s o observed as i n d i c a t e d i n F i g u r e 3. S i n c e t h e SAW d e v i c e i s e x t r e m e l y s e n s i t i v e t o s m a l l g r a v i m e t r i c c h a n g e s c a u s e d b y a d s o r p t i o n o f v a p o r s i n supported f i l m s , t h e r e i s s t i l l p o t e n t i a l f o r these c o a t i n g s as t h i n f i l m d e t e c t i o n elements. T h i n f i l m s o f t h e amidoxime t e r p o l y m e r s were p l a c e d on SAW d e v i c e s by solvent evaporation. The d e v i c e was then c h a l l e n g e d w i t h 500 t o 3000 ppm c o n c e n t r a t i o n l e v e l s o f s i m u l a n t vapor i n a p u r i f i e d a i r c a r r i e r c o n t i n u o u s f l o w e x p o n e n t i a l d i l u t i o n gas system. Device responses were r e c o r d e d as n e g a t i v e resonant frequency s h i f t s as a f u n c t i o n o f time. T y p i c a l d a t a f o r 1000 ppm c h a l l e n g e s o f MSF a n d DMMP a r e p r e s e n t e d i n F i g u r e 4. The i n i t i a l 200 seconds, where no response o c c u r s , i s used t o e s t a b l i s h a b a s e l i n e p r i o r t o s y r i n g e i n j e c t i o n o f the c h a l l e n g e vapor. A s t h e s i m u l a n t v a p o r i s swept f r o m t h e d i l u t i o n f l a s k t o t h e d e v i c e , a n e g a t i v e frequency s h i f t i s observed as t h e v a p o r a d s o r b s on t h e SAW c o a t i n g . With passage o f time and d i l u t i o n o f s i m u l a n t i n the flowing a i r , desorption o f the simulant 1

1



Fig.

3

IR Spectra of Butadiene (BD)-Acrylonitrile(AN)-Acrylamidoxime (AX) Terpolymer Exposed to Methanesulfonyl Fluoride (MSF) and Dimethyl Methylphosphonate (DMMP) Simulants.



Fig.

4

SAW D e v i c e ( 7 % A c r y l a m i d o x i m e Terpolymer c o a t i n g ) Response t o 1000 ppm MSF and DMMP.


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may o c c u r d e p e n d i n g on t h e s t r e n g t h o f the c o a t i n g - s i m u l a n t i n t e r a c t i o n a n d v a p o r p r e s s u r e o f the s i m u l a n t s i m i l a r t o the s i t u a t i o n observed i n gas chromatography. The MSF, which i s more v o l a t i l e than t h e DMMP, desorbs much more r a p i d l y and produces a s m a l l e r frequency shift. The s e n s i t i v i t y o f t h e c o a t e d d e v i c e may be a s s e s s e d by p l o t t i n g t h e maximum f r e q u e n c y s h i f t a g a i n s t t h e s i m u l a n t vapor c o n c e n t r a t i o n t h a t w o u l d m a x i m a l l y be o b t a i n e d i n the e x p o n e n t i a l dilution flask. T h i s d a t a i s p r e s e n t e d i n F i g u r e 5 f o r the t h r e e amidoxime t e r p o l y m e r s . Two i m p o r t a n t o b s e r v a t i o n s a r e : (a) the 7% a m i d o x i m e t e r p o l y m e r i s t h e most s e n s i t i v e t o e i t h e r MSF o r DMMP w h i l e the 45% amidoxime t e r p o l y m e r i s the l e a s t s e n s i t i v e and (b) t h e o r d e r o f s e n s i t i v i t y t o MSF and DMMP i s r e v e r s e d on p r o g r e s s i o n from the 7 t o 45% amidoxime t e r p o l y m e r . The l a r g e d r o p i n o v e r a l l s e n s i t i v i t y c o r r e l a t e s w i t h t h e g l a s s t r a n s i t i o n temperature i n c r e a s i n g above room temperature. As the i n c r e a s i n g c o n c e n t r a t i o n o f a m i d o x i m e f u n c t i o n a l groups causes the room temperature c h a r a c t e r o f t h e c o a t i n g t o c h a n g e f r o m r u b b e r y t o g l a s s y , the vapor permeation r a t e d e c r e a s e s r a p i d l y w i t h an accompanying decrease i n g r a v i m e t r i c sensitivity. The o r d e r o f s e n s i t i v i t y b e t w e e n MSF and DMMP c o r r e l a t e s w i t h t h e s o l u b i l i t y parameter match o f the c o a t i n g w i t h the s i m u l a n t a n d w i t h t h e r e l a t i v e vapor p r e s s u r e o f the s i m u l a n t ( 1 3 ) . The s o l u b i l i t y p a r a m e t e r s f o r DMMP ( c a l c u l a t e d from heat o f v a p o r i z a t i o n a n d m o l a r v o l u m e d a t a (_14)) and MSF (15) are 10.5 and 11.3 ( c a l / c m ) 1 , r e s p e c t i v e l y . The c l o s e r the match between s i m u l a n t and c o a t i n g s o l u b i l i t y p a r a m e t e r s , the more c o m p a t i b l e w i l l be the thermodynamic i n t e r a c t i o n f o r a d s o r p t i o n ; and the lower the s i m u l a n t s vapor p r e s s u r e , t h e slower t h e d e s o r p t i o n r a t e and g r e a t e r t h e accumulation o f adsorbed simulant. The 3 a n d 7% a m i d o x i m e t e r p o l y m e r s a r e r u b b e r y c o a t i n g s a n d more c l o s e l y m a t c h t h e DMMP s o l u b i l i t y parameter w h i l e t h e 45% amidoxime i s a r i g i d g l a s s y c o a t i n g and i s a b e t t e r match t o the MSF s o l u b i l i t y parameter. 3

1

2

Conclusions I n summary, t e r p o l y m e r s o f b u t a d i e n e , a c r y l o n i t r i l e and a c r y l a m i d oxime o f v a r y i n g comonomer c o n t e n t s were p r e p a r e d b y r e a c t i n g b u t a d i e n e - a c r y l o n t r i l e copolymers w i t h hydroxylamine. Infrared s p e c t r o s c o p y i n d i c a t e d t h a t i n c o r p o r a t i o n o f the amidoxime f u n c t i o n a l g r o u p i n t h e t e r p o l y m e r c o a t i n g was s u c c e s s f u l but t h a t a s e l e c t i v e a b s o r p t i o n o f t h e c h e m i c a l s i m u l a n t MSF based on a s p e c i f i c r e a c t i v i t y was not a c h i e v e d . I n s t e a d , b o t h the p h y s i c a l and the c h e m i c a l s i m u l a n t s were a b s o r b e d on t h e b a s i s o f t h e i r p h y s i c a l p r o p e r t i e s (i.e. s o l u b i l i t y parameter and vapor p r e s s u r e ) . When t h i n f i l m s o f t h e s e t e r p o l y m e r s a r e c o a t e d on a SAW d e v i c e , the a d s o r p t i o n o f the c h e m i c a l s i m u l a n t MSF and p h y s i c a l s i m u l a n t DMMP i s r e a d i l y d e t e c t a b l e a n d v a r i e s w i t h the c o a t i n g ' s g l a s s t r a n s i t i o n temperature and s o l u b i l i t y p a r a m e t e r a l t h o u g h no r a p i d o r q u a n t i t a t i v e c h e m i c a l r e a c t i o n was observed between the amidoxime f u n c t i o n a l group and the MSF v a p o r . C o r r e l a t i o n s a r e o b s e r v e d b e t w e e n t h e SAW d e t e c t o r s e n s i t i v i t y a n d t h e g l a s s t r a n s i t i o n temperature o f the c o a t i n g and between t h e s o l u b i l i t y parameter match o f t h e c o a t i n g and t h e simulant vapors. The o b j e c t i v e o f e m p l o y i n g f u n c t i o n a l g r o u p c h e m i s t r y f o r d i s c r i m i n a t i o n between c h e m i c a l and p h y s i c a l s i m u l a n t s was n o t a c h i e v e d . The i s s u e o f c o a t i n g s p e c i f i c i t y d e f i n e d as a u n i q u e a b s o r p t i o n o f a p a r t i c u l a r vapor and e x c l u s i o n o f a l l o t h e r s



318

3C 400

Tg

Ο

-35 °C

φ

1/2

δ

9.4

200

DMMP

(Τ Φ

LL

(cal/cm )

100


600

1200

1800

2400

3000

V a p o r C o n c e n t r a t i o n (ppm) 5001

Tg

DMMP

19 °C 1/2

9.7 (cal/cm )

600

1200

1800

2400

3000

V a p o r C o n c e n t r a t i o n (ppm)

Ν I

4BD> 55 Tg

I

400

CO

50 °C 1/2 3

16 (cal/cm )

>> ο c φ

σ

MSF

Φ

0

600

1200

1800

2400

3000

V a p o r C o n c e n t r a t i o n (ppm)

Fig. 5

MSF and DMMP Vapor Concentration Dependence of SAW Device Coated with 3,7 and 45% Aerylamidoxime Terpolymers and Correlation with Terpolymer Glass Transition Temperature and S o l u b i l i t y Parameter.


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has yet to be successfully addressed. Clearly, more elegant chem istry than simple functionalization of polymeric coatings is neces sary if a single SAW measurement is to be employed for detection of particular vapors in the presence of interference vapors. Acknowledgment This work was supported by the U.S. Army Chemical Research and Development Center. Literature Cited


1. 2. 3.

Snow, A.W.; Wohltjen, Η., Anal. Chem., 1984, 56, 1411. Poziomek, E.J.; Crabtree, E.V., U.S. Patent 3,972,783, 1976. Wohltjen, H., Proceedings Report No. ARCSL-SP-83030, Chemical Defense Research Conference, U.S. Army Chemical Research and Development Center, 1982. 4. Hurd, C.D.; Browstein, H.J., J. Am. Chem. Soc., 1925, 47, 67. 5. Hackley, B.E.; Plapinger, R.; Stolberg, M.; Wagner-Jauregg, T., J. Am. Chem. Soc., 1955, 77, 3651. 6. Davies, D.R.; Green, A.L., Disc. Faraday Soc., 1955, 70, 269. 7. Epstein, J.; Michel, H.O.; Rosenblatt, D.H.; Plapinger, R.E.; Stephani, R.H.; Cook, E., J. Am. Chem. Soc., 1964, 86, 4959. 8. Snow, A.W.; Wohltjen, H.; Jarvis, N.L.; Dominguez, D., NRL Memorandum Report 5050, 1983. 9. Aubort, J.D.; Hudson, R.F., J. Chem. Soc. Chem. Comm., 1969, 1342. 10. Bunton, C.A.; Cerichelli, G., J. Org. Chem., 1979, 44, 1880. 11. Eloy, F.; Lenaers, R., Chem. Rev.,1962, 62, 155. 12. Avram, M.; Mateescu, GH.D., "Infrared Spectroscopy", Wiley -Interscience, New York, NY, 1972, pp. 296-298. 13. Wohltjen, H.; Snow, A.W.; Lint, J.; Jarvis, N.L., Proceedings Report No. CRDC-SP-84014, Chemical Defense Research Conference, U.S. Army Chemical Research and Development Center, 1984. 14. Kosolapoff, G.M., J. Chem. Soc., 1955, 2964. 15. Snow, A.W., manuscript in preparation. RECEIVED November 14, 1985


Fundamentals and Applications of Chemical Sensors - American

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