The Effects of Hostile Environments on Coatings and Plastics

8 Model Fungicidal Monomers, Polymers, and Latices for Paints CHARLES U. PITTMAN, JR. Chemical Consultant, 132 Woodland Forrest, Tuscaloosa, A L 35405 The Effects of Hostile Environments on Coatings and Plastics Downloaded from pubs.acs.org by YORK UNIV on 12/03/18. For personal use only.

G. A L L A N STAHL Phillips Petroleum Company, Research and Development, Bartlesville, OK 74004

Summary

When a biocide is simply mixed into a paint it may subse quently be lost from the painted surface by leaching or vapori zation. To overcome this problem several biocidal compounds have been converted to vinyl monomers and subsequently incorpor ated into homo-, co-, and terpolymers. Latices have been pre pared for several systems. Since mildew defacement of painted surfaces is widespread problem, we have concentrated on polymer anchoring of fungicidal compounds and compounds with wide bio cidal activity. These included pentachlorophenol, 8-hydroxyquinoline, 2-(4'-thiozoyl)benzimidazole, 3,4',5-tribromosalicylanilide, o-benzyl-p-chlorophenol, o-acrylyl salicylanilide and 2-mercapto-pyridine-N-oxide. The reactivity ratios of the bio cidal monomer, pentachlorophenyl acrylate, were obtained with both vinyl acetate and ethyl acrylate. While it is possible that some biocides may function when incorporated into a macromolecule, it seems likely that many biocides must be released from the polymer to be active. Thus, the biocidal monomers were incorporated into the polymers using functions with different hydrolytic propensities. These included, fungicidal acrylates, 2-fungicidalethyl acrylates, and fungicidal vinyl ethers. The polymerization behavior of several such monomers was examined. S t a b l e terpolymer l a t i c e s were prepared from methyl methacrylate, η-butyl a c r y l a t e and each o f the f o l l o w i n g f u n g i c i d a l monomers: (1) pentachlorophenyl a c r y l a t e , (2) 2-pentachlorophenoxyethyl a c r y l a t e , (3) 2 - ( 8 - q u i n o l i n y l o x y ) e t h y l a c r y l a t e , (4) a c r y l o y l o x y 3 , 4 , 5 - t r i b r o m o s a l i c y l a n i l i d e , (5) 2 - ( 2 - a c r y l o y l e t h o x y ) - 3 , 4 , 5 t r i b r o m o s a l i c y l a n i l i d e , (6) 2-(o-benzyl-p-chlorophenoxy)ethyl a c r y l a t e and (7) v i n y l o-benzyl-p-chlorophenyl ether. A t e r polymer l a t e x o f v i n y l a c e t a t e , 2-ethylhexyl a c r y l a t e and a c r y l o y l o x y - 3 , 4 , 5 - t r i b r o m o s a l i c y l a n i l i d e was made. A l a t e x c o n t a i n i n g pentachlorophenol bound by two d i f f e r e n t r e l e a s i n g groups and a l a t e x with two d i f f e r e n t f u n g i c i d a l monomers was made. 1

1

f

0097-6156/83/0229-0099$10.75/0 © 1983 American Chemical Society

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EFFECTS OF HOSTILE ENVIRONMENTS

A c c e l e r a t e d growth t e s t i n g of monomers, polymers, and l a t i c e s c o n t a i n i n g chemically bound f u n g i c i d e s demonstrated that the concept of polymer-anchoring b i o c i d e s has promise. Several systems were shown to c o n t r o l microorganism growth i n minimum i n h i b i t o r y c o n c e n t r a t i o n t e s t s using both agar d i l u t i o n and aqueous n u t r i e n t broath methods. A v a r i e t y of i n v i t r o agar d i s h growth t e s t s and the "Zabel T e s t " were a l s o employed. Photochemical cleavage of b i o c i d e from some polymers was demonstrated i n UV i r r a d i a t i o n agar d i s h t e s t s . Taken together the r e s u l t s provide l a b o r a t o r y support f o r the concept that binder polymers, c o n t a i n i n g chemically bound b i o c i d e s , can be u s e f u l f o r c o n t r o l l i n g microorganism growth. Introduction Mercury-containing mildewcides have come i n t o d i s f a v o r due to the high t o x i c i t y of methyl mercury compounds to humans. Since mercury s a l t s have been widely used f o r b a c t e r i a l and fungal c o n t r o l i n p a i n t s more acceptable replacements have been i n c r e a s i n g l y sought i n recent years. A research program sponsored by the Paint Research I n s t i t u t e at the U n i v e r s i t y of Alabama was undertaken to look f o r organic b i o c i d e s which could r e p l a c e mercury s a l t s . Since organic compounds may l e a c h or v a p o r i z e from t h i n , high s u r f a c e area p a i n t f i l m s , the focus of the Alabama program became the development of polymer-anchored f u n g i c i d e s . A d e t a i l e d l i t e r a t u r e search* i n 1976 revealed that l i t t l e work had been done with t h i s concept i n connection with outdoor coatings except f o r some s t u d i e s of t r i a l k y l t i n e s t e r s ^ . D r i s c o and coworkers^"^ prepared p a i n t r e s i n s c o n t a i n i n g t r i - n b u t y l t i n a c r y l a t e . Laboratory t e s t s i n d i c a t e d these r e s i n s were r e s i s t a n t to Aureobâsidium p u l l u l a n s , A s p e r g i l l u s n i g e r , and A s p e r g i l l u s oryzae, and that f u n g i c i d e l e a c h i n g from the c o a t i n g was c o n s i d e r a b l y reduced compared to the use of the blended f u n g i c i d e . However, f i e l d t e s t s of these coating resins^»^ on pine and redwood t e s t panels began to show microorganism growth a f t e r three months. Mildew defacement of organic coatings has long been a major problem of the p a i n t i n d u s t r y . Aureobasidium p u l l u l a n s i s the major c a u s i t i v e organism r e s p o n s i b l e f o r t h i s defacement.6»7 A current approach to solve t h i s problem i s to blend a f u n g i c i d e i n t o the p a i n t formulation. Although t h i s s o l u t i o n has had success f o r short time p e r i o d s , the f u n g i c i d e tends to be vapori z e d or leached from the c o a t i n g over long time p e r i o d s . After the c o n c e n t r a t i o n of f u n g i c i d e drops below c r i t i c a l l e v e l s , mildew may s t a r t growing on the coatings surface.** Several f a c t o r s must be considered i n s e l e c t i n g a f u n g i c i d e f o r blending i n t o paints.9 The four most important f a c t o r s , other than c o s t , are t o x i c i t y , s o l u b i l i t y , v o l a t i l i t y , and UV

8. PITTMAN AND STAHL

Fungicides for Paints

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stability. T o x i c i t y t o f u n g i and b a c t e r i a must be h i g h , b u t t o x i c i t y t o humans s h o u l d be l o w . The s o l u b i l i t y o f any c a n d i d a t e f u n g i c i d e must be c a r e f u l l y c o n s i d e r e d f o r s e v e r a l reasons. The f u n g i c i d e must n o t be w a t e r s o l u b l e s i n c e i t w o u l d l e a c h from c o a t i n g s d u r i n g r a i n . Even a s l i g h t water s o l u b i l i t y e l i m i n a t e s many f u n g i c i d e s f o r s e l e c t i o n i n p a i n t s . A l s o , the f u n g i c i d e n e e d s t o be s o l u b l e i n t h e p a i n t o r t o be d i s p e r s e d without s e t t l i n g or agglomerating. I f the f u n g i c i d e agglomera t e s , d i s p e r s i n g a g e n t u s e i n t h e p a i n t may be r e q u i r e d l e a d i n g t o f o r m u l a t i o n c o m p l i c a t i o n s and h i g h e r c o s t s . Fungicides with a p p r e c i a b l e v a p o r p r e s s u r e s c a n n o t be c o n s i d e r e d f o r p a i n t u s e s i n c e they would v a p o r i z e from the p a i n t a f t e r a p p l i c a t i o n to a surface. U l t r a v i o l e t p h o t o d e c o m p o s i t i o n may d e g r a d e c e r t a i n f u n g i c i d e s and s u c h f u n g i c i d e s must be a v o i d e d . The concept of polymer-anchoring a b i o c i d e promises s e v e r a l advantages. V o l i t i l e b i o c i d e s may be c o n s i d e r e d b e c a u s e t h e y w o u l d be c h e m i c a l l y a t t a c h e d t o t h e p a i n t b i n d e r . Water-soluble b i o c i d e s a l s o may be c o n s i d e r e d s i n c e t h e p o l y m e r t h e y w o u l d be a n c h o r e d t o w o u l d be w a t e r i n s o l u b l e . The p o l y m e r - a n c h o r e d b i o c i d e w o u l d be m o l e c u l a r l y d i s p e r s e d t h r o u g h o u t t h e f i l m r a t h e r than present i n s m a l l p a r t i c l e s . S i n c e the b i o c i d e would r e m a i n w i t h i n t h e f i l m l o n g e r i f i t were p o l y m e r a n c h o r e d , a l o w e r l e v e l o f b i o c i d e i n c o r p o r a t i o n i n t h e p a i n t m i g h t be possible for a given useful mildewcidal l i f e t i m e . A l s o , the a n c h o r e d b i o c i d e s w o u l d be l e s s t o x i c t o humans w h i c h may p e r m i t t h e u s e o f c e r t a i n compounds w h i c h o t h e r w i s e w o u l d be a v o i d e d . H o w e v e r , w i t h t h e s e a d v a n t a g e s come s e v e r a l p o t e n t i a l p r o b l e m s . The p o l y m e r i z a t i o n o f p o t e n t i a l b i o c i d a l monomers c o u l d be troublesome. The i n c o r p o r a t i o n o f s u c h monomers i n t o t h e p o l y mer w o u l d h a v e t o be k e p t a t low m o l e p e r c e n t s t o a v o i d c h a n g i n g s u b s t a n t i a l l y the p o l y m e r ' s p r o p e r t i e s ( i . e . , T g , e t c . ) . Proper d e s i g n o f c o p o l y m e r s o r t e r p o l y m e r s c o u l d overcome t h i s p r o b l e m . A fundamental q u e s t i o n i n v o l v e s the b i o c i d a l a c t i v i t y o f t h e b i o c i d e when i t i s c h e m i c a l l y a t t a c h e d t o a p o l y m e r . Will t h e p o l y m e r be an a c t i v e b i o c i d e ? I f the b i o c i d a l a c t i v i t y r e s u l t s f r o m an i n t e r a c t i o n o f t h e b i o c i d e a t t h e c e l l w a l l o r by i n a c t i v a t i n g an e x o c e l l u l a r enzyme, t h e n i t i s p o s s i b l e t h a t t h e p o l y m e r , i t s e l f , c o u l d be an a c t i v e b i o c i d e . However, i f the b i o c i d e must be i n c o r p o r a t e d i n t o t h e o r g a n i s m t o f u n c t i o n , t h e n i t w i l l h a v e t o be c l e a v e d f r o m t h e p o l y m e r b i n d e r p r i o r t o exhibiting activity. F o r that reason polymers h a v i n g b i o c i d e s a t t a c h e d by f u n c t i o n a l g r o u p s o f d i f f e r i n g h y d r o l y t i c s u s c e p t a b i l i t y were made. D e s i g n o f p o l y m e r - b o u n d f u n g i c i d e s c a n accommodate a s l o w r e l e a s e mechanism o r a p e r m a n e n t l y a t t a c h e d b i o c i d e . The c h e m i cal l i n k a g e s used to a t t a c h f u n g i c i d e s to polymers c o u l d e i t h e r be h y d r o l y z a b l e o r n o n h y d r o l y z a b l e d e p e n d i n g on t h e t y p e c h e m i c a l


102

bonding used. E s t e r or amide l i n k a g e s , which undergo a c i d - , b a s e - , or enzyme-catalyzed h y d r o l y s i s , may be used to bind the f u n g i c i d e and, t h e r e f o r e , l a t e r r e l e a s e the free f u n g i c i d e upon cleavage of that l i n k a g e . These l i n k a g e s could be designed to cleave at v a r i o u s r a t e s under environmental c o n d i t i o n s (or by the enzymes released by microorganisms). I f environmental c o n d i t i o n s cause h y d r o l y s i s of the l i n k a g e , there would be some l o s s of f u n g i c i d e due to l e a c h i n g , but the r a t e of l e a c h i n g could be f a r l e s s than the l e a c h i n g r a t e of that same f u n g i c i d e i f i t were simply blended i n t o the p a i n t . Many f u n g i c i d e s might f u n c t i o n to r e t a r d growth only a f t e r they have been released from the c o a t i n g , but t h i s may not be true of a l l f u n g i c i d e s . Once r e l e a s e d from the polymer, the c o n c e n t r a t i o n of free f u n g i c i d e s might be too low to achieve the d e s i r e d r e s u l t . Nonhydrol y z a b l e l i n k a g e s , such as ether or hydrocarbon bonds, could a l s o be used. These l i n k a g e s would stop mildew growth only i f the f u n g i c i d e i s s t i l l a c t i v e when i t i s a part of the polymer. To our knowledge, no s t u d i e s of f u n g i c i d e s bound to polymers by these types of linkages have been done. Slow r e l e a s e h e r b i c i d e s which use the polymer-anchoring concept have been developed. Over the past few years s e v e r a l b i o c i d e s have been converted to monomers c o n t a i n i n g e s t e r , amide, or ether f u n c t i o n s which bind the b i o c i d e and the p o l y m e r i z a t i o n of these monomers was studied.12-16 ^ b i o c i d e s examined included pentachlorophenol, 1^12-16 8 - h y d r o x y q u i n o l i n e , 2 , ^ » 14-16 3 , 4 , 5 - t r i b r o m o s a l i c y l a n i l i d e , 3 , * 2 , 14-16 o-benzyl-p-chlorophenol,4,14"16 s a l i c y lanilide,5,*2 2-(4'-thiazoyl)benzimidazole,6, i 2-mercaptopyridine-N-oxide,7. e

1

a n (

OH

OH

CI

Pentachlorophenol

8-Hydroxyquinoline

1

2 OH

0

CI

Br

3,4», 5-Tribromosalicylanilide 3

o-Benzyl-p-chlorophenol 4


103


OCK) H 2-(4

f

-thiazoyDbenzimidazole 6

0"

fa" 2-Mercaptopyridine-N-oxide 7 Pentachlorophenol was chosen because i t i s a broad spectrum b i o c i d e w i d e l y used as a wood p r e s e r v a t i v e and as a slime c o n t r o l agent.17-20 8-Hydroxyquinoline had been used as a f u n g i c i d e before 1900 and i s thought to f u n c t i o n by c h e l a t i n g metal i o n s . ^ 1 - 2 3 T r i b r o m o s a l i c y l a n i l i d e i s an a c t i v e b i o c i d e w i t h low d e r m a t o l o g i c a l e f f e c t s to humans.24-26 j biocidal effects vary upon the a d d i t i o n of s u r f a c t a n t s to i t s m e d i u m . ^ » * oBenzyl-p-chloroDhenol i s known to be a broad spectrum commercial b a c t e r i a c i d e ^ ^ 2 8 but i t s f u n g i c i d a l p r o p e r t i e s have not been published. 2-(4 -thiazoyDbenzimidazole i s a fungicide, produced by Merck I n c . , which has been used i n p a i n t s . Due to i t s n o n v o l i t i l i t y and low s o l u b i l i t y 6^ can be mixed w i t h p a i n t s and remain i n the f i l m . 2-Mercaptopyridine-N-oxide i s a f u n g i c i d e produced by O l i n Inc. and used w i d e l y i n shampoos as an a n t i dandruff agent. Results t

s

J

u

s

f

Monomer P r e p a r a t i o n Each of the f u n g i c i d e s , 1-5 has a phenolic hydroxy group. Therefore, the a c r y l i c e s t e r s of each are r e a d i l y prepared. However, the s t a b l e phenoxide anions of 1-5 are good l e a v i n g groups. Thus, these a c r y l i c e s t e r s or t h e i r polymers should undergo reasonably f a c i l e h y d r o l y s i s . For t h i s reason, polymers of these a c r y l a t e s should be able to r e l e a s e the s p e c i f i c b i o c i d e as shown i n Scheme I. The h y d r o l y s i s of 8-hydroxyquinoline e s t e r s i s p a r t i c u l a r l y r a p i d due to neighboring group p a r t i c i p a t i o n of n i t r o g e n . * 2 , 1 To provide a s e r i e s of monomers (polymers) which would hyd r o l y z e more s l o w l y than the above-mentioned p h e n o l i c a c r y l a t e s , the p h e n o l i c group was f i r s t converted to i t s 2-hydroxyethyl ether d e r i v a t i v e which, i n t u r n , was converted to i t s correspond ing chain-extended a c r y l a t e (see Scheme I I ) . Ester hydrolysis


104

of these chain-extended e s t e r s r e l e a s e s an alkoxide anion which i s a stronger base, hence a poorer l e a v i n g group, than phenoxy anions. Thus, p o l y a c r y l a t e s o f these monomers should r e l e a s e the b i o c i d a l moiety more slowly than the phenolic p o l y a c r y l a t e s . Further, i t should be noted that the 2-hydroxyethyl ether of the o r i g i n a l f u n g i c i d e i s r e l e a s e d . T h i s may be b i o l o g i c a l l y i n a c t i v e or l e s s a c t i v e than i t s parent f u n g i c i d e ( i . e . 1-5). These ethers may (or may not) have to f u r t h e r degrade back to the parent f u n g i c i d e to d i s p l a y f u n g i c i d a l a c t i v i t y . Binder polymers c o n t a i n i n g both the a c r y l a t e and chain extended acryl a t e s might e x h i b i t extended p r o t e c t i o n against mildew defacement . A f u r t h e r task was the c o n s t r u c t i o n o f polymers from which a bound f u n g i c i d e would not h y d r o l y z e . Since a r y l secondary a l k y l ethers are only cleaved under vigorous c o n d i t i o n s , we s e l e c t e d the v i n y l ethers of f u n g i c i d e s 1-4 as t a r g e t monomers. A disadvantage recognized at the outset was the expected d i f f i c u l t y of copolymerizing v i n y l ethers (which undergo ready c a t i o n i c p o l y m e r i z a t i o n ) with a c r y l i c monomers which are polymerized using r a d i c a l or a n i o n i c i n i t i a t o r s but which r e s i s t c a t i o n i c i n i t i a t i o n (Scheme I I I ) . 2

A l l o f the a c r y l a t e and chain-extended a c r y l a t e synthèses* » 14-16 summarized i n Scheme IV together with y i e l d s . Scheme IV a l s o i l l u s t r a t e s the route that was u s e d * to convert 6^ to i t s acylamide analog 2-(4'-thiazoyDbenzimidazoyl acrylate,21· This monomer polymerizes to give polymers* which undergo f a c i l e h y d r o l y s i s to free 6^ because the 2 - ( 4 * - t h i a z o y D b e n z i m i d a z o l y l l e a v i n g group i s a s t a b l e anion (by v i r t u e of resonance s t a b i l i z a t i o n of negative charge by the benzimidazole r i n g ) . This ready h y d r o l y s i s was i l l u s t r a t e d by the i n a b i l i t y to prepare the monomer on treatment of 6^ with a c r y l o y l c h l o r i d e * - . Thus, the sodium s a l t of 6^ was made and reacted with a c r y l o y l c h l o r i d e but even t h i s method r e s u l t e d i n l o s s e s on work up and a poor o v e r a l l y i e l d (16-177o) of 2 1 . a

r

e

2

2

2

1 2

SCHEME I R-OH + CH CHC0C1

> R0C-Cft=CH

2

2

0 1-4 R = a r y l

I

ROH + —(-CHCH —)•< y o l y t i s COOH 2

h

d r

polymerize

" H * — CH COOR

r

8.

PITTMAN AND STAHL


105

SCHEME I I

R—OH

> ROCH CH OH 2

» ROCH CH OCCH—CH

2

2

2

2

I

1-4 R = a r y l

I polymeri2

HOCH CH OR + H-CHCH ->2

2

2

^

n

^

^ + CHCH -+

y

2

n

COOCH CH OR

COOH

2

2

ROH

SCHEME I I I

R—OH

>R-OCH=CH

Ρ

2

θ

1

^

β

Γ

ί

ζ

β

> ^-CHCH ^ 2

n

OR

1-4 R = a r y l

hydrolyze

SCHEME IV

OH Cl

Cl

ΟΙ

Cl

Θ

Θ

• ^

:

CH9=CHC0C1

c

E t N Y - 81%

l

C

H

2

=

=

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3

Cl °° C1CH CH 0H NaOH, Y=65% 2 0 ° , 48hrs 2

0

2

Q

^Z&Z** Cl H2Ç =€HC0C1 Et N, Et 0 D. C l Y=90% 3

^ °^° Λ

2

Cl

Cl

Cl N a H

OH

H C = CHC0C1 - 5 to~0° Y=89%

r

THF

e

9

H C=CHC0C1 0

ELU,—PÔT

®

Cl

©

106


Q

C1CH CH 0H > NaOH, Y=70% ?

2

OCH CH OH H C-=CHC0C1

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^ ^j^fffo.

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s

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o

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2

2

2

IT J6T ' B

B r ^ ^ ^ A J J^J)

CHC0 CH CH OTs, NaOH, Y=8%

H C =

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B r

y

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OH

H C -CHC0C1, 0° Ph 2

E t N , Y=71% 3

Θ

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Cl

C17)

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OCH CH OH C1CH CH 0H Ph ^\Js. H C —CHCOC1 L_i_^ k E t N , Y=30% NaOH, Y=65%, 80-90 2

9

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0

ph

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3

CI

Jl 0

Ph

H C"CHC0C1, 15° 2

Η I

E t N , Y=72% 3

0 ^

®

N

V-^S \NJ I Η

Θ

NaH DMF/BZ

60°

H C-=-CHCQCl reflux Y=16% 2

Ν

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©

Θ Ph

0


107


Several attempts to make the t h i o l a c r y l a t e of ]_ by t r e a t i n g _7 with a c r y o y l c h l o r i d e o r a c r y o y l anhydride f a i l e d to give the d e s i r e d product. This m a t e r i a l i s probably unstable due to the n u c l e o p h i l i c e f f e c t of the nearby oxygen on n i t r o g e n . Presumably a mixture o f r e a d i l y hydrolyzed 0- and N - s u b s t i t u t e d d e r i v a t i v e s was formed. Thus, an attempt was made to form the t h i o hemiacetal with formaldehyde. Unexpectedly, two moles o f formaldehyde condensed to g i v e hemiacetal, 22^ which was then converted to a c r y l a t e 23 (Scheme V ) . SCH 0H 2

-H-

0 t

0

+ HCHO

t

©

SCH OCH OH 2

2

Et 0 CHo-CHCOCl m ?— E t N , Y=42% 2

3

SCHEME V 2

A c r y l a t e and Extended-Chain A c r y l a t e Synthesis* >14-16 The syntheses o f both a c r y l a t e and extended-chain a c r y l a t e s of f u n g i c i d e s 1-5 are summarized together with y i e l d s i n Scheme IV. A c r y l a t e s 8, 11, 14, 17, and 20 were prepared i n good y i e l d s u s i n g a c r y l o y l c h l o r i d e under normal Shotten-Baumann c o n d i t i o n s . 12,14 This method worked w e l l even f o r the s t e r i c a l l y hindered 3,4 ,5-tribromosalicylanilide. Syntheses o f chain-extended a c r y l a t e s 10, 13 and 19 were accomplished by r e a c t i n g f u n g i c i d e s 1, 2, and 4, r e s p e c t i v e l y , with 2-chloroethanol and NaOH to f i r s t generate the 2-fungicidalphenoxyethanols*^»(i.e. 9, 12 and 18). Treatment of these chain-extended a l c o h o l s with a c r y l o y l c h l o r i d e under Shotten-Baumann c o n d i t i o n s gave the chainextended a c r y l a t e s 10, 13, and 19. This route was u n s u c c e s s f u l , however, s t a r t i n g with 3 , 4 , 5 - t r i b r o m o s a l i c y l a n i l i d e because d i s placement of c h l o r i d e from 2-chloroethanol f a i l e d to g i v e the chain-extended a l c o h o l . T h e phenoxy oxygen i n 3 , 4 , 5 - t r i b r o m o s a l i c y l a n i l i d e i s s e v e r e l y hindered by the ortho bromo and amide f u n c t i o n s , and t h i s hindrance r e t a r d s the r a t e o f Sjg-2 displacement. By using 2-iodoethanol, a more r e a c t i v e s u b s t r a t e to Sjg-2 displacements, the chain-extended a l c o h o l 15 was obtained 1

f

f


108

a l b e i t i n low (25%) y i e l d . 1 4 E s t e r i f i c a t i o n of 15 with a c r y l o y l c h l o r i d e gave the chain-extended a c r y l a t e 16.14 The s t r u c t u r e s of each of the monomers was confirmed by i n f r a r e d and nuclear magnetic resonance spectroscopy. V i n y l Ether

Syntheses

Three general s y n t h e t i c routes were examined f o r the preparat i o n of the v i n y l ether monomers of f u n g i c i d e s 1, 3, and 4.14 These r e s u l t s are summarized i n Scheme VI. F i r s t , the 2-bromoe t h y l ethers 24, 27, and 29 were prepared from 1, 3, and 4, r e s p e c t i v e l y , v i a n u c l e o p h i l i c displacement of bromide from 1,2dibromoethane i n the presence of NaOH or KOH. Then, base-catal y z e d dehydrohalogenation gave the d e s i r e d v i n y l ether monomers 25, 28 and 30 i n s a t i s f a c t o r y y i e l d s . 1 4 A second route, based on l i t e r a t u r e precedent,29,30 i n v o l v e d t r e a t i n g the f u n g i c i d a l phenols 1, 3, and 4 with v i n y l acetate i n the presence of mercuric a c e t a t e to g i v e the v i n y l ether i n an a d d i t i o n - e l i m i n a t i o n sequence. 14 This method d i d not work on s t e r i c a l l y hindered 3 and i t gave the a c e t a l 31 (and not v i n y l ether 30) when employed with b i o c i d e 4. The t h i r d route was based on the use of 1 , 2 - v i n y l bis(triphenylphosphonium)dibromide.31 Reaction of the f u n g i c i d e s 1 and 4 with t h i s s a l t i n chloroform and t r i e t h y l a m i n e , followed by treatment with aqueous NaOH, gave v i n y l ethers 25 and 30.14 This method was not s u c c e s s f u l i n generating the v i n y l ether 28 from t r i b r o m o s a l i c y l a n i l i d e . 1 4 8-Hydroxyquinoline was r e a d i l y converted to v i n y l ether 32 i n good y i e l d s 1 4 by treatment with acetylene i n base a t e l e v a t e d temperatures and pressures u s i n g methods s i m i l a r to previous reports.32-34 Known B i o l o g i c a l A c t i v i t y of the Monomers I t i s important to consider the b i o c i d a l p r o p e r t i e s of the monomers as w e l l as the parent f u n g i c i d e s s i n c e unreacted monomer may remain i n a l a t e x a f t e r i t s p r e p a r a t i o n . Pentachlorophenyl a c r y l a t e , 8, and i t s homopolymer both i n h i b i t the growth of S. aureus, A. n i g e r , Pénicillium c i t r i n u m , and Saccharomyces cervisia?5 The polymer was l e s s a c t i v e . Poly ( v i n y l c h l o r i d e ) compositions are p r o t e c t e d a g a i n s t m i c r o b i a l a t t a c k using 8 i n concentrations of 1-2% by weight.36 2-Pentachlorophenoxyethyl bromide, 24, i s known to be f u n g i s t a t i c 3 7 d 2-pentachlorophenoxyethanol, 9, has a f a i r l y h i g h f u n g i c i d a l a c t i v i t y but i t i s l e s s t o x i c (to mice) than pentachlorophenol.37 Extended-chain a c r y l a t e 10 has not been p r e v i o u s l y r e p o r t e d . 8 - Q u i n o l i n y l a c r y l a t e , 11, has only been t e s t e d i n the c o n t r o l of A l t e r n a r i a s o l a n i on tomatoes.38,39 V i n y l - 8 - q u i n o l i n y l ether, 32, i n the form of i r o n , t i n , g o l d , and z i n c complexes were a c t i v e a g a i n s t Staphylococcus33 but not as a c t i v e as 8-hydroxyquinoline, 2. 2 - ( 8 - Q u i n o l i n y l ) e t h a n o l , 12 i s a l s o l e s s a c t i v e than 2 but was f a i r l y e f f e c t i v e a g a i n s t Staphyloccus pyrogenes and S^_ aureus.40 a n

8.

109


PITTMAN A N D STAHL

OCH2CH Br 2

C

BrCH^CH^Br OH / Clv^s^Cl

LO

U y

NaOHÎ Y=72%

C H

C H 0 A c

H

C

1

DBU, 20°,-HBr

CK^y^Cl CI

f\ ^

Y=65% Ν * . 0 ClN^k^Cl

c l

C l J \ C\C1 l ™2* - » § 2 » H S 0 , - 2 2 ° , Y=24% CI CI M \Ph3P CH=:CHP Ph 2Br7 Q.2N HBrJCfrCl OCH=CHP*Ph NaOH \U E t N , CHC1 /Os Br"" - Y=15% 2

+

4

+

3

Q

5

3

0

0 H Br

>^V^^ —

B

r

DBU,20° Y

VËr ÔCH CHV 2

1

8 %

Hi Br

* -

\ \ V

CH ~CH0Ac, H g C l , H S 0 ,-22° ,Y=0 2

2

2

4

y

I

l

Ph P+CH=CHP" "Phq 2Br" E t N , CHC1

Y=0

3

3

3

OCH CH Br 2

BrCH„CH„Br

2

+

K ~0C(CH,J,

10% KOH, Y-73% OH

+

Ph P+CH=CHP Ph Et ψ. CHC1 ή 3

H C=CH0Ac o

2» "2""4 -22°,Y=30%

0 ^

OH

toe ©

HCS£CH, NaOH/H 0 2

200°, lOOOpsi Y=80% SCHEME VI

ÔXOJ


110

The extended chain a c r y l a t e 13 has not been r e p o r t e d . No r e p o r t s e x i s t concerning b i o l o g i c a l a c t i v i t y of monomers 14, 16, or 28, derived from t r i b r o m o s a l i c y l a n i l i d e , or 17, 19, or 30 d e r i v e d from o-benzyl-p-ehlorophenol. 2

PolymerizationsI ,14,16 F u n g i c i d a l a c r y l a t e s 8, 11, 14, and 17 were homopolymerized i n s o l u t i o n u s i n g r a d i c a l i n i t i a t i o n (AIBN).14 Only very low y i e l d s and low molecular weights were obtained with 17, presum ably due to the high c h a i n t r a n s f e r constant expected from the d i b e n z y l i c methylene f u n c t i o n w i t h i n t h i s monomer.14 A n i o n i c i n i t i a t i o n of 17 with LiAlIfy i n THF a l s o f a i l e d . A 24% y i e l d of a low molecular weight homopolymer of 17 r e s u l t e d from thermal p o l y m e r i z a t i o n at 150°C. Good y i e l d s and high molecular weights could be achieved i n the homopolymerizations o f 8, 11, and 14. Chain-extended a c r y l a t e s 10, 13, 16, and 19 r e s i s t e d homopolym e r i z a t i o n under AIBN i n i t i a t i o n . Sample homopolymerization r e s u l t s are summarized i n Table 1.14 A c r y l a t e s 8, 14, and 17 were a l s o copolymerized with nhexyl methacrylate o r η-butyl a c r y l a t e i n emulsion r e a c t i o n s (sodium l a u r y l s u l f a t e , K2S2OQ, 60°C) as were chain-extended a c r y l a t e s 10, 13, 16 and 19.14 The copolymers of 17 and 19 were low molecular weight m a t e r i a l s again due to easy c h a i n t r a n s f e r . The bulk copolymerization of 19 with n-hexyl methac r y l a t e gave reasonably high molecular weights.14 Some s o l u t i o n copolymerizations were a l s o c a r r i e d out. Representative r e s u l t s are summarized i n Table 2. A s e r i e s o f f i l m forming v i n y l acetate or e t h y l a c r y l a t e copolymers were prepared where the f u n g i c i d a l monomers was pentachlorophenyl a c r y l a t e , 8, 8 - q u i n o l y l a c r y l a t e , 11, or a c r y l y l s a l i c y l a n i l i d e , 20.I In these copolymers the mole f r a c t i o n o f the f u n g i c i d a l monomer was kept low ( i . e . between 0.04 and 0.11). Representative copolymers are summarized i n Table 3 . I These co polymers were prepared by bulk copolymerization using the f r e e r a d i c a l i n i t i a t o r s AIBN (with 8) and t - b u t y l p e r o x y p i v a l a t e (BPP) (with 11 and 20). The copolymer compositions were determined both by elemental analyses and p y r o l y s i s gas chromatography.12 As expected with bulk p o l y m e r i z a t i o n s , broad molecular weight d i s t r i b u t i o n s were obtained. As can be seen i n Table 3, the molecular weights were high. The g l a s s t r a n s i t i o n temperatures increased as the mole content of the f u n g i c i d a l monomer increased (Table 3 ) . I The s e n s i t i v i t y o f Tg to small i n c o r p o r a t i o n s of 8, 11, o r 20 i n d i c a t e s the homopolymers of these monomers would have high Tg v a l u e s . Bulk copolymerizations o f 2 - ( 4 - t h i a z o y l ) b e n z i m i d a z o l e a c r y l a t e , 21, with e t h y l a c r y l a t e were s u c c e s s f u l . ! However, attempts to copolymerize 21 with v i n y l a c e t a t e i n bulk gave only 2

2

2

f

2



111

Table 1-Representative Homopolymerization Reactions Of F u n g i c i d a l Monomers Fungicidal Monomer

Solvent

8 14 17 17 17 10 13 19 25 28 32

Benzene Benzene Benzene THF neat Benzene Benzene Ethylbenzene Benzene Benzene neat

(a)

MJJ =

80,000.

_

(b)

M

24,000,

M

N

=

W

=

Initiator

50,000.

AIBN AIBN AIBN LiAlH AIBN AIBN AIBN AIBN AIBN AIBN

4

Conditions °C/time, hr

Yield (%)

60/36 70/24 60/20 -78-*20/14 150/8 65/51 58/72 68/14 70/24 68/24 70/25

87 75b 0 0 24 0 0 0 0 0 0

a

(b)

(a)

n-HM n-HM n-HM n-HM n-BA MMA and n-BA n-HM n-HM n-BMA MMA n-BA n-BA

a

22 7.9 27.6 9.5 9.5 4.3 11.1 6.6 30 1.1 23 31 2

2

2

2

2

2

2

2

2

2

2

2

2

K S 0 K2S 0 K S 0 K S 0 K S 0 AIBN K S 0 AIBN AIBN K S 0 AIBN AIBN 7

8

8

8

8

8

8

b

b

b

b

b

SLS SLS SLSb SLS SLS Bz s o i n . SLS Bulk Bz/soln. SLS Bz/soln. Bz/soln.

b

l In Feed mole % I n i t i a t o r System

M

o f F u n g i c i d a l Monomers

52/5 48/41 70/24 72/22 70/18 74/23 65/20 70/20 63/28 61/20 66/24 66/26

98 34 51 79 68 48 10 49 19 90 0 0 15.6 3.2 33 9.3 4.8 3.2 9.7 2.7 1.5 0 0 0

-

1.3 0.9 0.21 1.53 13.3 5.1 0.2 0.87 0.24 5.8

Conditions Mole % Temp. Fungicidal °C/Time, Y i e l d Monomer i n I * i T H F hr Polymer (dl/g) (%)

Copolymerizations

4

M

W

-

-

13.6 8.4 17

-

17

-3.6 40 7.3 *0.5 6.3 3.1 9.3

50

8.6

-1.9 -9.3

xio- xi o-5

n-HM = hexyl methacrylate, n-BA = η-butyl a c r y l a t e , n-BMA = η-butyl methacrylate, and MMA = methyl methacrylate. Emulsion polymerizations using sodium l a u r y l s u l f a t e as the s u r f a c e a c t i v e agent.

8 14 17 10 13 16 19 19 25 28 30 32

Fungicidal Monomer Μχ Comonomer

Table 2-Representative

EA EA EA VA VA VA EA EA EA VA VA VA EA EA EA VA VA VA

8 8 8 8 8 8 11 11 11 11 11 11 20 20 20 20 20 20

2

M

jicidal lomer Μχ

b

131 283 2,860 61 329 3,320 40 200 2,000 47 233 2,330 34 267 2,670 62 311 3,107

2

Μ /Μχ 70 70 60 70 70 70 50 60 60 60 60 50 60 50 50 50 60 60

Temp. °C 2.5 2.5 2 3 3 4 3 2.5 2.5 3 3 2.5 1.5 2.0 2.5 3.0 3.5 2.0

Time hr 58 57 58 60 59 60 69 59 65 58 53 56 49 70 71 95 71 73

Conv. % 0.80 0.57 0.06 5.46 1.12 0.06 1.90 1.25 0.60 11.5 2.5 0.5 1.75 0.61 0.48 1.52 0.61 0.36

Mole % Ml i n Copolymer

c

N

Me

6.6 6.8 7.4 8.9 7.5 7.7 9.3 14.0 15.0 6.5 5.1 9.8 8.6 9.4 9.3 6.4 6.8 7.1

X10"

4

2.4 1.7 1.2 1.2 1.2 1.1 3.1 3.1 3.4 3.2 2.2 2.1 3.3 3.2 3.0 3.2 3.0 2.7

V , X10~ 5

f

-4 -6 -18 38 35 32 1 -3 -7 43 37 34 -7 -11 -12 37 32 30

xg °c

Table 3 — c o n t i n u e d on next page

0.95 0.60 0.10 5.50 1.15 0.2 2.25 1.35 0.65 12.3 2.4 0.5 1.85 0.70 0.65 1.75 0.75 0.45

Mole % Ml i n Copolymer

d

a

Table 3-Sample Bulk Copolymerizations o f F u n g i c i d a l A c r y l a t e s 8, 11, and 20 with E t h y l A c r y l a t e o r V i n y l A c e t a t e

5i

g:

f

32 r

D

> •z >

1

00

(d) (e) (f)

(b) (c)

(a)

Table

A z o b i s i s o b u t y r o n i t r i l e was the i n i t i a t o r i n copolymerizations of 8 w h i l e t - b u t y l p e r o x y p i v a l a t e was employed i n compolymerizations of 11 or 20. EA = E t h y l a c r y l a t e , VA = V i n y l a c e t a t e . Determined by c h l o r i n e a n a l y s i s ( i n copolymerizations of 8) or n i t r o g e n a n a l y s i s ( i n copolymerizations of 11 or 20). C a l c u l a t e d from p y r o l y s i s gas chromatography determinations. Determined by GPC. Evaluated from d i f f e r e n t i a l scanning c a l o r i m e t r y (DSC) where Tg f o r p o l y ( e t h y l a c r y l a t e ) = -24°C and p o l y v i n y l acetate) = 28°C.

3—continued

8.

PITTMAN A N D STAHL

115


low molecular weight, o i l y p r o d u c t s . I These c o p o l y m e r i z a t i o n s are summarized i n Table 4 where one can see the value of Tg i n c r e a s e s as the molar content of 21 i n c r e a s e s . 2

In order to determine the r e a c t i v i t y of pentachlorophenyl a c r y l a t e , 8, i n r a d i c a l i n i t i a t e d c o p o l y m e r i z a t i o n s , i t s r e l a t i v e r e a c t i v i t y r a t i o s were obtained w i t h v i n y l acetate ( M ) , τ χ = 1 . 4 4 and r =0.04 u s i n g 31 c o p o l y m e r i z a t i o n experiments, and w i t h e t h y l a c r y l a t e ( M ) , r]=0.21 and r =0.88 u s i n g 20 experiments.13 The composition conversion data was c o m p u t e r - f i t t e d to the i n t e g r a t e d form of the copolymer equation u s i n g the n o n l i n e a r l e a s t - s q u a r e s method of T i d w e l l and M o r t i m e r , ^ ! which had been adapted to a computerized format e a r l i e r . 2

2

2

2

4 2

In t h i s work,13 g l a s s t r a n s i t i o n temperatures were s t u d i e d as a f u n c t i o n of copolymer composition. Poly(pentachlorophenyl a c r y l a t e ) e x h i b i t e d the high Tg value of 143°. Table 5 summar i z e s these Tg values versus Μχ/Μ content of both v i n y l acetate and e t h y l a c r y l a t e copolymers.13 χ xg values f o r copolymers w i t h higher mole f r a c t i o n s of 8 depended on t h e i r thermal h i s t o r y . Tg i n c r e a s e s a f t e r h e a t i n g above Tg the f i r s t time. For example a v i n y l a c e t a t e copolymer (mole f r a c t i o n of 8 = 0.67) e x h i b i t e d Tg values of 7 7 ° , 9 9 ° , and 103°C i n three s u c c e s s i v e heating cycles.13 2

η β

Since a l l the f u n g i c i d a l monomers give homopolymers w i t h a high g l a s s t r a n s i t i o n temperature, Tg, p a i n t binder polymers con t a i n i n g the f u n g i c i d e s must be designed to have lower Tg v a l u e s . Therefore, a terpolymer a c r y l i c binder design c o n s i s t i n g of (1) the f u n g i c i d a l a c r y l a t e , (2) methyl m e t h a c r y l a t e , and (3) a low Tg a c r y l a t e such as η - b u t y l a c r y l a t e or 2 - e t h y l h e x y l a c r y l a t e was s e l e c t e d . S e v e r a l terpolymer samples were made i n s o l u t i o n i n small amounts. For example, s o l u t i o n t e r p o l y m e r i z a t i o n of 16 w i t h methyl methacrylate and η - b u t y l a c r y l a t e gave a good terpolymer, as d e s c r i b e d i n Table 2. I t i s of i n t e r e s t that extended-chain a c r y l a t e s , w h i l e r e s i s t i n g A I B N - i n i t i a t e d homop o l y m e r i z a t i o n , underwent t e r p o l y m e r i z a t i o n . This important o b s e r v a t i o n c l e a r e d the way f o r the s y n t h e s i s of s t a b l e t e r p o l y mer l a t i c e s c o n t a i n i n g these slower h y d r o l y z i n g monomers. Latex formulations were needed f o r f u r t h e r mixing i n t o sample p a i n t s for testing. F u n g i c i d a l v i n y l ethers 25 » 30 and 32 » r e s i s t e d r a d i c a l i n i t i a t e d homopolymerization. Copolymerizations of these mono mers w i t h η - b u t y l a c r y l a t e or methyl methacrylate were g e n e r a l l y u n s a t i s f a c t o r y . At low mole r a t i o s of f u n g i c i d a l v i n y l ether to a c r y l a t e , copolymers could be i s o l a t e d w i t h e i t h e r very low or no i n c o r p o r a t i o n of the v i n y l e t h e r s .

M

(b) (c)

(a)

23 49 98 248 498

l/M

2

f

2

a

% 48 48 53 60 63

24 24 24 24 8

Conv.

Time hr 6.4 4.4 2.5 2.4 1.9

χ

b

Mole % Μ in Copolymer 0.7 1.3 1.6 2.5 2.2

X10"

5

was

XI0""

In each run AIBN (0.04g) was used as i n i t i a t o r and 18 to 20g of e t h y l a c r y l a t e employed. C a l c u l a t e d from n i t r o g e n analyses. C a l c u l a t e d from GPC.

60 60 55 60 58

Temp. °C

Table 4-Sample Bulk Copolymerizations of 2 - ( 4 - T h i a z o y l ) b e n z i m i d a z o l e A c r y l a t e , 21, With E t h y l A c r y l a t e ( M )

°c

Tg

H on

m ζ

I

m τι m ο Η ζ/3 Ο τι Χ Ο Η r m m •ζ

3

Table 6-Composition of Stable L a t i c e s of Model P a i n t Binders Containing Chemically Bound F u n g i c i d e s

120


rs. ΝΟ co

co r»s m oo oo co ON Ή «H RH 1—1

o O O ON Γ"- o ON

The Effects of Hostile Environments on Coatings and Plastics

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