The Effects of Polyvinyl Alcohols on the Polymerization of Vinyl

2 The Effects of P o l y v i n y l Alcohols on the Polymerization of Vinyl Acetate

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on September 6, 2015 | http://pubs.acs.org Publication Date: June 1, 1976 | doi: 10.1021/bk-1976-0024.ch002

ALEXANDER S. DUNN, CHRISTOPHER J. TONGE, and SAMIR A. B. ANABTAWI Department of Chemistry, The University of Manchester Institute of Science and Technology, Manchester M60 1QD, England

Polyvinyl alcohol is an important component in the emulsifying systems used in practical formulations for the emulsion polymerisation of vinyl acetate (1) but, although i t is often used as a stabilising agent in suspension polymerisations, its use has not been found advantageous in the emulsion polymerisation of other monomers (2). Despite the unique importance of polyvinyl alcohol in the vinyl acetate polymerisation, few reports of its effects have been published. O'Donnell, Mesrobian, and Woodward (3) reported the effect of varying polyvinyl alcohol concentration to be in accordance with the Smith-Ewart theory (4) but it has subsequently been shown (2) that their results actually imply a first order dependence of rate on emulsifier concentration. By contrast, we found (5) that lower concentrations of the same grade of polyvinyl alcohol greatly reduced the rate of polymerisation of aqueous vinyl acetate solutions. These observations are reconciled by the recent work of Dimonie et al. (6) who find that the order in polyvinyl alcohol varies with vinyl acetate concentration from - 2.4 for a 1.5 mol dm solution to 0.2 for a saturated solution. For vinyl acetate solutions at lower temperatures, Hayashi, Iwase, and Hojo find that the order in polyvinyl alcohol depends on the initiator used, being zero for a persulphate redox system and a low order (0.2 - 0.3) which increases with temperature for a peroxide redox system. (7). -3

Commercial grades o f p o l y v i n y l a l c o h o l are customarily c h a r a c t e r i s e d by t h e i r r e s i d u a l a c e t y l content and the v i s c o s i t y of t h e i r 4% aqueous s o l u t i o n s . Grades containing 1 0 - 2 0 mole per cent a c e t y l are p r e f e r r e d f o r use as emulsifying agents ( 8 ) . These grades have a block copolymer s t r u c t u r e : random copolymers can only be produced by complete h y d r o l y s i s and r e a c e t y l a t i o n and have comparatively low surface a c t i v i t y . The d i s t r i b u t i o n o f r e s i d u a l a c e t y l groups i s c r i t i c a l l y a f f e c t e d by the h y d r o l y s i s procedure adopted: the • b l o c k i n e s s o f the copolymer (and i t s surface a c t i v i t y ) can be increased by adding a proportion o f benzene to the a l k a l i n e h y d r o l y s i s s o l v e n t ( 9 ) . Compatability o f these p o l y v i n y l acetate blocks with the l a t e x p a r t i c l e s explains 1

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In Emulsion Polymerization; Piirma, I., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1976.

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the unique s u i t a b i l i t y o f these grades o f p o l y v i n y l a l c o h o l f o r the v i n y l acetate emulsion p o l y m e r i s a t i o n .


Experimental Procedure. 2% v/v s o l u t i o n s of r e d i s t i l l e d v i n y l acetate were prepared i n d i s t i l l e d water from which oxygen had been s u b s t a n t i a l l y expelled by b o i l i n g . The i n i t i a t o r was 0.020 % w/v potassium persulphate. Although the same r a t e o f p o l y m e r i s a t i o n i s observed with t h i s procedure as when vacuum degassing i s used ( 5 ) the s i z e o f the l a t e x p a r t i c l e s formed i s reduced s l i g h t l y (10) presumably because o f adsorption o f s u r f a c e - a c t i v e oligomer formed during the i n h i b i t i o n p e r i o d . Rates were determined d i l a t o m e t r i c a l l y a t 60.0 C. At t h i s temperature aqueous s o l u t i o n s contract by 15.7 % on complete polymerisation (5, 11) much l e s s than i n bulk p o l y m e r i s a t i o n where the c o n t r a c t i o n i s 26.8 % . T h i s i s a t t r i b u t a b l e (10) to the e f f e c t o f v i n y l acetate on the hydrogen bonded s t r u c t u r e o f water: the c o n t r a c t i o n due to the polymerisation o f the s o l u t e i s p a r t i a l l y compensated by the expansion o f the solvent when the polymer p r e c i p i t a t e s . Stirred dilatometers were used f o r the emulsion p o l y m e r i s a t i o n s . The c o n t r a c t i o n observed a f t e r complete polymerisation o f an 8.0 % v/v emulsion was 18% although a c o n t r a c t i o n o f 21.6 % was expected on the basis o f the f i g u r e s given above f o r aqueous s o l u t i o n and bulk polymerisations: t h i s may be a consequence o f the i n c r e a s e d s o l u b i l i t y o f v i n y l acetate i n aqueous s o l u t i o n s o f p o l y v i n y l a l c o h o K 12). t

M a t e r i a l s . The p o l y v i n y l a l c o h o l s were commercial samples used as r e c e i v e d . ïhe DuPont 'Elvanol' was a sample used p r e v i o u s l y (5) obtained i n 1959 as t y p i c a l o f the m a t e r i a l i n commercial use a t that time: the r a t e s o f p o l y m e r i s a t i o n observed with i t were i d e n t i c a l with those observed e a r l i e r ( 5 ) . The ' P o l y v i o l grades were manufactured by Wacker Chemie i n 1968, the 'Gohsenol grades by Nippon Gohsei Kagaku Kogyo K.K., Osaka, Japan i n 1969, and the V i n o l grades by A i r Products & Chemicals Inc., C a l v e r t C i t y , Kentucky i n 1974: these l a s t were s p e c i a l l y selected s i n g l e batches, not blends o f s e v e r a l batches adjusted to conform to s p e c i f i c a t i o n . 1

1

l

l

Maximum Rates. Conversion-time curves are S-shaped but the r a t e i s u s u a l l y constant a t i t s maximum value (Rmax) between about 20% and 70% polymerisation: t h i s value i s used to c h a r a c t e r i s e the rate of reaction. Results E f f e c t o f P o l y v i n y l A l c o h o l Concentration. F i g . 1 shows r e s u l t s with 2% v/v aqueous v i n y l acetate s o l u t i o n s and 8% v/v emulsions together with the r e s u l t s o f e a r l i e r work (3, 5). 'Gohsenol GH-23 has a s i m i l a r a c e t y l content to the «Elvanol 1


1


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used i n the e a r l i e r work although i t s molecular weight i s higher. Although i t does reduce the r a t e o f polymerisation of 2% s o l u t i o n s at higher concentrations, i t has l i t t l e e f f e c t on the r a t e a t 0.36% w/v which was enough to halve the r a t e with the ' E l v a n o l * . On the other hand concentrations i n the same range i n c r e a s e the r a t e o f polymerisation of 8% emulsions as reported by O'Donnell et a l . (3) although the a c t u a l r a t e s are much higher a t a s i m i l a r i n i t i a t o r concentration despite the lower temperature used i n the present experiments. F i g . 2 shows the r e s u l t s f o r s o l u t i o n s i n more d e t a i l . Although e x c e l l e n t r e p e a t a b i l i t y was a t t a i n e d using a s i m i l a r technique with 1% v/v s o l u t i o n s (13), i t appears that the higher vagour pressure of 2% s o l u t i o n s (86 mmHg compared with 38 mmHg a t (11)) lead to some l o s s of monomer when f i l l i n g dilatometers: the higher of the observed r a t e s are thus l i k e l y to be the more r e l i a b l e and are given more weight i n drawing curves. I t i s c l e a r that there i s a considerable d i f f e r e n c e between the e f f e c t s of d i f f e r e n t grades even those from the same manufacturer. 2 5

c

c

a

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E f f e c t of A c e t y l Content of P o l y v i n y l A l c o h o l . F i g . 3 shows the e f f e c t of a low concentration (0.10% w/v) o f 'Gohsenol* samples which have s i m i l a r molecular weights but v a r y i n g a c e t y l contents on the rate o f polymerisation of v i n y l acetate s o l u t i o n s . Increase o f a c e t y l content decreases the r a t e o f polymerisation. However t h i s e f f e c t cannot account f o r the d i f f e r e n c e between the samples shown i n F i g . 2 because these d i f f e r by only 0.1% i n a c e t y l content. On the other hand any e f f e c t of a c e t y l content i n the ' V i n o l ' s e r i e s was small: r a t e s o f 5.8, 5.9, and 5.4 %/min were observed using *Vinol* 325, 425, and 523 which have s i m i l a r molecular weights and a c e t y l contents of 1.8, 4.0, and 12 mole % respectively. E f f e c t of Molecular Weight of P o l y v i n y l A l c o h o l . The t a b l e shows the r a t e s observed with a standard concentration (0.36% w/v) of grades of s i m i l a r a c e t y l content (12-13 mole %) f o r the polymerisation of 2% v i n y l acetate s o l u t i o n s . The 4% s o l u t i o n v i s c o s i t i e s are e i t h e r the means o f the range s p e c i f i e d f o r the grade o r , f o r the *Gohsenol* s e r i e s , a c t u a l batch values. I t i s c l e a r that the e f f e c t s of other d i f f e r e n c e s between samples f a r outweigh any e f f e c t that v a r i a t i o n of molecular weight may have. P o s s i b l e E f f e c t of Charged End-groups. A p o s s i b l e reason f o r d i f f e r e n c e s between samples might be the process used f o r polymerising the o r i g i n a l p o l y v i n y l acetate. Emulsion polymerisation i s l i k e l y to introduce a proportion o f i o n i c (sulphate o r carboxyl) end-groups which would not be expected i f bulk polymerisation with benzoyl peroxide had been used. An Antweiler M i c r o e l e c t r o p h o r e s i s apparatus was used to measure r a t e s of e l e c t r o p h o r e s i s of p o l y v i n y l a l c o h o l s i n s o l u t i o n i n a pH 7.8 phosphate b u f f e r . No s i g n i f i c a n t d i f f e r e n c e was observed between


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2% SOLUTIONS 60°C

fe%V Ac o

/ 60°C /GH-23

δ* k

——o-


>\

or A ε Δ i f **\S2-22 •a \

>-

52-22

./

Q'Doonellgtnl,

A -

1 2

3

/ '

4

PVOH-Ac o/

I (

2 1

3 I

0

Figure 1. Effects of polyvinyl alcohol grades on rates of solution ana emulsion polymerization of vinyl acetate

Figure 2.

Effect of polyvinyl alcohol concentration on rate of vinyl acetate polymerization


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E f f e c t o f V a r i a t i o n o f Molecular Weight o f P o l y v i n y l A l c o h o l


Grade

4% V i s c o s i t y _

Blank P o l y v i o l MD5/140 V i n o l 205 Gohsenol GL-05 Gohsenol GL-08 P o l y v i o l M13/140 Gohsenol GM-14L E l v a n o l 52-22 V i n o l 523 Gohsenol GM-14 P o l y v i o l W25/140 Gohsenol GH-17 P o l y v i o l W40/140 V i n o l 540 Gohsenol GH-20 Gohsenol GH-23

5 5 5.2 10.0 13 18.0 22 22 22.7 25 30.0 40 40 41.7 55.4

max (%/min) 5.8 3.1 5.4 4.5 5.0 3.6 4.7 3.3 5.1 5.1 2.7 4.5 3.3 3.2 5.8 5.3

1

•Gohsenol GM-14L and GH-23 (which were found to he weakly adsorbed) and P o l y v i o l W25/140 (which was s t r o n g l y adsorbed by p o l y v i n y l acetate l a t e x ) . 1

1

Adsorption o f P o l y v i n y l A l c o h o l s by P o l y v i n y l Acetate Latex. I t would be expected that the • b l o c k i e r samples o f p o l y v i n y l a l c o h o l would be the more s t r o n g l y adsorbed on p o l y v i n y l acetate l a t e x p a r t i c l e s . Adsorption isotherms ( F i g . 4) were determined by a procedure s i m i l a r to that used by Johnson and Lewis (15) to study adsorption o f p o l y v i n y l a l c o h o l by carbon b l a c k s . P o l y v i n y l a l c o h o l remaining i n s o l u t i o n i s determined c o l o r i m e t r i c a l l y using a b o r i c a c i d - i o d i n e reagent which minimises the e f f e c t o f s t r u c t u r a l d i f f e r e n c e s between the p o l y v i n y l a l c o h o l s on the colour developed: nevertheless the c a l i b r a t i o n curves f o r the d i f f e r e n t grades do d i f f e r s l i g h t l y . The l a t e x used was prepared by polymerising a 2.0% v/v s o l u t i o n o f v i n y l acetate f o r 2 i h a t 60 C using 0.020% w/v potassium persulphate i n i t i a t o r . R e s i d u a l i n i t i a t o r was decomposed by b o i l i n g f o r 5 h. The l a t e x was monodisperse: the diameter o f the p a r t i c l e s was approximately 260 nm. I t was found that adsorption o f two grades ('Gohsenol GM-14L, GH-23) was complete w i t h i n 15 min a t 20 C. F i g . 4 shows that there are l a r g e d i f f e r e n c e s between the extents to which the d i f f e r e n t grades are adsorbed. S u r p r i s i n g l y 'Gohsenol' NH-17 with a very low r e s i d u a l a c e t y l content (1 mole %) i s as s t r o n g l y adsorbed as 'Gohsenol' GH-17 (12 mole % a c e t y l ) w h i l s t •Gohsenol GM-14L and GH-23 ( a l s o 12 mole % a c e t y l but with lower and higher molecular weights than GH-17) are only weakly adsorbed. The more s t r o n g l y adsorbed grades do seem to be those which have the g r e a t e s t e f f e c t i n reducing the r a t e o f polymerisation but the c o r r e l a t i o n i s c e r t a i n l y not p r e c i s e 1

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2-0 %Ϋν vinyl acetate ο·θ2% K£p9 o i o % PVOH-Ac

II

Ο

1

1

1

ΙΟ

20

30

1

40

Mole % Acetyl Content Letters are used to indicate acetyl content.

Figure 3. Effect of the acetyl content of the polyvinyl alcohol co-acetate on the rate of polymerization of vinyl solutions at 60°C 6

5

-

"

GH-î? )

— — U _ _

—

^v^*.

A

GHi7 \

^

-52-22

PVOH-Ac %

Ο

O-l 1

PVOH-Ac

weakly adsorbed

L strongly adsorbed

^*^W25/I40J

0·2 t

0-3 1

t 1

0-4 1

Equilibrium Solution Cone. f>

%

Q

o n

PVAc htex.


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which i m p l i e s that some other f a c t o r i s also i n f l u e n c i n g one or other o f these e f f e c t s . I t i s p o s s i b l e that there are s i g n i f i c a n t d i f f e r e n c e s i n adsorption e n t h a l p i e s so that amounts adsorbed under polymerisation temperatures cannot be i n f e r r e d from isotherms determined at room temperature.


Seeded Polymerisation a f t e r P o l y v i n y l A l c o h o l Adsorption. To assess the e f f e c t of an adsorbed l a y e r of p o l y v i n y l a l c o h o l on the r a t e of polymerisation, the r a t e s of seeded polymerisation were measured a f t e r adsorption of v a r i o u s grades of p o l y v i n y l a l c o h o l on the seed l a t e x . The seed l a t e x was prepared i n the same way as the l a t e x used i n the adsorption experiments. A f t e r adsorption of p o l y v i n y l a l c o h o l from a 0.10 % w/v s o l u t i o n , the concentration of the seed l a t e x was 0.945 % w/v i n a 2.0 % v/v v i n y l acetate s o l u t i o n containing 7.4 χ 10~ mol dm" potassium persulphate. The r a t e s o f polymerisation (the means of two to four experiments) observed at 60°C are tabulated below. 6

P o l y v i n y l a l c o h o l grade Blank Gohsenol Gohsenol Gohsenol Gohsenol Polyviol

3

R

max/% min' 3.53 3.87 3.61 3.21 3.18 2.68

NH-17 GH-17 GM-14 L GH-23 W25/140

P o l y v i o l W25/140 which i s the most s t r o n g l y adsorbed grade ( F i g . 4) has the greatest e f f e c t i n reducing the r a t e of polymerisation but Gohsenol GM-14 L and GH-23 which are only weakly adsorbed ( F i g . 4) are more e f f e c t i v e than Gohsenol NH-17 and GH-17 which are more s t r o n g l y adsorbed. Once again i t seems that some other f a c t o r i s having more e f f e c t on the r a t e o f polymerisation than the extent o f adsorption of the p o l y v i n y l alcohol. Discussion We o r i g i n a l l y suggested- that t r a n s f e r to the p o l y v i n y l a l c o h o l could e x p l a i n the e f f e c t o f •Elvanol* 52-22 i n reducing the r a t e of polymerisation of v i n y l acetate s o l u t i o n s . The importance of t h i s t r a n s f e r r e a c t i o n has r e c e n t l y been confirmed by Dimonie e t a l . ( 6 ) who use ferrous ion/hydrogen peroxide redox i n i t i a t i o n . However Okamura, Yamashita, and Motoyama determined the t r a n s f e r r a t e constant o f v i n y l acetate to p o l y v i n y l acetate and p o l y v i n y l a l c o h o l i n homogeneous s o l u t i o n : they found f o r -4 -1 3 -1 t r a n s f e r to p o l y v i n y l acetate k . = 1.5 χ 10 mol dm s , t r a n s f e r to p o l y v i n y l a l c o h o l k^£j^ s 35 χ 10*" mol" dm s'" so that the more e x t e n s i v e l y hydrolysed grades o f p o l y v i n y l a l c o h o l might be expected to have most e f f e c t whereas the experiments with the • V i n o l samples suggest that v a r i a t i o n of (

4

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a c e t y l content has l i t t l e e f f e c t and those with 'Gohsenol samples ( F i g . 2) that the e f f e c t i n decreasing the r a t e i n c r e a s e s with a c e t y l content. However the h y d r o p h i l i c blocks of the e m u l s i f i e r may not be a c c e s s i b l e to polymer r a d i c a l s i n the l a t e x p a r t i c l e s and the e f f e c t of i n c r e a s i n g a c e t y l content might be to increase the concentration of a c c e s s i b l e groups adsorbed on the surface of latex particles. We have confirmed (10) that p o l y v i n y l a l c o h o l i s r e a d i l y o x i d i s e d by potassium persulphate (17) and induces a much enhanced r a t e o f decomposition of the persulphate but we have also shown (18) that any e f f e c t under polymerisation conditions i s small so that decreased r a t e s cannot be a t t r i b u t e d to r e d u c t i o n i n i n i t i a t o r concentrations below t h e i r nominal value by wastage i n s i d e reactions. Reynolds (19) has given a p r e l i m i n a r y r e p o r t o f experiments which show that persulphate resembles periodate i n o x i d i s i n g the 1:2-glycol groups of which there are about 2% i n p o l y v i n y l a l c o h o l although the r e a c t i o n i s not q u a n t i t a t i v e . Conjugated unsaturated ketone groups are also formed: these may r e t a r d polymerisation. Some samples of p o l y v i n y l a l c o h o l (e.g. a sample o f 'Gelvatol' 20-30 used i n other work) have undergone some o x i d a t i o n during manufacture but no conjugated ketone groups could be detected i n the 'Elvanol' 52-22 sample which had a l a r g e e f f e c t i n r e t a r d i n g polymerisation. However, i n a recent p u b l i c a t i o n , S h i r i n y a n , Mnatsakanov, e t (2Q.) f i n d that d i f f e r e n c e s between the r a t e s o f v i n y l acetate emulsion polymerisation observed with samples o f s i m i l a r p o l y v i n y l a l c o h o l s manufactured by the same process i n three d i f f e r e n t f a c t o r i e s could be a t t r i b u t e d to a condensation product of acetaldehyde derived from h y d r o l y s i s of r e s i d u a l v i n y l acetate: t h i s gave r i s e to a conjugated ketone type u l t r a - v i o l e t spectrum and could be extracted from the p o l y v i n y l a l c o h o l under s u i t a b l e c o n d i t i o n s . T h i s could be the u n c o n t r o l l e d f a c t o r which appears to have confounded many o f the experiments reported here. Even more r e c e n t l y the same l a b o r a t o r y (21) has reported that there i s an optimum sequence length of hydroxyl groups i n the p o l y v i n y l alcohol-acetate block copolymer f o r polymerisation r a t e and dispersion s t a b i l i t y . The blocky s t r u c t u r e o f incompletely hydrolysed grades of p o l y v i n y l a l c o h o l probably r e s u l t s i n m i c e l l i s a t i o n i n aqueous s o l u t i o n despite an e a r l y r e p o r t to the contrary ( 3 ) . Benzene has been found to be s o l u b i l i s e d i n p o l y v i n y l a l c o h o l s o l u t i o n s to an extent which increases with a c e t y l content (22). Enfiadzhyan et a l . (12) show that the e q u i l i b r i u m s o l u b i l i t y of v i n y l e s t e r s i s much increased at 60°C i n aqueous s o l u t i o n s of p o l y v i n y l a l c o h o l (0.92 % a c e t y l ) : s i m i l a r concentrations of methanol, ethanol e t c . may w e l l have a s i m i l a r e f f e c t to t h i s . The s o l u b i l i t y of v i n y l acetate increases l i n e a r l y reaching 62% v/v i n a 1% p o l y v i n y l a l c o h o l s o l u t i o n . However 11 hours had to be allowed to reach s a t u r a t i o n so that a slow r a t e of s o l u t i o n may e x p l a i n the



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EMULSION

POLYMERIZATION

p e r s i s t e n c e o f monomer d r o p l e t s under normal polymerisation c o n d i t i o n s when the times i n v o l v e d would probably not exceed two or three hours. An increase i n the s o l u b i l i t y o f the monomer i n the aqueous phase would reduce i t s concentration i n the l a t e x p a r t i c l e s and, consequently, the r a t e o f emulsion polymerisation and v a r i a t i o n s i n the amount o f monomer d i s s o l v e d i n the aqueous phase may e x p l a i n the comparatively poor r e p e a t a b i l i t y o f the r a t e s observed i n the presence o f p o l y v i n y l a l c o h o l . Tuzar and K r a t o c h v i l (23) have reported that styrenebutadiene block copolymers m i c e l l i s e i n s e l e c t i v e s o l v e n t s f o r polystyrene and s o l u b i l i s e l a r g e amounts o f polybutadiene homopolymer. Since the surface a c t i v e grades o f p o l y v i n y l a l c o h o l are p o l y v i n y l alcohol-acetate block copolymers and water i s a s e l e c t i v e solvent f o r p o l y v i n y l a l c o h o l a s i m i l a r e f f e c t may be expected which could a f f e c t the course o f the v i n y l acetate emulsion polymerisation. Summary The e f f e c t s o f commercial grades o f p o l y v i n y l a l c o h o l obtained from s e v e r a l manufacturers on the r a t e o f polymerisation of v i n y l acetate aqueous s o l u t i o n s and emulsions i n i t i a t e d by potassium persulphate a t 60°C have been i n v e s t i g a t e d . Increasing concentrations o f p o l y v i n y l a l c o h o l i n the same range tend to reduce the r a t e o f polymerisation o f the s o l u t i o n s but increase the r a t e o f polymerisation o f emulsions. Considerable d i f f e r e n c e s were noted between the e f f e c t s o f nominally s i m i l a r grades from d i f f e r e n t sources. Attempts to c o r r e l a t e the e f f e c t on the r a t e of polymerisation o f v i n y l acetate s o l u t i o n s with the a c e t y l content and molecular weight o f the p o l y v i n y l a l c o h o l appear to have been confounded by an u n c o n t r o l l e d v a r i a b l e . A subsequent p u b l i c a t i o n from the U.S.S.R. i n d i c a t e s that t h i s may be the concentration o f a by-product formed during the h y d r o l y s i s o f the p o l y v i n y l acetate. Other f a c t o r s which may account f o r the e f f e c t s are also discussed.

Literature Cited 1. Warson, Η., "Synthetic Resin Emulsions", Benn, London, 1972. 2. Reynolds, G.E.J., and Gulbekian, E.V., S.C.I. Monograph (1968) 30, 131. 3. O'Donnell, J.T., Mesrobian, R.B., and Woodward, A.E., J. Polym. Sci. (1958) 28, 171. 4. Smith, W.V., and Ewart, R.H., J. Chem. Phys. (1948) 16, 592. 5. Dunn, A.S., and Taylor, P.Α., Makromol. Chem. (1965) 83, 207. 6. Dimonie, V., Donescu, D., Munteanu, Μ., Hagiopol, C., and Gavat, I., Rev. Roum. Chim. (1974) 19, 903. 7. Hayashi, S., Iwase, Κ., and Hojo, Ν., Polymer J. (1972) 3, 226. 8. Toyoshima, Κ., in Finch,C.A.ed. 'Polyvinyl Alcohol', Chapter 2, Wiley, London, 1973.



2.

D U N N E T AL.

Polymerization

of Vinyl

Acetate

33

9. Hayashi, S., Nakano, C., and Motoyama, T., Kobunshi Kagaku, (1963) 20, 303. 10. Tonge, C.J., Ph.D. Thesis, Manchester, 1971. 11. Napper, D.H., and Parts, A.G., J. Polym. Sci., (1962) 61, 113. 12. Enfiadzhyan, M.A., Nazaryan, L.N., and Akopyan, A.E., Arm. Khim. Zhur. (1971) 24, 839. 13. Dunn, A.S., and Chong, L. C.-H., Br. Polym. J. (1970) 2, 49. 14. Coniglio, O.B., and Parts, A.G., Makromol. Chem. (1971) 150, 263. 15. Johnson,G.A.,and LewisK.Ε.,Br. Polym. J. (1969) 1, 266. 16. Okamura, S., Yamashita, T., and Motoyama, T., Kobunshi Kagaku, (1958) 15, 170. 17. Beileryan, L.M., Samvelyan, A.I., Chaltkyan, O.A. and Vardanyan, Arm. Khim. Zhur. (1967) 20, 338. 18. Dunn,A.S.,and Tonge,C.J.,Polymer Preprints (1972) 13, 1261. 19. Reynolds, G.E.J., contribution to C.S. Colloid and Interface Science Group Discussion on 'Characterisation and Colloidal Properties of PolymerLatices',Bristol, 26/27 June 1974. 20. Shirinyan, V.T., Mnatsakanov, S.S., Shirikova, G.A., Poznyakova, F.O., Popova, G.S., and Khvostyntseva, T.V., Plast. Massy. (1974) 15 (8): English translation, Int. Polym. Sci. Tech. (1975) 2, T82 (1). 21. Shirinyan, V.T., Mnatsakanov, S.S., Gromov, V.V., Perlova, T.I. and Ivanchev, S.S., Vysokomol. Soed. A (1975) 17, 182 (1), cf. Chem. Abstr. (1975) 82, 140547b. 22. Shakhova, Ye.M., and Meyerson, S.I., Vysokomol. Soed. A, (1972) 14, 2097: English translation, Polym. Sci. USSR, (1972) 14, 2354. 23. Tuzar, Ζ., and Kratochvil, P., Makromol. Chem. (1972) 160, 301, (1973) 170, 177.


The Effects of Polyvinyl Alcohols on the Polymerization of Vinyl

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