I
THOMAS M. LAAKSO and CORNELIUS C. UNRUH Research Laboratories, Eastman Kodak Co., Rochester 4, N. Y.
Preparation, Homopolymerization, and Copolymerization of Alp ha-Acyloxyacrylic Esters Possible variations in composition and polymer properties are many. Many of the monomeric compositions could be cast into clear, hard, colorless plates, and a number of the copolymeric compositions could be molded into small buttons of excellent appearance T H E extensive investigations of the polymerizability and copolymerizability of vinyl monomers have been restricted largely to monosubstituted ethylenes. I t seemed of interest to see if a monomer like ethyl a-acetoxyacrylate would show polymerization and copolymerization characteristics similar to those of ethyl acrylate or vinyl acetate.
Table I. A Wide Variety of Esters of P-Chlorolactic, a-Acyloxy-P-Chloropropionic, and a-Acyloxyacrylic Esters Were Prepared in Varying Yields R CH3
Preparation of Monomers
R'
... 9 . .
In general, three preparative routes were evaluated as feasible methods of preparing a-acyloxyacrylic esters. Method I. Enol-Acetylation of Pyruvic Esters with Isopropenyl Acetate
(CHdzCH-CHz CHaCHzCH2CH2
Physical Constants Analyses B.P., 'C. Mm. M.p., ' C. Calcd. Found P-Chlorolactic Acid 80-0.5
9
18-21
+ CH2-C.COOCHs
OH
65-6
1
I
+ CH2=d.O.CO.CHs
0 * CO . CHa
H+ I + CH%=C.CO.OCHaf
CHaCO*CHa
( 2 ) . Although a readily polymerizable monomer was obtained, the yield was low and involved pyruvic esters that are not readily available as starting compounds for the synthesis. Method 11. Alcoholysis of a-Acetoxyacrylonitrile ( 4 ) . This reaction required 0 CO .CH3
...
76-7
...
118-19
25
...
16
CHsCO
92.8-3.5
9
...
C2H5
C4HoCO
113-14
7
. ..
(CHs)zCHCHz
CHICO
117-17.5
8
...
CHsCHzCHzCHz
C2H5
CHBCO
0 - c o
130-1
12
...
183-6
15
...
1
...
CzHs
CHaCO
CH3
CHICO
83-4
10
CzHs
C4HiCO
95-6
11
(CHa)zCHCHz
CHaCO
CHzCl . AH
68.5-9
or-AcyloxyacrylicAcid
oczH5 CH2Ci.AH
1
+ H20
0 .C O . CH,
I
CH2Ci.CH
I
C=NH. HC1
co.ocas
OCzH6 0 .C O . CH3
0 .CO .CH a
I
I
CHzCl. CH
1
-+
-HCI COOCzH6
CHFC
I I
53.4
46.28 7.38 19.07
86.9
46.03 7.60 19.15
85
40.13 5.04 20.15
77
H, 4.98 C1, 19.67 C, 48.50 H, 6.70 C1, 16.60
49.16 6.88 16.45
55.7
C, 48.55 H, 6.74
91
C1, 15.97
48.88 6.82 16.26
C, 48.55 H, 6.74 C1, 15.97
49.51 6.77 15.03
87
C, 56.14 H, 5.06 C1, 13.84
56.23 5.10 13.90
40
43.13 5.66 18.25 22.1
43.08 5.40 18.10 22.3 22.5
90.2
C, H, C, H, C, H, C, H,
50.00 5.56
50.28 5.52
40
58.06 7.52
58.47 6.96
60
58.06 7.52
57.79 7.55
54.6
58.06 7.52
58.16 7.77
52
C, H, C, H,
64.9 5.4
64.01 5,. 24
49.6
53.16 6.32
53.20 6.35
60
C,46.54
H, 7.20 C1, 19.67 C, 45.54
H, 7.20 C1, 19.67
a-Acyloxy-P-Chloropropionic Acid CHs
0 .CO. CH3
0 .CO . CHI
39.20 6.08 23.28
C,39.33
25-7
CH2=&.CN f C2H60H f 2HC1+
I 1
41
38-9
8
C=NH * HCl
34.64 5.11 25.71
H, 5.9 C1, 23.28
CHI
CH2=C.COOCHS
C,34.67
H, 5.07 C1, 25.63
OH CHs.CO.CO.OCH3
% Yield
CH~CHZCHZCHI CHaCO CZH6
cZE5
a - c o CHsCO
C, H, C1, CHaCO--,
110.5-11
22
... ... ...
105-6.5
15
...
118-19 99-100
0.5 35
c,39.90
... ...
QO .OCzH 6 VOL. 50, NO. 8
AUGUST 1958
1 1 19
difficultly accessible a-acetoxyacrylonitrile as starting material. Yield in hydrolysis of the iminoethyl ether hydrochloride was fair. Method 111. Acetylation and Dehydrohalogenation of b-Chlorolactic 0
CHzCl. CHOH. CHzOH -+ CHzC1. CHOH COOH
Hf
+
CH8Cl.CHOH.COOH CzH5OH -+ CHzCl. CHOH. CO. OCzH5
+
CHzC1. CHOH. CO . OCzH5 (CHaC0)zO *
P co
CHzCl. CH
.
I
CH3
\ Go.OCzH5 0 * CO . CHa
CH2Ci.bH
I
CO.OCzH6
+ CH,COOH
On a laboratory scale, quinoline was used customarily; other reagents, such as anhydrous sodium acetate, could be used. Excess quinoline was not necessary, but aided in keeping the quinoline hydrochloride formed in solution. To give a satisfactory product, the quinoline had to be free of cresols. The practical grade of quinoline was washed with sodium hydroxide solution, then distilled. Three kilograms (15.4 moles) of ethyl a-acetoxy-P-c h l o r o p r o p i o n a t e , 3125 grams (25 moles) of Eastman White Label quinoline, and 3 liters of dry, sulfur-free benzene were stirred and heated under gentle reflux for 24 hours. After removal of the benzene at reduced pressure, the mixture was cooled. The crystalline sludge of quinoline hydrochloride was filtered off by suction.
Table II.
-HCl
-----+ I I
Acyloxy-
Sam&
Nd.
CO. OCzHs Esters ( 5 ) . This was essentially Koelsch's method ( 6 ) . The batch size was scaled up five times without difficulty, in laboratory equipment. The p-chlorolactic acid, essentially freed from water and nitric acid, was used without further purification. The ethyl ester was used for acetylation, after removal of excess ethyl alcohol but without distillation of the ester itself. The crude ethyl @-chlorolactate was dissolved in three times its weight of acetic anhydride and the solution was heated on a steam bath overnight. The excess anhydride was removed under reduced pressure. The residual oil was fractionated by using an 18-inch distillation column packed with glass helices and fitted with a total-reflux, variable-take-off still head. Ethyl aacetoxy-@-chloropropionate distilled a t 1O9-1Io C. a t 15 mm. Yield varied from 50 to 70%, based on the P-chlorolactic acid used. In the case of the corresponding ethyl a - benzoxy - P-chloropropionate, crude ethyl j3-chlorolactate (762 grams, 5 moles) was treated with 702.8 grams ( 5 moles) of benzoyl chloride, added slowly to warm (70' C.) ethyl p-chlorolactate, with continuous stirring. This mixture was distilled through a packed column equipped with a total-reflux, variable-take-off still head. The product was obtained in 40% yield; boiling point 183-6' C. at 15 mm. Ethyl a-benzoxy-p-chloropropionate did not crystallize when chilled to - 15 C. The a-acetoxy-@-chloropropionicesters could be dehydrohalogenated by using various hydrogen chloride acceptors.
1 120
Preparative Conditions for the Polymers
G..Z
Polymerization Time, Hr. 90 90 90 90 90 90 120 120 120 120 120 120 24 24 24 24 24 24 24 24 24 24 24 24 72
CY-
0 .C O . CHs
CHz=C
The filtrate was fractionally distilled through an 18-inch column packed with glass helices and fitted with a totalreflux, variable-take-off still head. The pressure was collected. It contained appreciable amounts of quinoline, which acted as a polymerization inhibitor. This crude ethyl or-acetoxyacrylate could be stored readily; the purified monomer could be kept only a few days without polymerizing, even in a refrigerator. The crude monomer was dissolved in an equal volume of sulfur-free benzene and the solution washed with a cold 570 aqueous solution of sulfuric acid until the wash waters were acid to litmus paper. The benzene layer was washed with cold water, then with 5% sodium bicarbonate solution, and finally with cold water. This layer was
11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
Ethyl
27
Ethyl
28 29 30 31 32 33 34 35 36 37
Ethyl n-Butyl n-Butyl n-Butyl n-Butyl Ethyl Ethyl Ethyl Ethyl Ethyl
38 39 40
%-Butyl %-Butyl Ethvl CY-%bkyroxyacrylate Ethyl Ethyl Ethyl
10
41 42 43
INDUSTRIAL AND ENGINEERING CHEMISTRY
Ester
Ethyl Ethyl Ethyl ELhyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl Ethyl
1 2 3 4 5 6 7 8 9
(I
acrylic
Benzoyl peroxide.
Cat-
Second G.
Monomer
Styrene Styrene Styrene 30 Styrene 40 Styrene 22.5 Styrene 1 Acrylonitrile 2 Acrylonitrile 4 Acrylonitrile 6 Acrylonitrile 8 Acrylonitrile Acrylonitrile 9 M e methacrylate 9 M e methacrylate 8 M e methacrylate 6 M e methacrylate 4 2 M e methacrylate 1 M e methacrylate 9 Vinyl acetate 8 Vinyl acetate 6 Vinyl acetate Vinyl acetate 4 2 Vinyl acetate 1 Vinyl acetate 8 n-Butyl a-acetoxyacrylate 8 Et oc-n-butyroxyacrylate 8 a-Acetoxyacrylonitrile 8 n-Butyl acrylate 18.6 Styrene 18.6 M e methacrylate 2.5 Acrylonitrile 18.6 Vinyl acetate Acrylic acid 8 Vinyl chloride 8 Vinyl chloride 8 p-Chlorostyrene 8 2,5-Dichloro8 styrene 18.6 Diethyl fumarate 18.6 Maleic anhydride 10.0 Styrene 5
10
20
7.9 7.9 7.9
Styrene Styrene Styrene
G. 45 40 30 20 10 2.5 9 8 6
4 2 1 1 2 4 6
8 9 1
2 4 6 8 1 9.3 9.3 5.6 6.4 10.4 10.0
10.0 8.6 3.6 1.0 3.2 7.0 8.7 17.2 9.8 5.6 5.2 5.2 5.2
Diluent
G.
... ...
... ... ...
alyst,
Dioxane
17.5
0.25 0.25 0.25 0.25 0.25 0.125 0.025 0.025 0.025 0.025 0.025 0.025 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.050 0.087
... ... ... ... ...
...
0.087
72
...
0.068
72
0.072 0.15 0.15 0.031 0.136 0.058 0.045 0.056 0.075 0.084
72 72 48 144 48 72 120 120 72 72
0.18 0,142 0.078
48 48 96
0.013
90 120 72
... ... ...
... ... ... ... Acetonitrile 7.5 Acetonitrile Acetonitrile Acetonitrile Acetonitrile Acetonitrile
... ... ... ... ... ... ... ... ... ... ... ...
7.5 7.5 7.5 7.5 7.5
..* ... ... ...
... ...
... ... ... . . I
... ...
... ...
... ... ... ...
Acetonitrile
18.7
... ... ...
... ... ... ... ...
... ... ... ... ... ...
...
Dioxane 1% gum arabic soh.
...
...
2Occ. 0.065 35cc. 0.065
Polyrnerizarion temperature 5 5 O C.; (No. 41,looo C.; No. 43, 50" C.).
ACYLOXYACRYLIC ESTERS then dried over Drierite and again distilled, the fraction distilling a t 67-8 C. and 15 mm. being collected. The yield for the dehydrohalogenation step varied between 60 and 90%. With higher esters, such as the nbutyl ester, it was advantageous to use a higher-boiling solvent, such as toluene, for dehydrohalogenation. Method 111 was by far the most useful. Readily available materials could be used, and it afforded related monomers by substituting alcohols other than ethyl alcohol and acylating agents other than acetic anhydride. A wide variety of a-acyloxyacrylic esters could be prepared (Table I).
Homopolymerization of Alkyl a-Acyloxyacrylates The esters of a-acyloxyacrylic acids
could be homopolymerized very readily by the usual vinyl polymerization catalysts (3), in bulk, solution, suspension, and emulsion. Bulk-polymerized samples were usually clear and colorless, their hardness depending upon the nature of the acyl and ester groups. Ethyl a-acetoxyacrylate (containing 0.1% of benzoyl peroxide catalyst) was poured into a glass mold, 8 X 6 X l/4 inches (inside dimensions), and the polymerization was allowed to proceed a t 60' C. in a nitrogen atmosphere. When polymerization was complete, the clear, colorless, hard plate was removed. Specimens were submitted to physical tests after curing a t 110' C. for several hours. Brinell hardness, scratch hardness, and impact value (Izod notch) were very similar to those of cast methyl methacrylate plates. The polymerized n-butyl ester of a-acetoxyacrylic acid was
Table Ill. Sample No.
Isolation and Appearance of Products Yield,
1 2 3
Color None None None
Hardness Hard Hard Hard
Clarity Clear Clear Clear
Solvent for Pptn. Dioxane Dioxane Dioxane
Pptn. MeOH MeOH MeOH
4
None
Hard
Clear
Dioxane
MeOH
5
None
Hard
Translucent
Dioxane
MeOH
6 7 8 9
None Amber-white Amber Amber
Hard Tough Tough Viscous
Opaque Opaque Opaque Hazy
Dioxane (hot) Dimethyl formamide Dimethyl formamide Acetone
MeOH MeOH MeOH MeOH
10
Amber
Viscous
Clear
Acetone
MeOH
11
Amber
Viscous
Clear
Acetone
MeOH
12
Dark amber
Viscous
Clear
Acetone
MeOH
Acetone Acetone Acetone Acetone Acetone Acetone Hot dioxane Hot dioxane Acetone Acetone Acetone Acetone Dioxane
Water Water Water Water Water Water MeOH MeOH Water Water Water Water MeOH
Hot dioxane Acetone Acetone Acetone Dimethyl formamide Acetone Hot dioxane Hot dioxane Hot dioxane Hot dioxane Acetone Acetone Acetone Acetone Acetone Acetone
None Hard Clear None Hard Clear 15 None Hard Clear None Hard 16 Clear None Hard Clear 17 None Hard Clear 18 None Hard Clear 19 None 20 Hard Clear None 21 Hard S1. hazy None Hard 22 S1. hazy None Hard S1. hazy 23 None Hard 24 S1. hazy None Soft 25 Clear Clear Yellow Hard 26 Yellow Hard Clear . 27 None Soft Clear 28 None Hard Clear 29 None Hard Clear 30 Light brown Tough Hazy 31 None Hard Hazy 32 None Hard 33 Clear SI. yellow Hard Clear 34 S1. yellow Hard Hazy 35 None Hard V. SI. haze 36 White Hard 37 Opaque None 38 Tough Clear Red-brown Tough Clear 39 40 Hard V. SI. yellow Clear None 41 Soft Clear Soft None 42 Clear None Hard 43 Clear All isolated polymers dried at 5 5 O C. 13 14
considerably harder than a similarly polymerized n-butyl methacrylate. A bulk-polymerized ethyl cr-acetoxyacrylate was insoluble or poorly soluble in most solvents. Solutions in chloroform showed extremely high viscosities. A bulk-polymerized n-butyl a-acetoxyacrylate, on the contrary, was soluble in common polymer solvents, even a t room temperature. I t was appreciably softer than the polymeric ethyl ester, as was. the poly(ethy1 a-butyroxyacrylate). When prepared as a bulk polymer, poly(ethyl a-acetoxyacrylate) did not show a true melting point. Before there was any sign of softening on heating a powdered sample of the polymer, decomposition had set in, the sample turning dark. Even well above 200' C., no softening point was evident. This thermal and solvent resistance of bulkpolymerized ethyl a-acetoxyacrylate
...
...
Repptn. Leached in M e O H Leached in M e O H From acetone s o h . into HzO From acetone s o h . into HzO From acetone s o h . into HzO Leached in M e O H Extracted with M e O H Extracted with M e O H From acetone s o h into M e O H From acetone s o h into M e O H From acetone s o h intp M e O H From acetone s o h into M e O H None None None None None None None None None None
G.
Appearance White, fibrous White, fibrous White fibrous
48 45 45
White, fibrous
48
White, fibrous
42
White, fibrous Tan, fibrous Tan, 5brous Tan, fibrous
42 9.5 9.0 9.0
Tan, fibrous
8.0
Tan, fibrous
7.5
Tan, fibrous
7.5
White, White, White, White, White, White, White, White, White, White,
fibrous fibrous fibrous fibrous fibrous fibrous fibrous fibrous fibrous fibrous rub-
9.5 9.5 9.5 9.5 9.5 9.5 9.5 9.5 9.5 9.5 9.5
Extracted with M e O H
White, fibrous
16.0
MeOH EtOH MeOH MeOH MeOH Skellysolve G
From acetone i n water From acetone in water From acetone in water Extracted with M e O H From acetone i n water
Yellow, horny White, fibrous White, fibrous White, fibrous Tan, fibrous White, fibrous
28.5 25.5 8 26.5
Me'OH MeOH MeOH MeOH MeOH Water Water MeOH MeOH MeOH
Extracted with M e O H Extracted with M e O H Extracted with M e O H Extracted with M e O H From acetone i n water Extracted with HzO Extracted with HzO Extracted with M e O H From acetone in water From acetone i n water
White, White, White, White, White, White, White, White, White, White,
...
...
... ...
...
VOL. 50, NO. 6
...
... ... 8
...fibrous ... ... fibrous 10 fibrous fibrous fibrous brittle fibrous fibrous fibrous fibrous
AUOUST 1958
15 15 16
...
14 11.5 7 9
1 12 1
could be of interest in cast clear sheets. A more soluble variety of poly (ethyl a-acetoxyacrylate) could be made by polymerization in a solvent. A solution consisting of 100 grams of ethyl a-acetoxyacrylate, 100 grams of dioxane, and 0.25 gram of benzoyl peroxide was placed in a glass ampoule and sealed. The ampoule was set in a 50" C. constant-temperature bath, after 24 hours, the tough, resilient, clear gel was dissolved in hot dioxane and a dilute solution poured in a thin stream into a large volume of agitated methanol. The white, fibrous polymer was washed thoroughly in hot water and dried at room temperature. Mixtures of monomers could be polymerized readily in all proportions, extending possible variations in composition and polymer properties. Bulk polymerization of a mixture of 9.3 grams of ethyl a-n-butyroxyacrylate, 7.9 grams of ethyl a-acetoxyacrylate, and 0.086 gram of benzoyl peroxide at 50" C. for 24 hours produced a hard, clear, and colorless polymer. A similar polymer was obtained when an equal quantity of iso-
Table IV. Acetyl Ethby oxyl. Sample Distn. % No. 1 2 3 4 5 6 7 8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39
40 41 42 43
1 122
... ... ... ... ... ... ... ... ... ... ... . . I
25.0 21.7 15.8 11.3
5.1 2.9
... ... ... ... ... ..* ... ...
...
19.9 17.0 17.5
... ...
... ...
... ... ...
21.8 22.8
... ...
... ...
2.2 4.4 9.9 15.1 21.9 25.0
butyl a-acetoxyacrylate was substituted for the ethyl a-n-butyroxyacrylate.
Copolymerization with Other Vinyl Monomers Whereas the homopolymerization characteristics of a-acyloxyacrylic esters tell little regarding their similarity to acrylic esters or vinyl esters, their copolymerization characteristics should give this information (Tables I1 to V). The monomers were mixed with the catalyst and diluent (if used) in a glass ampoule, the supernatant atmosphere replaced by nitrogen, and the ampoule sealed, and placed in a constant-temperature bath. After a definite time, the ampoules were opened, the contents were dissolved in an organic solvent. and the solution was filtered if necessary, and poured slowly into a large excess of a n organic nonsolvent. The precipitate was redissolved in a solvent and reprecipitated in a nonsolvent or extracted with a nonsolvent to remove residual unreacted monomers.
Analyses and Composition of Polymers Molar Ratio
N,
C1,
%
%
... ...
... ... . . . ... ... ... ... ... ... ... * . . 2 4 . 1 ... ... 2 0 . 7 ... ... 13.9 * . . * . . 9 . 1 ... ... 4 . 7 ... ... 2 . 8 ... ... ... ... ... ... ... ... . . . ... ... ... * . . ... ... ... ... ... ... 25.6 ... ... 24.4 ... ... 17.3 ... ... 11.6 ... ... 6.2 ... ... ... 2.9 ... ... ... ... ... ... ... 5.5 ... ... ... ... ... ... ... ... ... ... ... 1 9 . 1 ... ... ... ... ... ... ... ... ... 5 . 8 ... ... 7 . 0 ... ... 13.1 ... ... 2 2 . 4 ... ... ... ... ... ... 1 4 . 1 ... ... 1 4 . 9 ... ... 1 3 . 8 ... ... 1 5 . 0 ... ... . I .
Other Analysis
... ... ... ... ... ... ...
... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ...
... ... ... ... ... ...
COOH
... ...
1.3%
... ...
(IstZand) Mono. Poly. 1:13.7 1:6.1 1:2.3 1:l.O 1:0.38 1:0.17 1:27 1:12 1:4.5 1:Z.O 1:0.75 1:0.31 1:0.18 1:0.40 1:l.l 1:2.4 1:6.3 1:14 1:0.20 1:0.46 1:l.Z 1:2.8 1:7.3 1:16.5 1: 1
1:l 1:l 1:l 1:l 1:l 1:13.9 1:l 1:l 1:0.31 1:l 1:l 1:l 1:l 1:l 1:l 1:l 1:l 1:l
INDUSTRIAL AND ENGINEERING CHEMISTRY
( n ] in Solvent (0.25 G. in 100 Cc.)
1:18.2 1:8.4 1:Z.Q 1:1.3 1:0.46 1:0.21 1:26 1:11 1:3.3 1:1.6 1:0.66 1:0.35 1:0.14 1:0.40 1:l.l 1:Z.Z 1:6.8 1:13 1:0.21 1:0.31 1:l.Z 1:2.7 1:6.6 1:16.2
0.78 0.78 0.75 0.63
1:0.66 1:0.60 1:Q.Z
...
...
Dioxane Dioxane Dioxane Dioxane
...
...
3.89 3.11 1.41 0.62 0.39 0.38 1.97 1.46 1.19 1.08 0.93 0.80
Dimethyl formamide Dimethyl formamide Dimethyl formamide Dimethyl formamide Dimethyl formamide Dimethyl formamide Acetone Acetone Acetone Acetone Acetone Acetone
2.54
Dioxane
0.58 1.33 1.63
Dioxane Acetone Dimethyl formamide
...
... ... ... ... ...... ...... 1 : 1 . 1 3 ... 1 : 0 . 4 5 ...
...... ...... 1 : 0 . 2 9 ... 1 : 0 . 3 6 ... 1:l.Z ... 1:1.3 ...
...
1:0.21 1.42 1:0.02 0.30
Dioxane Dioxane
1:1.3 1:1.35 1:1.61 1:1.34
Dioxane Dioxane Dioxane Dioxane
0.51 0.53 0.32 0.76
... ... ... .. ... ..
... ... ... ... ... ...
Mechanistic study of the copolymerization behavior of two vinyl monomers can be carried out satisfactorily by polymerizing various ratios of the two monomers under standard conditions of catalyst content and temperature to a low conversion (7). The product is isolated and analyzed, and the reactivity ratios determined (7). Knowledge is thereby obtained of the mode of entry of the two monomers into the initial copolymer. Such a study constitutes an extension of the present investigation. By allowing the copolymerization to proceed to a very high conversion (as in the manufacture of most commercial copolvmers), technical utility of both process and products can be estimated. Haziness indicates a nonhomogeneity of composition, usually caused when One monomer enters the copolymer much more readily than the second one in the early stages; in the latter stages, this second monomer enters into the copolymerization as the major constituent or more nearly in an equitable proportion. A broad spectrum of compositions is obtained in which the compositions are not compatible. If the two monomers enter the copolymer in a ratio equivalent to or not too different from that in the original monomer mixture, incompatibility is minimized and the tendency is toward optically clear, bulk polymerizations. Bulk polymerizations, involving substantial amounts of each monomer, giving optically clear products in high yield, were taken to mean that copolymerization proceeded favorably. I n copolymerization of ethyl aacetoxyacrylate with styrene, optically clear products here obtained when the molar ratio of the two monomers was equal or styrene was in excess. When ethyl a-acetoxyacrylate was in considerable excess, the bulk-polymerization product showed signs of being a heterogeneous mixture. The clear samples were soluble in acetone, whereas neither polystyrene (except of very low molecular weight) nor poly(ethy1 a-acetoxyacrylate) is soluble in that medium. There was alwavs a somewhat higher proportion of styrene units in the copolymer than origina!ly in the corresponding monomer mixture. Ethyl acrylate will bulk-copolymerize with styrene in all proportions to give optically clear products. Vinyl acetate copolymerizes very poorly with styrene. Vinyl acetate products were hard and clear if the vinyl acetate monomer content was below an equimolar ratio of the two monomers. With increasing ratios of vinyl acetate, the products were not optically clear. Except for the member having the lowest vinyl acetate content, products were acetone-soluble, This appeared to indicate some copolymerization but that in the presence of significant amounts of vinyl acetate, a very
A C Y L O X Y A C R Y L I C ESTERS broad spectrum of copolymer composition was formed. The analyses shown, therefore, are meaningless for identifying the products. Like the ethyl ester, n-butyl a-acetoxyacrylate gave a heterogeneous product with vinyl acetate. In methyl methacrylate, analyses indicated an over-all composition of the polymeric products similar to that in the monomer mixture. The products were optically clear a t all ratios of monomers, and completely soluble in acetone. In contrast to poly(ethy1 aacetoxyacrylate), these copolymers were fusible, and small buttons could be compression-molded from them. No evidence was present as to the mode of entry of the monomer units in the polymer chain, but it appears that ethyl a-acetoxyacrylate is a more favorable comonomer with methyl methacrylate than vinyl acetate. In the copolymerization series with acrylonitrile, lack of clarity does not necessarily indicate polymer hetero-
Table V. Sample No.
I 2 3 4
5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20 21 \
22
23 24 25 26
27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
Solubilities of Polymers
Di-
Acetone oxane CHCls Benzene S S S S S I
S S S S S S
I I
I I I
S S S S S S S S S S
S S S S S S S S S S S
S S S S S S S S S S S S S S S S S S S S S
I
I
S
S I S S S S S S S S S S
I
I
S S PS PS S S S S S
s.
S = soluble. I
=
S S S S S S I
S S S S S S I
I
I
I
I
S S S S
PS S S S S S S S S
s
S S S S S S S S S S S S S S S S I S I S S S
S S S S
.s
S S
geneity but is due to the presence of a diluent and to the fact that polyacrylonitrile showed no tendency to dissolve in the monomer. The solubility characteristics indicate that copolymerization has taken place. This behavior is similar to that of many known copolymers of acrylonitrile. Worthy of note is the decreasing intrinsic viscosity of this series of polymers with increasing ethyl a-acetoxyacrylate content. I t appears that this monomer had some inhibitory effect upon the acrylonitrile. Attempts to copolymerize with other monomers are revealing. I n equimolar ratios with ethyl a-acetoxyacrylate, pchlorostyrene and 2,5-dichlorostyrene gave visibly heterogeneous mixtures, resembling styrene. Diethyl fumarate apparently copolymerized reluctantly with ethyl a-acetoxyacrylate, and little or not at a!l with maleic anhydride. Vinyl chloride in small ratios formed a clear copolymer; larger amounts gave a hazy polymer. n-Butyl acrylate
Acetic Acid
EtOH
I
I
I
I I I I I I I I I I I I I I
PS S S S I I I
MeOH I I I I I I I I I I
S S
PS S S S S S S S S I S S S S S S S S S S S
I
I
I I
S
S PS PS
S
I S
I I
S
I
I I
I
I
I
S S S S S S S I S
I S S S S
s.
S S S S S
I S S S S S S
insoluble. PS = partly soluble.
I I I
I I I
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appeared to give a homogeneous copolymer, but analysis indicated low butyl acrylate content The moderate yield may be dae to using ethyl alcohol as the precipitant; fractions high in nbutyl acrylate content may have been selectively removed. Copolymerization of ethyl a-acetoxyacrylate with styrene does not give optically clear bulk copolymers in all proportions, but over a considerable range of monomer compositions gives clear, hard products. Here, the copolymerizability more nearly resembles that of the acrylates and methacrylates with styrene than of vinyl acetate with styrene. Ethyl a-acetoxyacrylate, if it were to resemble vinyl acetate in its copolymerizability, might copolymerize with that monomer over a considerable range of ratios to give optically clear bulk polymers. This is apparently not so. Ethyl a-acetoxyacrylate copolymerizes with simple alkyl esters of acrylic and methacrylic acids in all proportions, giving clear bulk polymers. The very poor copolymerization tendency of ethyl a-acetoxyacrylate with maleic anhydride and with the esters of fumaric and maleic acids is unlike the behavior of vinyl acetate with these monomers. Here, vigorous copolymerizations occur,. giving products in which the monomers tend to be present in a n alternating sequence. Ethyl aacetoxyacrylate resembles ethyl acrylate in copolymerization behavior rather than vinyl acetate. This study has been extended to a more quantitative study of copolymerization behavior (7).
literature Cited (1) Alfrey, T., Jr., Bohrer, J. J., Mark, H., “Copolymerization,”pp. 27-31, New York, Interscience, 1952. (2) Hagemeyer, H. J., Jr., Hull, D. C., IND.ENC.CHEM.4i, 2920 (1949). (3) Kenyon, W. O., Laakso, T. M., Unruh, C. C . (to Eastman Kodak Co.), U. S. Patent 2,559,635 (July 10,1951). (4) Kenyon, W. O., Unruh, C. C. (to Eastman Kodak Co.), Zbid., 2,499,392 (March 7,1950). (5) Kenyon, W. O., Unruh, C . C., Laakso, T. M. (to Eastman Kodak Co.), Zbid., 2,499,393 (March 7, 1950). ( 6 ) Koelsch, C . F., J. Am. Chem. SOC. 52,1105 (1930). (7) Unruh, C . C., Laakso, T. M., IND. ENG.CHEM.,50, 1124 (1958).
RECEIVED for review July 23, 1956 ACCEPTED March 7, 1958 Communication 1805 from the Kodak Research Laboratories. VOL. 50, NO. 8
AUGUST 1958
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