NOTES 2085

Polymerization Studies of Isopropenylferrocene

Interest in polymers containing the ferrocene group has centered around their electri- cal and magentic' and their electron-exchange properties.* Polymerization studies on vinylferrocene have been reported by various investigators,**4 including a comprehensive study by Baldwin and Johmon.6 The polymerization studies on other alkenylferrocenes have been very limited;* however, studies have now been extended to include isopro- penylferrocene. This paper describes the attempted homopolymerization of isopro- penylferrocene and its copolymerization with methyl methacrylate and styrene by free- radical initiation.

EXPERIMENTAL

Materials

Isopropenylferrocene (IPF) was prepared from acetylferrocene by first reacting with methyl Grignard reagent followed by dehydration of the resulting Zhydroxy-Zferro- cenylpropane.

Acetylferrocene (0.44 mole) was placed in a pre- dried glass reactor, 750 ml of THF added, and methyl Grignard reagent (0.75 mole) added under a nitrogen atmosphere a t 0-5OC over a period of 1.15 hr. The mixture was stirred for approximately 16 hr. After adding 200 ml of ether, the mixture was treated with an ammonium hydroxide solution saturated with ammonium chloride until reflux stopped. Upon filtration the filtrate was washed twice with water, dried over anhydrous magnesium sulfate, and the solvents removed by evaporation. A red oil which crystal- lized on standing was obtained in 95% yield. Its infrared and 'H NMR spectra were indicative of the Zhydroxy-Zferrocenylpropane.

ZHydroxy-Zferrocenylpropane (0.41 mole) was dissolved in 2.5 liters of dry methylene chloride containing 21 meq of ptoluenesulfonic acid and 9.1 meq of N-phenyl-Znaphthylamine. The mixture was heated to reflux under nitrogen for 2.5 hr with the water eliminated as the azetrope. Upon completion, 10 ml of tri- ethylaniine was added to neutralize the acid and the solvent was totally removed by evaporation a t below ambient temperature (0-10°C). The oily residue was extracted several times with pentane, the extracts combined, methylene chloride added to give a 30: 1 pentane-methylene chloride mixture, and this solution passed through a silica gel column (2 in. ID, 12 in. high). One liter of the 30: 1 solvent mixture was used to elute the column. Removal of the solvents gave a yellow solid (64.3%) which WBS recrystal- lized from methanol-water, mp 66.5-67"C. The infrared and 'H NMR spectra were similar to those previously reported.'-9

&Hydroxy-2-frroeacylpropane.

Isopropenylferrocene.

ANAL. Calcd for CL3HllFe: C, 69.04%; H, 6.24%. Found:

Other monomers were fractionally distilled prior to use.

C, 68.40%; H, 6.44%.

All solvents were reagenb 2,2'-Azobis-isobutyronitrile (AIBN) were recrystallized from grade, distilled materials.

methanol, mp 102-103°C with decomposition.

Polymerization

Homopolymerization reactions of IPF were carried out with the use of 2.0 g monomer, in 20 ml of toluene in a small (50-ml capacity) glass flask. 2,2'-Azobisisobutyronitrile or benzoyl peroxide was added at the 0.1,0.5, and 1.0 mole-% levels and the flasks heated at 66, 80, and 100°C for periods of 24 hr. The solvent was removed by evaporation and the solid reside examined by infrared spectroscopy. I n all instances the solid isolated was almost identical with IPF by comparison of their infrared spectra.

acrylate.

@ 1971 by John Wiley I% Sons, Inc.

*Pittman et aL6 have studied the polymerization of ferrocenyl acrylate and meth-

2086 NOTES

Techniques

Dilatometric polymerization rate measurements have been described elsewhere.10 Solution viscosities were determined in Cannon dilution viscometers at 30°C. Tolu-

ene were used as solvent. Iron analyses were carried out on a Perkin-Elmer atomic absorption spectrophotom-

eter, Model 303. A Waters Associates analytical instrument was employed for GPC analyses. De-

gassed tetrahydrofuran flowing a t the rate of 1 ml/min was the eluting solvent. Styragel columns (lo4, los, 600, and 100 A mean permeability) in series were used to fractionate the polymers. Each column configuration was calibrated in terms of average length by using narrow molecular weight distribution polystyrenes supplied by Waters Associates, Inc.

RESULTS AND DISCUSSION

Copolymerization reactions were carried out at three different concentrations of iso- propenylferrocene (IPF) with both MMA and styrene to determine the concentration effects of IPF. Major emphasis was directed to the effect of low concentration of IPF on the rate of polymerization and properties of the copolymers. Experimental data for these reactions are presented in Table I. The Rpo and [?lo values refer to the rate of polymerization of MMA and styrene and the intrinsic viscosity of the appropriate homo- polymer, respectively.

Several inkresting observations were made from the MMA copolymerizations. The rate of the copolymerization was reduced drastically by the addition of IPF at even very low concentrations as evidenced by the low values (0.05-0.13) of R,/Rpo. In a similar manner, the intrinsic viscosities of the copolymers were severely reduced at low IPF concentrations and continued to decrease as the low IPF concentration increased. This fact was established by the low [ v ] / [ ~ ] o values of 0.12-0.06. Iron analysis of the co- polymers showed that IPF was entering the copolymers in a ratio considerably less than was present in the comonomer charge, particularly a t the higher IPF concentrations.

A similar effect of IPF on the copolymerization reactions with sytrene was noted ex- cept the reduction in rate of polymerization and in the intrinsic viscosity of the copoly- mers was not as severe. Both rates were reduced by approximately 40% at the highest IPF concentration. Iron contents of the styrene copolymers were slightly higher for the MMA copolymers, and they approached a composition equivalent to that of the co- monomer charge for the lower IPF concentration.

No quantitative description of the free radical polymerization behavior of IPF has been reported, although vinylferrocene has been studied in some detail."-6 Our attempts to homopolymerize IPF with either azobisisobutyronitrile or benzoyl peroxide in toluene solution at temperature up to 100°C were all unsuccessful, and no polymerization was observed. In this way, IPF appears to exhibit free-radical polymerization character- istics typical of a-methyl-styrene.", 12

Since or-methylstyrene readily enters into copolymerization with vinyl monomers in reactions involving free-radical initiation, it was expected that the structural related IPF would also behave in the same manner. The copolymerization reactions of IPF with MMA and styrene demonstrated that this expectation was essentially correct. Al- though IPF was an active monomer in the copolymerizations, its basic effect was to lower the rate of reaction and the intrinsic viscosity of the copolymers. These effects were notably severe for the MMA copolymers.

These results depict the copolymerization behavior of IPF as a monomer which is capable of interacting with radical intermediates in copolymerization reactions, but one that produces a chain-end radical which is either of very low reactivity or readily under- goes chain transfer with monomer as has been described for certain allylic monomers. The most likely reason for the behavior of IPF is that the chain-end radical is of low

TA

BL

E I

E

xper

imen

tal

Dat

a fo

r C

opol

ymer

izat

ions

Fe,

%

[MM

A],

[S

tyre

ne],

[IP

F],

M

ole

ratio

R

P,

No.

m

ole/

l.a

mol

e/l.b

m

ole/

l. co

mon

omer

s %

bin

R

PI

RP

O

[?I,

dl/g

[d

/[sl

o C

alcd

Fo

und

5.00

4.

75

4.25

3.

75

4.84

4.

56

4.09

3.

60

0.11

0.

33

0.55

0.11

0.

33

0.55

43.2

12

.9

6.8

41.5

12

.4

6.5

2.3

x 1

0-8

3.0

x 10

-4

2.0

x 10

-4

1.5

x 10

-4

7.0

x 10

-4

4.0

x 10

-4

4.0

x 10

-4

4.3

x 10

-4

1.00

0 0.

130

0.08

6 0.

065

1.00

0 0.

571

0.51

1 0.

614

1.58

0 0.

190

0.15

5 0.

090

0.26

0 0.

275

0.22

5 0.

170

1 ,0

00

0.12

0 0.

098

0.05

7 1 ,

000

1.05

7 0.

865

0.65

4

1.25

3.

69

6.18

1.23

3.

69

6.21

L6

5

2

4.08

M

3.

18

-

1.42

3.

87

5.12

* [A

IBN

] =

0.0

25 m

ole/

l. [A

IBN

] =

0.0

5 m

ole/

l.

2080 NOTES

reactivity because of resonance interaction possibilities with the ferrocene group, and thus, it fails to propogate chain growth to the usual extent. In this picture the inter- mediate radical may have a propensity to terminate via combination with other radical intermediates as has been observed for dimer formation in certain allylic radical systems.

The analytical contributions of Dr. K. E. Johnson and Mr. R. D. Strahm are grate-

This work was sponsored by the U. S. Army Missile Command, Redstone Arsenal, fully acknowledged.

Alabama, under Contract DAAH01-694-0772.

The technical assistance of Mr. J. 0. Woods is appreciated.

References

1. A. A. Dublov, A. A. Slinken, and T. M. Rubenshtein, Vysokomol. Soedin., 5,1441

2. D. A. Seanor, Fortsch. Hochpolym. Forsch., 4, 317 (1965). 3. F. S. Arimoto and A. C. Haven, Jr., J . Amer. Chem. Soc., 77,6295 (1955). 4. Y.-H. Chen, M. Fernandez-Refojo, and H. G. Cassidy, J . Polym. Sn'., 40, 433

5. M. G. Baldwin and K. E. Johnson, J . Polym. Sn'. A-I, 5,2091 (1967). 6. C. U. Pittman, J. C. Lai, and D. P. Vanderpool, MacromoZecules, 3,105 (1970). 7. C. R. Hauser, R. L. Pruett, and T. A. Mashburn, J . Org. Chem., 26,1800 (1961). 8. W. M. Horspool and R. G. Sutherland, Can. J . Chem., 46,3453 (1968). 9. W. P. Fitzgerald, Ph.D. Thesis, Purdue University, 1963.

(1963).

(1959).

10. M. G. Baldwin and S. F. Reed, Jr., J . Polym. Sn'., A I , 1919 (1963). 11. H. M. Stanley, Chem. Ind. (London), 58,1080 (1939). 12. A. B. Hersberger, J. C. Reid, and R. H. Heiligmann, Ind. Eng. Chem., 37, 1073

(1945).

MORRIS HOWARD SAMUEL F. REED, JR.

Rohm and Haas Company Philadelphia, Pennsylvania 19137

Received June 30, 1970 Revised March 2, 1971