NOTES WaY

Graft Copolymerisation of Vinyl Monomers Initiated b y Manganic Sulfcrte-Sulfuric Acid

In a series of interesting papers Duke' has reported that glycols can be oxidized by Mn.3 + The oxidation proceeds by electron transfer reaction via free radical mechanism. We have applied the above reaction for graft copolymerization of vinyl monomers onto polymers containing hydroxyl groups. We used the same principle earlier2 for the graft polymerization of methyl methacrylat,e onto cellulose using pentavalent vanadium.

We have found that manganic sulfate in excess sulfuric acid can be effectively used to form a redox system in the presence of organic polymeric reducing agents such as cellu- lose and poly(viny1 alcohol). Obviously, the reducing action of organic polymeric molecules produces manganous ions by the transfer of electrons, thus resulting in the formation of free radicals on the polymeric molecules. This initiates the graft co- polymerization of vinyl monomers.

We believe that the mechanism of the initiation reaction is similar to that of the ceric ion-glycol system3 and can be written as follows:

Mn+++ + RCHsOH S Mn++ + H+ + RCHOH or RCH20

The free radical produced can initiate graft copolymerization if a vinyl monomer i s present.

The polymers we investigated are cellulose pulp, natural cotton fibers, viscose, starch, carboxymethyl cellulose, and poly(viny1 alcohol).

EXPERIMENTAL

Materials

Monomers (freshly distilled before use): methyl methacrylate (BDH) ; acrylonitrile

Cellulose pulp: Supplied by From Silk, Germany. Natural cotton fibers: 54/48 square weave, 5.5 oz./sq. yd. Casement Fabric (Bombay

Viscose: 1750 Denier-Tyre Cord Viscose filament obtained from viscose pilot plant,

Poly(viny1 alcohol): commercially available powder, = 0.302 (0.5% solution in

Starch: maize starch (Ad Starch Products Ltd.) Carboxymethyl cellulose: Manganic sulfate: Prepared according to the procedure of Ubbelohde' by oxidizing

(BDH); methyl acrylate (BDH); styrene (BDH); vinyl acetate (BDH).

Dyeing and Manufacturing Co. Ltd., India).

Shri %m Institute.

water).

DS = 0.7 (M/S. Sardesai Brothers Ltd. Billimore, India).

manganous sulfate in sulfuric acid with potassium permanganate.

Graft Copolymerization Procedure

The graft copolymerization was carried out in an apparatus consisting of a three- necked flask fitted with a stirrer, a gas inlet, a gas outlet, and a thermometer. The temperature of the reaction was controlled to an accuracy of f l ° C . using a water bath. Cellulose, 2-2.5 g., or other polymer was added to the flask along with 100 cc. of distilled water. Sufficient excess (about 2-3 times the weight of substrate) of the vinyl monomer was added to the flask and the reaction temperature was raised to 50 f 1OC. within29 min. Nitrogen gas, free from oxygen, was bubbled to expel all air inside the flask. 25 cc. of manganic sulfate solution in water (initiator) of 4.0-5.0 X 10-2N were then added and the reaction mass stirred for a known time. The resulting product waa filter-presned in a Buchner funnel, and dried. In the case of poly(viny1 alcohol),

4290 JOUFUVAL OF POLYMER SCIENCE, VOL. A3, ISSUE NO. 12 (1965)

4000 3000 CM-1

4ooc so00 2000 IS00 C*’ lo00 900 800 700

WRVELLWK;TH tMICR0”)

/ C /

Fig. 1. Infrared spectra of grafted cellulme materials (u) cellulose pulp; ( b ) carboxy- methyl cellulose; (c) cellulose pulpgrafted poly(methy1 methacrylate); (d) cellulose

NOTES 4291

Wt

.U

* '

w

.

.

WAVELENOTH (MICRONS)

( d )

1 - O S 4 5 6 r 8 9 10 II I2 B I4

N M L C N G T H (MICRONS)

( e )

4oQo 3000 2000 1- CM-I iooo mo two 700 C O I

I . 1

( f )

' 3 4 5 C T 8 9 10 II 12 U I4 15 bWVELENoTH (mcRonS)

pulpgrafted poly(methy1 acrylate); (f) carboxymethyl cellulose-grafted poly(methy1 methacrylate).

(e) viscose-grafted poly( methyl methacrylate) ;

4292 JOURNAL OF POLYMER SCIENCE, VOL. A3, ISSUE NO. 12 (1965)

the resulting product was soluble and was precipitated with acetone-tilter, and dried. Any homopolymer formed was extracted with a suitable solvent for 72 hr. and then again dried. Benzene was used in the case of methyl methacrylate, methyl acrylate, styrene, and vinyl acetate. Dimethyl formamide was used in the case of acrylonitrile. The dried product was weighed. The increase in weight was taken as an indication of the formation of graft copolymers.

Results and Discussion

The results are given in Table I.

TABLE I

Type Time Solubility in Sample of reaction, Graft, cuprammonium

No. substrate Monomer hr . % hydroxide

1

2

3

4

5

6

7

8

9

10

11

12

13

Cellulose Pulp

Cellulose Pulp

Cellulose PU'P

Cellulose Pulp

Cellulose Pulp

Cellulose Pulp

Cellulose Pulp

Cellulose Pulp

Vicose

Casement fabric

Carboxy- methyl cellulose

Starch

Pol y( vinyl alcohol)

Methyl

Methyl

Acrylonitrile

methacrylate

methacrylate

Methyl

Methyl

Styrene

acrylate

acrylate

Styrene

Vinyl acetate

Methyl

Methyl

Methyl

methacrylate

' methacry late

methacrylate

Methyl

Methyl methacrylate

methacrylate

2 76.52

5 91.5

2 45.3

2 . 5 14.6

3 . 5 32.4

2.25 Nil

6.25 Nil

7 Nil

5 22.3

3 . 5 11.8

4 5 . 5

2 112.3

6 . 5 21.3

Insoluble

Insoluble

Insoluble

Insoluble

Insoluble

Soluble

Soluble

Soluble

Insoluble

Not completely soluble -

DISCUSSION

The results obtained show that monomers such as methyl methacrylate, acrylonitrile, and methyl acrylate are polymerized onto different substrates containing hydroxyl groups. In the case of carboxymethyl cellulose, the reduction in the available hydroxyl groups seems to have reduced the extent of graft polymerization. However, styrene and vinyl acetate did not form any graft polymer even after 6 hr. of reaction time. This could be explained on the bmis of poor solubility of styrene in water and low reactivity in the case of vinyl acetate.

NOTES 4293

The graft copolymers of methyl methacrylate, acrylonitrile, and methyl acrylate were insoluble in cuprammonium solution, whereas the cellulose obtained after treating with styrene and vinyl acetate was completely soluble, thus supporting the above conclusions.

Infr.red spectra The infrared spectra (Fig. l ) , in the case of cellulose graft poly(methy1 methacrylate)

and cellulose graft poly(methy1 acrylate), showed the presence of an ester group at 1720 cm.-1 and this further supported the formation of the graft polymers.

Further work on the use of manganic sulfate is in progress.

The authors are grateful to the Council of Scientific and Industrial b e a r c h for sponsoring this work at this Institute and Dr. Sukhdev of National Chemical Labor& tory, Poona for taking the infrared spectra of the samples.

References

1. Duke, F. R., J. Am. Chem. Soc., 69,2885 (1947). 2. Harcharan Singh, Thampy, R. T., Chipalkatti, V. B., J . Pdymer Sci., A3, 1247

3. Mino, G., and Kaizermann, S., J. Polymer Sci., 31,242 (1958). 4. Ubbelohde, A. R. J. P., J . Chem. Soc., 1935,1605.

(1965).

HARCHAI~AN SINQH R. T. T~haap~ V. B. CEIPALKATTI

High Polymer Division Shri Ram Institute for Industrial b e a r c h Delhi, India

Received July 15, 1965 Revised August 25,1965