Copolymerization of Poly(Ethylene Oxide) And

COPOLYMERIZATION OF POLY(ETHYLENE OXIDE) AND

POLY(METHYL METHACRYLATE) INITIATED BY ' ÁÍC ANMONIUH NITRATE

AILTON S. GOMES • ANTONIO A. FERREIRA FERNANDA M.B. COUTINHO JEAN RICHARD D. MARINHO

Instituto de Macromolér * »s Universidade Federal > *io de Janeiro

INTRODUCTION

Cerium (IV) sails such as the eerie ammonium nitrate and eerie ammonium sulfate in aqueous acid solution with reducing agents such as alcohols, thiols, glycols, aldehydes and amines are well known initiators of vinyl polymerization ^ \ In the case of alcohols the initiation of polymerization has been assumed to take place via the free radicals produced by the decomposition of cerium (IV)-alcohol complex that produces cerium (III) ion and free radical species. If the reducing agent is a polymeric molecule such as poly(vinyl alcohol) or cellulose, free radicals produced cnto the polymeric molecule are capable of grafting ^~6). In this work, the polymerization of methyl methacrylate initiated by eerie ammonium nitrate/ I!NO3 -poly(ethylene oxide) with hydroxyl end group system was studied in aqueous solution at 25'C to obtain block copolymers.

EXPERIMENTAL

MATERIALS Methyl methacrylate was clean of inhibitors by washing with a sodium hydroxide solution (5% weight) and washed with bidis- tilled water,was dried over anhydrous calcium chloride and distilled. Ceric ammonium nitrate, nitric acid and poly(ethylene oxide)

(Mn - 4.000) were used without further purification. Water was uistilled twice over alkaline permanganate and used to prepare all solutions.

.273. Nitrogen used to deaerate the experimental systems was freed from oxygen by passage through three columns of Fieser's solution, and finally through a washing bottle containing distilled water.

PROCEDURE The required quantities of water, nitric acid and poly(ethylene oxide) were put into a bottle fitted with a screw cap. The metal cap was lined with a self-sealing rubber gasket. The bottle was kept in a thermostated bath at 25*C The mixture was deaerated for 90 minutes and then methyl methacrylate and eerie salt solution in 1 M nitric acid similarly deaerated was injected into the bottle with a hypodermic syringe. After a specified time interval a knovn excess of ferrous ammonium sulfate solution was added to quench the reaction and the mixture was poured into a large a^ mount of methanol. The precipitated polymer was filtered off and the filtrate was concentrated and poured into a large amount of water. This second precipitate was filtered off, washed re- peatedly with water to remove polyfethylene oxide) and dried under reduced pressure at room temperature. Some reactions were carried out in non-aqueous solvent Idioxanc at 60»C).

RESULTS

The results are summarized in Table I. It is.observed from this table that the total conversion of the reaction decreased by increasing the concentration of eerie ammonium nitrate and increased by increasing the concentration of poly(ethylene oxide). The infrared spectrum of this fraction showed an absorption band at 1760cm"1, which was assigned to the carbonyl group . The fraction,insoluble in methanol but soluble in acetone, was increased by increasing the concentration of methyl methacrylate. When the polymerization of methyl methacrylate was carried out in the presence of eerie ion and in the absence of poly(ethylene oxide) very low conversion was obtained; it decreased by increasing the concentration of methyl methacrylate.

.274. The polymerization of methyl methacrylate in dioxane at 60»C during 7 hours resulted in partial hydrolysis of the ester groups and of fte ettier linkages by HN03.

TABLE I

POLYMERIZATION OF METHYL METHACRYLATE (MMA) INITIATED BY CERIUM (IV) - POLYETHYLENE OXIDE) (PEO) SYSTEM AT

PEO Ce** MMA CONVERSION METHANOL (mol/1) Uol/1) (mol/1) I») SOLUBLE FRACTION

0,01 0,01 0,04 11 m8

0,01 0,01 0,08 15 10

0,02 0,01 0,3 50 8

— 0,01 0,3 11 — 0,02 0,01 0,4 66 7

— 0,01 0,4 6 — 0,02 0,01 0,6 69 6

— 0,01 0,6 1 —

0,02 0,03 0,3 2? 7

.0,03 0,03 0,3 30 10

0,04 0,024 0,3 44 19

0,04 0,04 0,08 7 4

0,04 0,04 0,3 32 15

0,08 0,04 0,3 4 3 28

0,08 0,04 0,08 16 14

0,08 0,06 0,08 S —

(a) Reaction time: 5h; HNO3: 0,5mol/l.

,275. CONCLUSIONS

The polymer fraction soluble in methanol but insoluble in water and in acetone is not an admixture of polyCethylene oxide) and poly(methyl methacrylate) but a copolymer since poly(ethylene oxide) itself is soluble in these solvents and poly(methyl methacrylate) is insoluble in methanol and soluble in acetone. The infrared spectrum of this fraction showed the presence of both poly(ethylene oxide) and poly(methyl methacrylate). The polymer fraction insoluble in methanol and soluble in acetone would be ah admixture of poly(methyl methacrylate) and a block copolymer having high proportion of poly(methyl methacrylate) sequences.

REFERENCES

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