From the Istituto di Chimica Industriale del Politecnico and the Laboratorio Ricerche Settore Idrocarburi, SOC. Montecatini, Milano

Kurzmitteilung

A new Crystalline Polyamcrylate : Poly(ally1 acrylate)

By MARIO DONATI and MARIO FARINA

Dedicated to Prof. G . NATTA on the occasion of his 60 th birthday

(Eingegangen am 26. November 1962)

A crystalline non-cyclic polymer having an unequivocally acrylic struc- ture, was obtained by anionic polymerization of allyl acrylate. The mono- mer, obtained by trans-alcoholysis from methyl acrylate and allyl alcohol, was polymerized in toluene solution a t -50 "C. with either butyl lithium or phenylmagnesium bromide as catalyst. The polymerization proceeds without gel formation up to a conversion greater than 70 yo. The polymer obtained has an intrinsic viscosity between 1 and 2.100 ml./g. (in CHCl, a t 30 "C.), and is completely soluble in acetone, chloroform and aromatic hydrocarbons.

The polymer structure was determined by examination of the chemical properties and by I R and X-ray analyses.

Heterogeneous alkaline hydrolysis of the polymer in a hydro-alcoholic medium yielded an alkali-soluble and acid-insoluble product, i.e. one behaving as a polymeric acid.

The I R analysis of allyl polyacrylate demonstrated the presence of allyl unsaturation and the absence of acrylic unsaturation and 8-lactone rings. In addition, the analysis of the polyacid obtained by hydrolysis demonstrated the presence of carboxylic groups, the absence of ester groups, of primary alcoholic hydroxyls and of double bonds.

From X-ray analysis of an oriented fibre the conformation of the poly- meric chain was deduced. It consists of a ternary helix having an identity period of 6.5 8, corresponding to a main chain configuration of the iso- tactic type.

The melting point determined by a polarizing microscope appeared very sharp and, for the different samples examined, it ranged between 86 and 90°C.

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M. DONATI and M. FARINA

The polyacid obtained by hydrolysis was also crystalline by X-rays. Different drying conditions yielded the monohydrate and the semihy- drate of polyacrylic acid. Thus, on drying at 15 "C. and 0.1 Torr we obtained a polyacid with an equivalent weight of 89, whereas on drying a t 100°C. and 0.1 Torr the equivalent weight was only 80.

These titration and X-ray results agree with those obtained by KARGIN and co-workers1) for the hydrates of the polyacrylic acid,

The poly(ally1 acrylate) obtained with homogeneous catalytic systems, represents an example of a crystalline acrylic polymer from monomeric acrylates of unbranched primary alcohols. This fact does not agree with the hypotheses put forward by other authors, proposing that the use of an ester containing a secondary alkyl group 2, and the use of an heterogene- ous catalytic system3) are important conditions in order to obtain a crystalline polyacrylate.

A peculiar property of the polymerization described above is the purity of the chain structure obtained, in spite of the presence of other reactive groups and of the possibility of cyclopolymerizations. It is in fact known that from non conjugated w-dienes, it is possible to obtain either cross- linked or cyclic polymers, the latter being formed by intra-intermolecular processes. In theory, as well as irregular and cross-linked structures (in- compatible with the crystallinity and the solubility of the product), the polymerization of ally1 acrylate could yield homopolymers of acrylic (I), of allylic (11) or of cyclic type*) (111). The three different structures should be recognizable by their saponification products, i.e. polyacrylic acid (I a), polyallylic alcohol (I1 a) or a polyoxyacid (IIIa) respectively.

(1) (Ia) -CHz-CH- -CHz-CH-

1 - I CH2=CH-CHz-O-C0 COOH

(11) (IIa)

CH2=CH-COOCHz-CH=CHz + 1 - I / -CH,-CH- -CHz-CH-

CHz=CH-CO-O-CH2 CH,OH

\ L (111)

(IIIa)

CH- -CHz-CH-CHz-CH- /CHz\

-CH2-CH I I - + I I co CHZ COOH CH,OH \ / 0

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A New Crystalline Polyacrylate : Poly(ally1 acrylate)

The selectivity of the process, yielding only product (I) is caused by the different reactivity of the two types of unsaturations with respect t o the catalytic agent: the organometallic compounds which we used, behave as initiators acting through an anionic mechanism and promote exclusively the polymerization of the acrylic double bond. This is to be expected from the electron withdrawing effect of the carboxyl group.

1) V. A. KARGIN, V. A. KABANOV, S. YA. MIRLINA, and A. V. VLASOV, Vysokomol. Soedin.

'4 B. S. GARRETT, W. E. GOODE, S. GRATCH, J. F. KINCAID, C. L. LEVESQUE, A. SPELL,

3, T. MAKIMOTO, T. TSURUTA, and J. FURUKAWA, Makromolekulare Chem. 50 (1961) 116. 4, R. C. SCHULZ, H. MARX, and H. HARTMANN, Makromolekulare Chem. 44/46 (1961) 283.

3 (1961) 134.

J. D. STROUPE, and W. H. WATANABE, J. Amer. chem. SOC. 81 (1959) 1007.

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