Synthesis of tertiary amine polymers

Synthesis of tertiary amine polymers F. DANUSSO and P. FERRUTI

Systematic work, in Italy, on the synthesis of polymers having tertiary amino groups as structural units is reported. The polymers carry amino groups, (a) situated in the molecular main chain; (b) directly bound to the main chain as side groups; or (c) situated on side groups. Type (a) were synthesized by poly-addition of mono- or diamines (or aminoacids) to a compound having two vinyl double bonds activated by adjacent electron attracting groups. These polymers have different chemical functions regularly arranged along the main chain. For (b), the synthesis of polymeric compounds using enamines as monomers is discussed; results of practical interest were obtained by copolymerizing enamines with acrylonitrile to give products which may reach an alternating disposition of the co-units along the chain. In type (c) polymers which are partially stereoregular could also be synthesized, using anionic catalysts at low temperatures.

UP TO NOW, macromolecular chemists have shown little interest in developing convenient methods for the synthesis of high polymers containing tertiary amino groups, either aliphatic or cycloaliphatic. However, such polymers may be extensively used in different applications, as materials or (more generally) as reagents. Amino polymers have been described, particularly in the patent literature, although their structure and characterization is still uncertain. Such polymers are however extensively used in industry. Some tertiary polyamines and their N-oxides may also be used in pharmacology. For example, a number of these polymers have preventive properties against silicosis 1-3 and others are anti-heparinic 4. Due to their basicity and chemical reactivity, amino polymers may interact with a number of biological macromolecular substances present in living organisms. Hence this sort of application may well increase. In this paper we describe results obtained recently in the preparation of polymers containing tertiary amino groups (either aliphatic or cycloaliphatic) mostly by original methods of synthesis.

Classification of the polymers In view of the purposes of this work, it may be useful to propose a classification scheme for polymers containing tertiary amino groups. Substances of this type may be grouped in three main classes: (A) Polymers in which they are situated in the main chain. (B) Polymers in which they are directly bound to the main chain as side groups. In this case they may, or may not, be the only side substituents present. 88

SYNTHESIS OF TERTIARY AMINE POLYMERS

(C) Polymers in which the amino groups are not directly bound to the main chain, but which exist with other groups as constituents of side chains. This paper is divided into three main sections according the above classification.

(A) POLYMERS CONTAINING AMINO GROUPS IN THE MAIN CHAIN:

polyamines by poly-additon of amines to compounds containing vinyl double bonds The addition of primary or secondary amines to vinyl double bonds activated by electron attracting groups is well known. In this reaction, nitrogen is always bound to the carbon/3 to the activating group, whereas hydrogen migrates to the a-carbonL Under suitable conditions and with the use of bifunctional compounds, this reaction may lead to new linear polymers. The only example previously known is described in a patent claim 6. The polymers we obtained by this reaction have the character of saturated polyamines, often of high molecular weight. The amine groups form an integral part of the macromolecular chain, and are usually accompanied by other functional groups in the main chain according to predetermined regular sequences.

Polymers from disecondary diamines and bis-acrylamides We have particularly studied the poly-addition of disecondary diamines to

bis_acrylamides7, 8. x HN--R'--NH + x CHz=CH--C--N--R'"--N

I

I

R

I1[

R

O

R"

C--CH=CH2---~

I

R"

- - N[ - - R ' - - N [- - C H 2 - - C H 2 - - C[T - - N -[ - R ' " - - N [ R

R

O

R"

R"

tl

O

C--CH2--CH, II ~--] O

x

Poly-addition substantially takes place in the absence of secondary reactions; apart from the lack of elimination of a by-product, the reaction is similar to that of a bifunctional polycondensation (i.e. a branching scheme poly-addition) 9. We confirmed 6 that this polymerization is a nucleophilic polyaddition, with an ionic mechanism. It is not influenced by the presence of the typical inhibitors of radical polymerization, and it does not require acidic or basic catalysts. Poly-addition takes place most easily in solution, and generally the choice of solvent is of great importance in determining the reaction rate. 89

F. DANUSSO AND P. FERRUTI

Contrary to a previous paper 5, the dielectric constant of the solvent does not seem to play an important role; but the solvents that most rapidly lead to a high molecular weight are protic solvents, such as water or alcohols. Table 1 gives the intrinsic viscosities (in chloroform at 30°C) of the products obtained by polyaddition of 2-methylpiperazine to 1,4-diacrylylpiperazine (Table 2, polymer II) in solvents with different dielectric constants; the monomer concentration, temperature and polymerization time are the same for each case. Table 1 Poly-addition of 2-methylpiperazine to 1,4-diacrylylpiperazine in different

solvents* Dielectric constant

~

Solvent

80'2 at 20°C 47 at 23°C 36' 1 at 20 °C 24'3 at 25°C 12.5 at 20°C

water dimethylsulfoxide nitrobenzene anhydrous ethanol pyridine

[v]t

yieM

(dl/g)

95 80 90 95 85

0.81 0.13 0" 11 0"33 0-17

*Temp., 17°C; m o n o m e r concentration, 3 0 ~ ; p o l y m e r i z a t i o n time, 192 h t M e a s u r e d in c h l o r o f o r m at 30°C

Figure 1 shows the increase with time of the average molecular weight, as indicated by intrinsic viscosity (in chloroform at 30°C) for the polyaddition 100"C

020 I

0.15 '

u

/

I

1

5

10

1

15 Reaction time [hi

I

I

20

25

Figure 1 Molecular weight (as intrinsic viscosity in chloroform at 30°C) versus reaction

time in poly-additions of 1,4-diacrylylpiperazine with 2-methylpiperazine, at different temperatures, in pyridine7

of 2-methylpiperazine to 1,4-diacrylylpiperazine in equimolar amounts, at different temperatures, in anhydrous pyridine. In this solvent, an increase in 90

SYNTHESIS OF TERTIARY AMINE POLYMERS

molecular weight with time of reaction is always observed. On increasing the temperature, the polymerization rate increases, and for an equal polymerization time, the products obtained have higher molecular weights. Figure 2 shows the results obtained under the same conditions using water as a reaction solvent. At 100°C the molecular weight, after a rapid initial increase, reaches a maximum and then decreases with time.

17"C

~,~

60"C

E 0.2 t~ O

I00"C

d~

0.1

Ir

I

5

J

1

10 15 Reaction t i m e [h]

i

I

20

25

Figure 2 Molecular weight (as intrinsic viscosity in chloroform at 30°C) versus reaction

time in polyadditions of 1,4-diacrylylpiperazine with 2-methylpiperazine, at different temperatures, in water ~

At 60°C, after a short initial period in which it increases more slowly than at 100°C, the molecular weight reaches higher values, for an equal reaction time. Finally, at 17°C, the molecular weight first increases more slowly than at 60°C, then the increase is more rapid and far higher values are reached. This behaviour, which may seem anomalous, can be explained by the occurrence, in the aqueous solution, of simultaneous hydrolysis of the 91

F. DANUSSOAND P. FERRUTI amide link. The rate of polymerization, and of hydrolysis, increases on increasing the temperature; the rate of hydrolysis is greater at high temperatures for the reaction times we have used. In agreement with the mechanism scheme of this type of polyaddition, if other conditions are the same, the molecular weight of the polymers depends on the relative concentrations of the two monomers and increases to a maximum which corresponds to equimolar proportions. Figure 3 shows a typical example.

I

×

0"4

0-3

Q

×

/

0.2

x/j

0'1

1 0.4

×

×\ )¢

i 0.5 M o l e °/o p i p e r a z i n e

\\ 1 0.6

Figure 3 Polyaddition of 1,4-diacrylylpiperazine with piperazine: molecular weight (as intrinsic viscosity)versus initial ratio between the amounts of the two monomers (I-q]in 0-1 N HCI/1N NaCl aq. soln at 30°C)7 Table 2 shows the structure of some polymers obtained by polyaddition of di-secondary diamines to bis-acrylamides. On the basis of the experimental results mentioned above, their synthesis was generally accomplished in water or in alcohol, at temperatures ranging from 15°C to 60°C and for reaction times varying from a few hours to several days. Equimolecular amounts of the monomers were always used 6, 7 92

SYNTHESIS OF TERTIARY AMINE POLYMERS Table 2 Polyamide amines from disecondary diamines and

Ref.

[hi*

Unit

dl/g at m.p. Crystallinity

30'C

[°C]

N-COCH2CH2-

0-46 t

270

dec.

high

N-CH2CH2CO-N N-COCH2CH2\__/ ".,__//

0"81

218

low

0'21

113

high

0"12

97

high

0"27

217

low

0"31

--

amorphous

0"55

210

high

no.

/--\ 1 -N

II III

/--\ N~CH2CH2CO-N

\ \ __.,/

\--,/

/ - - × CH3

/--\

-N

-N-CHeCHe-N-CHaCH2CO-N

1

CHa

-N-CHe-CH2-N-CH2CHeCO-N

I

CH(CH3)2 V

VI VII

/--\

-N

/-x -N \_/ /--\ -N

"\_/

VIII

N-COCH2CH2-

~_/ /--\

I

CHa IV

bis-acrylamides

N-COCH2C H~-

\_/

I

CH(CHa)2

/--x

CH3

N-CH2CH2CO-N

N-COCH2CH2-

CHa

CHa

N-CH2CH2CO-N

/-x

\_/

N-COCH2CH2-

N -CH~CHzCO-N-CH2CH~-N-COCH2CH2-

I

1

CH(CHa)2 CH(CHa)2 -N-CHzCH2-N-CH2CH2CO-N-CH ~CH2-N-COC H~C H2I I I I 0"17 CHa CH3 CH(CHa)2 CH(CHa)2

102

medium

/--\

IX

-N

\_/ /--\ X

-N

N-CH2CH2CO-N-CH~CH2-N-COCHzCH2-

I

C2H5

0"35

--

amorphous

I

C2H5

N-CH2CH2CO-NH-CH2CH2-NH-COCH2CH2- 0"12++ 231

high

dec. *In c h l o r o f o r m were n o t otherwise indicated tin aqueous 0.1 M hydrochloric acid/1 M sodium chloride :~ln aqueous 0.5 M acetic acid/l M sodium acetate

The polymerization time required to reach a sufficiently high molecular weight product, other conditions being the same, depends on the nature of the monomer and in particular on the structure of the diamine. The following inverse scale of the reaction times has been observed: N,N'-diisopropylethylendiamine ~ N,N'-dimethylethylendiamine < 2-methylpiperazine piperazine. Such an order most likely reflects the order of reactivity of the diamines toward polyaddition; consequently one must conclude that the steric bulkiness of the secondary amino group is, in our case, determinant, for the following reasons.

93

F. DANUSSO AND P. FERRUTI

When comparing the rates of addition to the activated double bonds of amines, such as piperidine and morpholine, where there is a practically identical steric bulkiness, it was found that a higher basicity of the amine is associated with a higher reactivity5. The basicities of the amines studied showed the following increasing order10: piperazine ~< 2-methylpiperazine < N,N'-dimethylethylenediamine ~< N,N'-diisopropylethylenediamine. Such an order is the exact reverse of the order of reactivities found by us in the polyaddition; however, in this case, it also shows the effect of increasing steric bulkiness in the diamines. Polyamide amines obtained by polyaddition of disecondary diamines to bis-acrylamides are generally soluble in water, alcohol, and chloroform, and insoluble in aliphatic hydrocarbons. They are often very hygroscopic. The polymers reported in Table 2 can be crystallized, except for polymers VI and IX; the latter is rubber-like at room temperature. It may seem surprising that polymers I and V, although scarcely crystalline, are not completely amorphous. In these polymers, in fact, a structural irregularity should exist since the direction of the methyl group with respect to the polymer chain varies. Their partial crystallinity can be explained by considering that the methyl group has a relatively small dimension in comparison with the base unit. The thermal stability of the polyamide amines described has been evaluated by thermogravimetric measurements under vacuum, under nitrogen, and in air, with heating rates of 150°C/h. Using this method, volatilization starts at about 200°C under vacuum, and a few tens of degrees higher under nitrogen and in air, without there being any large differences between the various polymers.

Polymers from primary amines and bisacrylamides The above polyaddition of disecondary diamines to bis-acrylamides leads to polyamide amines in which the amine groups (a) and amide groups (b) are regularly arranged along the main chain according to the repeating sequence: --a--a--b--b---a--a--b---b-Contrary to previous work 11, we have also synthesized linear high polymers by polyaddition of primary amines to bis-acrylamideslL x RNH2 + x CH2~CH--CO--N--R"--N--CO---CH--CH2

I

I

R'

R'

pt

- - N - - C H z C H ~ C O N - - R --NCOCH2CH2 ] ~ .

II

i

L R

R' 94

i

R'

I

J~

SYNTHESIS OF TERTIARY AMINE POLYMERS

In this case, the product obtained from a first addition of a primary amine to an activated double bond is a secondary amine, which may be further added to a second double bond. Therefore, the primary amine must be considered as a bifunctional monomer, useful for the formation of linear high polymers, if cyclization reactions can be avoided. The polyamide amines obtained in this way have amine and amide groups following one another along the main chain according to the repeat sequence: --a--b--b--a--b--b--a--b--b-The structures of some polyamide amines obtained by this method are shown in Table 3. The operating conditions for polyaddition are analogous to those adopted for disecondary diamines. Table 3 Polyamide amines from primary amines and bis-acrylamides

Re]'. no.

Unit

[d//g]

/-\ I

-CH2-CHa-CO-N

N-CO-CH2-CH2-N-

0-40

I

\_/

CH3

/-\ I[

-CH2-CH2-CO-N

\__/

N-CO-CH2-CH2-NC2H5

/--\ Ill

-CH~-CH~o-CO-N

\__/

N-CO-CH2-CH2-N-

-CH~-CHa-CO-N

CzHv-n N-CO-CHz--CHz-N-

-CHz-CHe-CO-N

0-11

I

\__/ /--\ V

0" 11

[

/--\ IV

0"24

[

CH(CHa) 2 N-CO-CH2-CH2-N-

0'27

I

\_/

C4H~-n

/-\ VI

-CH2-CH2~O-N

VII

-CH2-CH,~-CO-N

N-CO-CH2-CH2-N-

0-15

/ - - x CHa

VI I I

N-CO-CH2-CHz-N-

CH3 -CHz-CHz-CO-N-CHz~CH~-N-CO-CH~-CH2-N-

I

IX

0"43

I

0'20

1

C2H5 C2Hs CH3 -CH2~CH~-CO-N-CH2-CH2-N~CO-CH.o-CH2-N -

1 CH(CHz)2

I CH(CH3)2

*Measured in chloroform,at 30°C

95

I CH3

0-54

F. DANUSSO AND P. FERRUTI

From x-ray analysis all these new polymers are amorphous during preparation. Some of them, however, after crystallizing treatment with nonsolvents, revealed considerable crystallinity (polymers I, VI, IX); however, crystallization could not be induced in others even though they possess regular structures. Several properties, including solubility and thermal stability, of polyamide amines obtained from primary amines are substantially similar to those from disecondary diamines.

Polymers from disecondary diamines and acrylic diesters or divinylsulphone The poly-reaction that leads to the polyamide amines described up to now may also be accomplished with acrylic diesters or divinylsulphone instead of bis-acrylamides 13. In this case, disecondary diamines could be used quite conveniently as co-monomers. Under the conditions we used, primary amines do not yield well defined products with acrylic diesters, whereas with divinylsulphone they yield cyclic dimeric products14. Some of the polymers obtained in this way are listed in Table 4. These Table 4 Polymers from disecondary diamines and bi~-acrylic esters or divinylsulphone

[~]*

Ref.

at 30°C m.p. Crystal-

no.

(dl/g) [°C] linity

Unit

/--\ 1 - C H 2 ~ H z - C - O - C H 2 - C H 2 - O - C - C H 2 - C H ~-N

IL

il

O

N-

O

.

It

O

\=~

0'41

93

high

0'48t

189

high

164

high

145

high

0.60~ 200

high

~/

\_/

It

O

CH3

II

O "

O

\--/=

I1

\_/

O CHo

CHz

O

/--\

V - C H 2 - C H~-SOz-CHz-CH 2-N

/--× VI - C H 2 - C H z - S O 2 - C H ~ - C H z - N

NCHa

0.29

N-

* In chloroform, unless otherwise specified 1"n sp/conc. (conc. = 0"5 %) in glacial acetic acid In dimethylsulphoxide, at IO0°C

96

--

amorphous

SYNTHESIS OF TERTIARY AMINE POLYMERS

polymers show the following repeating sequences along the main chain: --a--a--c--c--a--a--c~---a--a--d--a--a--d-where a represents the tertiary amine group, c, the ester group, and d the sulphone group. When examined by x-rays, all these p o l y m e r s - except polymer V I - are seen to be highly crystalline. In spite of its apparent structural disorder, polymer III shows a very high crystallinity, which is higher than that of the earlier polyamide amines, which also contain one group derived from 2methylpiperazine. The polymers reported in Table 4 show a behaviour towards solvents which is different from the polyamide amines previously described; in particular, except for polymer I, they show a lower affinity toward water and alcohols. Other properties, including thermal stability, are substantially the same.

Polymers from aminoacids and bis-acrylamides Aminoacids may be used as the monomers for a polyaddition to give regular-structured polyampholites. By this route, it should also be possible to obtain water-soluble polymers showing optical activity by a simple method from fairly common and cheap substances, such as natural m-aminoacids. The problem, however, is more complex than for disecondary diamines or primary monoamines. In f a c t - i n agreement with predictions from the reaction m e c h a n i s m - u n d e r the conditions we used, primary or secondary amine salts did not react with the double bonds of acrylamides or bisacrylamides. In the same way, neutral aminoacids, which are in the form of internal salts, are not suitable monomers. Actually, on mixing aqueous solutions of 1,4-diacrylpiperazine and glycine or fl-alanine, and by maintaining the mixture at 20°C for several days, no reaction occurs and the reagents can be recovered in practically quantitative amounts. In addition, a great many aminoacids are not sufficiently soluble in the solvents which are suitable for poly-addition, except for water. However, the disadvantage of water lies in secondary reactions, such as the hydrolysis of the amide bond, which may occur when operating under severe temperature conditions or when long reaction times are used. It should be theoretically possible to use aminoacids as monomers if the amine group is present in the polymerization system in the non-ionized state, and if side reactions are simultaneously prevented. A further important condition is the possibility of purifying the resulting polymer from added reagents. We obtained a5 interesting results when we carried out poly-addition of some aminoacids with bis-acrylamides in an aqueous solution at room 97 P~G

F. DANUSSO AND P. FERRUTI

temperature in the presence of a fairly volatile tertiary amine, such as triethylamine. It is well known that aminoacids do not form stable salts with ammonia and amines; however, in aqueous solution, the existence of the following equilibrium may be reasonably expected: +

+

HaN-R-COO- + R~N ~ HzN-R-COO- + RaNH Once the polymer has been obtained, it may be substantially freed from triethylamine by prolonged high vacuum treatment. The use of hydroxides, or of alkaline carbonates, instead of triethylamine did not lead to satisfactory results. This method allowed the preparation of polymers with fairly high inherent viscosities (in water or methanol) from 1,4-diacrylylpiperazine and aminoacids such as glycine, fl-alanine, taurine and others which do not contain substituents on the carbon atom adjacent to the amino nitrogen. Some of the polymers obtained are listed in Table 5 (I to VI). Table 5

Polymers from aminoacids and 1,4-diacryloylpiperazine

~lnh* a t Ref . no.

Unit

30°C [dl/g]

/--\ I

-CH~-CHz-CO-N

N-CO-CH2-CH,z-NCH2-COOH

/--\ II

-CH2-CH2420-N

0" 121

N~O-CH2-CH,z--N-

0"27

(CH2)2-COOH III

~H2-CH~420-N

N-CO-CH~-CH2-N-

\_/ /--\ IV

-CI-[2-CH2-CO-N

(CH2)a-COOH N-CO-CH~-CH2-N-

\__/ /--\ V

-CH2-CH2-CO-N

(CH2)~-COOH N-CO-CH2-CH2-N-

-CH~H2-CO-N

-CH2-CH~-CO-N

(CH2)~COOH N-CO-CHa-CHa-N-

/--\ ~_/

-CHe-CHe-CO-N

0" 13

I

(CH2)~SOaH COOH

Y--x ~_/

N-CO-CH~-CH2-N HOOC

VIII

0" 12

L

\_/

VII

0"12

I

\_/ /--\ VI

0" 18

I

N-CO-CH~-CH2-N

*In 90 ~ methanol/lO~ water, were not otherwise specified (cone. = 0.5 ~) tin water :~[n 80~ methanol

98

N-

0'28++

COOH N-

0"30t

SYNTHESIS OF T E R T I A R Y AMINE P O L Y M E R S

Corresponding results were also obtained with cyclic aminoacids, such as piperazine-2-carboxylic acid and piperazine-2,3-dicarboxylic acid (Table 5, VII and VIII). In the former case, a polymer may be obtained without addition of triethylamine, but with a far lower polymerization rate. Further difficulties are encountered when natural aminoacids, other than glycine are used as monomers; this is due to steric hindrance. In this case, even in the presence of equimolar amounts of triethylamine, only low molecular weight polymers were obtained in aqueous solution and at room temperature. It is also rather difficult to prepare high polymers from primary amines which are very sterically hindered (e.g. isopropylamine) 8. The reaction rate cannot be increased by conducting the polymerization in water at higher temperatures since hydrolysis will occur. We did succeed in obtaining polymers with fairly high intrinsic viscosities, and possessing optical activity, by using dipeptides such as glycyl- or fl-alanyl derivatives of a-aminoacids 15. Some results obtained by us with optical isomers of glycyl or fl-alanyl alanine are listed in Table 6. It is also theoretically possible to use tri- or polypeptides, as monomers, provided that the first residue is derived from glycine or fl-alanine. In this case, polymers with a regular structure should be obtained, with peptide side chains arranged in a predetermined sequence.

Polymers from hydrazine (or 1,1-dimethylhydrazine) and bis-acrylamides It may also be of interest to report the results obtained when monomers with a nucleophilic character different from amines are used. For example, linear polyamide hydrazines may be obtained with hydrazine (or 1,1-dimethylhydrazine) and bis-acrylamides16. As far as we know, polymers of this type have not been described in the literature; their basicity, solubility and chemical reactivity make them interesting from, a practical point of view. Since hydrazine has four mobile hydrogens, it must be considered to be a polyfunctional monomer in the poly-addition under examination. However, as previously observed, in the poly-addition of disecondary diamines to bis-acrylamides, the steric bulkiness of the amino group exerts a dominant influence on the rate of polymerization. This can also be expected with hydrazine derivatives. This may be the reason why hydrazine reacts with an equimolar amount of bis-acrylamide according to the equation: x NH2NH2 + x C H 2 - C H - - C O - - N - - R ' - - N - - C O - - C H - - C H 2

I

I

R

--> ~ [

R

N H--NH--CH 2--CH2--CO--N--R'--N--CO--CH2--CH2

to give an essentially linear polymer. 99

]

F. DANUSSO AND P. FERRUTI

%

I

+

6

<

I

6

6

Y

,y o

Y

t.

=

~-~

~

t

-

,b II

= e~

0

z

ff

z

o

o

o

© I

/Z\ 0

\

z, /

z

\z,

o

o

o

o

z

~

z

Z

z,

Z I

100

8

/

-

SYNTHESIS OF TERTIARY AMINE POLYMERS

For the end-group R--NH--NH2 (a)

(b)

(where R is the growing polymeric chain), an addition to the nitrogen atom (a) is expected to be more difficult that an addition to the nitrogen atom (b) due to the steric hindrance of the growing polymer chain. Addition involving the - - N H - - N H groups present in the chain, with consequent crosslinking, is similarly improbable. The experimental results were found to be in agreement with the data expected. The polymers obtained are shown in Fable 7 (from I to III). Table 7 Polyamide hydrazines

Ref.

[~] at 30°C *

Unit

no.

[dl/e]

/--\ 1

-CHz-CH2-CO-N

N-CO-CH2-CHz-NH-NH-

0-18

/ - - × CH3 II

-CH~-CI-I~-CO-N

N-CO-CH2-CH2-NH-NH-

III

-CH2-CH2-CO-N-CH~H2-N-CO-CH2-CH2-NH-NH-

I

CH(CH~)2

/--\

IV

-CH2-CH2-CO-N

CH(CH3)2

N-CO-CH~CH2-N-

0' 10

I

N(CH3)~

/--\ -CII[2-CH2-CO-N

0' 16

I

\__j V

0"18

N-CO-CH2-CH~N-

0-08

N(CH3)z *In chloroform

The structure of linear polyamide hydrazines obtained from hydrazine and bis-acrylamides has been confirmed not only by elemental analysis, but also by spectroscopic data. It is interesting to observe that linear polymers are obtained from equimolar amounts of hydrazine and bis-acrylamide, whereas crosslinked polymers are obtained with higher amounts of bisacrylamide, although fairly long reaction times are necessary. Hydrazine is fairly reactive in this type of poly-addition; polyamide hydrazines, like polyamide amines, are prepared in aqueous solution at room temperature. Under these conditions, the molecular weight of the product increases rapidly to a maximum, and then decreases. As mentioned above, this also occurs in the preparation of polyamide amines under similar experimental conditions. Again, this behaviour may be explained by the simultaneous hydrolysis of the amide link. lO1

F. D A N U S S O A N D P. F E R R U T I

The presence of the - - N H - - N H - - group in these polymers makes it possible to carry out modification reactions. In particular, a further reaction with monofunctional compounds containing activated double bonds, such as acrylonitrile or phenylisothiocyanate, is possible: - - N H - - N H - - + C6HsNCS

> --N--NH--

I I

C=S HN--C6H5 Under conditions corresponding to those described, linear polymers may also be obtained from bis-acrylamides and typical derivatives of hydrazine, such as 1,1-dimethylhydrazine. The polymers obtained are listed in Table 7 (IV, V). The intrinsic viscosity values show that their molecular weight is not very high. We may conclude that the poly-addition of dialkylhydrazine or, under suitable conditions, of hydrazine, to bis-acrylamides, must be considered as a particularly easy reaction and up to now the only route available for the synthesis of linear polymers with amide and hydrazine groups regularly arranged along the main chain.

Polymers from primary phosphines and bis-acrylamides Good results were obtained when the above method of polymerization was applied to phosphines17. Polyphosphines obtained by radical catalysed poly-addition of primary phosphines to diolefins- such as diallyl or its derivatives- are described in patent literature18. However, these products have low molecular weights and their structure is still uncertain. The polyamide phosphines obtained by us, however, were pr~lpared in the absence of catalysts and in the presence of radical polymerization inhibitors, using a process similar to that used for the synthesis of polyamide amines. The reaction is carried out in a toluene-ethanol solution under nitrogen at about 40°C. Under such conditions, the time required to reach a satisfactory molecular weight varies from one to four days. Some examples of polymers obtained from 1,4-diacrylylpiperazine or 1,4-diacrylyl-2-methylpiperazine and phenylphosphine or benzylphosphine, as monomers, are given in Table 8. The thermal stability of these polymers is fairly good. As observed from the thermobalance under vacuum, weight loss starts above 360°C, whereas under the same conditions polyamide amines with similar structure start to decompose at about 200°C.

Conclusions The foregoing remarks on the branching scheme poly-addition which we have used to synthesize polymers with a tertiary amine group (or related 102

SYNTHESIS OF TERTIARY AMINE POLYMERS

groups) suggest that an extremely high number of variants is possible for this method of synthesis, since the number of substances that may be used as monomers is particularly high. This poly-reaction can be performed using mild conditions and in the presence of various other groups; these groups can be chosen so as to exclude interchange reactions, thus conferring a high stability to even very complex macromolecules.

Table 8

Polyamide phosphines [r/]* at

Ref. no.

Unit

30°C ldl/g]

j--\ I

-CH2-CH2-CO-N

N-CO-CHz-CH2-P-

\_/

0

CH3 I!

-CH~-CH2-CO-N

0'25

I

N-CO-CH2~SH~-P-

\_/

0-31

1

J\ j--\ III

-CH2-CH2-CO-N

N-CO-CH2-CH2-P-

j--× IV

-CM2-CH2-CO-N

\-/

0'90t

CHz N-CO-CH2-CH2-P-

0'23

*In chloroform were not otherwise specified Tn sp/conc. (conc. = 0.5 %) in glacial acetic acid

Furthermore, by using suitable reaction conditions one can synthesize polymers consisting of segments of different lengths, or polymers with an ordered structure from monomers of complex structure. This poly-reaction could have important applications in the synthesis of very complex macromolecules such as biopolymers. It is a simple and spontaneous poly-reaction which occurs at normal temperatures, to give polymers containing base units of predetermined length with a number (possibly a large number) of different chemical groups regularly arranged along the main chain. 103

F. DANUSSO AND P. FERRUTI (B) POLYMERS WITH AMINE GROUPS DIRECTLY BOUND TO THE MAIN CHAIN:

homopolymers and copolymers of enamines No significant reports on the polymerization of enamine compounds have appeared in the literature. However, the enamines isolated so far in the pure state are derived from aldehydes higher than acetaldehyde or from ketones higher than acetone. With regard to, for example, N-vinyl or isopropenyl amines, we can definitely say that apart from a few patent claims 19 the literature does not report any certain examples of isolation. The results described in patents do not seem to be reproducible. For a vinyl homopolymerization, monomers of N-vinyl amine character are of greater interest than enamines of complex structure; the latter are more widely known at present. In fact, even apart from catalysis problems, enamines are expected to have little tendency to homopolymerize because monomers of the vinyl or vinylidene type with a highly hindered double bond generally give very poor yields of high polymers on homopolymerization. The N-vinyl amines that have definitely been isolated have at least one aromatic substituent bonded to nitrogen. However, the presence of phenyl substituents substantially decreases the basicity of the amino group. We examined the case of N-vinylmorpholine (I) in detail. By reacting acetaldehyde and excess morpholine, in the presence of basic dehydrating agents, we isolated 1, l-dimorpholinethane (II) in good yield2°. This compound was shown to exist in equilibrium with morpholine and N-vinylmorpholine.

/-\ N

0

/ \_/ CHs--CH \/-\ N

\_/

/-\ -~

CH2=CH--N

/-'\ 0

+

HN

\_/

O

0

(II)

(I)

(III)

Such an equilibrium is displaced to the right by an increase in temperature, but it exists even at room temperature when the compound is liquid. Mannich and Davidsen zl, had previously suggested a similar dissociation of the analogous derivatives of piperidine, only at a higher temperature and in the vapour phase. This equilibrium is responsible for some apparent anomalies in the behaviour of 1,1-dimorpholinethane. This compound, melting at about 25 °C, may be distilled at 50-55°C and 20 mmHg. Surprisingly, the boiling point depends on the rate of heating and the distillate spontaneously gives off a large amount of heat in the collection vessel. By gradually decreasing the pressure, the distillation occurs at progressively higher temperatures; at 0.1 mmHg the temperature of the vapour reaches about 80°C. This may be 104

SYNTHESIS OF TERTIARY AMINE POLYMERS

explained if distillation at 20 mmHg occurs after dissociation and codistillation of the two products occurs. Under high vacuum, at least a part of the original compound may be distilled unchanged. If the 20 mmHg distillate is collected in a vessel at --78°C and the i.r. spectrum taken immediately, a sharp band due to the vinyl group is observed. If the distillate is heated to room temperature, heat is evolved and this band disappears. Finally, in the i.r. spectra run at different temperatures on the liquid compound, the bands of the vinyl double bond (e.g. at 6.05 /zm) become evident and gradually become stronger on increasing the temperature; at 80°C a substantial amount of N-vinylmorpholine is present in the system. The chemical behaviour of 1, l-dimorpholinethane is also in agreement with the existence of a dissociation equilibrium in morpholine and N-vinylmorpholine 22. Some typical reagents that form compounds with enamines, such as 4-nitrophenylazide or benzonitryloxide, give quite good yields of the corresponding derivatives of N-vinylmorpholine in the presence of 1,1dimorpholinethane, and under mild reaction conditions. CH2----N

l

/\ II ~- A r - - N z

---->

/

\

[ \\

/

JI

CH

/

N

N f

l

Ar

+ llI

O [Ar : 4-NO2-C6Hs-] Other secondary amines introduced into the system may participate in the dissociation equilibrium. For example, derivatives of N-vinyldiethylamine are obtained in the presence of diethylamine22: CH2

N

I

I

CH II + (C~Hs)2NH -q- Ar-N3

•

/ (C~Hs)2N

N

\

/

+ m

N

r

Ar [Ar : 4-NOe-C6H4-] Two factors are important in these exchange reactions: the basicity of the added amine and its steric bulkiness. The other conditions being constant, amines with a higher basicity tend to displace morpholine; however, this does not occur if amines have a high basicity but are very hindered, (e.g. dicyclohexylamine). 105 P--H

F. D A N U S S O A N D P. F E R R U T I

All attempts to isolate pure N-vinylmorpholine by chemical or physical methods have been unsuccessful20,22. N-Vinylmorpholine is apparently unstable in the absence of morpholine, and decomposes during its isolation yielding brown polymeric products of a non-polyvinyl type. However, a dilute solution of vinyl morpholine, which quickly decomposes to tars and morpholine, has been obtained2L By analogy with observations under suitable conditions, of enamines derived from acetone (N-isopropenylamines), or of methyl-n-alkylketones2~, we may suppose that free N-vinylmorpholine tends to give rise to oligomeric or polymeric selfcondensation products with loss of morpholine, under the experimental conditions used. It is difficult to obtain homopolymers of N-vinylmorpholine directly from 1, l-dimorpholinethane. The high electronic density on the vinyl double bond excludes the use of anionic and radical initiators. 1,1-Dimorpholinethane is actually inert to the action of initiators such as azobisisobutyronitrile. The use of cationic-type initiators is, however, complicated because the system contains several chemical species capable of interacting with them. However, we succeeded in obtaining low molecular weight polymers from 1,1dimorpholinethane using protonic acids (e.g. sulphuric, p-toluensulphonic or even acetic acid) in an alcoholic solution. Even hydroquinone and water can initiate the polymerization although they are very weak acids. The use of iodine or alkyl iodides gives identical results. The polymers obtained have molecular weights not exceeding several thousands and they are yellow or light brown. As shown by i.r. and n.m.r. analyses, their structure is somewhat irregular, although reproducible, and only roughly corresponds to that of polyvinylmorpholinez°. Enamines are known to react by an ionic mechanism, in the absence of catalysts, with acrylonitrile and with other compounds containing vinyl double bonds activated by electron-attracting groups in the a-position~5-2s; the reaction takes place under mild conditions. The first reaction products are cyclic products, such as:

C2H5

/-\ C~Hs--CH=CH--N

\_/

CN

0 +CH2=CHCN N

\_/

0

These products are thermally quite stable when they are obtained from enamines of aldehydes but, if they are derived from enamines of ketones, they decompose on heating, to give cyanethylated enamines with opening of the ring27: 106

SYNTHESIS OF TERTIARY AMINE POLYMERS

/\_

/~/"

I I_f __+ \/I \ /N,,, CN I f

I \~ /N\ I

"\0 /

CH2CH~CN

\0 /

I

However, if acrylonitrile and enamine are allowed to react in the presence of radical initiators, copolymers of fairly high molecular weight are formed and copolymerization predominates over simple addition, or side reactions. The best results are obtained using enamines of aldehydes; enamines of ketones, e.g. 1-morpholinocyclohexene or 1-morpholinocyclopentene also give copolymers with acrylonitrile, although high yields are seldom obtained. We particularly investigated the copolymerization with acrylonitrile of some enamines of butyraldehyde, especially 1-piperidinobutene and 1-morpholinobutene ~a, to give the following eopolymers:

CN

Jx I_ C2H5

/

N

I\

Jy

\ //

1

X [X = -CH2-, o r - O - ] Azo compounds, and in particular azodiisobutyronitrile, were used as radical initiators. The copolymerization is best carried out in bulk with carefully purified monomers, in an inert atmosphere, at temperatures between 40°C and 707C, and for times varying from a few hours to several days. The curve of composition with 1-morpholinobutene, (Figure 4), is similar to that obtained for other enamines. The enamines being examined do not homopolymerize appreciably in the presence of radical initiators; consequently the enamine content of the copolymers increases with the concentrations of enamine in the monomer phase, but never rises above 50 (in moles). It is interesting to observe, (e.g. in Figure 4), that the experimental results are best interpreted by considering an effect of the penultimate unit on the reactivity of the growing copolymeric radical. A radical ending with two acrylonitrile units reacts far more readily with the enamine than with acrylonitrile; however, this difference disappears if the penultimate unit is an enamino group. The rate of copolymerization increases with increasing concentration of acrylonitrile in the monomer mixture as well as with temperature. 107

F. DANUSSOAND P. FERRUTI 50

3O X/~X

u_-

10 I

I

I

I

I

I

I

I

I

10

20

30

40

50

60

70

80

90

100

fl Figure 4 Composition curve of the copolymerization of acrylonitrile with l-morpholino-

butene (60°C; AzBN as initiator). [Incremental polymer composition (mole fraction F1) versus the monomer composition (mole fraction fl).]. The solid curve is calculated taking into account the penultimate effect z4

3

X / 5 8 - 8 %

2 r",

Xd/¢~/

I

/

51"C

/X j

~ .~.x.-X/X 0

0

l

1

1

2 % Azo compound

I

:3

Figure 5 Copolymerization of acrylonitrile with l-morpholinobutene: demonstration of the unitary overall reaction order with regard to the initiator

Further kinetic features have been found on studying the copolymerization of equimolar mixtures of monomers, and at low yields. The overall reaction rate is proportional to the concentration of the initiator (see, e.g. Figure 5) and has a fairly high energy of activation of about around 30kcal mole -1. Moreover, the molecular weight of the copolymer is not very high and it is 108

SYNTHESIS OF TERTIARY AMINE POLYMERS

fairly insensitive to variations in the composition of the monomer phase, the concentration of the initiator, and the degree of conversion. These observations suggest that an appreciable chain transfer with the monomer, particularly a degradation chain transfer with enamine, occur. If the copolymerization is carried out at higher conversions, the reaction tends to stop at a fairly low degree of conversion. The threshold conversion, which we have determined, does not only depend on temperature but also on the amount of initiator used. This may be connected with the presence of a degradative transfer, which in this case predominates; the kinetic chain length is consequently rather short. In the cases we considered, the intrinsic viscosities in acetone at 30°C of enamine-acrylonitrile copotymers varied from 0.09 to 0.14dl/g. The copolymers are white powders, stable in the air, and amorphous by x-rays. They are generally soluble in chloroform, acetone, acetonitrile, dimethylformamide, pyridine and glacial acetic acid. They are mostly insoluble in alcohols, aliphatic hydrocarbons and water. The copolymers having an enamine unit content above 7-8 ~ dissolve in dilute aqueous acid and they may be reprecipitated unchanged from these solutions with alkalis, as shown by comparison of intrinsic viscosities and i.r. spectra. Having demonstrated that it is possible to obtain acrylonitrile-enamine copolymers in the pure state, it was interesting to check whether Nvinyl morpholine copolymers could be obtained directly from 1,1-dimorpholinethane and acrylonitrile. Here the reaction system appears to be complex, in that the morpholine that is present in the dissociation equilibrium of 1,l-dimorpholinethane, in equimolar amounts to N-vinylmorpholine, may react with acrylonitrile to give a simple co-dimer as a by-product. However, under suitable conditions and in the presence of radical initiators, good yields of the copolymers considered and substantial amounts of 4(fl-cyano)ethylmorpholine are obtained 24.

J----\

N

O

/ \__/ CHa--CH \/---\ N

\

AzBN

+ CH 2 = C H - - C N

/

O

[CH CU ] fCH CH] -t =--I ].--tJL CN

>

/-\ +

N

0 109

O

\_/

N--CH2--CH2CN

F. DANUSSO AND P. FERRUT1

The composition of the copolymers varies on varying the ratio of the monomers; but the complexity of the system makes the use of the traditional equations of radical copolymerization complicated. However, contents of enamine units in the copolymer of about 30% may be obtained. The molecular weight, solubility and chemical reactivity of the copolymers obtained are similar to those of the copolymers of acrylonitrile with more substituted enamines. On the contrary, their thermal stability is much higher. Using the Adamel CT 59 thermo-balance, Chevenard-Journier system, and heating rates of 105°C/h, decomposition commences at about 320°C with the copolymer of N-vinylmorpholine in air and at about 260°C in the case of copolymers of enamines of higher aldehydes.

(C) POLYAMINES IN W H I C H T H E A M I N E G R O U P S A R E IN T H E SIDE C H A I N

Polymers with the amine groups bound to the main chain by aliphatic hydrocarbon residues Amino-olefins with the general formula CH2=CH--(CHz)n--NR2

(n >/2)

have been recently polymerized in the presence of conveniently modified Ziegler-Natta catalysts, to give stereoregular high polymers29. However, the polymerization of allyl amine monomers (n = 1) to high polymers has not so far been accomplished. However, high molecular weight tertiary poly(allyl amines) may be synthesized by modification of other macromolecular substances, although this method is not always as easy as it might appear at first sight. The main diffÉculty is to find reactions which give quantitative transformations of the required chemical groups. In fact, at least in fundamental research, the aim is to prepare a homopolymer that formally corresponds to a well defined monomer. There are relatively few methods of synthesizing tertiary amines and, therefore, there are few available polymers suitable for modification. For the reasons mentioned before, we reject reactions which are difficult to control and those (e.g. the Hoffman condensation) that usually lead to mixtures of products. Satisfactory results were obtained by reducing the carbonyl groups of poly-N,N-dialkyl acrylamidesa°: -

Ik

NRAx

k

NRAx

The reducing agent used was excess lithium aluminium hydride dissolved in dioxane, N-methylmorpholine or anisole, at a reaction temperature of 110

SYNTHESIS OF T E R T I A R Y AMINE POLYMERS

100°C to 150°C; this has been previously used with fairly good results for the reduction of other polymers31. From polyacrylamides we obtained poly(allyl amines) in yields ranging from 6 0 ~ to 90~. Their intrinsic viscosities varied between 0.2 and l dl/g and we may assume therefore that the molecular weights of these polymers is high and of the same order of magnitude as that of the starting polyacrylamides. The high degree of reduction evidenced by the disappearance of the absorption band of amide C ~ O (6-Item), which was very intense in the starting polymers. Moreover, the elemental analysis of poly(allyl amines) is in excellent agreement with the calculated values. Polyacrylamides often dissolve or swell in water, but the poly(allyl amines) obtained by us are insoluble in water, except for poly-N-allyl-morpholine which dissolves below 10°C, although they reprecipitate on heating. On the other hand, n-heptane acts as a precipitant for all the polyacrylamides considered, whereas it easily dissolves aliphatic or cycloaliphatic poly(allyl amines) (except for poly-N-allylmorpholine). All poly(allyl amines) considered dissolve easily in diluted aqueous acids (even in the weak acids like acetic acid) and reprecipitate on the addition of alkali. Open chain aliphatic poly(allyl amines) like poly-N,N-diethylallylamines, are flexible, hard materials which resemble some polyhydrocarbons, such as polyethylene. The presence of cyclic structures, derived from pyrrolidine, piperidine and morpholine, makes these polymers hard and somewhat brittle when moulded in thin sheets. All the poly(allyl amines) obtained by us were amorphous by x-rays, even the modified stereoregular polyacrylamines. This may be due to a lack of stereoregularity from racemization that occurred during modification. It is well known that stereoregular vinyl polymers, especially those containing a carbonyl group in the a-position at the tertiary carbon atom, may lose stereoregularity by heat treatment with basic catalysts32.

Amine polymers of the type of poly(acrylic acid) derivatives Most amine polymers previously known with a well defined structure fall into this present class. Well known examples are polyacrylates or polymethacrylates of amino alcohols. In research carried out in an attempt to prepare polymers with pharmacological activity capable of preventing silicosis 1 we obtained interesting resultsza by preparing substituted polyacrylamides of the type I--CH2--CH--

!

I

CO--N---CH~--CH~--N

I R

/

\

\

/

0 x

The behaviour of the monomers toward polymerization is substantially 111

F. DANUSSO AND P. FERRUTI

the same as that of the usual N,N-dialkyl substituted acrylamides, when the initiator does not interact with the amino groups. We obtained high polymers of these monomers both by radical polymerization in the presence of azo-bisisobutyronitrile and by anionic polymerization in the presence of butyl lithium or Grignard compounds. The former method yielded polymers amorphous to x-rays. The latter (in a toluene solution at --78°C) gave different polymers. These are partially insoluble in solvents that dissolve radical polymers; their x-ray diffraction spectra exhibit broad crystallinity bands, which are absent from the spectra of the corresponding free radical produced polymers. These bands may be attributed to the presence of imperfect crystals, that is, to a paracrystalline arrangement, which might be due to substantially regular chains. The presence of crystallinity was surprising since there are reports in the literature that the presence of tertiary amines hinders the corresponding stereospecific anionic polymerization of N,N-dialkyl substituted acrylamides a4. In our work, the monomer itself had the character of a tertiary amine. The polymerization of monomers like fl-dialkyl(amino)ethyl methacrylates with various organometallic catalysts, such as phenyl magnesium bromide, which had been previously studied 35, gave amorphous polymers when the tertiary amino group present had an aliphatic or cycloaliphatic character. Under the same conditions, analogous nitrogenous monomers, in which the nitrogen atom is not basic but is present in a heterocyclic structure of the carbazole type, yielded crystallizable isotactic polymers35. At present, the acrylamides studied by us seem to be the only monomers with basic amino substituents that may be polymerized stereospecifically. This is apart from the amino olefins mentioned previously 29, since in this case the amino group must here be previously protected by complex formation. lstituto Chimica Industriale del Politecnico, Milano, Italy

(Received 25 July 1969) (Revised 27 October 1969)

REFERENCES

1 Natta, G., Vigliani, E. C., Danusso, F., Pernis, B., Ferruti, P. and Marchisio, M. A. Rend. Accad Naz. Lincei (VIII) 1966, 40, 1l 2 Ferruti, P. and Marchisio, M. A. La Medicina delLavoro 1966, 57, 481 3 Vigliani, E. C., Pernis, B., Marchisio, M. A., Ferruti, P. and Parazzi, E. 15th Congr6s Inernat. de M6dicine du Travail, Wien, Sept. 19-24, 1966, 2, 665 4 Marchisio, M. A., Sbertoli, C. and Farina, G. La Medicina del Lavoro 1968, 59, 136 5 Mallik, K. L. and Das, M. N. Z. Phys. Chem. 1960, 25, 205 6 Hulse, G. E. U.S. Patent 2, 759, 913 (C.A. 50, 17533) 7 Danusso, F., Ferruti, P. and Ferroni, G. Chimica e Industria (Milan) 1967, 49, 271 8 Danusso, F., Ferruti, P. and Ferroni, G. Chimica e Industria (Milan) 1967, 49, 453 9 Danusso, F. 'New trends in chemistry teaching, UNESCO, 1969, 2, 172 10 Perrin, D. D., 'Dissociation Constants of Organic Bases in Aqueous Solution' Butterworth, London, 1965 112

SYNTHESIS OF TERTIARY AMINE POLYMERS 11 Morgan, P. W. 'Condensation polymers: by interfacial and solution methods' Interscience New York 1965, p 423 12 Danusso, F., Ferruti, P. and Ferroni, G. Chimica e lndustria (Milan) 1967, 49, 587 13 Danusso, F., Ferruti, P. and Ferroni, G. Chimica e lndustria (Milan) 1967, 49, 826 14 Bellaart, A. C. Rec. Tray. Chim. 1962, 81, 156 15 Danusso, F., Ferruti, P. Communication to the 10th Meeting of the Italian Chemical Society, Padova, June 19, 1968 16 Ferruti, P. and Brzozowski, Z. Chimica e Industria (Milan) 1968, 50, 441 17 Ferruti, P. and Alimardanov, R. Chimica e lndustria (Milan) 1967, 49, 831 18 Garner, A. Y. U.S. Patent 3,010,946 (C.A. 56, 61704) Niebergall, H. German Patent 1,086,897 (C.A. 55, 14977) Gutweiler, K. and Niebergall, R. German Patent 1,103,590 (C.A. 55, 24102) G utwieler, K., Saiider, M., Schneider, G. German Patent 1,131,412 (C.A. 57, 12722) 19 See for example: Geigy, A. G. British Patent 832,078 (C.A. 54, 20877); Blumenkopf, N., Heicht, O. F. U.S. Patent 3,126,363 (C.A. 61, 4368); and also Von Braun, J., Pinkernelle, W. Bet. 1927, 70, 1230; Gardner, C., Kerrigan, V., De Rose, J., Weedon, B. C. L. J. Chem. Soc. 1949, p 789 20 Danusso, F., Ferruti. P. and Peruzzo, G. F. Atti Accad Naz. Lincei 1965, 39, 498 21 Mannich, C., Davidson, H. Bet. 1936, 69, 2016 22 Ferruti, P., Bianchetti, G. and Pocar, D. Gazz. Chim. ltal. 1967, 97, 109 23 See for example: Bianchetti, G., Pocar, D., Dalla Croce, P., Gallo, G. G., Vigevani, A. Tetrahedron Letters 1966, p 1637; Bianchetti, G., Dalla Croce, P., Pocar, D. Tetrahedron Letters 1965, p 2039 24 Danusso, F., Ferruti, P., Ferd, A: European Polymer J. in press 25 Stork, G., Brizzolara, A., Landesman, H., Szmuskovicz, J. and Terrel, R. J. Amer. Chem. Soc. 1963, 85, 207 26 Brannock, K. C., Bell, A., Burpitt, R. D. and Kelly, C. A. J. Org. Chem. 196l, 26 625 27 Fleming, I. and Harley-Mason, J. J. Chem. Soc. 1964, p 2165 28 Danusso, F. and Ferruti, P. unpublished results 29 Giannini, U., Briickner, G., Pellino, E. and Cassata, A. J. Polym. Sci. (B) 1967, 5, 527 30 Danusso, F. and Ferruti, P. Chimica e Industria (Milan) 1968, 50, 71 31 Petit, J. and Houel, B. Compt Rend. 1958, 246, 1427 Houel, B. Compt Rend. 1958, 246, 2488 Cohen, H. L. and Minsk, L. M. J. Org. Chem. 1959, 24, 1404 Cohen, H. L., Borden, D. G. and Minsk, L. M. J. Org. Chem. 1961, 26, 1274 32 Veno, A. and Schuerch, C. J. Polym. Sci., (B) 1965, 3, 53 33 Danusso, F., Ferruti, P., Peruzzo, G. F. and Natta, G. Chimica e lndustria (Milan) 1966, 48, 357 34 Butler, K., Thomas, P. R. and Tyler, G. J. J. Polym. Science 1960, 48, 357 35 Natta, G., Longi, R. and Pellino, E. Makromol. Chem. 1964, 71,212

113