Azoic compounds functionalized with heterocycles

Details Azoic compounds functionalized with heterocycles Azoic compounds functionalized with heterocycles

2000-07-03

2001-11-06

Powers, Fiona T. (Department: 1626)

Organic compounds -- part of the class 532-570 series

Organic compounds

Azo

C534S799000, C525S204000, C526S204000, C526S218100

Reexamination Certificate

active

06313275

ABSTRACT:

The present invention relates to heterocycle-functionalized azo compounds of the formula (I)
where:
Y is C
1
-C
20
-alkyl, C
6
-C
14
-aryl, C
6
-C
14
-aryl substituted with functional groups based on the nonmetallic elements of groups IVA, VA, VIA or VIIA of the Periodic Table, C
3
-C
10
-cycloalkyl, aralkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 14 carbon atoms in the aryl radical, C
1
-C
20
-alkyl substituted with functional groups based on the nonmetallic elements of groups IVA, VA, VIA or VIIA of the Periodic Table, or a radical of the formula (II)
 where, as in formula (I):
R
a
and R
a′
, independently of one another, are hydrogen, C
1
-C
20
-alkyl, C
6
-C
14
-aryl, aralkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 14 carbon atoms in the aryl radical, or C
3
-C
10
-cycloalkyl, or, but not both simultaneously, functional groups based on the non-metallic elements of groups IVA, VA, VIA or VIIA of the Periodic Table,
Z is oxygen, sulfur or —N(R′)—,
X is —(C(R
b
) (R
b′
))
1
— or [═N]—(C(R
b
) (R
b′
))
m
—A—(C(R
b
) (R
b′
))
n
—(E)
p
—, where
R
b
and R
b′
, independently of one another, are defined as for R
a
and R
a′
,
A is —C(O)O—, —O—, —S—, —C(O)N(R″)—, —N(R″)—, —C(O)—, —C (R″)═N—,
E is substituted or unsubstituted C
6
-C
14
-arylene,
R′ and R″ are hydrogen, alkyl, aryl or aralkyl,
k is 2 or 3,
l is an integer from 1 to 24,
m and n are integers from 0 to 12, and
p is 0, 1, 2 or 3,
where m+n≧1 and n+p≧1.
The invention also relates to the use of the azo compounds mentioned above as initiators for the free-radical polymerization of olefinically unsaturated compounds, and also to a process for preparing heterocycle-functionalized azo compounds. The invention relates, furthermore, to processes for preparing (co)polymers containing heterocyclic end groups, and also to a process for preparing graft copolymers and block copolymers, and to the resultant (co)polymers, block copolymers and graft copolymers and the use of these for producing films, fibers and moldings. Finally, the invention relates to the use of the (co)polymers for preparing block copolymers and graft copolymers.
The suitability of azo compounds as initiators for free-radical reactions, and in particular also for free-radical polymerization of olefinically unsaturated compounds, has been known for a long time (cf. R. T. Morrison R. N. Boyd, Lehrbuch der Organischen Chemie, Verlag Chemie, 3rd impression of the 2nd edition, 1984, pages 1110 and 1111). Azoisobutyronitrile (AIBN) has exceptional importance among these compounds as a free-radical chain initiator. A consequence of the mechanism of initiation is generally that at least a fragment of the azo compound becomes incorporated as a terminal member of the polymer chain. As described in EP-A 0 356 026, this property of azo initiators has already been utilized to tie an amide function containing aromatic and/or nitrogen-containing ring systems to the terminal member of a polymer chain. It is claimed in EP-A 0 356 026 that the resultant polymer is suitable for downstream reactions such as the formation of block copolymers and/or graft copolymers. The application mentioned does not provide further details on this topic. In addition, the yields obtained in the polymerization of, for example, acrylonitrile are much too low for the process to be technically and economically acceptable.
It is apparent from JP-A 08225504 that the azo compounds disclosed in EP-A 0 356 026, e.g. 2,2′-azobis[N-(isopropyl)-2-methylpropionamide], are possible initiators for free-radical polymerization of styrene and acrylonitrile. There is no report of downstream reactions. Carboxyl-terminated homopolymers and copolymers of styrene, and their preparation using dicarboxylic-acid-functionalized azo initiators in the presence of 2,2,6,6-tetramethyl-1-piperidyloxyl radical, are proposed by Baumert and Mülhaupt in Macromol. Rapid Commun. 1997, 18, 787-794, but without describing terminal groups of other types. Reactions leading to downstream products are likewise not described. EP-A 0 792 869 makes reference to azo initiators which are soluble in organic solvents and retain their activity at high temperatures. This object is achieved by means of 2,2′-azobisamides with amido substituents which have at least two carbon atoms. It is not disclosed whether these compounds give polymeric products with which downstream reactions can be carried out, and this is also not within the subject matter of EP-A 0 792 869.
Sivaram et al. (Macromol. Rapid Commun. 1991, 12, 435-438) use the carbanion of 2-methyl-1,3-oxazoline as an initiator for the anionic polymerization of methyl acrylate. The authors propose that the oxazoline group incorporated into the polymer chain in this way be used for preparing graft copolymers. There is no disclosure of further details or of corresponding descriptions of experiments. A disadvantage of the process of Sivaram et al. is that the synthesis of oxazoline-terminated (meth)acrylates requires much technical resource, and gives satisfactory results only at very low temperatures, too low to be economically acceptable. A further disadvantage is that the oxazoline group can only be incorporated into those polymers which are obtainable by anionic polymerization, i.e. primarily acrylates and methacrylates.
It would therefore be desirable to have access to initiator systems which can be used to incorporate a reactive functional group into a polymer chain without restriction to a limited number of polymerizable monomers.
It is an object of the present invention to develop initiator systems in which the disadvantages described are absent or are present only to a subordinate extent, which are easy to obtain, and which can readily be used for specific incorporation into a wide variety of polymers of a functional group, which does not undergo side and/or coupling reactions during the polymerization process but is suitable for downstream reactions.
We have found that this object is achieved by means of the heterocycle-functionalized azo compounds described at the outset. The invention also provides a process for preparing azo compounds of this type, and also their use as initiators for the free-radical polymerization of olefinically unsaturated compounds. It further provides a process for preparing copolymers containing heterocyclic end groups, and also a process for preparing graft copolymers and block copolymers. It likewise provides the (co)polymers, block copolymers and graft copolymers obtainable by the processes, and the use of these for producing films, fibers and moldings. Finally, it provides the use of the (co)polymers for preparing block copolymers and graft copolymers.
The novel azo compounds have at least one five- or six-membered heterocycle having, integrated into its ring, at least two, 1,3-positioned, heteroatoms, one of these being nitrogen. The other heteroatoms may be oxygen, sulfur or nitrogen. In the compounds of the formula (I), Z is preferably oxygen, sulfur or nitrogen, in particular oxygen. Examples of suitable ring systems are oxazoline, thiazoline and imidazoline, the heterocycle generally being bonded to the skeleton of the azo compound via the 2-position. Preference is given to 1,3-oxazoline and 1,3-thiazoline, but in particular 1,3-oxazoline.
Possible radicals R
a
and R
a′
in compounds of the formula (I) are very generally hydrogen, linear or branched C
1
-C
20
-alkyl, in particular C
1
-C
10
-alkyl, such as methyl, ethyl, isopropyl or tert-butyl, C
6
-C
14
-aryl, in particular C
6
-C
10
-aryl, such as phenyl, aralkyl having from 1 to 10 carbon atoms in the alkyl radical and from 6 to 14 carbon atoms in the aryl radical, preferably having from 1 to 6 carbon atoms in the alkyl radical and from 6 to 10 carbon atoms in the aryl radical, for example benzyl, substituted or unsubstituted C
3
-C
10
-cycloalkyl, preferably C
5
-C
8
-cycloalkyl, such as cyclopentyl or cyclo

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