Graft polymer to which combined nitrogen molecules are grafted

1. A modified polymer obtained by grafting a compound comprising at least one group Q, and at least one group A bonded together by at least, and one “spacer” group Sp wherein:

Q comprises an azo-dicarbonyl-containing group,

A comprises an associative group comprising at least one nitrogen atom wherein the associative group is selected from the group consisting of an imidazolidinyl, triazolyl, ureyl, bis-ureyl and ureido-pyrimidyl group,

Sp is an atom or a group of atoms forming a bond between Q and A.

2. The modified polymer according to claim 1 , wherein the polymer is a diene elastomer.

3. The modified polymer according to claim 1 , wherein the diene elastomer is essentially saturated.

4. The modified polymer according to claim 1 , wherein the diene elastomer is essentially unsaturated.

5. A modified polymer obtained by grafting a compound comprising at least one group Q, and at least one group A bonded together by at least, and one “spacer” group Sp wherein:

Q comprises an azo-dicarbonyl-containing group,

A comprises an associative group comprising at least one nitrogen atom wherein the group A corresponds to one of the following formulae (II) to (VI):

where:

R denotes a hydrocarbon group which may optionally contain heteroatoms,

X denotes an oxygen or sulphur atom, or a group —NH.

6. The modified polymer according to claim 1 , wherein the modifying agent is represented by the formula (VII)

W—CO—N═N—CO-Sp-A   (VII)

in which:

A is an associative group comprising at least one nitrogen atom,

Sp is a divalent spacer group bonding the azodicarbonyl-containing functional group to the associative group A,

W represents a group of formula:

R′—Z—

in which:

Z represents an oxygen or sulphur atom or a group —NH or —NR′,

R′ represents a C 1 -C 20 alkyl,

or

a group of formula:

-Sp′-A′

in which:

Sp′, which is identical to or different from Sp, is a divalent spacer group bonding the azodicarbonyl-containing functional group to another associative group A′,

A′, which is identical to or different from A, is an associative group comprising at least one nitrogen atom.

7. The modified polymer according to claim 6 , wherein the modifying agent is chosen from the compounds of the following formulae (VIII) or (IX):

R′—Z—CO—N═N—CO-Sp-A   (VIII)

or

A′-Sp′—CO—N═N—CO-Sp-A   (IX)

in which R′ represents a C 1 -C 20 alkyl, Z represents an oxygen or sulphur atom or a group —NH or —NR′, Sp is an atom or a group of atoms forming a bond, A is an associative group comprising at least one nitrogen atom, Sp,′ which is identical to or different from Sp, is a divalent spacer group bonding the azodicarbonyl-containing functional group to another associative group A′, and A′, which is identical to or different from A, is an associative group comprising at least one nitrogen atom, and wherein A, Sp and Sp′ may contain one or more heteroatoms.

8. The modified polymer according to claim 7 , wherein the modifying agent is selected from the compounds of the following formulae (X) or (XI):

wherein:

Y represents a divalent group chosen from a methylene group, an oxygen or sulphur atom, and a group —NH—, and

R″ represents a C 1 -C 6 alkoxy.

9. The modified polymer according to claim 1 , wherein the “spacer” group Sp or Sp′ of the modifying agent is selected from —(CH 2 ) y —, —NH—(CH 2 ) y —, and —O—(CH 2 ) y —, y being an integer from 1 to 6.

10. The modified polymer according to claim 8 , wherein the modifying agent is chosen from the compounds of the following formulae (XII) to (XV):

11. A crosslinked or crosslinkable rubber composition comprising a reinforcing filler and a modified polymer as defined in claim 1 .

12. A tire comprising a rubber composition as defined in claim 11 .

13. The modified polymer according to claim 3 , wherein the diene elastomer is selected from the group consisting of copolymers of ethylene-propylene-diene monomer (EPDM) and butyl rubbers.

14. The modified polymer according to claim 4 , wherein the diene elastomer is selected from natural rubber, synthetic polyisoprenes, isoprene copolymers and mixtures of these elastomers.

15. The modified polymer according claim 6 , wherein R′ represents C 1 -C 6 alkyl.

16. The modified polymer according to claim 15 , wherein R′ represents C 1 -C 4 alkyl.