We Claim:
1. A composition resulting from the mixing of at least
o one polydiol random copolymer A1 comprising at least from 2 mol% to 50 mol%
of at least one monomer M3 of general formula (X):
> in which:
Zi, Zs and Z3, which may be identical or different, represent groups chosen from
a hydrogen atom, a C1-C12 alkyl, and a group -OZ' or-C(0)-0-Z' with Z' being a C1-
C12 alkyl.
and 3 o a compound A2 comprising at least two boronic ester functions.
2. The composition as claimed in claim 1, in which the polydiol random copolymer A1 is a copolymer resulting from the copolymerization:
■ of at least one first monomer M1 of general formula (I):
i.- 1- UA2
in which:
R1 is chosen from the group formed by -H, -CH3 and -"CH2-CH3;
x is an integer ranging from 1 to 18 and preferably from 2 to 18;
y is an integer equal to 0 or 1;
X1 and X2, which may be identical or different, are chosen from the group formed by hydrogen, tetrahydropyranyl, methyloxymethy], tert-butyl, benzyl, trimethylsilyl and t-butyldimethylsilyl;

or
XT and X2 form, with the oxygen atoms, a bridge having the following formula
in which:
the asterisks (*) symbolize the bonds to oxygen atoms,
R'2 and R"2, which may be identical or different, are chosen from the group formed by hydrogen and a d-Cn alkyl, preferably methyl; or
X1 and X2 form, with the oxygen atoms, a boronic ester having the following formula:
in which:
the asterisks (*) symbolize the bonds to oxygen atoms,
Rm2 is chosen from the group formed by a C6-C30 aryl, a C7-C30 aralkyl and a C2-C3o alkyl, preferably a C6-Cia aryl;
■ with at least one second monomer M2 of general formula (II):
in which:
R2 is chosen from the group formed by -H, -CH3 and -CH2-CH3;
R3 is chosen from the group formed by: -CtOHD-R's; -0-R'3; -S-R'3 and -qoj-NfHJ-R'swith R'3 being a C1-C30 alkyl group, and
■ with at least one third monomer M3 of general formula (X):

Zi, Z2 and Z3, which may be identical or different, represent groups chosen from a hydrogen atom, a C1-C12 alkyl, and a group-OZ' or-C(0)-0-Z' with Z' being a C1-C12 alkyl.
3. The composition as claimed in claim 1 or in claim 2, in which the third monomer M3 is styrene.
4. The composition as claimed in claim 2 or in claim 3, in which the random copolymer A1 results from the copolymerization of at least one monomer M1 with at least two monomers M2 bearing different groups R3 and at least one monomer M3.
5. The composition as claimed in claim 4, in which the two monomers M2 of the random copolymer A1 have the general formula (ll-B):
o
(ll-B) in which:
R2 is chosen from the group formed by -H, -CH3 and -CH2-CH3; R'"3 is a C9-C30 alkyl group.
6. The composition as claimed in any one of claims 2 to 5, in which the side chains of the random copolymer A1 have a mean length ranging from 8 to 20 carbon atoms, preferably from 9 to 18 carbon atoms.
7. The composition as claimed in any one of claims 2 to 6, in which the random copolymer A1 has a molar percentage of monomer M1 of formula (I) in said copolymer ranging from 1% to 30% and preferably from 5% to 25%.
8. The composition as claimed in any one of the preceding claims, in which the random copolymer A1 has a number-average degree of polymerization ranging from 40 to 2000 and preferably from 40 to 1000.
9. The composition as claimed in any one of the preceding claims, in which the random copolymer A1 has a poiydispersity index (Ip) ranging from 1.05 to 4.0, preferably ranging from 1.10 to 3.8.

10. The composition as claimed in any one of the preceding claims, in which compound A2 is a compound of formula (III):
in which:
wi and W2, which may be identical or different, are integers chosen between 0 and 1;
R4, R5, Re and R7, which may be identical or different, represent a group chosen from a hydrogen atom, a hydrocarbon-based group comprising from 1 to 30 carbon atoms, optionally substituted with one or more groups chosen from: a hydroxyl, a group -OJ or -C(0)-0-J with J being a hydrocarbon-based group comprising from 1 to 24 carbon atoms;
L is a divalent bonding group chosen from the group formed by a Ce-Cig aryl, a C6-CIB aralkyl and a C2-C24 hydrocarbon-based chain.
11. The composition as claimed in any one of claims 1 to 9, in which compound A2 is a random copolymer resulting from the copolymerization ■ of at least one monomer M4 of formula (IV):
in which:
t is an integer equal to 0 or 1;
u is an integer equal to 0 or 1;
M and R8 are identical or different divalent bonding groups, chosen from the group formed by C6-Ci8 aryl, a C7-C24 aralkyl and a C2-C24 alkyJ, preferably a C6-Ciaaryl,
X is a function chosen from the group formed by-O-C(O)-, -C(0)-0-, -C(0)-N(H)-. -N(H)-C(0)-, -S-, -N(H)-, -N(R'„)- and -O- with R'4 being a

hydrocarbon-based chain comprising from 1 to 15 carbon atoms;
R9 is chosen from the group formed by -H, -CH3 and -CH2-CH3;
R10 and R11, which may be identical or different, represent a group chosen from a hydrogen atom, a hydrocarbon-based group comprising from 1 to 30 carbon atoms, optionally substituted with one or more groups chosen from: a hydroxyl, a group -OJ or -C(0)-O-J with J being a hydrocarbon-based group comprising from 1 to 24 carbon atoms;
■ with at least one second monomer M5 of general formula (V):
in which:
R12 is chosen from the group formed by -H, -CH3 and -CH2-CH3;
R13 is chosen from the group formed by a C6-Ci8 aryl, a C6-Cie aryl substituted with a group R'13, -C(0)-0-R'i3; -0-R'13, -S-R'13and -C(0)-N(H)-R'i3 with R'i3 being a C1-C30 alkyl group.
12. The composition as claimed in claim 11, in which at least one of the following three conditions is met:
• either, in formula (IV): u - 1, Rg is H and R& represents a Ce-Cis aryl or a C7-C24 aralkyl and the double bond of the monomer M4 of formula (IV) is directly connected to the aryl group;
• or, in formula (V): R12 represents H and R13 is chosen from the group formed by a Ce-Ci8 aryl and a C6-Ci8 aryl substituted with a group R'13 with R'13 being a C1-C25 alkyl group and the double bond of the monomer M5 of formula (V) is directly connected to the aryl group.
• or, copolymer A2 comprises at least one third monomer M3 of formula (X)

Zi, Z2 and Z3, which may be identical or different, represent groups chosen from a hydrogen atom, a C1-C12 alkyl, and a group -OZ' or -C(0)-0-Z' with Z' toeing a d-C12 alkyl.
13. The composition as claimed in claim 11 or in claim 12, in which the chain formed by the sequence of groups R10, M, X and (Rg)u with u equal to 0 or 1 of the monomer of formula (IV) has a total number of carbon atoms ranging from 8 to 38 and preferably from 10 to 26.
i 14. The composition as claimed in any one of claims 11 to 13, in which the side chains of copolymer A2 have a mean length of greater than or equal to 8 carbon atoms, preferably from 11 to 16 carbon atoms.
15. The composition as claimed in any one of claims 11 to 14, in which copolymer A2
; has a molar percentage of monomer of formula (IV) in said copolymer ranging from
0.25% to 30% and preferably from 1% to 25%.
16. The composition as claimed in any one of claims 11 to 15, in which copolymer A2
has a number-average degree of polymerization ranging from 50 to 1500 and preferably
i from 50 to 800.
17. The composition as claimed in any one of claims 11 to 16, in which copolymer A2
has a polydispersity index (Ip) ranging from 1.04 to 3.54, preferably ranging from 1.10
to 3.10.
>
18. The composition as claimed in any one of the preceding claims, in which the
content of copolymer A1 ranges from 0.1 % to 50% by weight relative to the total weight
of the composition.
) 19. The composition as claimed in any one of the preceding claims, in which the content of compound A2 ranges from 0.1% to 50% by weight relative to total weight of the composition.
20. The composition as claimed in any one of the preceding claims, in which the mass
> ratio between copolymer A1 and compound A2 (ratio A1/A2) ranges from 0.005 to 200,
preferably from 0.05 to 20 and even more preferably from 0.1 to 10.
21. The composition as claimed in any one of the preceding claims, which also
comprises at least one exogenous compound A4 chosen from 1,2-diols and 1,3-diols.

22. A lubricant composition resulting from the mixing of at least: one lubricant oil; and one composition as defined in any one of claims 1 to 21.