Block polymers and cosmetic compositions and processes comprising them

A block polymer comprising

• at least one first block and at least one second block that are incompatible with each other and that have different glass transition temperatures (Tg),
• wherein the block polymer is not an elastomer;
• wherein the at least one first and second blocks are linked together via an intermediate block comprising at least one constituent monomer of the at least one first block and at least one constituent monomer of the at least one second block;
• wherein said intermediate block is a random copolymer block;
• wherein the block polymer has a polydispersity index I ranging from 2.8 to 6;
• wherein the at least one first block has a Tg of greater than or equal to 40° C. and is present in an amount ranging from 50% to 90% by weight relative to the total weight of the block polymer;
• wherein the at least one second block has a Tg of less than or equal to 20° C. and is present in an amount ranging from 5% to 45% by weight relative to the total weight of the block polymer;
• wherein each of the at least one first and second blocks comprises at least one monomer chosen from acrylic acid, acrylic acid esters, methacrylic acid, and methacrylic acid esters;
• wherein the at least one first block is totally or partially derived from monomers chosen from:
• (a) methacrylates of formula CH2═C(CH3)—COOR1, wherein R1 is chosen from linear and branched unsubstituted alkyl groups comprising from 1 to 4 carbon atoms, or R1 is chosen from a C4 to C12 cycloalkyl group;
• and
• (b) acrylates of formula CH2═CH—COOR2, wherein R2 is chosen from C4 to C12 cycloalkyl groups, and a tert-butyl group;
• wherein the at least one second block is totally or partially derived from monomers chosen from:
• (c) acrylates of formula CH2═CHCOOR3, wherein R3 is chosen from linear and branched C1 to C12 unsubstituted alkyl groups, with the exception of the tert-butyl group;
• and
• (d) methacrylates of formula CH2═C(CH3)—COOR4, wherein R4 is chosen from linear and branched C6 to C12 unsubstituted alkyl groups;
• and wherein the intermediate block is totally or partially derived from a combination of monomers chosen from monomers of types (a) and (b) above with monomers chosen from types (c) and (d) above, the monomers chosen from monomers of types (a) and (b) being interspersed with the monomers chosen from monomers of types (c) and (d), wherein said intermediate block does not comprise acrylates or methacrylates comprising a —COOR side chain in which R comprises an intercalated heteroatom chosen from O, N and S.