The present invention relates to a copolymer with a rigid polyamide block and a flexible polyether or polyester block, wherein said polyamide block is semicrystalline and consists of a copolyamide of W/Y.Z type, wherein: (i) W is a lactam or an alpha, omega-aminocarboxylic acid; (ii) Y is a cycloaliphatic diamine; (iii) Z is an aliphatic and/or aromatic dicarboxylic acid; and the W/Y.Z molar ratio is between 10/1 and 27/1 limits excluded.