In addition, if A1 is a radical chosen from linear and branched, saturated and unsaturated alkylene and hydroxyalkylene radicals, B1 can also denote a group ???(CH2)n???CO???D???OC???(CH2)n??? in which n??? may range from 1 to 100, such as from 1 to 50, and D may be chosen from: [0148] a) a glycol residue of formula: ???O???Z???O???, where Z may be chosen from linear and branched hydrocarbon-based