Abstract
The invention relates to a process for preparing a block or comb copolymer comprising at least one hydrophilic part and at least two hydrophobic parts by solventless anionic polymerization from a prepolymer selected from a poly(ethylene glycol) and a polyvinyl alcohol, and from a lactone or dilactone monomer. The process is performed in the presence of an alkaline earth metal hydride in an inert atmosphere, and the polymerization step is not carried out under vacuum. The invention also relates to copolymers obtained by this process.