The present invention is a process to make a composition comprising at least a monovinylaromatic polymer and at least a dispersed phase of one or more polymers made from renewable resources comprising: a) forming a polymerizable mixture comprising: at least a monomer or a dimer (a1) selected among an hydroxy carboxylic acid, a precursor of said hydroxy carboxylic acid, a cyclic component polymerizable by ring-opening polymerization (ROP) and a mixture of an epoxide and carbon dioxide, dispersed in at least (a2) one monovinylaromatic monomer, optionally a rubber dissolved in (a2) the monovinylaromatic monomer, b) contacting an appropriate catalyst with the polymerizable solution at conditions effective to produce a polymer A1 comprising the repeating units (a1) dispersed in the (a2) monovinylaromatic monomer, c) polymerizing through a radical pathway the solution obtained at step b); optionally in the presence of a free radical initiator, optionally in the presence of chain transfer agents, to obtain a monovinylaromatic polymer A2 comprising a dispersed phase of the polymer A1, d) degassing the product of step c) to separate the optional unpolymerized monomers and comonomers and recovering a composition comprising at least a (A2) monovinylaromatic polymer and at least (A1) wherein, the weight proportion A1/(A2+A1) is up to 50%. In a second embodiment steps b) and c) are made inone step. The polymerizable mixture is contacted with an appropriate catalyst at conditions effective to essentially simultaneously produce a polymer A1 and a monovinylaromatic polymer. (a1) is advantageously a lactide. The monovinylaromatic monomer is advantageously styrene.