2,2’-Bis(2-oxazoline) and 2,2’-bis[5,6-dihydro-(4H)-1,3-oxazine] have been used as chain coupling reagents (CC) and reacted in the bulk with alpha,omega-dicarboxy-poly(2,2’-oxydiethylene adipate) (PS) or with alpha,omega-dicarboxy-polyamide 12 (PA). The reactions have been followed by viscosimetry, titration of COOH groups and H-1- and C-13-NMR spectroscopy. Either with the PS/CC or PA/CC systems, or with the model system dodecanoic acid (DA)/CC, the reactions were fast, since in most cases 80% conversion was reached after 15 min reaction, The expected DA dimer or high molar mass PA or PS polymers were obtained. No significant side reaction has been detected. The thermal stability of the resulting polymers is higher than that of starting oligomers. Due to the introduction of CC units in the chains, the crystallinity of PA/CC is lower than that of starting PA.