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Poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) PHB are grafted onto poly(methyl methacrylate) (PMMA) by reactive extrusion. Two catalysts are used, 1.5.7-triazabicyclodec-5-ene (TBD) and tin (II) bis(2-ethylhexanoate) (SnOct2). 1H NMR spectroscopy is used to characterize the structures of the products of the reactive blends. A higher amount of graft copolymer is obtained by increasing the temperature. Grafting is also influenced by the type of catalyst. TBD is more efficient than (SnOct2) for PHB grafting onto PMMA (substitution rate (SR) 19% at 230 °C). Likewise, when grafting PLA, significantly lower grafting is obtained and SnOct2 is more efficient than TBD. Thermal analyses showed that amorphous and miscible products are obtained. In the case of PMMA- g-PHB synthesis, increasing the temperature improves the SR from 5 to 11% with SnOct2 and from 14 to 24% with TBD. The same effect is observed in the case of PMMA- g-PLA synthesis. The results obtained by size exclusion chromatography corroborate both the results obtained by 1H NMR analysis and the possibility to synthesize the copolymer by reactive extrusion with a short residence time. The results obtained by thermal analysis show that two Tg are obtained in physical blends but that using a catalyst at low temperature yields in a miscible product. [ABSTRACT FROM AUTHOR]