Interaction of four synthetic polymers viz., poly- $$\upvarepsilon $$ -caprolactone (PCL), polyglycolide (PGA), polylactic acid (PLA) and Poly(lactic-co-glycolic) acid (PLGA) used as protein delivery vectors with a few amino acids have been studied by using density functional theory. Association geometries of polymer–amino acid adduct are modelled in a vacuum and in four solvents. Nature and strength of interaction have been analyzed in terms of interaction energy and thermochemical parameters of adducts as well as vibrational frequency shifts upon adduct formation. Results suggest comprehensive stability of adducts in the gas phase. Progressive destabilization of adducts with increasing polarity of solvent is observed. Redshifts in vibrational frequencies of X-H bonds ( $$\hbox {X}= \hbox {H}$$ donor in hydrogen bonding) upon adduct formation are noticed. The study asserts the potentiality of the considered synthetic polymers as an amino acid carrier. Synopsis Synthetic polymers can form stable complexes with amino acids and are potential vectors for protein delivery.