Functionalization of polymers is an attractive approach to introduce specific molecular forces that can enhance drug-polymer interaction to achieve higher drug loading when used as drug delivery systems. The novel amphiphilic block copolymer of methoxy poly(ethylene glycol) and poly(jasmine lactone) , mPEG--PJL, derived from renewable jasmine lactone provides free allyl groups on the backbone thus, allowing flexible and facile post-synthesis functionalization. In this study, mPEG--PJL and its carboxyl functionalized polymer mPEG--PJL-COOH were utilised to explore the effect of ionic interactions on the drug-polymer behaviour. Various drugs with different p values were employed to prepare drug-loaded polymeric micelles (PMs) of mPEG--PJL, mPEG--PJL-COOH and Soluplus® (polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer) a nanoprecipitation method. Electrostatic interactions between the COOH pendant on mPEG--PJL-COOH and the basic drugs were shown to influence the entrapment efficiency. Additionally, molecular dynamics (MD) simulations were employed to understand the polymer-drug interactions at the molecular level and how polymer functionalization influenced these interactions. The release kinetics of the anti-cancer drug sunitinib from mPEG--PJL and mPEG--PJL-COOH was assessed, and it demonstrated a sustainable drug release pattern, which depended on both pH and temperature. Furthermore, the cytotoxicity of sunitinib-loaded micelles on cancer cells was evaluated. The drug-loaded micelles exhibited dose-dependent toxicity. Also, haemolysis capacity of these polymers was investigated. In summary, polymer functionalization seems a promising approach to overcome challenges that hinder the application of polymer-based drug delivery systems such as low drug loading degree.