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The present work systematically investigates the hydrolysis mechanism of cyclic ketene acetal (CKA) monomers in detail and explores polymerization in water under organic solvent‐free and surfactant‐free conditions. To understand the effect of CKA structure on hydrolysis, the ring size of the monomers is varied from 5–8‐membered rings systematically and hydrolysis experiments are performed. In all cases, hydrolysis yields monoacetylated diol products. Deuterium and 17O‐isotopic labeled experiments are carried out for 5‐ and 7‐membered‐(2‐methylene‐1,3‐dioxepane, MDO) CKAs to understand the reaction pathway. The experimental analysis from the reaction of CKA with water revealed that the increasing hydrophobicity from 5–8‐membered rings and the pH of the reaction medium play important roles in the order of reactivity. Density functional theory (DFT) and experimental studies demonstrated that basic reaction conditions have some control over the hydrolysis rate of CKA. Despite this progress, achieving controlled polymerization of CKA in water while suppressing hydrolysis remains challenge. Only up to 3 mol% CKA incorporation is attained in polyacrylate and polyacrylamide backbone via radical ring‐opening polymerization (rROP) of MDO and 8‐membered CKAs with 2‐hydroxyethyl acrylate (HEA) and acrylamide (AAm) in water. The results serve a proof of concept for advancing aqueous copolymerizations using CKA monomers. [ABSTRACT FROM AUTHOR]

In this study, the effect of the polymer structural difference introduced by radical ring-opening polymerization (rROP) of a cyclic ketene acetal (CKA) monomer, analogous to ε-caprolactone (CL), on the nanoencapsulation and controlled release of hydrophobic actives curcumin and fenofibrate was explored. The two chosen polymers are amphiphilic diblock copolymers namely methoxy poly(ethylene glycol)- b -poly(ε-caprolactone) (mPEG- b -PCL) and methoxy poly(ethylene glycol)- b -poly(2-methylene-1,3-dioxepane) (mPEG- b -PMDO). Both polymers serve as a good comparison as they have a similar average molecular weight (M n) and the same hydrophilic PEG chains with the main difference in microstructure of hydrophobic PCL and PMDO chains. Nuclear magnetic resonance spectroscopy (NMR) (1H and 13C), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (X-RD) confirmed the structures of the polymers. mPEG- b -PMDO possesses less crystallinity or is more amorphous as compared to the linear mPEG- b -PCL due to branching or polymer disorder in the hydrophobic segment as a result of radical mechanism operating in rROP. The subsequent nanoencapsulation of hydrophobic active curcumin with mPEG- b -PMDO yielded higher loading content (LC) and encapsulation efficiency (EE) in the hydrophobic core of the nanoparticle (NP) due to more hydrophobic interactions between hydrophobic core and hydrophobic active. In contrast, lower LC and EE were observed for the nanoencapsulation of fenofibrate with mPEG- b -PMDO. The further release experiments were carried out in the aqueous and hydro-alcoholic systems over a period of 24 h at 37 °C. These experiments further supported our hypothesis regarding the influence of polymer structure, revealing slower, controlled, and more consistent release profiles for both curcumin and fenofibrate with mPEG- b -PMDO compared to mPEG- b -PCL. Our approach could open new opportunities for utilizing this polymer in personal care and biomedical applications. [Display omitted] • Compared mPEG-b-PCL and mPEG-b-PMDO of similar molecular weights to reveal how polymer microstructure affects active release. • MPEG- b -PCL demonstrates semi-crystalline behaviour, while mPEG- b -PMDO displays a more amorphous nature due to branching. • For higher active loading, mPEG-b-PCL is better for fenofibrate, while mPEG-b-PMDO is better suited for curcumin. • For both Curcumin and fenofibrate mPEG- b -PMDO releases the active slowly due to increased hydrophobic interactions. • The structural interactions between the polymer and active compounds affect both loading and release. [ABSTRACT FROM AUTHOR]