Enthalpic incompatibility between two steric stabilizer blocks provides control over the vesicle size distribution during polymerization-induced self-assembly in aqueous media. Issue 39 (29th June 2020)

• Record Type: Journal Article
• Authors: Beattie, Deborah L.; Mykhaylyk, Oleksandr O.; Armes, Steven P.
• Is Part Of: Chemical science. Volume 11:Issue 39(2020)
• Page Start: 10821
• Page End: 10834
• Publication Date: 2020-06-29
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d0sc01320j
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : SAXS studies confirm that a judicious binary mixture of enthalpically incompatible steric stabilizer blocks enables the synthesis of relatively small, well-defined vesicles via polymerization-induced self-assembly in aqueous media. Abstract : Over the past two decades, block copolymer vesicles have been widely used by many research groups to encapsulate small molecule drugs, genetic material, nanoparticles or enzymes. They have also been used to design examples of autonomous self-propelled nanoparticles. Traditionally, such vesicles are prepared via post-polymerization processing using a water-miscible co-solvent such as DMF or THF. However, such protocols are invariably conducted in dilute solution, which is a significant disadvantage. In addition, the vesicle size distribution is often quite broad, whereas aqueous dispersions of relatively small vesicles with narrow size distributions are highly desirable for potential biomedical applications. Alternatively, concentrated dispersions of block copolymer vesicles can be directly prepared via polymerization-induced self-assembly (PISA). Moreover, using a binary mixture of a relatively long and a relatively short steric stabilizer block enables the convenient PISA synthesis of relatively small vesicles with reasonably narrow size distributions in alcoholic media (C. Gonzato et al., JACS, 2014, 136, 11100–11106). Unfortunately, this approach has not yet been demonstrated for aqueous media, which would be much more attractive for commercial applications. Herein we show that this important technical objective can be achieved by judicious use of two chemically distinct, enthalpically incompatible steric stabilizer blocks, which ensures the desired microphase separation across the vesicle membrane. This leads to the formation of well-defined vesicles of around 200 nm diameter (size polydispersity = 13–16%) in aqueous media at 10% w/w solids as judged by transmission electron microscopy, dynamic light scattering and small-angle X-ray scattering.