Testing Vesicles to Destruction: SAXS and Mass Spectrometry Studies on Block Copolymer Vesicles Prepared via Polymerization-Induced Self-assembly

摘要

It is well known that amphiphilic diblock copolymers self-assemble in water to form either spherical micelles, cylindrical micelles (sometimes called worms) or vesicles depending on the relative volume fractions of each block. Recently, polymerization-induced self-assembly (PISA) has provided a route to self-assembled nano-objects at much higher concentrations (up to 25% w/w) than can be achieved using conventional post-polymerization processing routes. For example, detailed predictive phase diagrams have been constructed for the reversible addition fragmentation chain transfer (RAFT) polymerization-mediated PISA of 2-hydroxypropyl methacrylate (HPMA) allowing pure phases of spherical micelles, worms or vesicles to be consistently produced using either poly(glycerol monomethacrylate) (PGMA), poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) or poly(ethylene glycol) based macro-CTAs. Such formulations provide an excellent opportunity to investigate the properties of these nano-objects since the synthesis and self-assembly of the block copolymer chains can be carried out in one pot. Herein we utilise PISA as a convenient method of preparing a series of PGMA55-PHPMAx (herein denoted G55-Hx) diblock copolymer vesicles with varying PHPMA degrees of polymerization (DP) at 10% w/w solids (Figure 1). Subsequently, these vesicles are characterized by small-angle x-ray scattering (SAXS) and transmission electron microscopy (TEM) to investigate the effect of varying the DP of the core-forming block on the morphology. In addition, we use electrospray ionization charge detection mass spectrometry (CDMS), to determine the effect on the overall mass of the vesicles.