Rational Synthesis of Low-Polydispersity Block Copolymer Vesicles in Concentrated Solution via Polymerization-Induced Self-Assembly

Abstract

Block copolymer self-assembly is normally conducted via post-polymerization processing at high dilution. In the case of block copolymer vesicles (or "polymersomes"), this approach normally leads to relatively broad size distributions, which is problematic for many potential applications. Herein we report the rational synthesis of low-polydispersity diblock copolymer vesicles in concentrated solution via polymerization-induced self-assembly using reversible addition-fragmentation chain transfer (RAFT) polymerization of benzyl methacrylate. Our strategy utilizes a binary mixture of a relatively long and a relatively short poly(methacrylic acid) stabilizer block, which become preferentially expressed at the outer and inner poly(benzyl methacrylate) membrane surface, respectively. Dynamic light scattering was utilized to construct phase diagrams to identify suitable conditions for the synthesis of relatively small, low-polydispersity vesicles. Small-angle X-ray scattering (SAXS) was used to verify that this binary mixture approach produced vesicles with significantly narrower size distributions compared to conventional vesicles prepared using a single (short) stabilizer block. Calculations performed using self-consistent mean field theory (SCMFT) account for the preferred self-assembled structures of the block copolymer binary mixtures and are in reasonable agreement with experiment. Finally, both SAXS and SCMFT indicate a significant degree of solvent plasticization for the membrane-forming poly(benzyl methacrylate) chains.

Polymerization-induced self-assembly of block copolymer nanoparticles via RAFT non-aqueous dispersion polymerization

“…Although styrene is a relatively cheap monomer, it suffers from a relatively slow rate of polymerization when utilized in non-aqueous PISA formulations [28,[52][53][54][55][56][57] Construction of a suitable phase diagram allowed reproducible targeting of a desired morphology for a given PMAA 71 -PBzMA x block copolymer composition ( Figure 6). …”

“…More recently, Gonzato et al [71] reported the synthesis of low-polydispersity PMAAPBzMA vesicles via RAFT dispersion polymerization of BzMA in ethanol. This was achieved by selecting an appropriate binary mixture of a PMAA 171 and a PMAA 62 stabilizer macro-CTA, which preferentially occupy the outer and inner leaflets of the vesicle membrane respectively (Scheme 1).…”

Self-Organization of Polyurethane Pre-Polymers as Studied by Self-Consistent Field Theory

“…vesicles, [8,9] disk-shaped vesicle, [10] rods, [11] small disks, [12] to micelles. [13,14] Self-organized structure from binary amphiphiles mixtures was studied both experimentally and theoretically.…”

“…[13,14] Self-organized structure from binary amphiphiles mixtures was studied both experimentally and theoretically. [9,15] In comparison to those studies, a dispersion of polyurethane pre-polymers is a more complex system in the sense that these PU particles are the outcome of co-assembled multiple hydrophobic, hydrophilic, and amphiphilic polymers. To have clear distinction between these complex structures with the single component micelle, we refer them as (swollen) micelles.…”

A Vesicle‐to‐Worm Transition Provides a New High‐Temperature Oil Thickening Mechanism

“…Transmission electron microscopy (TEM) studies have shed new light on the nature of the worm‐to‐vesicle transition that can occur under these conditions, which proceeds via a “jellyfish” intermediate 10. PISA formulations have enabled the rational synthesis of low‐polydispersity vesicles using a binary mixture of two macro‐CTAs11 and the precise mechanism of vesicle growth during such syntheses has been recently elucidated 10a, 12…”