Efficient Synthesis of Sterically‐Stabilized Nano‐Objects via RAFT Dispersion Polymerization of Benzyl Methacrylate in Alcoholic Media

Abstract

Synthesis of diblock copolymer nano-objects: alcohol is a good idea! RAFT dispersion polymerization of benzyl methacrylate in alcohol using weak polyelectrolyte-based chain transfer agents allows the facile synthesis of sterically stabilized diblock copolymer nano-objects with very high monomer conversions. Such syntheses are usually problematic when conducted in water due to electrostatic repulsion between highly charged stabilizer chains, which impedes in situ self-assembly. Construction of a detailed phase diagram facilitates reproducible syntheses of well-defined diblock copolymer spheres, worms or vesicles, since it allows mixed phase regions to be avoided. Aqueous electrophoresis studies confirm that these nano-objects can acquire substantial surface charge when transferred to aqueous solution due to ionization (or protonation) of the polyacid (or polybase) stabilizer chains.

Semi-crystalline diblock copolymer nano-objects prepared via RAFT alcoholic dispersion polymerization of stearyl methacrylate

“…For alcoholic dispersion polymerization formulations, we have examined using PBzMA as the core-forming block. [22][23][24][25][26] For example, a detailed phase diagram has been reported for PDMA-PBzMA diblock copolymers prepared via RAFT dispersion polymerization of BzMA in ethanol. 23 In the present study, this prototypical amorphous core-forming block has been replaced with semi-crystalline poly(stearyl methacrylate) (PSMA).…”

“…[14][15][16][17][18][19][20] This highly attractive approach enables bespoke organic nanoparticles to be prepared directly during the copolymer synthesis at much higher concentrations. The most versatile PISA formulation is based on dispersion polymerization, which can be performed in either water, 21 polar solvents such as alcohols, [22][23][24][25][26][27][28][29][30][31] or non-polar solvents such as n-alkanes. [32][33] In each case, a soluble macromolecular chain transfer agent (macro-CTA) is chain-extended using a soluble vinyl monomer in a suitable solvent that is a non-solvent for the growing second block.…”

RAFT dispersion polymerization in non-polar solvents: facile production of block copolymer spheres, worms and vesicles in n-alkanes

“…Currently, there is strong academic interest in polymerization- 25 induced self-assembly (PISA) [1][2][3] using living radical polymerization techniques such as reversible additionfragmentation chain transfer (RAFT) polymerization. [4][5][6][7][8] This approach has enormous potential for the design of bespoke - 30 any further processing steps.…”

“…28 Similarly, RAFT dispersion polymerization in polar solvents 50 such as lower alcohols has been extensively explored by Pan et al, [29][30][31][32][33][34] by Charleux and co-workers, 35,36 and also by our own research group. 25,26 Again, pure spherical, worm-like and vesicular morphologies have all been observed, depending on the targeted diblock composition. GPC analyses confirm that fairly 55 good control over the copolymer molecular weight distribution (e.g.…”

“…[9][10][11][12][13][14] Spherical morphologies are most 35 commonly obtained, [9][10][11][12][13] but systematic variation of the block copolymer composition coupled with a detailed knowledge of the block copolymer phase diagram also allows access to higher order morphologies such as worms [14][15][16] and vesicles. [17][18][19][20][21][22][23][24][25][26] In most cases good blocking efficiencies and reasonably low final 40 polydispersities (e.g. M w /M n < 1.20) can be achieved, along with very high monomer conversions within relatively short reaction times (e.g.…”