Sequence-Defined Multiblock Copolymer Nanoengineered Particles from Polymerization-Induced Self-Assembly (PISA): Synthesis and Film Formation

Abstract

Multiblock copolymers synthesized via reversible addition–fragmentation transfer (RAFT) emulsion polymerization offer a pathway to creating new nanoengineered materials. Emulsion polymerization results in a so-called polymer latex, a dispersion of polymer nanoparticles in water, which has the potential to be employed toward environmentally friendly waterborne coatings provided film formation (particle coalescence) can occur satisfactorily. An interesting feature of macroRAFT-mediated approaches is that the polymer chains are anchored at the particle surface via the hydrophilic segment, thus leading to a system where microphase separation between distinct blocks can occur, as chains are orientated from the particle surface to the particle core, leading to multiphase particles. Utilizing this feature, we here demonstrate that multiblock copolymer nanoparticles synthesized via RAFT polymerization-induced self-assembly (PISA) emulsion polymerization demonstrate drastically different film-forming behaviors depending on the nature of the outermost layer (shell) of the polymer nanoparticles (i.e., the seed latex employed, given this forms the outer layer). High molecular weight multiblock copolymers are synthesized via sequential seeded emulsion polymerizations using poly( n -butyl acrylate) (PBA), polystyrene (PS), and P(BA- stat -S) seed latexes. By employing a low glass transition temperature PBA seed, a high molecular weight multiblock copolymer was able to undergo film formation directly from the latex, resulting in a high toughness elastomeric material with mechanical properties drastically different from those of an equivalent statistical copolymer material. The present work highlights the customizability of multiblock copolymer synthesis and the potential of these systems to tailor polymer properties toward creation of novel materials.

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