The Effect of Hydrophile Topology in RAFT‐Mediated Polymerization‐Induced Self‐Assembly

Abstract

Polymerization-induced self-assembly (PISA) was employed to compare the self-assembly of different amphiphilic block copolymers. They were obtained by emulsion polymerization of styrene in water using hydrophilic poly(N-acryloylmorpholine) (PNAM)-based macromolecular RAFT agents with different structures. An average of three poly (ethylene glycol acrylate) (PEGA) units were introduced either at the beginning, statistically, or at the end of a PNAM backbone, resulting in formation of nanometric vesicles and spheres from the two former macroRAFT architectures, and large vesicles from the latter. Compared to the spheres obtained with a pure PNAM macroRAFT agent, composite macroRAFT architectures promoted a dramatic morphological change. The change was induced by the presence of PEGA hydrophilic side-chains close to the hydrophobic polystyrene segment.

Beyond Simple AB Diblock Copolymers: Application of Bifunctional and Trifunctional RAFT Agents to PISA in Water

“…[9,10] It is nowadays well established that numerous parameters, mainly the monomer concentration, the chemical nature and the respective length of the blocks have an impact on the nanoobject morphology. [1,[9][10][11][12][13][14][15][16] Another important parameter that has been less considered in PISA so far is the macromolecular architecture. [17] Indeed, it has previously been observed for amphiphilic block copolymers synthesized in solution that the macromolecular architecture (e.g., AB versus symmetrical (AB) 2 block copolymers possessing the same overall number-average molar mass, M n , and the same A/B ratio) had an impact on the size and the aggregation number of the resulting micelles prepared by direct dissolution of the copolymer in water.…”

“…PISA is considered as an efficient and reliable strategy not only to produce amphiphilic diblock copolymers but also to prepare nanoobjects with controllable morphologies including spheres, worms, or vesicles in high yields and at high solid contents (typically 10–40 wt%) . It is nowadays well established that numerous parameters, mainly the monomer concentration, the chemical nature and the respective length of the blocks have an impact on the nanoobject morphology . Another important parameter that has been less considered in PISA so far is the macromolecular architecture .…”

“…The authors compared the morphologies obtained with those from a monofunctional macro‐RAFT agent, yielding conventional PEG‐ b ‐PDAAm diblock copolymers, and demonstrated that the Y‐shaped copolymer, PEG‐ b ‐(PDAAm) 2 , promotes the production of nanoobjects with high‐order morphologies through the formation of bulky hydrophobic segments. Moreover, other groups have also shown that the topology of the macro‐RAFT agent (linear vs graft) has an impact on the resulting particle morphology (and that pendant graft structures are favorable to the formation of higher order morphologies) . These examples clearly highlight the importance of the macromolecular architecture but the number of available studies, especially in pure water, are too limited for the elucidation of generic design rules.…”

“…Moreover, other groups have also shown that the topology of the macro-RAFT agent (linear vs graft) has an impact on the resulting particle morphology (and that pendant graft structures are favorable to the formation of higher order morphologies). [15,33] These examples clearly highlight the importance of the macromolecular architecture but the number of available studies, especially in pure water, are too limited for the elucidation of generic design rules. There is thus a need to perform deeper investigations in order to better understand the influence of the macromolecular architecture on morphologies obtained by PISA.…”

Self‐assembly of block copolymers with an alkoxysilane‐based core‐forming block: A comparison of synthetic approaches

“…More recently, polymer–silica colloidal nanocomposites have been prepared using polymerization‐induced self‐assembly (PISA) . The PISA method enables the design of nanoparticles with distinct morphologies (such as spheres, rods/“worms,” and vesicles) via the chain extension of a solvophilic polymer with a solvophobic block to drive in situ assembly, either under dispersion or emulsion polymerization conditions . Benicewicz and coworkers have recently used surface‐initiated PISA to assemble silica nanoparticles (∼15 nm diameter, dispersed in ethanol) into nanoparticle “strings” and vesicles, driven by the balance of solvophilic and solvophobic polymers grafted onto the silica surface.…”