Star Block Copolymer Nanoassemblies: Block Sequence is All-Important

Abstract

Star and linear block copolymers of [poly(4vinylpyridine)-block-polystyrene] n [(P4VP-b-PS) n ] and [polystyrene-block-poly(4-vinylpyridine)] n [(PS-b-P4VP) n ] (n = 1−4) with similar chemical composition but different block sequence were synthesized by RAFT polymerization. Star (P4VP-b-PS) n is composed of a jointed P4VP core and several outer PS arms, and (PS-b-P4VP) n has just the opposite block sequence and different conformation. The effect of block sequence on the block copolymer nanoassemblies is explored. It is discovered that star (P4VP-b-PS) n tends to form complicated nanoassemblies in the block selective solvent for P4VP due to the PS arms bridging, and star (PS-b-P4VP) n acts somewhat like linear amphiphilic block copolymers. Our study demonstrates the crucial role of block sequence in star block copolymer nanoassemblies.

RAFT‐Mediated Polymerization‐Induced Self‐Assembly

“…Virtually from the start of PISA, bifunctional symmetrical RAFT agents have also been implemented successfully to produce ABA structures, but more recently, trifunctional or tetrafunctional RAFT agents—leading to the formation of trifunctionalized or tetrafunctionalized star polymers—have also been used. These studies show that the structure of the RAFT agent, that is, the number of functional groups (mono‐, bi‐, or multifunctional) as well as the inversion of the Z and R groups leading to BAB or (BA) n stars has a crucial impact not only on the polymerization mechanism and control but also on the resulting particle morphology. Although it was not always straightforward to correlate the macromolecular architecture and morphology in the examples, the An group has proposed an elegant approach to rationally increase the packing parameter through design of the macromolecular architecture.…”

RAFT‐vermittelte polymerisationsinduzierte Selbstorganisation (PISA)

“…Praktisch seit den Anfängen von PISA sind auch bifunktionelle symmetrische RAFT-Agenzien, die ABA-Strukturen produzieren, erfolgreich eingesetzt worden, [223][224][225][226] aber in jüngster Zeit wurden auch trifunktionelle [227] oder tetrafunktionelle RAFT-Agenzien [228] verwendet, die zur Bildung von Doppelarm-oder Vierarmpolymeren führen. All diese Artikel zeigen, dass die Struktur des RAFT-Agens,d .h.d ie Anzahl seiner funktionellen Gruppen (mono-, bi-oder multifunktionell) und die Vertauschung von Z-und R-Gruppen, die zu BAB- [183,[229][230][231] oder (BA) n -Sternen [228,232,233] führt, nicht nur auf den Polymerisationsmechanismus und seine Kontrolle einen entscheidenden Einfluss haben, sondern auch auf die resultierende Partikelmorphologie.W ährend es in den genannten Beispielen nicht immer einfach war, makromolekulare Architektur und Morphologie zu korrelieren, [227,229] hat die Gruppe von An [234] einen eleganten Ansatz vorgeschlagen, um den Packungsparameter durch rationales Design der makromolekularen Architektur zu erhçhen. Sie synthetisierten ein bifunktionelles asymmetrisches RAFT-Agent, an das eine PEG-Kette über eine zusätzliche funktionelle Gruppe an seinem Symmetriezentrum gekoppelt war (Abbildung 7).…”

Hierarchical self-assembly of miktoarm star copolymers with pathway complexity

“…Similarly, amphiphilic star copolymers, including block copolymer stars 40 and miktoarm stars, 41 can also self-assemble in selective solvents to generate micellelike aggregates. [42][43][44][45][46][47][48][49][50][51] Notably, the resulting micellar structures are much more complicated than those formed by linear block copolymers. For example, star block copolymers can self-assemble into nanoparticle clusters 42 and lacunal 43 and bicontinuous nanospheres.…”

“…[42][43][44][45][46][47][48][49][50][51] Notably, the resulting micellar structures are much more complicated than those formed by linear block copolymers. For example, star block copolymers can self-assemble into nanoparticle clusters 42 and lacunal 43 and bicontinuous nanospheres. 42 Moreover, stepwise self-assembly of μ-ABC miktoarm star terpolymers results in multiple levels of structural hierarchy.…”

“…For example, star block copolymers can self-assemble into nanoparticle clusters 42 and lacunal 43 and bicontinuous nanospheres. 42 Moreover, stepwise self-assembly of μ-ABC miktoarm star terpolymers results in multiple levels of structural hierarchy. Typical hierarchical morphologies include segmented worm-like micelles, 44,45 polygonal bilayered sheets, 45 patchy nanofibrils, 46 and woodlouse-like particles.…”