Formation and Reversible Morphological Transition of Bicontinuous Nanospheres and Toroidal Micelles by the Self‐Assembly of a Crystalline‐b‐Coil Diblock Copolymer

Abstract

We herein report the formation of two complex nanostructures, toroidal micelles and bicontinuous nanospheres, by the self-assembly of the single structurally simple crystalline-b-coil diblock copolymer poly[bis(trifluoroethoxy)phosphazene]-b-poly(styrene), PTFEP-b-PS, in one solvent (THF) and without additives. The nature of these nanostructures in solution was confirmed by DLS and cryo-TEM experiments. The two morphologies are related by means of a new type of reversible morphological evolution, bicontinuous-to-toroidal, triggered by changes in the polymer concentration. WAXS experiments showed that the degree of crystallinity of the PTFEP chains located at the core of the toroids was higher than that in the bicontinuous nanospheres, thus indicating that the final morphology of the aggregates is mostly determined by the ordering of the PTFEP core-forming blocks.

Functional Polymeric Materials Based on Main‐Group Elements

“…[60] Theexclusive monodirectional growth enabled the synthesis of many well-defined telechelic and block-copolymer structures (37). [62] Theensuing variations in the polymer microstructure can have atremendous impact on materials properties such as the glass transition temperature (T g values of polyphosphazenes span at emperature range of over 400 8 8C) [65] as well as their aggregation behavior.P resa Soto et al employed "living" polymerization methods to generate self-assemblies with reversible morphological transitions between unilamellar vesicles and spherical micelles (Figure 7, top) [63] or between bicontinuous nanospheres and toroidal micelles, [66] all in response to acid/base addition or concentration changes.I n addition, the degradability of polyphosphazenes is of great interest in the biomedical field and for controlled release applications. Forinstance,phosphite-mediated polymerization of phosphoranimines (XR 2 )P = N-SiMe 3 (33 b), where Xi s typically ah alogen, and Rc an be any alkyl, aryl, or alkoxy group,although not achieving the level of control as with 33 a, give high molecular weight polymers that are functionalized even with otherwise challenging P-alkyl and P-aryl moieties.…”

“…Forinstance,phosphite-mediated polymerization of phosphoranimines (XR 2 )P = N-SiMe 3 (33 b), where Xi s typically ah alogen, and Rc an be any alkyl, aryl, or alkoxy group,although not achieving the level of control as with 33 a, give high molecular weight polymers that are functionalized even with otherwise challenging P-alkyl and P-aryl moieties. [62] Theensuing variations in the polymer microstructure can have atremendous impact on materials properties such as the glass transition temperature (T g values of polyphosphazenes span at emperature range of over 400 8 8C) [65] as well as their aggregation behavior.P resa Soto et al employed "living" polymerization methods to generate self-assemblies with reversible morphological transitions between unilamellar vesicles and spherical micelles (Figure 7, top) [63] or between bicontinuous nanospheres and toroidal micelles, [66] all in response to acid/base addition or concentration changes.I n addition, the degradability of polyphosphazenes is of great interest in the biomedical field and for controlled release applications. [58c, 67] Teasdale et al targeted self-immolative polyphosphazenes,w hich can rapidly disintegrate into phosphate and ammonia.…”

Funktionelle polymere Materialien auf der Basis von Hauptgruppen‐Elementen

“…Zum Beispiel ergibt die Phosphit-vermittelte Polymerisation von Phosphoraniminen (XR 2 )P = N-SiMe 3 (33 b; wobei Xtypischerweise ein Halogen ist und Reine beliebige Alkyl-, Aryl-oder Alkoxy-Gruppe) -w enngleich sie nicht den Kontrollgrad wie bei 33 a erreicht -hochmolekulare Polymere,die auch mit ansonsten anspruchsvollen P-Alkyl-und P-Aryl-Komponenten funktionalisiert sind. Presa Soto et al nutzten "lebende" Polymerisationsmethoden, um selbstorganisierte Anordnungen mit reversiblen morphologischen Übergängen zwischen unilamellaren Vesikeln und sphärischen Micellen (Abbildung 7, oben) [63] oder zwischen bikontinuierlichen Nanokugeln und ringfçrmigen Micellen zu erzeugen [66] -alles als Reaktion auf Säure/ Base-Zusatz oder Konzentrationsänderungen. Presa Soto et al nutzten "lebende" Polymerisationsmethoden, um selbstorganisierte Anordnungen mit reversiblen morphologischen Übergängen zwischen unilamellaren Vesikeln und sphärischen Micellen (Abbildung 7, oben) [63] oder zwischen bikontinuierlichen Nanokugeln und ringfçrmigen Micellen zu erzeugen [66] -alles als Reaktion auf Säure/ Base-Zusatz oder Konzentrationsänderungen.…”

“…[62] Resultierende Va riationen in der Polymermikrostruktur kçnnen einen enormen Einfluss auf die Werkstoffeigenschaften wie die Glasübergangstemperatur (T g -Werte von Polyphosphazenen überspannen einen Te mperaturbereich von mehr als 400 8 8C) [65] sowie das Aggregationsverhalten haben. Presa Soto et al nutzten "lebende" Polymerisationsmethoden, um selbstorganisierte Anordnungen mit reversiblen morphologischen Übergängen zwischen unilamellaren Vesikeln und sphärischen Micellen (Abbildung 7, oben) [63] oder zwischen bikontinuierlichen Nanokugeln und ringfçrmigen Micellen zu erzeugen [66]…”

Branched Macromolecular Architectures for Degradable, Multifunctional Phosphorus‐Based Polymers

“…[48] The development of a room temperature polymerization of trichloro(trimethylsilyl)phosphoranimine (Cl 3 PNSi(CH 3 ) 3 ) has provided much needed control over the synthesis of [NPCl 2 ] n to achieve not only polymers with narrow polydispersities, but also to gain access to block polymers and more advanced structures. [10,32,[49][50][51][52] The most frequently used initiator for the polymerization of the monomer Cl 3 PNSi(CH 3 ) 3 to [NPCl 2 ] n is PCl 5 . [49,53] 3 in a living cationic polymerization with the number of repeat units determined by the further equivalents of monomer added.…”