Bisurea-Functionalized RAFT Agent: A Straightforward and Versatile Tool toward the Preparation of Supramolecular Cylindrical Nanostructures in Water

Abstract

Bis-ureahydrophilic polymer sticker RAFT polymerizationTTC unit Hydrogen bonding unit , , , … µm ABSTRACTWe report a versatile and simple approach to produce cylindrical micelles by the direct dissolution of polymers in water. The developed strategy relies on a RAFT agent functionalized by a bisurea sticker that allowed to synthesize a series of α-bisurea functionalized poly(N,Ndimethylacrylamide) (PDMAc), poly(acrylic acid) (PAA), polyacrylamide (PAM) and poly(2-(N,N-dimethylamino)ethyl acrylate) (PDMAEA) with number-average degrees of polymerization (DPn) varying from about 10 to 50. Their spontaneous self-assembly in water was studied by electron microscopy (cryo-TEM), neutron scattering (SANS) and calorimetry (ITC) analyses that showed that long cylindrical micelles are spontaneously formed in water.The crucial role of the bisurea sticker end-groups was established by comparison with the corresponding bisurea-free model polymers that only formed spherical micelles. Finally, we have shown that it is possible to trigger reversibly the assembly/disassembly of the nanofibers by pH changes. AUTHOR INFORMATIONCorresponding authors *

Unexpected thermo-responsiveness of bisurea-functionalized hydrophilic polymers in water

“…Cryo-TEM analyses showed that they assembled into cylindrical and/or spherical micelles (Figure 2 and Figure S2), as described before for PDMAc-U2 and PAA-U2. 12 Our data show that a lower DPn favored the formation of cylindrical over spherical micelles (see Table 1). For † Except PHEA2, which was not soluble.…”

“…A series of bisurea-functionalized hydrophilic polymers (Scheme 1), namely poly(N,Ndimethylacrylamide) (PDMAc), poly(acrylic acid) (PAA), polyacrylamide (PAM), poly(N-4acryloylmorpholine) (PNAM) and poly(2-hydroxyethylacrylate) (PHEA), were synthesized using the recently reported bisurea-functionalized RAFT agent TTC-U2. 12,15 The polymerizations were performed in DMF, at 70 °C, using AIBN as an initiator and targeting a number-average degree of polymerization (DPn) ranging from 10 to 50. Generally, 70% monomer conversion was reached in less than 5 h (see Table S1), and after precipitation the polymers were analyzed by SEC and 1 H NMR.…”

“…We selected bisurea stickers that drive the formation of supramolecular polymer bottlebrushes through directional assembly of the sticker by hydrogen bonds. 11,12,13 The assembly of the polymers in long 1D nanostructures, where the polymer chains are densely packed, might actually alter their solubility properties. 14 If successful, this strategy could allow converting well-known hydrophilic homopolymers into thermosensitive polymers with a CP near body temperature, without copolymerization with hydrophobic monomers.…”

Straightforward preparation of supramolecular Janus nanorods by hydrogen bonding of end-functionalized polymers

“…Hydrophilic polymers decorated with a bisurea sticker are known to form long rod-like assemblies in water 16 – 18 . Interestingly, Sijbesma et al showed that the length of the alkylene spacer connecting two urea groups plays an essential role: if two bisurea stickers differing by the size of the alkylene spacer are mixed, they form self-sorted assemblies, so that urea–urea hydrogen bonds are maximized 19 .…”

RAFT‐vermittelte polymerisationsinduzierte Selbstorganisation (PISA)

“…Während die letztgenannten Beispiele auf supramolekularen Interaktionen zwischen Monomereinheiten der Polymerketten im Kern basierten, haben Rieger, Stoffelbach und Mitarbeiter erst kürzlich eine Bausatz‐Strategie entwickelt, die auf Interaktionen zwischen einzelnen Hafteinheiten am ω‐Ende jeder Polymerkette basiert. Sie entwarfen nämlich ein MacroRAFT‐Agens, das durch eine wasserstoffbrückengebundene Bis‐Harnstoff‐Hafteinheit funktionalisiert wurde, um den PISA‐Prozess über eine eindimensionale, gerichtete Selbstorganisation der Hafteinheiten in Richtung Nanofasermorphologie zu treiben, die durch die Bildung hydrophober Domänen während des PISA‐Prozesses noch verfestigt wird (Abbildung ). Dieses Konzept wurde erfolgreich bei der Synthese von Poly( N , N ‐dimethylacrylamid)‐ b ‐poly(2‐methoxyethylacrylat)‐Diblockcopolymeren getestet, die durch Dispersionspolymerisation in Wasser hergestellt wurden.…”