Photocontrolled Growth of Cross-Linked Nanonetworks

Abstract

We report the preparation of photoresponsive nanomaterials and the increase of their nanoscopic size through a “photogrowth” mechanism. The photogrowable nanonetworks (PGNNs) were synthesized by cross-linking two components, a thiolated acrylate copolymer and a symmetrical bismaleimide trithiocarbonate (TTC), utilizing thiol-maleimide click chemistry. With this strategy, nanonetwork growth was achieved through a photoinduced polymerization from the integrated trithiocarbonate by either direct photolysis or photoredox catalysis. Via direct photolysis, we generated a series of expanded particles by polymerizing methyl acrylate (MA) under irradiation with violet light (400 nm) over a period of 1, 3, and 6 h, starting from a 58 nm parent particle, resulting in particles of increased sizes of 77, 156, and 358 nm, respectively. Nanoparticle expansion reactions catalyzed by 10-phenylphenothiazine (PTH) were experienced to progress faster in 20 and 30 min to reach particle sizes of 195 and 300 nm. The addition of the photoredox catalyst to the expansion polymerizations with MA resulted in an increased control over the dispersity of the particles as well as of the promoted disassembly products. In this work, we demonstrated that nanoparticle structures designed as cross-linked networks with integrated trithiocarbonates can be expanded by photocontrolled radical polymerizations (photo-CRPs) in the presence or absence of a photoredox catalyst. These proof-of-concept experiments showcase the dynamic growth and integration of functional units into existing scaffolds and open up the possibility to prepare highly tailorable nanomaterials.

Polymer Networks: From Plastics and Gels to Porous Frameworks

“…[95] Iniferter-based CRP methods have undergone ar enaissance in recent years, particularly with the advent of photoredox catalysis; [107,108] these methods have proven useful for the synthesis of photoactive polymer networks with topologies and compositions that can be spatiotemporally modulated using various wavelengths of light. [39,41,[109][110][111] Though polymer networks can be synthesized using conventional free radical polymerization of vinyl monomers and divinyl crosslinkers,the low rate of initiation compared to propagation along with extensive radical termination inherent to this process lead to large network density fluctuations that negatively impact the mechanical properties of the resulting materials ( Figure 5B). In contrast, the high initiation relative to propagation rates of RDRP processes provide ar elatively homogeneous distribution of dormant branched polymers in the early stages of network formation (Figure 5B); these network fragments can diffuse before they are reactivated, preventing the formation of densely-crosslinked network clusters and producing am ore homogeneous network.…”

“…Notably, RAFT was originally strictly defined as lacking reversible termination, thus distinguishing it from initiation, chain transfer, termination, i.e., “iniferter” processes (Figure A), that used similar CTAs . Iniferter‐based CRP methods have undergone a renaissance in recent years, particularly with the advent of photoredox catalysis; these methods have proven useful for the synthesis of photoactive polymer networks with topologies and compositions that can be spatiotemporally modulated using various wavelengths of light …”

Polymernetzwerke: Von Kunststoffen und Gelen zu porösen Gerüsten

“…Bemerkenswerterweise wurde RAFT ursprünglich streng definiert als Fehlen reversibler Abbruchprozesse, auf diese Weise erfolgte eine Abgrenzung von Prozessen mit Kettenstart, Kettenübertragung, Kettenabbruch, d. h. “Iniferter”‐Prozessen (Abbildung A), bei denen ähnliche CTAs genutzt wurden . Auf Inifertern basierende CRP‐Methoden haben in den letzten Jahren, insbesondere mit dem Aufkommen der Photoredoxkatalyse, eine Renaissance erlebt; diese Methoden erwiesen sich als nützlich für die Synthese von photoaktiven Polymernetzwerken mit Topologien und Zusammensetzungen, die mit unterschiedlichen Wellenlängen des Lichts räumlich und zeitlich moduliert werden können …”

“…[95] AufI nifertern basierende CRP-Methoden haben in den letzten Jahren, insbesondere mit dem Aufkommen der Photoredoxkatalyse,e ine Renaissance erlebt; [107,108] diese Methoden erwiesen sich als nützlich fürd ie Synthese von photoaktiven Polymernetzwerken mit Topologien und Zusammensetzungen, die mit unterschiedlichen Wellenlängen des Lichts räumlich und zeitlich moduliert werden kçnnen. [39,41,[109][110][111] Obwohl Außerdem wurden auch ATRP [113][114][115] und RAFT-Polymerisation [116] Wenn in Polymernetzwerke Initiatorzentren eingebaut werden, kçnnen RDRP-Methoden eine einfache Modifizierung nach der Synthese ermçglichen, um die Eigenschaften der Polymernetzwerke deutlich zu verändern. Außerdem ermçglichen neuere Entwicklungen von lichtgesteuerten lebenden radikalischen Polymerisationen (Photo-CRP) [108] eine räumliche und zeitliche Kontrolle dieser Netzwerkumwandlungen nach der Synthese.2 013 demonstrierten Johnson und Mitarbeiter,dass Tr ithiocarbonate enthaltende Stränge eines Polymernetzwerks in Gegenwart von Monomeren bei Bestrahlung mit langwelligem UV-Licht (ca.…”

PET-RAFT Facilitated 3D Printing of Polymeric Materials

“…One promising approach to enable monomer insertion into an initially fabricated polymer networks [28][29][30][31] or to fabricate dynamic polymer networks 29,[32][33][34][35][36][37][38] , is by introduction of living functional groups such as trithiocarbonate (TTCs) iniferters-also known as reversible addition fragmentation chain transfer (RAFT) agents [39][40][41][42][43][44][45] into the strands of cross-linked networks. For instance, Johnson's group synthesized a gel network containing TTCs and demonstrated post-synthesis monomer insertion into these networks upon reactivation of TTC groups (under UV light).…”