Living Supramolecular Polymerization of an Aza-BODIPY Dye Controlled by a Hydrogen-Bond-Accepting Triazole Unit Introduced by Click Chemistry

An aza-BODIPY dye 1 bearing two hydrophobic fan-shaped tridodecyloxybenzamide pendants through 1,2,3-triazole linkages was synthesized by a click reaction and characterized. ¹H NMR studies indicated that dye 1 exhibited variable conformations through intramolecular H-bonding interaction, which is beneficial for the polymorphism of aggregation. The thermodynamic, structural, and kinetic aspect of the supramolecular polymerization of dye 1 was investigated by UV/Vis absorption spectroscopy, IR spectroscopy, AFM, TEM, and SEM. Biphasic aggregation pathways of dye 1 , leads to the formation of off-pathway, metastable Agg. I and thermodynamically stable Agg. II with distinct H-aggregation spectra and nanoscale morphology. The living manner of the supramolecular polymerization of dye 1 was demonstrated in seeded polymerization experiments with temperature-modulated successive cooling–heating cycles.     

Fabrication of Chiral‐Selective Nanotubular Heterojunctions through Living Supramolecular Polymerization

Novel, chiral‐selective linear nanotubular heterojunctions were achieved by living supramolecular polymerization of perylenediimide (PDI) derivatives. We demonstrate that the chiral seed can effectively bias achiral PDI molecules to polymerize on its ends in the identical helical sense. More interestingly, the chiral seed can bias the opposite enantiomers to grow expitaxially from its ends even in excess amounts relative to the seed. Furthermore, we demonstrate that the biasing effect of the chiral seed on the opposite enantiomer is not dependent on the length of the chiral seed but is related to the intrinsic length of the elongated nanotube from the opposite enantiomer. The fabrication of chiral‐selective nanotubes was achieved by application of the unique biasing effect of the chiral seed in living supramolecular self‐assembly.     

Consecutive Supramolecular Polymerization of a Rylene-Based Twistacene

The synthesis and self-assembling features of twistacene 1 are reported. The supramolecular polymerization of 1 displays a consecutive pathway to afford slipped ( AggI ) and rotationally displaced ( AggII ) aggregates conditioned by the formation of intramolecularly H-bonded pseudocycles. In methylcyclohexane, both AggI and AggII are highly stable and the interconversion of the kinetically controlled AggI into the thermodynamically controlled AggII takes several weeks to occur. The utilization of toluene as solvent changes the energetic level for both aggregates and favors a faster conversion of AggI into AggII within a period of minutes. This conversion can be accelerated by the addition of seeds. Furthermore, concentration dependent kinetic studies demonstrate the consecutive character of the supramolecular polymerization of 1 .     

Pathway Complexity Versus Hierarchical Self‐Assembly in N‐Annulated Perylenes: Structural Effects in Seeded Supramolecular Polymerization

Studies were carried out on the hierarchical self‐assembly versus pathway complexity of N‐annulated perylenes 1 – 3 , which differ only in the nature of the linking groups connecting the perylene core and the side alkoxy chains. Despite the structural similarity, compounds 1 and 2 exhibit noticeable differences in their self‐assembly. Whereas 1 forms an off‐pathway aggregate I that converts over time (or by addition of seeds) into the thermodynamic, on‐pathway product, 2 undergoes a hierarchical process in which the kinetically trapped monomer species does not lead to a kinetically controlled supramolecular growth. Finally, compound 3 , which lacks the amide groups, is unable to self‐assemble under identical experimental conditions and highlights the key relevance of the amide groups and their position to govern the self‐assembly pathways.     

First Nitroxide‐Mediated Controlled/Living Free Radical Polymerization in an Ionic Liquid

Summary: The controlled/living radical polymerizations of methyl acrylate in 50% v/v of an ionic liquid initiated by the alkoxyamine generated in situ from 4‐oxo‐2,2,6,6‐tetramethyl‐1‐piperidinyl‐N‐oxyl (4‐oxo‐TEMPO) and 2,2′‐azoisobutyronitrile (AIBN) at 140–155 °C are reported. The number‐average molecular weights increased linearly with conversion, and polydispersity indices are approximately 1.4 in the best case. The rates of polymerization were greater than in anisole, and similar to the rate of spontaneous polymerization in the ionic liquid.

(filled symbols) and (open symbols) vs. conversion for the MA polymerization in the presence of [4‐oxo‐TEMPO]/[AIBN] (2.8:1) in 50% v/v anisole with 0.03 M AIBN (squares) and 50% v/v [hmim][PF₆] with 0.03 M AIBN (circles), and 0.06 M AIBN (triangles).     

Tuneable Transient Thermogels Mediated by a pH‐ and Redox‐Regulated Supramolecular Polymerization

A multistimuli‐responsive transient supramolecular polymerization of β‐sheet‐encoded dendritic peptide monomers in water is presented. The amphiphiles, which contain glutamic acid and methionine, undergo a glucose oxidase catalyzed, glucose‐fueled transient hydrogelation in response to an interplay of pH and oxidation stimuli, promoted by the production of reactive oxygen species (ROS). Adjusting the enzyme and glucose concentration allows tuning of the assembly and the disassembly rates of the supramolecular polymers, which dictate the stiffness and transient stability of the hydrogels. The incorporation of triethylene glycol chains introduces thermoresponsive properties to the materials. We further show that repair enzymes are able to reverse the oxidative damage in the methionine‐based thioether side chains. Since ROS play an important role in signal transduction cascades, our strategy offers great potential for applications of these dynamic biomaterials in redox microenvironments.     

The Metal–Metal‐to‐Ligand Charge Transfer Excited State and Supramolecular Polymerization of Luminescent Pincer PdII–Isocyanide Complexes

Pincer Pd^II–isocyanide complexes are described that display intermolecular interactions and emissive ³MMLCT excited states in aggregation state(s) at room temperature. The intermolecular Pd^II?Pd^II and ligand–ligand interactions drive these complexes to undergo supramolecular polymerization in a living manner. Comprehensive spectroscopic studies reveal a pathway with a kinetic trap that can be modulated by changing the counteranion and metal atom. The Pd^II supramolecular assemblies comprise two different aggregation forms with only one to be emissive. DFT/TDDFT calculations lend support to the MMLCT absorption and emission of these pincer Pd^II–isocyanide aggregates.     

Controlled Alternating Copolymerization of (Meth)acrylates and Vinyl Ethers by Using Organoheteroatom‐Mediated Living Radical Polymerization

Alternating copolymers comprised of (meth)acrylates and vinyl ethers with controlled molecular weights and polydispersities were synthesized for the first time by living radical polymerization using organotellurium, stibine, and bismuthine chain transfer agents. Combining living alternating copolymerization and living radical or living cationic polymerization afforded hitherto unavailable block copolymers with controlled macromolecular structures.

     

Living Supramolecular Polymerization of a Perylene Bisimide Dye into Fluorescent J‐Aggregates

The self‐assembly of a new perylene bisimide (PBI) organogelator with 1,7‐dimethoxy substituents in the bay position affords non‐fluorescent H‐aggregates at high cooling rates and fluorescent J‐aggregates at low cooling rates. Under properly adjusted conditions, the kinetically trapped “off‐pathway” H‐aggregates are transformed into the thermodynamically favored J‐aggregates, a process that can be accelerated by the addition of J‐aggregate seeds. Spectroscopic studies revealed a subtle interplay of π–π interactions and intra‐ and intermolecular hydrogen bonding for monomeric, H‐, and J‐aggregated PBIs. Multiple polymerization cycles initiated from the seed termini demonstrate the living character of this chain‐growth supramolecular polymerization process.     

Synthesis of Styrenic‐Terminated Methacrylate Macromonomers by Nitroanion‐Initiated Living Anionic Polymerization

N‐Isopropyl‐4‐vinylbenzylamine (PVBA) was synthesized and used as an initiator for the polymerization of methacrylates to synthesize macromonomers with terminal styrenic moieties. LiPVBA initiated a living polymerization and block copolymerization of methyl methacrylate, 2‐(N,N‐dimethylamino)ethyl methacrylate and tert‐butyl methacrylate and produced polymers having well‐controlled molecular weights and very low polydispersities (M̄_w/M̄_n < 1.1) in quantitative yield. ¹H NMR analysis revealed that the polymers contained terminal 4‐vinylbenzyl groups. The macromonomers were reactive in the copolymerization with styrene.     

End‐Group Characterization of Poly(acrylic acid) Prepared by Nitroxide‐Mediated Controlled Free‐Radical Polymerization

Summary: A low‐molar‐mass poly(acrylic acid) with a narrow molar‐mass distribution, prepared by SG1 nitroxide‐mediated controlled free‐radical polymerization, was subjected to end‐group analysis to confirm its living nature. ¹H and ³¹P NMR spectroscopy confirmed the presence of the SG1‐based alkoxyamine end group. Furthermore, chain extension with styrene and n‐butyl acrylate demonstrated the ability of the homopolymer to initiate the polymerization of a second block. These results open the door to the synthesis of poly(acrylic acid)‐based block copolymers by direct nitroxide‐mediated polymerization of acrylic acid.

Acrylic acid polymerization using an alkoxyamine initiator based on SG1 (N‐tert‐butyl‐N‐(1‐diethyl phosphono‐2,2‐dimethylpropyl) nitroxide resulting in a homopolymer capable of initiating the polymerization of a second block.     

Plasma‐Initiated Controlled/Living Radical Polymerization of Methyl Methacrylate in the Presence of 2‐Cyanoprop‐2‐yl 1‐dithionaphthalate (CPDN)

Summary: Plasma‐initiated controlled/living radical polymerization of methyl methacrylate (MMA) was carried out in the presence of 2‐cyanoprop‐2‐yl 1‐dithionaphthalate. Well‐defined poly(methyl methacrylate) (PMMA), with a narrow polydispersity, could be synthesized. The polymerization is proposed to occur via a RAFT mechanism. Chain‐extension reactions were also successfully carried out to obtain higher molecular weight PMMA and PMMA‐block‐PSt copolymer.

Dependence of ln([M]₀/[M]) on post‐polymerization time (above), and \overline M _{\rm n} and PDI against conversion (below) for plasma initiated RAFT polymerization of MMA at 25 °C.     

Living Coordination Polymerization of a Six‐Five Bicyclic Lactone to Produce Completely Recyclable Polyester

The development of chemically recyclable polymers promises a closed‐loop approach towards a circular plastic economy but still faces challenges in structure/property diversity and depolymerization selectivity. Here we report the first successful coordination ring‐opening polymerization of 4,5‐trans‐cyclohexyl‐fused γ‐butyrolactone ( M1 ) with lanthanide catalysts at room temperature, producing P( M1 ) with M_n up to 89 kg mol^?1, high thermal stability, and a linear or cyclic topology. The same catalyst also catalyses selective depolymerization of P( M1 ) back to M1 exclusively at 120 °C. This coordination polymerization is also living, enabling the synthesis of well‐defined block copolymer.     

SET‐RAFT Polymerization of Progargyl Methacrylate and a One‐Pot/One‐Step Preparation of Side‐chain Functionalized Polymers via Combination of SET‐RAFT and Click Chemistry

A clickable alkyne monomer, PgMA, was successfully polymerized in a well‐controlled manner via single electron transfer initiation and propagation through the radical addition fragmentation chain transfer (SET‐RAFT) method. The living nature of the polymerization was confirmed by the first‐order kinetic plots, the linear relationships between molecular weights and the monomer conversions while keeping relatively narrow (≤1.55), and the successful chain‐extension with MMA. The better controllability of SET‐RAFT than other CRP methods is attributed to the less competitive termination in view of the presence of the CTA as well as the Cu(II) that is generated in situ. Moreover, a one‐pot/one‐step technique combining SET‐RAFT and “click chemistry” methods has been successfully employed to prepare the side‐chain functionalized polymers.

     

Highly Efficient Synthesis of Low Polydispersity Core Cross‐Linked Star Polymers by Ru‐Catalyzed Living Radical Polymerization

The efficient formation of low polydispersity core cross‐linked star (CCS) polymers via controlled/living radical polymerization (LRP) and the arm‐first approach was found to be dependant on the mediating catalyst system. The Ru catalyst, Ru(Ind)Cl(PPh₃)₂ Cat. 1 , and tertiary amine co‐catalyst were used to synthesize highly living poly(methyl methacrylate) (PMMA) macroinitiators, which were then linked together with ethylene glycol dimethacrylate (EGDMA) to form PMMA_armPEGDMA_core CCS polymers. The quantitative and near‐quantitative synthesis of CCS polymers were observed for low to moderate molecular weight macroinitiators ( = 8 and 20 kDa), respectively. Lower conversions were observed for high‐molecular weight macroinitiators ( ≥ 60 kDa). Overall, an improvement of between 10 and 20% was observed when comparing the Cat. 1 system to a conventional Cu‐catalyzed system. This significant improvement in macroinitiator‐to‐star conversion is explained in the context of catalyst system selection and CCS polymer formation.

     

Controlled Polymerization of Protic Ionic Liquid Monomer by ARGET‐ATRP and TERP

The direct synthesis of structurally well‐defined protic polymeric ionic liquid (PIL) with controlled molecular weight and molecular weight distribution is examined using N,N‐diethyl‐N‐(2‐methacryloylethyl) ammonium bis(tri‐fluoromethylsulfonyl)imide (DEMH‐TFSI) as a monomer. Three polymerization methods, namely, atom transfer radical polymerization (ATRP), activators regenerated by electron transfer (ARGET)‐ATRP, and organotellurium‐mediated living radical polymerization (TERP) are employed in this study. While the polymerization by ATRP is slow and does not reach high monomer conversion that under ARGET‐ATRP and TERP proceeds smoothly and affords structurally well‐defined poly(DEMH‐TFSI)s. TERP is especially efficient for the control and poly(DEMH‐TFSI)s with low to high molecular weights ( = 49 100–392 500) and narrow molecular weight distributions (/ = 1.17–1.46) are obtained. These results represent the first example of synthesis of a structurally well‐defined protic, ammonium PIL by direct polymerization of the protic ionic liquid monomer. The polymerization of N,N‐diethyl‐N‐(2‐methacryloylethyl)‐N‐methylammonium bis(trifluoromethylsulfonyl)imide (DEMM‐TFSI), which possesses a quaternary ammonium salt, also proceeds in a highly controlled manner under TERP conditions. A diblock copolymer, polystyrene‐block‐poly(DEMH‐TFSI), is also successfully synthesized by TERP.

     

Formation of Supramolecular Nanotubes by Self‐assembly of a Phosphate‐linked Dimeric Anthracene in Water

The assembly of supramolecular polymers from a phosphodiester‐linked dimeric anthracene is described. AFM and TEM imaging reveals that the supramolecular polymers self‐assemble into nanotubes in water. Subsequent photodimerization experiments indicate that the supramolecular polymerization occurs via end‐to‐end stacking rather than an interdigitation arrangement of the building blocks.     

In Situ Controlled Construction of a Hierarchical Supramolecular Chiral Liquid‐Crystalline Polymer Assembly

Hierarchical supramolecular chiral liquid‐crystalline (LC) polymer assemblies are challenging to construct in situ in a controlled manner. Now, polymerization‐induced chiral self‐assembly (PICSA) is reported. Hierarchical supramolecular chiral azobenzene‐containing block copolymer (Azo‐BCP) assemblies were constructed with π–π stacking interactions occurring in the layered structure of Azo smectic phases. The evolution of chirality from terminal alkyl chain to Azo mesogen building blocks and further induction of supramolecular chirality in LC BCP assemblies during PICSA is achieved. Morphologies such as spheres, worms, helical fibers, lamellae, and vesicles were observed. The morphological transition had a crucial effect on the chiral expression of Azo‐BCP assemblies. The supramolecular chirality of Azo‐BCP assemblies destroyed by 365 nm UV irradiation can be recovered by heating–cooling treatment; this dynamic reversible achiral–chiral switching can be repeated at least five times.