pH‐Responsive Supramolecular Polymerization in Aqueous Media Driven by Electrostatic Attraction‐Enhanced Crown Ether‐Based Molecular Recognition

All the previously reported supramolecular polymers based on crown ether‐based molecular recognition have been prepared in anhydrous organic solvents. This is mainly due to the weakness of crown ether‐based molecular recognition in the presence of water. Here we report a linear supramolecular polymer constructed from a heteroditopic monomer in an aqueous medium driven by crown ether‐based molecular recognition through the introduction of electrostatic attraction. In addition, the reversible transition between the linear supramolecular polymer and oligomers is achieved by adding acid and base. This study realizes the breakthrough of the solvent for supramolecular polymerization driven by crown ether‐based molecular recognition from anhydrous organic solvents to aqueous media. It is helpful for achieving supramolecular polymerization driven by crown ether‐based molecular recognition in a completely aqueous medium.     

Specific recognition of a nucleobase-functionalized poly(3,4-ethylenedioxithiophene) (PEDOT) in aqueous media

In this Letter we report the synthesis, characterization, and electrochemical investigation of a 3,4-ethylenedioxythiophene (EDOT) derivative covalently linked to the nucleobase uracil. The successful electrochemical polymerization of this derivative has provided modified electrodes with a novel functional poly(3,4-ethylenedioxythiophene) derivative. Recognition experiments in aqueous media have shown the specific recognition of the complementary base adenine. The electrochemical detection of the selective binding of nucleobases to this PEDOT derivative in aqueous media can be of particular interest for electrochemical sensor applications in physiological media.     

A Supramolecularly Activated Radical Cation for Accelerated Catalytic Oxidation

Tuning the activity of radicals is crucial for radical reactions and radical‐based materials. Herein, we report a supramolecular strategy to accelerate the Fenton reaction through the construction of supramolecularly activated radical cations. As a proof of the concept, cucurbit[7]uril (CB[7]) was introduced, through host–guest interactions, onto each side of a derivative of 1,4‐diketopyrrolo[3,4‐c]pyrrole (DPP), a model dye for Fenton oxidation. The DPP radical cation, the key intermediate in the oxidation process, was activated by the electrostatically negative carbonyl groups of CB[7]. The activation induced a drastic decrease in the apparent activation energy and greatly increased the reaction rate. This facile supramolecular strategy is a promising method for promoting radical reactions. It may also open up a new route for the catalytic oxidation of organic pollutants for water purification and widen the realm of supramolecular catalysis.     

An AIE singlet oxygen generation system based on supramolecular strategy

The design of supramolecular system s with efficient singlet oxygen generation has attracted considerable interests.Herein,an AIE-based singlet oxygen generation system with chemiluminescence properties is reported in aqueous media based on supramolecular host-guest assembly between a water-soluble pillar[5]arene(WP5) and an AIE photosensitizer(TPEDM).The formed supramolecular nanoparticles exhibit significant singlet oxygen generation ability as well as enhanced fluorescence.In addition,by introducing catalase,this H_2 O_2-responsive supramolecular system shows increased ~1 O_2 generation efficiency compared with the blank nanoparticles.An efficient chemiluminescence system can also be achieved by entrapping an energy donor adamantane derivative(AMPPD).Moreover,the present system can function as nanoreactors to perform the photooxidation of dopamine to form polydopamine with visible light irradiation.This wo rk provides a new strategy for the construction of ~1 O_2 generation system based on supramolecular nanomaterials,which has potential applications in the fields such as chemiluminescence imaging and controlled photocatalysis.     

Formation mechanism of supramolecular hydrogels in the presence of L-phenylalanine derivative as a hydrogelator

A novel chiral hydrogelator, L-phenylalanine derivative can self-assemble in aqueous media at different pH values to form supramolecular hydrogels. The images of the FE-SEM indicate that different aggregates of TC(18)PheBu in morphology were formed, which further lead to the formation of spherical crystallites as observed by polarized optical microscope (POM). The FT-IR spectra of the supramolecular hydrogels reveal that intermolecular hydrogen-bonding and hydrophobic interactions are the driving forces for the self-assembly of TC(18)PheBu. Fluorescence spectra of TC(18)PheBu in aqueous solutions in the presence of pyrene as a probe further confirm the importance of hydrophobic interactions for the self-assembly. The circular dichroism (CD) spectra of TC(18)PheBu in supramolecular hydrogels in the presence of KF indicate that the hydrogen-bonding interaction can be disrupted by fluoride ions, which further confirm the importance of hydrogen bonding for the self-assembly of TC(18)PheBu.     

Dimensionally confined nanosheets self-assembled through self-shielding multiple hydrogen bonding interactions in aqueous media

Herein, we adopt a simple supramolecular strategy to effectively control the tautomerism of ureidopyrimidinone (UPy) moiety and ultimately realize the complete arrangement of enol configuration. The obtained UPy derivatives containing self-complementary quadruple hydrogen bonding interactions can spontaneously self-assemble towards the formation of well-controlled, self-organized supramolecular nanostructure morphologies in both chloroform and water. The resulting aggregates had been fully characterized by various spectroscopy (absorption, emission) and microscopy (TEM, SEM and AFM) studies. It is anticipated that this study can provide an exact and excellent monomeric unit for controllable and precise supramolecular polymerization. The results achieved here also demonstrate the utility and feasibility of multiple hydrogen bonds to direct the self-assembly of small-molecule building blocks in aqueous media, which provides a strategy for the construction of well-defined and stable supramolecular architectures with chemical functionalities and physical properties as advanced materials for biological applications.     

Elucidating the structure of poly(dopamine)

Herein we propose a new structure for poly(dopamine), a synthetic eumelanin that has found broad utility as an antifouling agent. Commercially available 3-hydroxytyramine hydrochloride (dopamine HCl) was polymerized under aerobic, aqueous conditions using tris(hydroxymethyl)aminomethane (TRIS) as a basic polymerization initiator, affording a darkly colored powder product upon isolation. The polymer was analyzed using a variety of solid state spectroscopic and crystallographic techniques. Collectively, the data showed that in contrast to previously proposed models, poly(dopamine) is not a covalent polymer but instead a supramolecular aggregate of monomers (consisting primarily of 5,6-dihydroxyindoline and its dione derivative) that are held together through a combination of charge transfer, π-stacking, and hydrogen bonding interactions.     

Supramolecularly Catalyzed Polymerization: From Consecutive Dimerization to Polymerization

Herein, we propose a new method for promoting covalent polymerization by supramolecular catalysts. To this end, we employed cucurbit[8]uril (CB[8]) as a supramolecular catalyst, and successfully prepared polyelectrolytes in an aqueous solution by taking advantage of the CB[8]‐enhanced photodimerization of Brooker merocyanine moieties. Interestingly, 10 mol % CB[8] is enough to effectively catalyze this polymerization, because CB[8] can be spontaneously replaced by terminal groups from photodimerized products. In addition, the molecular weights of the obtained polyelectrolytes can be varied by the irradiation time or the monomer. By combining supramolecular catalysis and polymer chemistry, this line of research may enrich the methodology of polymerization and open up new horizons for supramolecular polymer chemistry.     

Solvent-controlled E/Z isomerization vs. [2 + 2] photocycloaddition mediated by supramolecular polymerization

Control over the photochemical outcome of photochromic molecules in solution represents a major challenge, as photoexcitation often leads to multiple competing photochemical and/or supramolecular pathways resulting in complex product mixtures. Herein, we demonstrate precise and efficient control over the photochemical behaviour of cyanostilbenes in solution using a straightforward solvent-controlled approach based on supramolecular polymerization. To this end, we designed a π-extended cyanostilbene bolaamphiphile that exhibits tuneable solvent-dependent photochemical behaviour. Photoirradiation of the system in a monomeric state (in organic solvents) exclusively leads to a highly reversible and efficient E/Z photoisomerization, whereas a nearly quantitative [2 + 2] photocycloaddition into a single cyclobutane (anti head-to-tail) occurs in aqueous solutions. These results can be rationalized by a highly regular and preorganized antiparallel J-type arrangement of the cyanostilbene units that is driven by aqueous supramolecular polymerization. The presented concept demonstrates a novel approach towards solvent-selective and environmentally friendly photochemical transformations, which is expected to broaden the scope of supramolecular polymerization.

Controlled supramolecular polymerization is used to switch the photoresponsive behaviour of cyanostilbenes from a reversible E/Z photoisomerization in organic solvents to a highly efficient and selective [2 + 2] photocycloaddition in aqueous media.     

界面超分子聚合

超分子聚合物诞生于高分子化学与超分子化学的交叉融合,一般是指单体间通过非共价键作用连接形成的聚合物,并在溶液或体相中表现出类似聚合物的性质。目前超分子聚合物一般通过均相溶液聚合制备得到,但溶液中的超分子聚合是一个自发的组装过程,具有浓度依赖性,组装过程不易可控。为解决此问题,研究人员可以将超分子聚合从均相溶液转移到界面,在界面上可控地制备超分子聚合物。通过界面聚合制备超分子聚合物具有一些独特的优势,如可以制备得到分子量更高的超分子聚合物,易于制备一些缺陷少、面积大、有序的二维超分子聚合物等。本文基于在液-液、气-液和固-液三种界面上制备超分子聚合物的一些代表性工作,介绍了界面超分子聚合方法和应用,并展望其未来发展。     

Supramolecular chemistry in water

Supramolecular chemistry in water is a constantly growing research area because noncovalent interactions in aqueous media are important for obtaining a better understanding and control of the major processes in nature. This Review offers an overview of recent advances in the area of water-soluble synthetic receptors as well as self-assembly and molecular recognition in water, through consideration of the functionalities that are used to increase the water solubility, as well as the supramolecular interactions and approaches used for effective recognition of a guest and self-assembly in water. The special features and applications of supramolecular entities in aqueous media are also described.     

Phototriggered Supramolecular Polymerization

Photo‐initiated supramolecular polymerization of a naphthalenediimide (NDI‐1) derivative containing an ortho‐nitrobenzyl (ONB)‐protected amide group is demonstrated. In a hydrocarbon solvent (methylcyclohexane), it remains as monomer. Upon photo‐irradiation, deprotection of the ONB group produces NDI‐2 with a free amide group, which drives supramolecular polymerization by self‐complementary H‐bonding between the amide groups, leading to gelation. The polymerization rate can be controlled by tuning the energy of the light source. During photopolymerization, a gradual increase in hydrodynamic radius and viscosity is noticed. More interestingly, the morphology of the supramolecular polymer of NDI‐2, produced by photo‐irradiation, was a spherulite, which is in sharp contrast with the fibrillar morphology of NDI‐2 polymer, when assembled spontaneously without a phototrigger. This is ascribed to the ability of the ONB‐caged pro‐monomer (NDI‐1) to act as a chain‐stopper by forming a H‐bonded complex with the active monomer during the growth of the supramolecular polymer under photo‐irradiation.     

Supramolecular polymerization from polypeptide-grafted comb polymers

The helical and tubular structures self-assembled from proteins have inspired scientists to design synthetic building blocks that can be "polymerized" into supramolecular polymers through coordinated noncovalent interactions. However, cooperative supramolecular polymerization from large, synthetic macromolecules remains a challenge because of the difficulty of controlling the structure and interactions of macromolecular monomers. Herein we report the synthesis of polypeptide-grafted comb polymers and the use of their tunable secondary interactions in solution to achieve controlled supramolecular polymerization. The resulting tubular supramolecular structures, with external diameters of hundreds of nanometers and lengths of tens of micrometers, are stable and resemble to some extent biological superstructures assembled from proteins. This study shows that highly specific intermolecular interactions between macromolecular monomers can enable the cooperative growth of supramolecular polymers. The general applicability of this strategy was demonstrated by carrying out supramolecular polymerization from gold nanoparticles grafted with the same polypeptides on the surface.     

Chemical evolution of biomolecule building blocks. Can thermodynamics explain the accumulation of glycine in the prebiotic ocean?

It has always been a question of considerable scientific interest why amino acids (and other biomolecule building blocks) formed and accumulated in the prebiotic ocean. In this study, we suggest an answer to this question for the simplest amino acid, glycine. We have shown for the first time that classical equilibrium thermodynamics can explain the most likely selection of glycine (and the derivative of its dipeptide) in aqueous media, although glycine is not the lowest free energy structure among all (404) possible constitutional isomers. Species preceding glycine in the free energy order are either supramolecular complexes of small molecules or such molecules likely to dissociate and thus get back to the gas phase. Then, 2-hydroxyacetamide condensates yielding a thermodynamically favored derivative of glycine dipeptide providing an alternative way for peptide formation. It is remarkable that a simple equilibrium thermodynamic model can explain the accumulation of glycine and provide a reason for the importance of water in the formation process.     

Influence of Ester versus Amide Linkers on the Supramolecular Polymerization Mechanisms of Planar BODIPY Dyes

We report the H‐type supramolecular polymerization of two new hydrophobic BODIPY derivatives equipped with ester and amide linkages. Whereas the ester‐containing BODIPY derivative undergoes an isodesmic supramolecular polymerization in which the monomers are parallel‐oriented, the replacement of the ester by amide groups leads to a highly cooperative self‐assembly process into H‐type aggregates with a rotational displacement of the dye molecules within the stack. The dye organization imposed by simultaneous π–π and hydrogen bonding interactions is the driving force for the cooperative supramolecular polymerization, whereas the absence of additional hydrogen bonds for the ester‐containing moiety does not suffice to induce cooperative phenomena.     

水介质中2,6-二甲基苯酚的氧化偶合聚合

聚2,6-二甲基苯醚(PPO)是重要的工程塑料,一般采用在有机溶剂中使2,6-二甲基苯酚(DMP)氧化聚合的方法合成,这就需要溶剂回收装置和防爆反应器,且污染环境.从绿色化学观点出发,以水作为反应介质,不仅对环境友好,而且PPO不溶于水,容易分离.近年来,一些学者研究了在油/水两相或全水介质中使DMP氧化聚合合成PPO的新方法.本文主要综述了该方法的研究进展,包括DMP氧化聚合的机理,油/水两相或水介质中对聚合速率、氧化偶合选择性及PPO分子量等的影响因素.     

Studies in some new initiator systems for vinyl polymerization. III. Amine–halogen systems as redox initiators

Amine–halogen redox systems are very efficient initiators of polymerization of a number of vinyl monomers in benzene media and are rather inefficient initiators in aqueous media. A large number of aliphatic amines and a few aromatic amines have been used. Among the halogens, chlorine and bromine are very effective. Iodine initiates with a few amines only. Endgroups incorporated are halogen and amine totalling an average of nearly one per chain in the case of polymerization in benzene media and 0.5–0.7 per chain in polymerization in aqueous media. In the light of endgroup results, a mechanism of initiation through halogen and amine radicals has been suggested.     

Diketopyrrolopyrrole-based functional supramolecular polymers: next-generation materials for optoelectronic applications

The very concept of dye and pigment chemistry that was long known to the industrial world underwent a radical revision after the discovery and commercialization of dyes such as mauveine, indigo, and so on. Apart from their conventional role as coloring agents, organic dyes, and pigments have been identified as indispensable sources for high-end technological applications including optical and electronic devices. Simultaneous with the advancement in the supramolecular chemistry of π-conjugated systems and the divergent evolution of organic semiconductor materials, several dyes, and pigments have emerged as potential candidates for contemporary optoelectronic devices. Of all the major pigments, diketopyrrolopyrrole (DPP) better known as the ‘Ferrari Pigment’ and its derivatives have emerged as a major class of organic functional dyes that find varied applications in fields such as industrial pigments, organic solar cells, organic field–effect transistors, and in bioimaging. Since its discovery in 1974 by Farnum and Mehta, DPP-derived dyes gained rapid attention because of its attractive color, synthetic feasibility, ease of functionalization, and tunable optical and electronic properties. The advancement in supramolecular polymerization of DPP-based small molecules and oligomers with directed morphological and electronic features have led to the development of high performing optoelectronic devices. In this review, we highlight the recent developments in the optoelectronic applications of DPP derivatives specifically engineered to form supramolecular polymers.     

Unveiling Polymerization Mechanism in pH-regulated Supramolecular Fibers in Aqueous Media

An amine functionalized C₃-symmetric benzotrithiophene (BTT) monomer has been designed and synthetized in order to form pH responsive one-dimensional supramolecular polymers in aqueous media. While most of the reported studies looked at the effect of pH on the size of the aggregates, herein, a detailed mechanistic study is reported, carried out upon modifying the pH to trigger the formation of positively charged ammonium groups. A dramatic and reversible change in the polymerization mechanism and size of the supramolecular fibers is observed and ascribed to the combination of Coulombic repulsive forces and higher monomer solubility. Furthermore, the induced frustrated growth of the fibers is further employed to finely control the one-dimensional supramolecular polymerisation and copolymerization processes.     

Supramolecular Polymerization Controlled through Kinetic Trapping

A method of controllable supramolecular polymerization through kinetic trapping is developed. To this end, two bifunctional monomers with cucurbit[7]uril (CB[7]) and adamantane end groups were synthesized. The CB[7]‐containing monomer was presaturated with a pH‐responsive competitive guest for kinetic control. Then, the kinetics of supramolecular polymerization of the two monomers was easily controlled through the modulation of pH. As a result, supramolecular polymerization was kinetically trapped at certain stages, and supramolecular polymers with different molecular weights were obtained. It is anticipated that this research will enrich the methods of controllable supramolecular polymerization.