Marangoni self-propulsion refers to motion of liquid or solid driven by a surface tension gradient, and has applications in soft robots/devices, cargo delivery, self-assembly etc. However, two problems remain to be addressed for motion control (e.g., ON–OFF) with conventional surfactants as Marangoni fuel: (1) limited motion lifetime due to saturated interfacial adsorption of surfactants; (2) in- situ motion stop is difficult once Marangoni flows are triggered. Instead of covalent surfactants, supra-amphiphiles with hydrophilic and hydrophobic parts linked noncovalently, hold promise to solve these problems owing to its dynamic and reversible surface activity responsively. Here, we propose a new concept of ‘supra-amphiphile fuel and switch’ based on the facile synthesis of disodium-4-azobenzene-amino-1,3-benzenedisulfonate (DABS) linked by a Schiff base, which has amphiphilicity for self-propulsion, hydrolyzes timely to avoid saturated adsorption, and provides pH-responsive control over ON-OFF motion. The self-propulsion lifetime is extended by 50-fold with DABS and motion control is achieved. The mechanism is revealed with coupled interface chemistry involving two competitive processes of interfacial adsorption and hydrolysis of DABS based on both experiments and simulation. The concept of ‘supra-amphiphile fuel and switch’ provides an active solution to prolong and control Marangoni self-propulsive devices for the advance of intelligent material systems.

Macroscopic self-assembly of µm-to-mm components (dimension from 100 µm to millimeters), is meaningful to realize the concept of "self-assembly at all scales" and to understand interfacial phenomena such as adhesion, self-healing, and adsorption. However, self-assembly at this length scale is different from molecular self-assembly due to limited collision chances and binding capacity between components. Long-time contact between components is requisite to realize µm-to-mm assembly. Even though the recent idea of adding a compliant coating to enhance the molecular binding capacity is effective for such self-assembly, a trade-off between coating thickness (several micrometers) and assembly efficiency exists. Here a new compliant coating of surface-initiated polymer brush to address the above paradox by both realizing fast assembly and reducing the coating thickness to ≈40 nm by two magnitudes is demonstrated. Millimeter-sized quartz cubes are used as components and grafted with oppositely charged polyelectrolyte brushes, enabling assembly in water by electrostatic attraction and disassembly in NaCl solutions. A rule of thickness-dependent assembly chance is obtained and understood by in situ force measurements and a multivalent theory. The polymer brush strategy pushes the thickness limit of requisite compliant coating to the nanoscale for fast µm-to-mm self-assembly and provides insights into rapid wet adhesion.

We demonstrate molecular-conformation-dependent macroscopic supramolecular self-assembly (MSA) driven by electrostatic interactions. Evidence from single molecular force spectroscopy reveals that polyelectrolytes modified on MSA component surfaces make MSA possible with a loop conformation, while those with a flat conformation lead to no assembly, which is attributed to distinct molecular mobility. We believe that this finding is also applicable in fundamental phenomena such as surface adsorption and adhesion regarding polymers.

Macroscopic supramolecular assembly (MSA) refers to rapid molecular recognition between macroscopic components (> 10 mm). Normally, MSA of rigid materials relies on a so-called "flexible spacing coating "beneath surface groups to provide high molecular mobility to realize multivalent binding. However, design principle of such coatings remains elusive. Here, we report an intuitive metric based on self-healing phenomena to judge whether a film can be a "flexible spacing coating "and apply this metric to extend film systems for MSA of rigid materials. The correlation between MSA and self -healing based on poly(ethylenimine)/poly(acrylic acid) films is revealed by similar dependence of assembly ratios and healing performance on film rigidity. Films capable of self-healing within 30 s can be used as flexible spacing coating for MSA. This metric is applied to three different film systems and proven effective to design coatings for MSA of rigid materials, which is applied in advanced manufacture of heterogeneous structure.

Three-dimensional (3D) scaffolds with chemical diversity are significant to direct cell adhesion onto targeted surfaces, which provides solutions to further control over cell fates and even tissue formation. However, the site-specific modification of specific biomolecules to realize selective cell adhesion has been a challenge with the current methods when building 3D scaffolds. Conventional methods of immersing as-prepared structures in solutions of biomolecules lead to nonselective adsorption; recent printing methods have to address the problem of switching multiple nozzles containing different biomolecules. The recently developed concept of macroscopic supramolecular assembly (MSA) based on the idea of "modular assembly" is promising to fabricate such 3D scaffolds with advantages of flexible design and combination of diverse modules with different surface chemistry. Herein we report an MSA method to fabricate 3D ordered structures with internal chemical diversity for site-selective cell adhesion. The 3D structure is prepared via 3D alignment of polydimethylsiloxane (PDMS) building blocks with magnetic pick-and-place operation and subsequent interfacial bindings between PDMS based on host/guest molecular recognition. The site-specific cell affinity is realized by distributing targeted building blocks that are modified with polylysine molecules of opposite chiralities: PDMS modified with films containing poly-l-lysine (PLL) show higher cell density than those with poly-d-lysine (PDL). This principle of selective cell adhesion directed simply by spatial distribution of chiral molecules has been proven effective for five different cell lines. This facile MSA strategy holds promise to build complex 3D microenvironment with on-demand chemical/biological diversities, which is meaningful to study cell/material interactions and even tissue formation.

A rapid and reversible thermochromic fluorescent supramolecular polymer hydrogel prepared by orthogonal self-assembly of host–guest and metal coordination interactions, has been used in protected quick response codes.

Two supramolecular monomers 1 and 2 were first designed and synthesized in order to introduce both metal ligand interaction and host-guest interaction into a same supramolecular system. A cross-linked supramolecular polymer was then formed by hierarchical self-assembly of these two supramolecular monomers, which were further constructed to form a supramolecular polymer gel with multiple stimuli-responsiveness and good self-healing properties. Furthermore, this supramolecular system also showed a strong fluorescence emission in the gel state due to the tetraphenylethene chromophore with aggregation induced emission property in the supramolecular system. As host molecule, monomer 1 as a host molecule was a dibenzo-24-crown-8 (DB24C8) moiety, with two tetraphenylethene fluorescent chromophores in the middle and two terpyridine units at both ends. Monomer 2, as guest molecule, was a bisammonium salt with two dibenzylammonium (DBA) units at both ends. After addition of metal ligand Zn(OTf)(2) into monomer 1 solution (V(CHCl3): V(CH3CN) = 3: 1)), monomer 1 formed a linear supramolecular polymer 3 based on the metal-ligand coordination interactions between terpyridine and Zn(OTf)(2). By continuous addition of monomer 2 as cross-linker, the cross-linked supramolecular polymer 4 was obtained based on the host-guest interactions between DB24C8 and dibenzylammonium salt. The formations of the linear and the cross-linked supramolecular polymers were characterized by H-1-NMR, DOSY and viscosity measurement. Furthermore, when the concentration of this cross-linked supramolecular polymer was increased up to 30 mmol/L, a fluorescence supramolecular polymer gel was constructed. The results showed that this fluorescent supramolecular polymer gel had a multiple stimuli-responsiveness (such as temperature, pH, K+ ions and competitive ligand) property, arising from the intrinsic characters of the metal ligand and host-guest interactions. The gel was characterized by fluorescence measurement and photograph method The results also showed that this new fluorescent supramolecular polymer gel was shown to have good self-healing property as confirmed by rheological test.

Conjugated polymers containing distinct molecular units are expected to be very interesting because of their unique properties endowed by these units and the formed conjugated polymers. Herein, four new conjugated copolymers based on fluorene and 4,4'-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) have been designed and synthesized via Sonogashira polymerization. The fluorene unit was attached to the 3,5- or 2,6-positions of BODIPY by ethynylenes or p-diacetylenebenzene. The obtained polymers show good thermal stability and broad absorption in the wavelength range from 300 to 750 nm. The effects of site-selective copolymerization and conjugation length along the polymer backbone on the optoelectronic and electrochemical properties of these copolymers were systematically studied by UV-Vis spectroscopy, photoluminescence (PL) and cyclic voltammetry. Besides, it is found that the BODIPY-based copolymers exhibit selectively sensitive responses to cyanide anions, resulting in obvious change of UV-Vis absorption spectra and significant fluorescence quenching of the polymers among various common anions.

Controlling the topologies of polymers is a hot topic in polymer chemistry because the physical and/or chemical properties of polymers are determined (at least partially) by their topologies. This study exploits the host-guest interactions between dibenzo-24-crown-8 and secondary ammonium salts and metal coordination interactions between 2,6-bis(benzimidazolyl)-pyridine units with metal ions (Zn(II) and/or Eu(III) ) as orthogonal non-covalent interactions to prepare supramolecular polymers. By changing the ratios of the metal ion additives (Zn(NO3 )2 and Eu(NO3 )3 ) linkers to join the host-guest dimeric complex, the linear supramolecular polymers (100 mol% Zn(NO3 )2 per ligand) and hyperbranched supramolecular polymers (97 mol% Zn(NO3 )2 and 3 mol% Eu(NO3 )3 per ligand) are separately and successfully constructed. This approach not only expands topological control over polymeric systems, but also paves the way for the functionalization of smart and adaptive materials.

A BODIPY-based 1 as a colorimetric fluorescence sensor was synthesized, and its metal sensing property was investigated. 1 displayed high selectivity and sensitivity towards Hg2 + and Cu2 + ions among 15 different metal cations. The addition of Hg2 + and Cu2 + ions into 1 in CH3CN resulted in a significant bathochromic shift of the UV absorption spectra from 533 nm to 560 nm and 593 nm, respectively, changing the corresponding colors from pink to purple and blue. When excited at 530 nm, the fluorescence intensity of 1 was quenched over 75% upon addition of Hg2 + ions, while 1 with Cu2 + ions exhibited significant fluorescence enhancement with a 23 nm red-shift. Based on these results, three logic gates (OR, IMPLICATION, and INHIBIT) were obtained by controlling the chemical inputs.

A group of novel polyacetylenes containing BODIPY pendants have been synthesized in satisfactory yield using a [Rh(nbd)Cl](2)-Et3N catalyst. The pendant BODIPY unit has been directly conjugated to the polyacetylene backbone either through the 8 position of the BODIPY cores in P1, or through the 3 position in P2 and P3. Their optoelectronic properties have been investigated by UV-vis, FL, CV and Z-scan techniques. Interestingly, the spectroscopy results show that little electronic interaction exists between the BODIPY chromophoric units and the polyacetylene main chain for P1. However, the electronic interaction between the side pendant and the main chain becomes notable for P2 and P3, resulting in a significant broadening and red-shift of their UV-vis absorption and fluorescence emission wavelengths in comparison with those of their respective monomers. The polymers display thermal stabilities and nonlinear optical properties that are dependent on the connectivities of the BODIPY pendants and the polyacetylene backbones. P1 exhibits relatively better thermal stability and poorer nonlinear optical properties than P1 and P2. The third-order nonlinear optical coefficient (chi((3))) of P1 is 8.5 x 10(-12) esu, which is shown to be similar to 5 times smaller than those of P2 and P3.