Jiaxi Cui

Multivalent H-bonds for self-healing hydrogels

UPy is used as a reversible and dynamic crosslinker to prepare hydrogels that are injectable and undergo rapid self-healing in response to damage.

Dynamic polymer systems with self-regulated secretion for the control of surface properties and material healing

Approaches for regulated fluid secretion, which typically rely on fluid encapsulation and release from a shelled compartment, do not usually allow a fine continuous modulation of secretion, and can be difficult to adapt for monitoring or function-integration purposes. Here, we report self-regulated, self-reporting secretion systems consisting of liquid-storage compartments in a supramolecular polymer-gel matrix with a thin liquid layer on top, and demonstrate that dynamic liquid exchange between the compartments, matrix and surface layer allows repeated, responsive self-lubrication of the surface and cooperative healing of the matrix. Depletion of the surface liquid or local material damage induces secretion of the stored liquid via a dynamic feedback between polymer crosslinking, droplet shrinkage and liquid transport that can be read out through changes in the systems optical transparency. We foresee diverse applications in fluid delivery, wetting and adhesion control, and material self-repair.

Antibacterial Strategies from the Sea: Polymer-Bound Cl-Catechols for Prevention of Biofilm Formation

Inspired by the amino acid 2-chloro-4,5-dihydroxyphenylalanine (Cl-DOPA), present in the composition of the proteinaceous glue of the sandcastle worm Phragmatopoma californica, a simple strategy is presented to confer antifouling properties to polymer surfaces using (but not releasing) a bioinspired biocide. Cl-Dopamine is used to functionalize polymer materials and hydrogel films easily, to prevent biofilm formation on them.

Bioinspired Actuated Adhesive Patterns of Liquid Crystalline Elastomers

Gecko-inspired arrays of micropillars made of a liquid crystalline elastomer display thermoswitchable adhesive behavior as a consequence of elongation changes caused by reorientation of the mesogens at the nematic-isotropic (N-I) phase transition.

Light-Triggered Multifunctionality at Surfaces Mediated by Photolabile Protecting Groups

Photoremovable protecting groups (PRPGs) are applied to organic surfaces, thin polymer films, and hydrogels to achieve light-based remote control of their (bio)chemical and physical properties. These can be localized (i.e. patterned), tunable by exposure dose, and generated on-demand. Using PRPGs with independent response to different wavelengths, multifunctional materials with a number of individually addressable functional states can be generated. Light-triggered polymerization, crosslinking, and degradation processes as well as release of attached molecules can be realized. Light-responsive surfaces and materials based on PRPGs open interesting possibilities for the next generation of instructive materials for cell culture and tissue regeneration.

Polymer Brushes with Phototriggered and Phototunable Swelling and pH Response

Photolabile polymer brushes with tailored length containing a photoremovable protecting group (NVOC) are prepared via the SI-ATRP method. Upon light irradiation, the NVOC group is removed to generate controlled densities of free amine groups (PAMA) randomly distributed along the brush. The presence of the ionizable groups induces a photo-triggered swelling response. The swelling degree can be tuned by the irradiation dose. A dual (light and pH), tunable response is demonstrated.

Near-infrared electrochromic and chiroptical switching polymers: synthesis and characterization of helical poly(N-propargylamides) carrying anthraquinone imide moieties in side chains

Optically active poly(N-propargylamides) containing chiral anthraquinone imide (AQI) side groups have been synthesized. The chiroptical and electrochromic properties of the polymers are investigated. The polymers exhibit intense Cotton effects in the absorption regions of both main- and side-chains, strongly suggesting a helical conformation of the polymer backbone and a skewed packing of pendant chromophores. Additionally, the polymers show two reversible redox states (radical anion and dianion). Intense circular dichroism (CD) signals centered at 780 nm and 530 nm are assigned to the radical anion and dianion intermediates, respectively. The voltage-controlled reversible Cotton effects demonstrate the newly synthesized AQI-containing poly(N-propargylamides) as potential electrochemically driven chiroptical switching materials that operate in the near-infrared wavelength region.

Hydrogen bonding of helical vinyl polymers containing alanine moieties: a stabilized interaction of helical conformation sensitive to solvents and pH

Three alanine-bearing vinyl terphenyl helical polymers, poly{(+)-2,5-bis[4′-((N-(L)-α-methoxycarbonylethylamino)carbonyl)phenyl]styrene}, (PSt-(Ll)-M), poly{(-)-2,5-bis[4′-((N-(D)-α-methoxycarbonylethylamino)carbonyl)phenyl]styrene} (PSt-(Dd)-M) and poly{(+)-2,5-bis[4′-((N-(L)-α-tert-butoxycarbonylethylamino)carbonyl)phenyl]styrene} (PSt-(Ll)-B), were synthesized. Formation of hydrogen-bonding of those polymers in various solvents as well as the corresponding monomers was testified by using 1H NMR and FT-IR. The role of hydrogen-bonding between amino acid residues of these polymers in the stability of their helical conformation as well as steric repulsion of bulky side groups were investigated by varying the solvent nature. PSt-(Ll)-M displays a larger optical rotation and stronger Cotton effect in CHCl3 than in the polar solvent methanol, indicating that hydrogen-bonding stabilize the helical conformation. The helicities of PSt-(Ll)-M change with the solvent polarity and also are reversible during the recycled titration process in the binary solvents methanol/CHCl3. However, PSt-(Ll)-B has similar optical properties in various solvents, implying that the steric repulsion of bulky side groups other than hydrogen bonding also play an important role in stabilization of the helical conformation. The helicity of poly{(+)-2,5-di[4′-((N-(L)-α-carboxyethylamine)carbonyl)phenyl]styrene} (PSt-(Ll)-A) obtained from PSt-(Ll)-B is also sensitive to pH when KOH solution was added into its methanol solution.

New photolabile BAPTA-based Ca2+ cages with improved photorelease.

The efficient synthesis, physicochemical and photolytical properties of a photoactivable BAPTA-based Ca(2+) cage containing two photosensitive o-nitrobenzhydryl groups attached to the aromatic core are described. Ca(2+) release in living cells was evaluated. The double substitution with the chromophores caused a significant improvement of the Ca(2+) release properties of nitr-T versus singly substituted reported nitr-x derivatives without compromising Ca(2+)/Mg(2+) selectivity or pH insensitivity. Our results demonstrate a general strategy to improve light-triggered Ca(2+) release which may result in more efficient, selective, and pH-insensitive photolabile Ca(2+) chelators.

Photo-induced helix-helix transition of a polystyrene derivative

Poly(2,5-bis[4-((S)-2-methylbutyloxy)phenyl]styrene) having a helical conformation underwent helix–helix transition upon photo-irradiation. Conformational transition can significantly alter polymer properties, and so far thermal stereomutation has been studied. However, as for photo-induced mutation, only helix–helix transition (irreversible CD-active to CD-silent helix transition) of a polyacrylate has been explored. Here, we present mutation of the polystyrene derivative. Chiroptical, viscometric, and vibrational spectroscopic analyses indicated the polymer mutated from an optically active helix to another optically inactive helix with a different shape.