Nanostructured Multiphase Condensation of Complex Coacervates in Polymerization-Induced Electrostatic Self-Assembly

We present the nanostructured multiphase condensation of complex coacervates in the dynamic evolving aqueous medium of liquid-liquid phase separation driven polymerization-induced electrostatic self-assembly (LLPS-PIESA). We show that the parent droplets evolve into nanostructured coacervate-in-coacervate multiphase condensates with diverse morphologies, such as dandelions, worms, lamellae, vesicles, and vesicle polymers, upon the kinetically dictated recruitment of anionic free chains, cationic growing chains, and nascent clusters from the dynamic evolving aqueous medium of LLPS-PIESA, under the interplay of electrostatic and arginine-like salt bridge interactions.

DNA-Polymer Nanostructures by RAFT Polymerization and Polymerization-Induced Self-Assembly

Nanostructures derived from amphiphilic DNA-polymer conjugates have emerged prominently due to their rich self-assembly behavior; however, their synthesis is traditionally challenging. Here, we report a novel platform technology towards DNA-polymer nanostructures of various shapes by leveraging polymerization-induced self-assembly (PISA) for polymerization from single-stranded DNA (ssDNA). A "grafting from" protocol for thermal RAFT polymerization from ssDNA under ambient conditions was developed and utilized for the synthesis of functional DNA-polymer conjugates and DNA-diblock conjugates derived from acrylates and acrylamides. Using this method, PISA was applied to manufacture isotropic and anisotropic DNA-polymer nanostructures by varying the chain length of the polymer block. The resulting nanostructures were further functionalized by hybridization with a dye-labelled complementary ssDNA, thus establishing PISA as a powerful route towards intrinsically functional DNA-polymer nanostructures.

ABA-type triblock copolymer micellar system with lower critical solution temperature-type sol-gel transition

A temperature sensitive sol-gel transition induced by the self-assembly of amphiphilic copolymers and its application in industry have been the objects of increasing study. We demonstrate here a two-step, reversible addition-fragmentation chain transfer (RAFT) polymerization of an ABA-type copolymer consisting of poly(N,N-dimethylacrylamide)-b-poly(diacetone acrylamide)-b-poly(N,N-dimethylacrylamide) (PDMAA-b-PDAAM-b-PDMAA). This copolymer can be easily dispersed in water, and this dispersion is critical for its lower critical solution temperature (LCST)-type sol-gel transition, which was monitored using dynamic light scattering (DLS), transmission electron microscopy (TEM), and rheology analysis, in addition to temperature-dependent ¹H nuclear magnetic resonance (¹H NMR) and Fourier transform infrared spectroscopy (FTIR). Results revealed an abnormal sphere-to-worm micellar transition of this ABA copolymer at the LCST point, which could be affected by the length of the PDAAM block (B-block), the length as well as the distribution of the PDMAA block (A-block), and the concentration of the copolymer dispersion. Thus, copolymer dispersion could be feasibly used for drug loading at a low temperature, which could then be transformed into a gel at an elevated temperature. The loading and controllable release of the model drug of paracetamol into and out of a copolymer gel was further determined. The sustained release behavior was also studied using the Rigter-Peppas model.

A versatile method for the selective core-crosslinking of hyaluronic acid nanogels via ketone-hydrazide chemistry: from chemical characterization to in vivo biodistribution

Nanogels show long in vivo blood circulation time and high tumor accumulation.

Hydrogen bonding reinforcement as a strategy to improve upper critical solution temperature of poly(N-acryloylglycinamide-co-methacrylic acid)

HB-type copolymers with suitably tunable UCST and corresponding core–shell nanogels showing UCST–LCST type behavior.

Self-healable hydrogels with cross-linking induced thermo-responsiveness and multi-triggered gel–sol–gel transition

Self-healable hydrogels with cross-linking induced thermo-responsiveness (CIT) were prepared from ketone-group containing P(DMA-stat-DAA).

Synthesis of Hydrogen-Bonded Pore-Switchable Cylindrical Vesicles via Visible-Light-Mediated RAFT Room-Temperature Aqueous Dispersion Polymerization

Analogous to cellulose, polymers whose monomer units possess both hydrogen donators and acceptors are generally insoluble in ambient water because of hydrogen bonding (HB). Herein we present stimuli-responsive long aqueous cylindrical vesicles (nanotubes) synthesized directly using HB-driven polymerization-induced self-assembly (PISA) under visible-light-mediated RAFT aqueous dispersion polymerization at 25 °C. The PISA undergoes an unprecedented film/silk-to-ribbon-to-vesicle transition and films/silks/ribbons formed at low DPs (∼25-85) of core-forming block in free-flowing aqueous solution. Pore-switchable nanotubes are synthesized by electrostatic repulsive perturbation of the HB association in anisotropic vesicular membranes via inserting minor ionized monomer units into the core-forming block. These nanotubes are synthesized at >35% solids, and tubular membranes are more sensitive than spherical counterparts in response to aqueous surroundings. This facile, robust, and general strategy paves a new avenue toward scale-up production of advanced intelligent nanomaterials.

Self-healing hydrogels containing reversible oxime crosslinks

Self-healing oxime-functional hydrogels have been developed that undergo a reversible gel-to-sol transition via oxime exchange under acidic conditions. Keto-functional copolymers were prepared by conventional radical polymerization of N,N-dimethylacrylamide (DMA) and diacetone acrylamide (DAA). The resulting water soluble copolymers (P(DMA-stat-DAA)) were chemically crosslinked with difunctional alkoxyamines to obtain hydrogels via oxime formation. Gel-to-sol transitions were induced by the addition of excess monofunctional alkoxyamines to promote competitive oxime exchange under acidic conditions at 25 °C. The hydrogel could autonomously heal after it was damaged due to the dynamic nature of the oxime crosslinks. In addition to their chemo-responsive behavior, the P(DMA-stat-DAA) copolymers exhibit cloud points which vary with the DAA content in the copolymers. This thermo-responsive behavior of the P(DMA-stat-DAA) was utilized to form physical hydrogels above their cloud point. Therefore, these materials can either form dynamic-covalent or physically-crosslinked gels, both of which demonstrate reversible gelation behavior.

The direct synthesis of interface-decorated reactive block copolymer nanoparticles via polymerisation-induced self-assembly

Enzyme inspired interface-decorated media-accessible reactive nanoparticles are now available via PISA by aqueous dispersion RAFT of commodity-DAAM with minimal NH₃⁺-monomer.

Oximes as reversible links in polymer chemistry: dynamic macromolecular stars

We demonstrate the formation of oxime-functional macromolecular stars that are able to dissociate and reconstruct themselves upon application of a stimulus.