So Young An

Dual Sulfide-Disulfide Crosslinked Networks with Rapid and Room Temperature Self-Healability.

Polymer-based crosslinked networks with intrinsic self-repairing ability have emerged due to their built-in ability to repair physical damages. Here, novel dual sulfide-disulfide crosslinked networks (s-ssPxNs) are reported exhibiting rapid and room temperature self-healability within seconds to minutes, with no extra healing agents and no change under any environmental conditions. The method to synthesize these self-healable networks utilizes a combination of well-known crosslinking chemistry: photoinduced thiol-ene click-type radical addition, generating lightly sulfide-crosslinked polysulfide-based networks with excess thiols, and their oxidation, creating dynamic disulfide crosslinkages to yield the dual s-ssPxNs. The resulting s-ssPxN networks show rapid self-healing within 30 s to 30 min at room temperature, as well as self-healing elasticity with reversible viscoelastic properties. These results, combined with tunable self-healing kinetics, demonstrate the versatility of the method as a new means to synthesize smart multifunctional polymeric materials.

Dual location disulfide degradable interlayer-crosslinked micelles with extended sheddable coronas exhibiting enhanced colloidal stability and rapid release

Amphiphilic block copolymer-based micellar nanocarriers hold great promise as a drug delivery platform; however, the colloidal stability of nanoassemblies upon intravenous injection remains a significant challenge. Further, enhanced/controlled release of encapsulated drugs by cleavage of dynamic covalent linkages in response to external stimuli is highly desired. Herein, we report new polylactide (PLA)-based triblock copolymers (PssDL) possessing thiol-responsive dynamic disulfide linkages at dual locations using a combination of ring opening polymerization and controlled radical polymerization techniques. These well-defined PssDL copolymers are designed to self-assemble to form aqueous micellar aggregates having multiple pendant disulfide linkages in a hydrophobic interlayer as well as single disulfides at interfaces of the interlayer and PLA core, surrounded by hydrophilic coronas. Through thiol-responsive cleavage of these dually located disulfide linkages, novel interlayer-crosslinked micelles (ICMs) with a crosslinkable and sheddable extended corona can be formed, thus combining the enhanced colloidal stability of crosslinked nanocarriers with rapid destabilization or disintegration of micelles typically found with sheddable systems. This dual location degradation process results in enhanced colloidal stability, along with controlled release of encapsulated anticancer drugs to promote the inhibition of cell proliferation after internalization into cancer cells.

Dual Redox and Thermoresponsive Double Hydrophilic Block Copolymers with Tunable Thermoresponsive Properties and Self-Assembly Behavior

The synthesis, tunable thermoresponsive properties, and self-assembly of dual redox and thermoresponsive double hydrophilic block copolymers having pendant disulfide linkages (DHBCss) are reported. Well-defined DHBCss composed of a hydrophilic poly(ethylene oxide) block and a dual thermo- and reduction-responsive random copolymer block containing pendant disulfide linkages are synthesized by atom transfer radical polymerization. Their lower critical solution temperature (LCST) transitions are adjusted through modulating pendant hydrophobic-hydrophilic balance with disulfide-thiol-sulfide chemistry. Further, these DHBCss derivatives are converted to disulfide-crosslinked nanogels at temperatures above LCST through temperature-driven self-assembly and in situ disulfide crosslinking. They exhibit enhanced colloidal stability and further reduction-responsive degradability, thus demonstrating versatility of dual thermo- and reduction-responsive smart materials.

Rosin-based block copolymer intracellular delivery nanocarriers with reduction-responsive sheddable coronas for cancer therapy

Block copolymer-based self-assembled micellar nanocarriers exhibiting glutathione-responsive enhanced release of encapsulated drugs have been considered as promising candidates for tumor-targeting drug delivery applications. Herein, we report a novel rosin-based block copolymer designed to self-assemble toward micellar nanocarriers with positioned disulfides at interfaces of hydrophobic rosin cores and hydrophilic poly(ethylene glycol) (PEG) coronas. The rosin-based micellar nanocarriers exhibit excellent colloidal stability under pseudo-physiological conditions and in the presence of proteins. Further, they enable the delivery of anticancer drugs to cancerous tissues for the enhanced release of encapsulated drugs through the destabilization of micelles with loosened structures of cores as a consequence of reduction-responsive shedding PEG coronas from rosin-based cores in response to glutathione. The results obtained from in vitro cell culture experiments including cell viability and cellular uptake suggest that reduction-responsive detachment of coronas promotes the inhibition of cell proliferation after internalization into cancer cells. These results suggest that the current design of rosin-based block copolymers and their assembled nanostructures with reduction-responsive sheddable coronas offer great versatility as intracellular drug-delivery nanocarriers for cancer therapy.

Multiblock Copolymer‐Based Dual Dynamic Disulfide and Supramolecular Crosslinked Self‐Healing Networks

A new multiblock copolymer self-healing strategy is reported that centers on the synthesis of block copolymers designed with different self-healing motifs incorporated into individual blocks. As a proof of concept, a novel pentablock copolymer (ABCBA) consisting of a poly(ethylene glycol) middle block and self-healable symmetric blocks of a polymethacrylate with pendant disulfide linkages and carboxylic acids is synthesized by a combination of consecutive controlled radical polymerization with hydrolytic cleavage. Disulfide exchange reactions of pendant disulfide linkages and metal-ligand interactions of pendant carboxylic acids with ferric ions allow for the formation of dual crosslinked networks with dynamic disulfide and supramolecular crosslinkages. The resultant networks possessing self-healing viscoelasticity enable self-healing on macroscale damages through supramolecular metal-ligand interactions and disulfide exchange reactions at room or moderate temperatures. These preliminary results suggest that the strategy can offer the versatility in the development of multifunctional self-healable materials in dual or multiple self-healable mechanisms.

Reduction‐Responsive Sheddable Carbon Nanotubes Dispersed in Aqueous Solution

A new approach to stabilize carbon nanotubes (CNTs) in aqueous solution with a reduction-responsive water-soluble polymer is reported. The novel polymer synthesized by a controlled radical polymerization is functionalized with pendant pyrene groups capable of adhering to the surface of CNTs through π-π noncovalent interactions, and labeled with disulfide linkages to exhibit reduction-responsive cleavage. Upon the cleavage of junction disulfide linkages in a reducing environment, water-soluble polymers are shed, retaining clean CNT surfaces for electrochemical catalytic reactions.