Self-healing Polymers

Self-healable polymeric materials are gaining much attention because of the increasing demands of polymeric materials replacing conventional inorganic (metals and ceramics) materials in various industrial fields with advantages of light-weight, comparable mechanical strength, and long-term stability. We're working on self-repairable acrylic and polyurethane polymers for coating applications by using equilibrium covalent bond and recyclable organometal/ligand coordination mechanism.

Graphene/CNT Dispersions

Graphene, a two-dimensional material composed of carbon atoms arranged in a hexagonal structure with sp² bonding, exhibits exceptional properties such as optical transparency, mechanical strength, thermal conductivity, and high electron mobility. However, its poor processability limits its widespread availability.

Recently, various methods for graphene preparation have been developed, including chemical vapor deposition, mechanical exfoliation, molecular assembly, epitaxial growth on SiC, and liquid-phase exfoliation. Among these, liquid-phase exfoliation is considered the most efficient approach for industrial applications due to its low cost and scalability.

In liquid-phase exfoliation, both covalent and non-covalent functionalizations of graphene have been extensively studied. Covalent functionalization typically involves oxidation of graphite, which introduces defects such as carboxylic acid, hydroxyl, and carbonyl groups or even structural holes. In contrast, non-covalent functionalization can yield pristine graphene, but it requires the use of dispersants or stabilizers to prevent aggregation after exfoliation.

To achieve stable graphene dispersions with minimal aggregation, various types of solvents (e.g., inorganic, organic, and fluorinated oils) and surfactants (ionic, non-ionic, short-chain, and polymeric) have been employed. Among them, block copolymer dispersants offer several advantages over short-chain surfactants, including improved colloidal stability, reduced need for additional polymeric binders, slower migration, and tunable compatibility with different systems.

Stimuli-responsive Polymers

Of all of the organisms in the animal kingdom capable of colour modulation, cephalopods (squid, cuttlefish and octopus) are able to produce the widest range of colours and patterns to help them adapt to their visually diverse marine environments as well as signal and communicate with their own species and others. The skin contains three distinct structures (chromatophores, iridophores and leucophores) that contribute to the colour and pattern adaptation. The skin is also capable of flattening or wrinkling on demand, providing surface texturing, and which provide camouflage functionality, so called adaptive coloration. In the adaptive coloration, there should be several hierarchical structures that perform unique and each functions against environmental changes, because it has all the features necessary to respond to stimuli and achieve an appropriate adaptation in colour or information communicated.

In this work, we developed random and block copolymers with having heat- and photo-responsive moieties. They can form droplets, hollow particle, polymersomes showing stimuli-responsive behavior like coloration, phase separation, volume expansion-shrinkage, and so on. We introduced spironaphthoxazine (SPO) or spiropyran derivatives are well-known photochromic compounds. SPOs undergo photo-cleavage of the spiro bond (closed ring) when subjected to UV irradiation, creating a merocyanine (open ring) form with a deep blue color, which has a broad absorption band at approximately 610 nm. The merocyanine can be converted reversibly back to the spiro form under visible light or dark conditions (or upon heating). The unidirectional aggregation and internal phase separation of SPO-containing random copolymers in water-in-oil (W/O) droplets under 365 nm UV irradiation were recently reported. The droplets containing the copolymer were then exploited to control the morphology from symmetric to asymmetric Janus particles This strategy could overcome the cross-mixing problems39,40 arising in the coflow stream composed of two immiscible fluids for a biphasic (Janus) morphology.

Recently stimuli-responsive polymeric materials have attracted great attention. Stimuli-responsive polymers can rapidly change their nature (e.g., solubility, morphology, reactivity, etc.) according to the change of external conditions like pH, temperature, magnetic or electric field, shear rate, ionic strength, and light. Such abilities can be used in the form of film, brush, membrane, micro- or macro-gel, micelles, vesicles, core-shell particles, and so on. Owing to their versatility, stimuli-responsive polymers have been a fascinating research subject as intelligent materials for drug delivery systems, smart hydrogels, chemical sensor, biomimetics and actuator systems.