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

Amphiphilic Block Copolymers for Stable Graphene Exfoliation and Dispersion (funded Graphene, a two-dimensional structured material, is a type of carbon allotrope exhibiting a hexagonal structure with sp2-bonding. This unique structure gives superior properties, such as light transparency, mechanical strength, thermal conductivity, and electron mobility amongst others. Nevertheless, graphenes are not readily available due to their poor processability. Recently, several preparation methods for graphene have been developed, such as, chemical vapor deposition, mechanical exfoliation, molecular assembly, epitaxial SiC, and liquid-phase exfoliation. Among these, liquid-phase exfoliation has been considered as the most efficient approach for industrial applications due to its low cost for mass production. Both covalent and non-covalent functionalizations of graphene have been extensively studied in liquid-phase exfoliation. The former includes oxidation of graphite leading to defects (i.e., carboxylic acid, hydroxyl, and carbonyl groups or holes) of graphite structure. The latter, on the other hand, can give pristine graphenes but it requires inclusion or dispersants or stabilizers in order to avoid a massive aggregation of graphenes after exfoliation.by MOTIE)

In order to prepare stable graphene dispersions with minimal aggregation, various types of solvents (e.g., inorganic, organic, and fluorinated oils) and surfactants (ionic, non-ionic, short and polymeric) have been exploited. A block copolymer dispersant for graphene dispersion has several advantages over short chain surfactants, such as better colloidal stability, minimal use of addition polymeric binders, slow migration, and controllable compatibility.

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.