Young-Jae Jin

Fluorescent Actuator Based on Microporous Conjugated Polymer with Intramolecular Stack Structure

IO N Artifi cial smart materials that respond to external stimuli, such as heat, light, chemicals, and electric fi elds, have recently attracted considerable attention for applications to actuators and sensors. [ 1 ] An wide range of conjugated polymers have been developed as functional active materials not only for soft actuation but also for optical sensing. [ 1h , 2 ] To our best knowledge, however, there are no reports on conjugated polymers showing a simultaneous optical output signal and actuation behavior. The actuation of soft materials in response to chemical stimuli is based on a reversible expansion/contraction in volume. [ 3 ]

Properties, Functions, Chemical Transformation, Nano-, and Hybrid Materials of Poly(diphenylacetylene)s toward Sensor and Actuator Applications

ABSTRACT This review examines poly(diphenylacetylene)s (PDPAs) as a special class of conjugated polymers. Various properties of PDPAs, including liquid crystallinity, fluorescence (FL) emission, and chirality are described in detail. The FL origin of PDPAs is intramolecular excimer emission that comes from the intramolecular stack structure of side phenyl rings. PDPAs show remarkable FL responses to external stimuli such as solvents, heat, surface tension, and pressure. PDPAs are easily transformed to desired forms via polymer reactions, chiral solvent annealing, and coupling with long alkyl chains. Very useful nanomaterials and hybrid materials can be prepared by chain quenching and in situ hybridization methods. PDPAs and their nano- and hybrid materials show highly advanced functions toward sensors and actuators.

Fluorescence turn-on response of a conjugated polyelectrolyte with intramolecular stack structure to biomacromolecules

An anionic conjugated polyelectrolyte based on polydiphenylacetylene showed a significant fluorescence turn-on response to positively-charged proteins through a conformational relaxation of its intramolecular stack structure.

Fluorescent Molecular Rotor-in-Paraffin Waxes for Thermometry and Biometric Identification

Novel thermoresponsive sensor systems consisting of a molecular rotor (MR) and paraffin wax (PW) were developed for various thermometric and biometric identification applications. Polydiphenylacetylenes (PDPAs) coupled with long alkyl chains were used as MRs, and PWs of hydrocarbons having 16-20 carbons were utilized as phase-change materials. The PDPAs were successfully dissolved in the molten PWs and did not act as an impurity that prevents phase transition of the PWs. These PDPA-in-PW hybrids had almost the same enthalpies and phase-transition temperatures as the corresponding pure PWs. The hybrids exhibited highly reversible fluorescence (FL) changes at the critical temperatures during phase transition of the PWs. These hybrids were impregnated into common filter paper in the molten state by absorption or were encapsulated into urea resin to enhance their mechanical integrity and cyclic stability during repeated use. The wax papers could be utilized in highly advanced applications including FL image writing/erasing, an array-type thermo-indicator, and fingerprint/palmprint identification. The present findings should facilitate the development of novel fluorescent sensor systems for biometric identification and are potentially applicable for biological and biomedical thermometry.

Fluorescence Response of Conjugated Polyelectrolyte in an Immiscible Two-Phase System via Nonelectrostatic Interaction with Surfactants.

This paper reports a unique fluorescence (FL) response and diverse applications of conjugated polyelectrolyte (CPE) through nonelectrostatic interaction with appropriate (bio)surfactants in an immiscible two-phase system. A sulfonated microporous conjugated polymer (SMCP) with a conformation-variable intramolecular stacked structure was used as the CPE film. Despite the extremely high hydrophilicity, the SMCP film responded significantly to the hydrophobic circumstances, either physicochemically or electronically, in the presence of water-in-oil (w/o)-type nonionic surfactants with appropriate hydrophile-lipophile balance (HLB) values. The polymer film became fully wet with hydrophobic solvents due to the addition of small amounts of (bio)surfactant to reveal remarkable FL emission enhancement and chromism. Microcontact and inkjet printing using the SMCP film (or SMCP-adsorbed paper) and the surfactant solution as substrate and ink, respectively, provided high-resolution FL images due to the distinctive surfactant-induced FL change (SIFC) characteristic. Moreover, the additional electrostatic interaction of SMCP film with oppositely charged surfactants further enhanced the FL emission. Our findings will help comprehensive understanding of the nonelectrostatic SIFC mechanism of CPEs and development of novel SIFC-active materials.

Influence of a hydrodynamic environment on chain rigidity, liquid crystallinity, absorptivity, and photoluminescence of hydrogen-bonding-assisted helical poly(phenylacetylene)

The chain rigidity, liquid crystallinity, absorptivity, and photoluminescence of a helical poly(phenylacetylene) derivative varied significantly depending on the solvent employed, owing to the conformational changes caused by the formation or destruction of intramolecular hydrogen bonds. The polymer chains were rigid and liquid crystalline when dissolved in such non-solvents as toluene and THF to show lower absorptivity and intramolecular excimer emission while the same polymer chains became flexible in piperidine having a high hydrogen-bonding acceptor strength to exhibit strong absorption in the visible region and the emission was significantly quenched.

Solvent-tuned dual emission of a helical poly[3,5-bis(hydroxymethyl)phenylacetylene] connected with a π-conjugated chromophore

AbstractFor THF solutions of an optically active helical poly[3,5-bis(hydroxymethyl)phenylacetylene] derivative bearing a biphenyl group, photoexcitation of the terphenyl moiety at 300 nm led to photoluminescence at 390 nm. On the other hand, the photoluminescence resulting from excitation at 280 nm caused dual emission at 310 and 390 nm, whose intensities were tuned by the polar-solvent stimuli which induced the collapse of the intramolecular stack structure of the side groups, and the change in the emission wavelength accompanied disappearance of the optical activity.For THF solutions of an optically active helical poly[3,5-bis(hydroxymethyl)phenylacetylene] derivative bearing a biphenyl group, photoexcitation of the terphenyl moiety at 300 nm led to photoluminescence at 390 nm. On the other hand, the photoluminescence resulting from excitation at 280 nm caused dual emission at 310 and 390 nm, whose intensities were tuned by the polar-solvent stimuli which induced the collapse of the intramolecular stack structure of the side groups, and the change in the emission wavelength accompanied disappearance of the optical activity.

Comparative photophysical properties of poly(diphenylacetylene)s with different central atoms in side group

ABSTRACT Polydiphenylacetylene (PDPA) derivaitves consisting of different central atoms of C, Si, and Ge in the pendent group were comparatively investigated in normal, swollen, and acid-treated states. The Ge-containing PDPA was more emissive than the other two both in solution and in solid states. All the polymers showed emission enhancement in a swollen state: The PL quantum yields increased remarkably when swollen in an appropriate non-solvent. The Si and Ge atoms were easily removed from the polymer chain under acidic condition, as a result, the PL intensity was significantly decreased and the polymers turned to be insoluble in common organic solvents. Although the tert-butyl group of C-containing PDPA remained intact during the acid exposure, similar PL attenuation occurred.

Fluorescence emission enhancement of poly(phenylacetylene) via thermal annealing

ABSTRACT Both cis- and trans-rich poly[p-(trimethylsilyl)phenylacetylene]s (PTM-SPAs) were synthesized using [Rh(norbornadiene)Cl]2-TEA (TEA: triethylamine) and WCl6-Ph4Sn as catalysts, respectively. The Rh-based cis-rich polymer exhibited a remarkable fluorescence (FL) emission enhancement after thermal annealing (heating at 200°C in N2 atmosphere for 1 min), while the pristine polymer was almost entirely non-emissive. NMR and Raman spectroscopic studies clarified the occurrence of irreversible cis-trans isomerization under thermal annealing and suggested that the FL emission increased with an increase in the trans content of PTMSPA. Computer simulations of 12-mer model compounds clarified that the FL emission is a result of intramolecular excimers formed from side-on π-stacking of phenyl groups, which is possible only along the backbone of the trans-based polymer.