Association Strength of Metal Ions with Poly(4-vinylpyridine) in Inorganic/Poly(4-vinylpyridine)-b-poly(ε-caprolactone) Hybrids

Electrochemical and Electronic Properties of Transparent Coating from Highly Solution Processable Graphene Using Block Copolymer Supramolecular Assembly: Application toward Metal Ion Sensing and Resistive Switching Memory

Here, we have discussed the preparation of a highly solution processable graphene from a novel supramolecular assembly consisting of block copolymer polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) and pyrenebutyric acid (PBA)-modified reduced graphene oxide (RGO). The PBA molecules anchored on the graphene surface form supramolecules with PS-b-P4VP through H-bonding between the carboxylic acid group of 1-pyrenebutyric acid and the pyridine ring of P4VP. The formation of a supramolecular assembly results in a highly stable solution of reduced graphene oxide in common organic solvents, such as 1,4-dioxane and chloroform. Highly transparent and mechanically stable thin films can be deposited from these supramolecular assemblies on a relatively smooth surface of different substrates such as silicon wafer, glass, indium tin oxide, and flexible polymer substrates like poly(ethylene terephthalate). The graphene surface modifier (PBA) can be selectively removed from the thin film of the hybrid material by simple dissolution, resulting in a porous structure. Hybrid thin films of around 50 nm thickness exhibit interesting electrochemical properties with an areal capacitance value of 17.73 μF/cm2 at a current density of 2.66 μA/cm2 and good electrochemical stability. The pendent P4VP chains present in the composite thin film were further exploited for electrochemical detection of metal ions. The electrical measurement of the thin film sandwich structure of the composite shows a bipolar resistive switching memory with hysteresis-like current-voltage characteristics and electrical bistability. The OFF state shows ohmic conduction at a lower voltage and trap-free space-charge-limited current (SCLC) conduction at high voltage, whereas the ON state conduction is controlled by ohmic at low bias voltage, trap-free SCLC at moderate voltage, and tarp-assisted SCLC at high voltage.

Thermally Stable Metallic Nanoparticles Prepared via Core-Cross-linked Block Copolymer Micellar Nanoreactors

Thermally stable metallic nanoparticles (MNPs) are highly desirable for the melt processing of polymer nanocomposites. However, due to the high surface energy penalty and decreased melting temperature, MNPs are easy to agglomerate and lose their unique properties if there is no protection or confinement layer. In this work, we report a facile and efficient way to synthesize thermally stable MNPs using core-cross-linked polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) reverse micelles as nanoreactors. From infrared results, gold, silver, and palladium ions exhibited distinctive coordination to the 4VP groups with varying chelation strengths. Compared to the non-cross-linked micelles, 1,4-dibromobutane (DBB)-cross-linking of the P4VP cores provided several advantages. First, it prevented severe swelling of the P4VP cores caused by the reducing agents and subsequent merger of swollen micelles. Second, the quaternized P4VP with hydrophilicity enhanced the uptake speed of precursor metal ions into the cores. Third, the cross-linked cores greatly stabilized the MNPs against the high-temperature environment (e.g., 110 °C for 40 h in toluene). In addition, the solubility of the reducing agents also played an important role. Anhydrous hydrazine could swell the P4VP cores and concentric core-shell particle morphology was obtained. On the contrary, triethylsilane could not swell the P4VP cores and thus eccentric core-shell particle morphology was observed. Only the concentric core-shell MNPs exhibited good thermal stability, whereas the eccentric core-shell MNPs did not. This work suggested that these thermally stable MNPs could be good candidates for the melt processing of functional polymer nanocomposites.

Hybrid single-chain nanoparticles via the metal induced crosslinking of N-donor functionalized polymer chains

A set of single-chain nanoparticles was prepared via the intramolecular crosslinking of functionalized copolymers with various metal salts.

An ABA triblock containing a central soft block of poly[2,5-di(n-hexogycarbonyl)styrene] and outer hard block of poly(4-vinylpyridine): synthesis, phase behavior and mechanical enhancement

A new ABA triblock copolymer (P4VP-PHCS-P4VP) with strong microphase separation was successfully synthesized and showed phase transformation and mechanical enhancement by blending with metal salt.

Cross-linked reverse micelles with embedded water pools: a novel catalytic system based on amphiphilic block copolymers

The shell cross-linked reverse micelles were used as a more reactive and recoverable catalytic system.

Stimuli-responsive color films of poly(4-vinylpyridine)-b-poly(ε-caprolactone) complexed with cyano-capped chromophores

Here, we develop a method to fabricate stimuli-responsive color films using block copolymer, poly(4-vinylpyridine)-b-poly(ε-caprolactone) (P4VP-PCL), as a template complexed with functionalized chromophores. The P4VP block in the P4VP-PCL can be associated with a cyano end-capped chromophore via charge transfer, which is a noncovalent interaction that can be conveniently manipulated by external stimuli, giving a specific color. The color of the film can be switched by tuning the charge transfer interaction between the chromophore and P4VP with controlled environmental conditions, such as pH, temperature, and moisture, while maintaining high transmittance for visible light due to the formation of the nanostructure of chromophore/P4VP-PCL complex. However, the association/dissociation process between chromophore and P4VP is diffusion-dominated, which may limit the kinetic response time for color change. A way to create quick and reversible color switching can be achieved by a combination of stimuli. The contrasting color change of the responsive chromophore/P4VP-PCL thin films which exhibit RGB primary colors can provide a sensor film that is flexible, fast-responsive, and convenient.

Fabrication and modification of ordered nanoporous structures from nanophase-separated block copolymer/metal salt hybrids

We report facile preparation of nanoporous thin films by rinsing out a metal salt from nanophase-separated hybrid films composed of a block copolymer and a water-soluble metal salt. Nanophase-separated hybrids were prepared by mixing polystyrene-b-poly(4-vinylpyridine) (PS-P4VP) and iron(III) chloride in a solvent of pyridine, followed by solvent-casting and thermal-annealing. Film samples with a thickness of ca. 100 nm were fabricated from the nanophase-separated hybrids by using a microtoming technique. Metal salts in the films were removed by immersion into water to fabricate nanopores. Morphological observations were conducted by using transmission electron microscopy (TEM). Ordered cylindrical nanopores were clearly observed in the thin films prepared from the water-immersed hybrids which originally present cylindrical nanodomains. These nanoporous films were modified by loading another metal salt, samarium(III) nitrate, into the nanopores on the basis of the coordination ability of P4VP tethered to the pore walls. The samples after loading treatment were evaluated by TEM observation and elemental analysis with energy dispersive X-ray spectroscopy.