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Single crystalline nanoneedles of polyaniline (PANI) and polypyrrole (PPY) were synthesized using an interfacial polymerization for the first time. The interfacial crystallization of conductive polymers at the liquid/liquid interface allowed PANI and PPY polymers to form single crystalline nanocrystals in a rice-like shape in the dimensions of 63 nm x 12 nm for PANI and 70 nm x 20 nm for PPY. Those crystalline nanoneedles displayed a fast conductance switching in the time scale of milliseconds. An important growth condition necessary to yield highly crystalline conductive polymers was the extended crystallization time at the liquid/liquid interfaces to increase the degree of crystallization. As compared to other interfacial polymerization methods, lower concentrations of monomer and oxidant solutions were employed to further extend the crystallization time. While other interfacial growth of conducting polymers yielded noncrystalline polymer fibers, our interfacial method produced single crystalline nanocrystals of conductive polymers. We recently reported the liquid/liquid interfacial synthesis of conducting PEDOT nanocrystals; however, this liquid/liquid interfacial method needs to be extended to other conductive polymer nanocrystal syntheses in order to demonstrate that our technique could be applied as the general fabrication procedure for the single crystalline conducting polymer growth. In this report, we showed that the liquid/liquid interfacial crystallization could yield PANI nanocrystals and PPY nanocrystals, other important conductive polymers, in addition to PEDOT nanocrystals. The resulting crystalline polymers have a fast conductance switching time between the insulating and conducting states on the order of milliseconds. This technique will be useful to synthesize conducting polymers via oxidative coupling processes in a single crystal state, which is extremely difficult to achieve by other synthetic methods.

Extracellular matrix (ECM) protein adsorption and organization serves as a critical first step in the development and organization of tissues. Advances in tissue engineering, therefore, will depend on the ability to control the rate and pattern of ECM formation. Fibronectin is a prominent component of the ECM, which undergoes fibrillogenesis in the presence of cells. Using sulfonated polysyrene surfaces, we showed that fibronectin undergoes a transition from monolayer to multilayer adsorption at calculated surface charge densities above 0.03 Coulombs (C)/m(2). At charge densities above approximately 0.08 C/m(2), distinct fibronectin fibrillar networks are observed to form with a fibril morphology similar to those observed to form in situ on cell surfaces. This self-organization process is time dependent, with the fibrils achieving dimensions of 30-40 microm in length and 1 microm in height after 72 h of incubation. We suggest that the polarization of charge domains on the polyampholytic fibronectin molecules near high charge density surfaces is sufficient to initiate the multilayer adsorption and the organization of these fibrillar structures. These results suggest that the nonlinear dependence of adsorption on surface charge density may play an important role in the self-organization of many matrix components.

Tetragonal ferroelectric BaTiO3 nanoparticles are hydrolyzed inside peptide‐ring templates at room temperature and pressure (see figure). The sizes of the monodisperse BaTiO3 nanoparticles are controlled between 6 and 12 nm by varying the cavity size of the nanorings as a function of pH. The nanoparticles possess switching behavior under the influence of external electric fields.

Science at the nanoscale has been one of the most exciting areas of recent investigation, with activities that are of both fundamental and technological significance. New physical phenomena and revolutionary nanoeletronic devices based on novel nanomaterials are anticipated. Organic conjugated systems have been successfully applied to electronics because of their versatile electronic properties and their adaptability to a broad range of processing methods. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] However, the development of polymer electronics at the nanoscale is in its infancy.Here we report the first synthesis of polythiophene nanoneedles that exhibit fast, field-induced conductance switching in a single nanocrystalline element.Most of the bulk conducting-polymer systems studied contain regions that are inhomogeneous. The investigation of processes in a nanodomain of a single crystal is critical in ascertaining the inherent electronic properties of polymer nanoelements. Single nanocrystals of conducting polymers have not been reported, although needle-shaped bulk crystals of the quarterphenyl cation radical salt have previously been studied, [15,16] and highly ordered polymer structures have been prepared by methods including electrochemical epitaxial polymerization, [10] solution spin-coating on functionalized surfaces, [17] and solid-state polymerization of monomer crystals. [18] To date, polythiophenes, together with polyanilines and polypyrroles, represent the most important classes of conducting polymers. [19] Applying an interfacial polymerizationcrystallization process, we have prepared single crystals of poly(3,4-ethylenedioxythiophene) (PEDOT) as nanoneedles.The aqueous/organic interface used consists of 3,4-ethylenedioxythiophene (EDOT) in an organic solvent and an oxidant, ferric chloride, in deionized (DI) water. The use of ferric chloride as an oxidant in the precipitation polymerization of thiophenes has been documented. [20][21][22] In these reactions, polymer chains are generally formed first, followed by the precipitation of crystals. Our system uses, for the first time, ferric chloride in the interfacial polymerization of thiophenes.As the crystal growth is simultaneous with polymerization, more ordered crystal packing can be expected. In a typical synthesis, EDOT dissolved in dichloromethane (DCM, 5 mL, 1 mg mL -1 ) served as the lower organic layer, and FeCl 3 dissolved in DI water (5 mL, 1 mg mL -1 ) formed the upper layer. After 2 days, the aqueous layer was carefully collected for purification. To prevent the hydrolysis of FeCl 3 , 5 drops of concentrated HCl (37 %) were added to the collected suspension. The nanoneedle suspension was then centrifuged, and the precipitate was re-suspended. This process was repeated twice and was followed by a final dialysis step in ultrapure water (resistivity 18.2 MX cm, total organic carbon level 10 ppb) for 10 h. The oxidative coupling polymerization of EDOT at the aqueous/organic interface was facilitated by FeCl 3 [23] and is an example of a s...

Amphiphilic acrylic copolymers with hexamethyleneamine and poly­(ethylene glycol) side chains can show >100-fold selectivity toward Escherichia coli over red blood cells. Homopolymer with cationic pendant amine groups is highly hemolytic and antibacterial. Incorporation of approximately 33 mol % of poly­(ethylene glycol) methyl ether methacrylate (PEGMA) led to 1300 times reduction in hemolytic activity, while maintaining high levels of antibacterial activity. The hemolytic activity of these PEGylated copolymers depends on the overall content and spatial distribution of the PEGMA units. Higher activity against Escherichia coli than Staphylococcus aureus was observed for this polymer system, likely due to hydrogen bonding ability of the PEG side chains with polysaccharide cell wall of the bacteria. Field emission scanning electron microscopy analysis confirmed the bacterial membrane rupture activity exerted by these copolymers, whereas time-kill studies revealed significantly different bactericidal kinetics toward the Gram-negative Escherichia coli and the Gram-positive Staphylococcus aureus.

Acrylic copolymers with appropriate compositions of counits having cationic charge with 2-carbon and 6-carbon spacer arms can show superior antibacterial activities with concomitant very low hemolytic effect. These amphiphilic copolymers represent one of the most promising synthetic polymer antibacterial systems reported.

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