The photoinduced back-and-forth deformation behavior of poly(arylene ether)s containing bis-azobenzene groups in the main chain

A novel series of poly(arylene ether)s containing various bis-azobenzene groups in the main chain were synthesized and showed photoinduced back-and-forth deformation behavior.

Design of Collective Motions from Synthetic Molecular Switches, Rotors, and Motors

Precise control over molecular movement is of fundamental and practical importance in physics, biology, and chemistry. At nanoscale, the peculiar functioning principles and the synthesis of individual molecular actuators and machines has been the subject of intense investigations and debates over the past 60 years. In this review, we focus on the design of collective motions that are achieved by integrating, in space and time, several or many of these individual mechanical units together. In particular, we provide an in-depth look at the intermolecular couplings used to physically connect a number of artificial mechanically active molecular units such as photochromic molecular switches, nanomachines based on mechanical bonds, molecular rotors, and light-powered rotary motors. We highlight the various functioning principles that can lead to their collective motion at various length scales. We also emphasize how their synchronized, or desynchronized, mechanical behavior can lead to emerging functional properties and to their implementation into new active devices and materials.

Polyvalent Diazonium Polymers Provide Efficient Protection of Oncolytic Adenovirus Enadenotucirev from Neutralizing Antibodies while Maintaining Biological Activity In Vitro and In Vivo

Oncolytic viruses offer many advantages for cancer therapy when administered directly to confined solid tumors. However, the systemic delivery of these viruses is problematic because of the host immune response, undesired interactions with blood components, and inherent targeting to the liver. Efficacy of systemically administered viruses has been improved by masking viral surface proteins with polymeric materials resulting in modulation of viral pharmacokinetic profile and accumulation in tumors in vivo. Here we describe a new class of polyvalent reactive polymer based on poly( N-(2-hydroxypropyl)methacrylamide) (polyHPMA) with diazonium reactive groups and their application in the modification of the chimeric group B oncolytic virus enadenotucirev (EnAd). A series of six copolymers with different chain lengths and density of reactive groups was synthesized and used to coat EnAd. Polymer coating was found to be extremely efficient with concentrations as low as 1 mg/mL resulting in complete (>99%) ablation of neutralizing antibody binding. Coating efficiency was found to be dependent on both chain length and reactive group density. Coated viruses were found to have reduced transfection activity both in vitro and in vivo, with greater protection against neutralizing antibodies resulting in lower transgene production. However, in the presence of neutralizing antibodies, some in vivo transgene expression was maintained for coated virus compared to the uncoated control. The decrease in transgene expression was found not to be solely due to lower cellular uptake but due to reduced unpackaging of the virus within the cells and reduced replication, indicating that the polymer coating does not cause permanent inactivation of the virus. These data suggest that virus activity may be modulated by the appropriate design of coating polymers while retaining protection against neutralizing antibodies.

Resistive memory devices based on novel functionalized poly(aryl ether)s with pendant azobenzene

We designed and synthesized two novel azobenzene functionalized poly(aryl ether)s (PAEs), PAE-azo-1 and PAE-azo-2, from a new azobenzene monomer via nucleophilic aromatic substitution polycondensation. This direct polymerization approach via azobenzene monomer has the advantages of controlling the distribution and amount of the azobenzene chromophores in the polymer. Both of the polymers showed very good thermal stability and excellent solubility for future application in the electronics industry. These polymers were fabricated as films by simple spin-coating and both of them were then prepared as sandwich memory devices. PAE-azo-1 and PAE-azo-2 exhibit write-once-read-many-times-type memory behavior, which can be encoded as “0” and “1,” and possess the low operation voltage below −3.0 V. The memory mechanism was investigated through ultraviolet–visible optical absorption spectrum and the cyclic voltammetry. These obtained results indicate that the novel azobenzene functionalized PAEs are a promising candidate for low power consumption and high-performance materials for data storage.

Reversible switching of PEDOT:PSS conductivity in the dielectric–conductive range through the redistribution of light-governing polymers

One of the biggest challenges in the field of organic electronics is the creation of flexible, stretchable, and biofavorable materials. Here the simple and repeatable method for reversible writing/erasing of arbitrary conductive pattern in conductive polymer thin film is proposed. The copolymer azo-modified poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) was synthesized to achieve reversible photo-induced local electrical switching in the insulator–semimetal range. The photoisomerization of the polymer was induced by grafting nitrobenzenediazonium tosylate to the PSS main chains. While the as-deposited PEDOT:PSS thin films showed good conductivity, the modification procedure generated polymer redistribution, resulting in an island-like PEDOT distribution and the loss of conductivity. Further local illumination (430 nm) led to the azo-isomerization redistribution of the polymer chains and the creation of a conductive pattern in the insulating polymer film. The created pattern could then be erased by illumination at a second wavelength (470 nm), which was attributed to induction of reverse azo-isomerization. In this way, the reversible writing/erasing of arbitrary conductive patterns in thin polymer films was realized.

Chemical modification of PEDOT:PSS allows grafting light-switchable moieties to PSS chains and light induced reversible tuning of materials conductivity in dielectric-semimetal range.

Rare earth complexes using azobenzene-containing poly(aryl ether)s with different absorption wavelengths as macromolecular ligands: synthesis, characterization, fluorescence properties and fabrication of fluorescent holographic micropatterns

In this paper, two novel azobenzene-containing poly(aryl ether)s with different absorption wavelengths were synthesized via Ullmann coupling and Sonogashira coupling, respectively. The obtained polymers were characterized and evaluated by elemental analysis, IR, ¹H NMR, UV-vis, DSC and TGA. Rare earth complexes were prepared by using the two novel azobenzene-containing poly(aryl ether)s as macromolecular ligands. The obtained rare earth complexes were characterized by elemental analysis, IR and WAXD. The influence of the absorption wavelength of azobenzene chromophores on the fluorescent properties was investigated. The polymer whose absorption wavelength was far from the excitation wavelengths of the rare earth complexes showed a much larger fluorescence intensity. By exposing the films of the rare earth complexes to two interference laser beams, SRGs can be formed on the films and can also be detected by fluorescence microscopy measurement.

Preparation and fluorescence properties of rare earth complexes using azobenzene-containing poly(aryl ether)s with different absorption wavelengths as macromolecular ligands.

Novel photoactive poly(aryl ether)s containing bisazobenzene pendants for optical storage

A series of novel poly(aryl ether)s containing bisazobenzene moieties (bisazo-PAEs) have been synthesized based on a new bisazobenzene monomer, 4-(4-(4-nitrophenyl)diazenylphenyl)diazenylphenyl)-2,6-difluorobenzenesulfonate. Their chemical structures and properties were characterized by means of infrared, proton nuclear magnetic resonance, and ultraviolet–visible spectroscopies. These polymers show good thermal stability with glass transition temperatures above 160°C. the bisazo-PAEs show significant photoisomerization effect after irradiation with 405 nm light. By exposing the bisazo-PAEs films to an interference pattern of laser beams at modest intensity, significant surface-relief gratings can be formed.

Postpolymerization of a fluorinated and reactive poly(aryl ether): an efficient way to balance the solubility and solvent resistance of the polymer

A new fluorinated poly(aryl ether) with reactive benzocyclobutene groups as the side chain was successfully synthesized. This polymer showed a number-average molecular weight (Mn) of 200,000 and had good solubility and film-forming ability. After being postpolymerized at high temperature (>200 °C), the polymer film converted to a cross-linked network structure, which was insoluble in the common organic solvents. Such results suggest that the postpolymerization is an efficient way to achive the balance between the solubility and the solvent resistance of the polymer. TGA data showed that the postpolymerized polymer had a 5 wt % loss temperature at 495 °C and a residual of 61% at 1000 °C under N2. The cross-linked film also exhibited good dielectric properties with an average dielectric constant of about 2.62 in a range of frequencies from 1 to 30 MHz. With regard to the mechanical properties, the cross-linked film had hardness, Young's modulus, and bonding strength to a silicon wafer of 1.22, 8.8, and 0.89 GPa, respectively. These data imply that this new polymer may have potential applications in the electrical and microelectronics industry.

Photoresponsive smectic liquid crystalline multipods and hyperbranched azo polymers

Liquid crystalline azobenzene containing triped and tetraped monomers were designed and synthesized and further used as B3 and B4 type monomers to form hyperbranched polymers with tetraethylene glycol as the A2 type comonomer. The mesophase characteristics of the multiarm-star mesogens and hyperbranched polymers were analyzed using various instrumentation techniques like differential scanning calorimetry (DSC), polarized light microscopy (PLM) and variable temperature XRD. The multipod monomers as well as hyperbranched polymers exhibited thermotropic smectic liquid crystalline characteristics with a tendency toward higher ordered smectic LC phases with increased branching. The hyperbranched polymers exhibited lamellar organization even in the as-solvent precipitated powder sample indicating higher extent of nanosegregation. Their potential application as fast switching photochromic materials was highlighted by carrying out isothermal photoswitching experiments in the LC state. Reversible isothermal smectic-isotropic phase transition could be achieved by UV irradiation in <1 s in the multipod monomers, while it required >2 s UV irradiation in the case of the hyperbranched polymers.

Halogenated polyaryletherketones with enhanced thermal stability

Based on newly synthesized hydroquinone monomers, two series of halogenated polyaryletherketones, PEEKs and PEEKKs, were synthesized through nucleophilic aromatic substitution polycondensations. The chemical structures of the monomers and the polymers were carefully characterized using Fourier transform infrared and 1H-NMR spectroscopies. Some interesting results about the relationships between the structure and properties of these polymers having comparable chemical structures were revealed for the first time. Despite the similar chemical structure of –F, –Cl and –Br substituted polyaryletherketones, they exhibited different thermal behaviors. The thermogravimetric analysis results showed that chlorinated PEEKK had the best thermal stability and its limited oxygen index (LOI) value was 42.80. The results indicated some of them will be promising high-performance polymers.

Fabrication of fluorescent holographic micropatterns based on azobenzene-containing host-guest complexes

On the basis of photoinduced surface relief gratings (SRGs) with fluorophore/azo-complexes, a novel and facile method for fabricating stable and bright fluorescent two-dimensional micropatterns, whose color could be easily adjusted by changing the corresponding fluorophores, was developed for the first time.