Polyhedral Oligomeric Silsesquioxane (POSS) Nanoscale Reinforcement of Thermosetting Resin from Benzoxazine and Bisoxazoline

Summary: The reaction between octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) and 2,2′‐(1,3‐phenylene)‐bis(4,5‐dihydro‐oxazoles) (PBO) over different temperature ranges was confirmed by FT‐IR spectroscopy. The OAPS was used to modify benzoxazine (BZ) in the presence of PBO. The novel polybenzoxazine (PBZ)‐PBO/OAPS hybrid nanocomposite was prepared by solvent methods. Dynamic mechanical analyses indicated that the nanocomposites exhibited much higher T_g values than the pristine PBZ and PBZ‐PBO resin, and the storage modulus of the nanocomposites was maintained at higher temperatures, although only a small amount of OAPS was incorporated into the systems. Dynamic thermogravimetric analysis showed that the thermal stability of the hybrid was also improved by the inclusion of OAPS.

DMA of PBZ (a), PBZ‐PBO (b), and PBZ‐PBO/OAPS nanocomposites (c–e).     

Photolithographic Patterning of a Conductive Polymer Using a Polymeric Photoacid Generator and a Traceless Removable Group

Summary: In the present communication we describe a photolithographic method to produce polyaniline (PANI) patterns using PANI modified with a traceless removable functional group (nitrosated polyaniline, PANI‐NO) and external inexpensive polymeric photoacid generators (poly(vinyl chloride), PVC). Therefore, residual sub‐products created by irradiation of the plate do not remain occluded in the polymeric films. The borders of the patterns are better defined than in the case of chemical lithography using inorganic acids as the hydrolyzing agent.

     

Poly(4‐vinylpyridine) Nanocrosslinked by Polyhedral Oligomeric Silsesquioxane

Summary: Octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane (OpePOSS) was used as the crosslinking agent to prepare the nanocrosslinked poly(4‐vinylpyridine) (P4VP) with POSS content up to 55.2 wt.‐%. The formation of the crosslinked structure is ascribed to the macromolecular reaction between pyridine rings of P4VP and epoxide groups of OpePOSS. The POSS‐crosslinked P4VP displayed enhanced glass transition temperatures (T_gs) and an improved thermal stability in terms of the results of thermal analysis.

Crosslinking of poly(4‐vinylpyridine) with octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane.     

Synthesis of Highly Hydrophilic Polyaniline Nanowires and Sub‐Micro/Nanostructured Dendrites on Poly(propylene) Film Surfaces

Summary: Polyaniline (PANI) nanowires and sub‐micro/nanostructured dendrites are synthesized and immobilized on PP‐g‐PAA film surfaces via routine oxidative polymerization of aniline under different conditions, where grafting poly(acrylic acid) (PAA) served as a template and dopant, and SDS as a surfactant. The immobilized PANI enhances the surface hydrophilicity of the poly(propylene) (PP) films, and a superhydrophilic surface is obtained in this way. The mechanism of forming different morphologies of PANI and of correspondingly obtaining a superhydrophilic surface are briefly discussed.

FESEM image shows the PANI sub‐micro/nanostructured dendrites immobilized on the surfaces of PP films. The modified surface is highly hydrophilic with a water contact angle of 3°.     

The Self‐Assembled Structure of the Diblock Copolymer PCL‐b‐P4VP Transforms Upon Competitive Interactions with Octaphenol Polyhedral Oligomeric Silsesquioxane

This paper describes the miscibility and self‐assembly, mediated by hydrogen‐bonding interactions, of new block copolymer/nanoparticle blends. The morphologies adopted by the immiscible poly[(ε‐caprolactone)‐block‐(4‐vinyl pyridine)] (PCL‐b‐P4VP) diblock copolymer changes upon increasing the number of competitive hydrogen‐bonding interactions after adding increasing amounts of octaphenol polyhedral oligomeric silsesquioxane (OP‐POSS). Transmission electron microscopy reveals morphologies that exhibit high degrees of long‐range order, such as cylindrical and spherical structures, at relatively low OP‐POSS contents, and short‐range order or disordered structures at higher OP‐POSS contents. Analyses performed using differential scanning calorimetry, wide‐angle X‐ray diffraction, and FT‐IR spectroscopy provide positive evidence that the pyridyl units of the P4VP block are significantly stronger hydrogen‐bond acceptors toward the OH group of OP‐POSS than are the CO groups of the PCL block, thereby resulting in excluded and confined PCL phases.

     

Enhanced Conductivity of Polyaniline by Conjugated Crosslinking

A novel crosslinked conductive polyaniline (PANI) was prepared by chemically copolymerizing aniline (An) and p‐phenylenediamine (PPDA) with triphenylamine (TPA) as crosslinker, using ammonium peroxydisulfate (APS) as an oxidant. The effects of different preparation conditions on the electrical conductivity of polymers were systematically investigated by adjusting acid kinds, concentration, the ratio of APS/An, the mounts of TPA and PPDA. The crosslinked PANI displayed a conductivity increase of up to 25% compared with the linear one. Their structures were characterized by Fourier‐transformed infrared spectroscopy and X‐ray photoelectron spectroscopy, and the electrical conductivity was also tested by a typical four‐point probe (RTS‐8) technique.

     

Simultaneous Preparation of PI/POSS Semi‐IPN Nanocomposites

Summary: This investigation presents a simultaneous and convenient approach to produce a high‐performance polyimide with a low dielectric constant by introducing the octa‐acrylated polyhedral oligomeric silsesquioxane (methacrylated‐POSS) into a polyimide matrix to form polyimide semi‐interpenetrating polymer network (semi‐IPN) nanocomposites. The differential scanning calorimetry (DSC) and Fourier‐transform infrared (FT‐IR) results indicate that the self‐curing of methacrylated‐POSS and the imidization of polyamic acid (PAA) occurs simultaneously. The morphology of a semi‐IPN structure of polyimide/POSS‐PI/POSS nanocomposites with POSS nanoparticles embedded inside the matrix is elucidated. The POSS particles are uniform and are aggregated to a size of approximately 50–60 nm inside the polyimide matrix. The interconnected POSS particles are observed at high POSS content. The structure is highly cross‐linked, so the PI/POSS nanocomposites have an enhanced glass transition temperature. The high porosity of the PI/POSS nanocomposites markedly reduces the dielectric constant of PI because of the nanometer‐scale porous structure of POSS.

FT‐IR spectra of the various compounds of A) methacrylate‐POSS before curing, B) methacrylate‐POSS after curing, C) PAA containing 15 wt.‐% POSS, and D) PI/POSS containing 15 wt.‐% POSS.     

Self‐supporting Polymer from a POSS Derivative

A new polyhedral oligomeric silsesquioxane macromer, octakis[N‐(6‐aminopyridin‐2‐yl)undecanamide‐10‐dimethyl‐siloxy]silsesquioxane (POSS‐C11‐Py), containing eight diaminopyridine arms, is able to self‐assemble to form a physically crosslinked polymer‐like structure with good mechanical properties (tensile strength = 46.1 MPa, tensile modulus = 0.58 GPa, elongation = 49.3%) through quadruple hydrogen bonding interactions between these arms. POSS‐C11‐Py is the first organic/inorganic supermolecule possessing polymer‐like mechanical properties as a result of self‐complementary interactions, providing a potential route toward the design and fabrication of polymer‐like supramolecular materials.

     

Self‐Assembled Hollow Polyaniline/Au Nanospheres Obtained by a One‐Step Synthesis

Self‐assembled hollow nanosphere composites of polyaniline and Au nanoparticles (PANI‐p‐TSA/Au) were chemically synthesized from solutions containing p‐toluenesulfonic acid (p‐TSA) with the addition of gold chloride trihydrate as the oxidant. The composite materials were characterized by SEM, TEM, and a range of spectroscopic methods. Spectroscopic characterizations confirmed that the polymeric product is a form of doped PANI, while electron diffraction and X‐ray diffraction showed that elemental Au was present in the PANI‐p‐TSA/Au nanocomposites. The room temperature electrical conductivity of the PANI‐p‐TSA/Au nanocomposites was two orders of magnitude greater than a PANI‐p‐TSA obtained in the presence of ammonium persulfate as the oxidant under the same conditions.

     

Nanofibrilar Polyaniline: Direct Route to Carbon Nanotube Water Dispersions of High Concentration

Water dispersible nanofibrilar polyaniline (NF‐PANI) provides a novel and direct route towards carbon nanotube water dispersions of high concentration. Carrying out the chemical synthesis of NF‐PANI in the presence of carbon nanotubes (CNTs) results in an entirely nanostructured nanofibrilar polyaniline/carbon nanotube (NF‐PANI/CNT) composite material that contains well segregated CNTs partially coated by NF‐PANI. This new approach is simple, fast, and inexpensive, and enables the direct preparation of stable and homogeneous dispersions of the composites in water at concentrations up to 10 mg · mL⁻¹, even for the highest CNT loadings of 50 wt.‐% without the participation of surfactants or stabilizers.

     

Synthesis of Polyaniline Nanobelts

Summary: Polyaniline nanobelts have been synthesized by a self‐assembly process using the chemical oxidative polymerization of aniline in a surfactant gel. The morphologies of polyaniline nanostructures were characterized by field‐emission scanning electron microscopy and transmission electron microscopy. The effects of the concentrations of cetyltrimethylammonium bromide on the morphologies of polyaniline nanostructures have also been investigated.

A scanning electron microscopy image of polyaniline nanobelts synthesized with 0.12 M cetyltrimethylammonium bromide at −7 °C.     

Rose‐Like Microstructures of Polyaniline by Using a Simplified Template‐Free Method under a High Relative Humidity

3‐D rose‐like microstructures of polyaniline (PANI), which are self‐assembled from 2‐D nanosheets consisted of 1‐D nanofibers, were synthesized by a template‐free method in the presence of ammonium peroxydisulfate (APS) as both oxidant and dopant under a high relative humidity of 80% for the first time. When the relative humidity increases from 25 to 80%, not only morphology of the micro/nanostructured PANI undergoes a change from 1‐D nanofibers to 2‐D nanosheets to 3‐D rose‐like microstructures, but also increase in crystallinity. It is proposed that a cooperation effect of the oriented water molecules at the vapor–water interface and difference in hydrogen bonding energies between the interface and the bulk induced by the relative high humidity results in the formation of the 3‐D rose‐like microstructures self‐assembled from 2‐D nanosheets. Moreover, the method reported may provide a simple approach for understanding self‐assembly of complex micro/nanostructures of PANI.

     

Ordered Honeycomb‐Structured Films from Dendronized PMA‐b‐PEO Rod‐Coil Block Copolymers

Summary: Fabrication of honeycomb‐patterned films from amphiphilic dendronized block copolymer (PEO₁₁₃‐b‐PDMA₈₂) by ‘on‐solid surface spreading’ and ‘on‐water spreading’ method is reported. Highly ordered honeycomb films with quasi‐horizontally paralleled double‐layered structure can be fabricated by the on‐solid surface spreading method. This work raises the possibility that such structures can be formed in amphiphilic dendronized block copolymers and extends the family of source materials.

     

Thermal and Surface Properties of Phenolic Nanocomposites Containing Octaphenol Polyhedral Oligomeric Silsesquioxane

Summary: We have synthesized a new polyhedral oligomeric silsesquioxane (POSS) containing eight phenol functional groups and copolymerized it with phenol and formaldehyde to form novolac‐type phenolic/POSS nanocomposites exhibiting high thermal stabilities and low surface energies. Our DSC results indicate that the glass transition temperature of these nanocomposites increased initially upon increasing their POSS content, but then decreased at POSS content above 10 wt.‐%, presumably because of the formation of relatively low molecular weight species and POSS aggregation as evidenced from MALDI‐TOF mass analyses. Our TGA analyses indicated that the 5‐wt.‐%‐mass‐loss temperatures (T_d) increased significantly upon increasing the POSS content because the incorporation of the POSS led to the formation of an inorganic protection layer on the nanocomposite's surface. XPS and contact angle data provided positive evidence to back up this hypothesis. In addition, contact angle measurements indicated a significant enhancement in surface hydrophobicity after increasing the POSS content.

Syntheses procedures of phenolic/OP‐POSS nanocomposites.     

Synthesis of Large‐Area Three‐Dimensional Polyaniline Nanowire Networks Using a “Soft Template”

Summary: Three‐dimensional polyaniline (PANI) nanowire networks were synthesized in high yield using a “soft template” self‐assembled with hexadecyltrimethylammonium bromide and oxalic acid. The PANI nanowire networks had diameters from 35–100 nm depending on synthesis conditions and/or procedures. The networks and the “cross‐linking points” were clearly observed by field‐emission scanning electron microscopy and transmission electron microscopy. A possible mechanism for the formation of three‐dimensional PANI nanowire networks is discussed.

FESEM image of PANI with three‐dimensional nanowire networks.     

Anionic Polysaccharides as Templates for the Synthesis of Conducting Polyaniline and as Structural Matrix for Conducting Biocomposites

A green chemoenzymatic pathway for the synthesis of conducting polyaniline (PANI) composites is presented. Laccase‐catalyzed polymerization in combination with anionic polysaccharides is used to produce polysaccharide/PANI composites, which can be processed into flexible films or coated onto cellulose surfaces. Different polysaccharide templates are assessed, including κ‐carrageenan, native spruce O‐acetyl galactoglucomannan (GGM), and TEMPO‐oxidized cellulose and GGM. The resulted conducting biocomposites derived from natural materials provide a broad range of potential applications, such as in biosensors, electronic devices, and tissue engineering.

     

A New Strategy for the Synthesis of Polyaniline Nanostructures: From Nanofibers to Nanowires

A new approach for the synthesis of polyaniline (PANI) nanostructures under UV light illumination has been developed, which is the first report of a templateless chemical process for preparing pure PANI nanowires. The acceleration effect of photo‐assistance on the polymerization can promote the homogeneous nucleation and elongation of the nanofibers and nanowires, leading to easy preparation of tunable diameters of the nanowires and nanofibers of PANI.

     

Self‐Organizing Alignment of Carbon Nanotubes in Thermoplastic Polyurethane

Summary: A simple compounding technique for the fabrication of polymer nanocomposites with single‐walled carbon nanotubes having exceptional alignment and improved mechanical properties is described. The aligned‐nanotube composite was prepared by dissolving single‐walled carbon nanotubes in a solution of thermoplastic polyurethane and tetrahydrofuran. Solvent‐polymer interactions that induce the orientation of soft chain segments during the swelling and moisture curing stage are believed to serve as a driving force for the macroscopic alignment of the carbon nanotubes.

Alignment of single‐walled carbon nanotubes in thermoplastic polyurethane during polar solvent exposure.     

Electrical Conductivity of an Individual Polyaniline Nanotube Synthesized by a Self‐Assembly Method

Camphor sulfonic acid (CSA) doped polyaniline (PANI) nanotubes (175 nm in outer diameter and 120 nm in inner diameter) were synthesized successfully by a self‐assembly method. It is found that the room‐temperature conductivity of an individual PANI nanotube is 30.5 S · cm⁻¹; in particular, the intrinsic resistance of an individual nanotube (30 kΩ) is much smaller than the contact resistance of crossed nanotubes (500 kΩ).

A SEM image of two crossed PANI‐CSA nanotubes and the attached Pt electrodes.