Alternative Synthesis of C60‐Diphenylaminofluorene Derivatives for Nonlinear Photonic Applications: Method of Preparation and Characterization

An alternative synthetic route for the preparation of key intermediate synthons 7‐α‐bromoacetyl‐2‐diphenylaminofluorene (α‐BrDPAF‐H) and 7‐α‐bromoacetyl‐9,9‐dialkyl‐2‐diphenylaminofluorene (α‐BrDPAF‐C_n) was demonstrated. The latter reactions involved the first step of dialkylation of 2‐bromofluorene at C₉ position of the fluorene moiety, the second step of a diphenylamino group attachment at C₂ position of the resulting dialkylfluorene, and the third step of Friedel‐Craft acylation of α‐bromoacetyl group at C₇ position of dialkylated diphenylaminofluorene. From the intermediates α‐BrDPAF‐H and α‐BrDPAF‐C_n, a series of C₆₀‐keto‐DPAF nanostructures, such as the fullerene monoadducts C₆₀(>DPAF‐H) and C₆₀(>DPAF‐C_n), where n is 2, 4, or 10, were synthesized in a reasonable yield. Molecular mass ions of the dyads C₆₀(>DPAF‐H), C₆₀(>DPAF‐C₂), C₆₀(>DPAF‐C₄), and C₆₀(>DPAF‐C₁₀) were clearly detected in positive ion matrix‐assisted laser desorption ionization mass spectrum (MALDI–MS) that confirmed the composition mass of each compound synthesized.     

Organic sol–gel synthesis of microporous molecular networks containing spirobifluorene and tetraphenylmethane nodes

The microporous molecular networks based on rigid tetrafunctional units are synthesized via organic sol–gel polymerization of 2,2′,7,7′‐tetraamino‐9,9′‐spirobifluorene (TASBF) and/or tetrakis(4‐aminophenyl)methane (TAPM) with a diisocyanate, hexamethylene diisocyanate (HDI), or p‐phenylene diisocyanate. This study is performed as an extension of our previous report on the first organic sol–gel method, which enabled the synthesis of microporous molecular networks via a two‐stage mechanism involving the formation of colloidal dispersions of the nanoparticulate molecular networks and their subsequent growth to monolithic networks on solvent evaporation. The sol–gel‐synthesized molecular networks obtained by incorporating TASBF as a network former show improved porosity, processability, and thermal stability than the TAPM‐based system. The improved porosity of TASBF‐based networks is attributed to higher rigidity of the spirobifluorene compared with the tetraphenylmethane units. We also demonstrate the synthesis of mixed organic molecular networks by sol–gel copolymerization of the two network formers, TASBF and TAPM, and a diisocyanate monomer. The sol–gel transformation of TASBF/TAPM/HDI occurred at longer reaction times with increasing the amount of TASBF in the TASBF/TAPM/HDI mixture. The results indicate that the organic sol–gel method can be further optimized by adjusting various synthesis parameters to create new functional organic molecular network materials. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Nanocomposites derived from in situ grafting of linear and hyperbranched poly(ether‐ketone)s containing flexible oxyethylene spacers onto the surface of multiwalled carbon nanotubes

Linear and hyperbranched poly(ether‐ketone)s (PEKs) containing flexible oxyethylene spacers grafted multiwalled carbon nanotube (PEK‐g‐MWNT) nanocomposites were prepared by direct Friedel‐Crafts acylation as the polymer forming and grafting reaction. To achieve the composites, in situ polycondensations of AB monomers 3‐(2‐phenoxyethoxy)benzoic acid (3‐PEBA) and 4‐(2‐phenoxyethoxy)benzoic acid (4‐PEBA), and AB₂ monomer 3,5‐bis(2‐phenoxyethoxy)benzoic acid (3,5‐BPEBA) were carried out in the presence of multiwalled carbon nanotubes (MWNTs). The reaction conditions, polyphosphoric acid (PPA) with additional phosphorous phentoxide (P₂O₅) in the temperature range of 110–120 °C, were previously optimized. The conditions were used as the polymerization and grafting medium that were indeed benign not to damage MWNTs but strong enough to promote the covalent attachment of PEKs onto the surface of the electron‐deficient MWNTs. From scanning electron microscopy (SEM) and transmission electron microscopy studies, the polymers were uniformly grafted onto the MWNTs. The resultant nanocomposites are soluble in most strong acids such as trifluoroacetic acid, methanesulfonic acid, and sulfuric acid. Both isothermal and dynamic TGA studies in air showed that nanocomposites displayed improved thermo‐oxidative stability when compared with those of corresponding PEK homopolymers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3471–3481, 2008     

Surface Structure and Stereocomplex Formation of Enantiomeric Polylactide Blends Using Poly(dimethyl siloxane) as a Probe Polymer

In the stereocomplex between enantiomeric poly(l-lactide) (l-PLA) and poly(d-lactide), crystallites formed as a result of stereocomplexation, equimolar l- and d-lactide unit sequences are packed side by side. The stereocomplex exhibits a melting temperature higher by about 50 °C than that of each homopolymer. In this study, we attempt to obtain further insight into the stereocomplex-induced surface structure of enantiomeric PLA blend films. The design of the blend systems is based on principles of surface segregation of multicomponent polymeric systems with a low surface energy, triblock copolymer (l-PLA-b-PDMS-b-l-PLA) of l-PLA and poly-(dimethyl siloxane). (l-PLA-b-PDMS-b-l-PLA/l-PLA) blend films showed the surface segregation of PDMS, regardless of blend composition while the surface composition of PDMS in the (l-PLA-b-PDMS-b-l-PLA/d-PLA) blend films was strongly depended on blend composition or a degree of complexation. These results are likely due to strong interaction between d- and l-lactide unit sequences, which prevents the surface segregation of PDMS.     

Advancement trends in dye-doped polymer dispersed liquid crystals—a survey review

At present there is significant interest in the doping of various types of dyes into polymer dispersed liquid crystals (PDLCs) in display films. Till to date, various types of dyes have been employed to improve the electro-optical properties of PDLC films in various situations by different research groups. Some of the advantageous features of dye-doped PDLC predict that such dye-doping into the PDLC films resolve the scattering effect, improve the films absorbance, enhance the degree of alignment, stability, and the electro-optical properties of the film such as reflectance, contrast ratio and better transmittance. The current article contains a short review on the present and past studies conducted on the dye-doped polymers dispersed liquid crystals films. The fabrication techniques and their various applications in the different display areas are reviewed, along with the new key findings are discussed.     

A New Application of Dynamic Indentation: Indentation Machining Technology

While the indentation method is an excellent way to evaluate the mechanical properties of various sizes of materials, from the nano-scale to the macro-scale, its applications have been limited to measuring mechanical properties. In this study we propose a new application of the dynamic indentation method, in an indentation machining technology for mass-production. The core idea is that the array of residual indentations generated by dynamic indentation testing can be used to fabricate a lens array suitable for thinner and brighter displays. We developed an advanced system from a dynamic indentation system, whose maximum speed and maximum specimen size were about 10Hz and 250 mm*250 mm, respectively. Using dual actuating heads this system was used to produce arrays of lenses having depths of 1 μm to 6 mm. Pile-up is a critical reason why indentation machining technology had been not widely used in display industries. Since lower pile-up is observed in more ductile copper-based metals, we increased the annealing time of the metal molds to reduce the amount of pile-up. Then, following a quantitative analysis of the annealing heat treatment and resulting amount of pile-up, a lens array was successfully machined on a metal mold fabricated by the developed system. The machined metal mold was used to manufacture optical plates for a lens array. The results verified that the indentation machining technology proposed in this study, based on the dynamic indentation method, can be applied for the manufacturing of optical components for better displays.     

Improving the gas barrier properties of a-SiOxCyNz film at low temperature using high energy and suitable nitrogen flow rate

Amorphous silicon oxycarbonitride thin films were synthesized on polyethylene terephthalate (PET) substrates at low temperatures (～80 °C) by plasma-enhanced chemical vapor deposition (PECVD). A high ion flux and suitable nitrogen flow rate improved the gas barrier properties and deposition rate of the resulting a-SiO_xC_yN_z film. The a-SiO_xC_yN_z films were deposited at a high deposition rate and low water WVTR properties as a result of the high ion flux and nitrogen chemistry. The high ion flux modified the chemical structure and nitrogen atomic composition of the resulting a-SiO_xC_yN_z film coatings. The substrate temperature was characterized using a thermometer. In addition, the coating properties were characterized by Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and the water vapor transmission rate (WVTR).