Fabrication and Characterization of GRIN Plastic Rods Containing Silver Nanoparticles with Novel Surfmers

Summary: Both novel polymerizable surfactants of 2‐(methacroyloxy)ethyl succinate (MAES) and succinic acid mono{11‐[2‐(2‐methylacryloyloxy)ethoxy]undecyl} ester (SAME‐11) were synthesized in this investigation. A novel method was also developed for the preparation of gradient refractive index (GRIN) plastic rods containing inorganic nanoparticles with the polymerizable surfactants (surfmers). Silver nanoparticles were prepared using W/O (water in oil) reverse micelle technique in the presence of the surfmers. The effect of w values (w = [H₂O]/[surfmer]), silver nitrate concentration, surfmer/isooctane/H₂O ratio, and initiator concentration on the nanoparticle size was investigated. The optical absorption spectra of the micellar samples were recorded on a spectrophotometer at room temperature in the range of 200–900 nm. The nanoparticle size was confirmed with a transmission electron microcopy (TEM) technique. To introduce the nanoparticles into the GRIN plastic rods, methyl methacrylate (MMA) was used instead of isooctane in the organic phase. Nanoparticles were found to increase the refractive index of plastic rods effectively. Light scattering and an opaque appearance due to the aggregation of nanoparticles and the existence of surfactants were solved using the polymerizable surfmers in this investigation. We estimated both the real image transmission and the three dimensional refractive index distributions of the prepared GRIN plastic rods. The results of this investigation suggested that nanoparticles could be used as a kind of dopant to fabricate GRIN plastic rods and increased its refractive index effectively. Polymerizable surfactant could further raise the refractive index of the core of the GRIN rods leading to an increase of the numerical apertures (NA) and the acceptance angle (θ_max) of the plastic rods.

Three dimensional refractive index distribution of GRIN plastic rod prepared in this investigation.     

Synthesis of Poly(urethane acrylate‐co‐styrene) Films Containing Silver Nanoparticles by a Simultaneous Copolymerization/in situ Electron Transfer Reaction

Summary: A novel process for the synthesis of nanocomposite films containing silver nanoparticles is presented. Unlike conventional synthetic processes, silver nanoparticles and the polymer film constituting the nanocomposite film were synthesized simultaneously through an in situ electron transfer reaction and the copolymerization of styrene and amphiphilic urethane acrylate nonionomer (UAN), which contains hydrophobic poly(propylene oxide) segments and hydrophilic poly(ethylene oxide) segments along the same backbone. Silver nitrate crystals were first dissolved in a UAN/styrene solution through the formation of a complex between silver salts and the poly(ethylene oxide) chains of UAN, and then the transparent solutions obtained were directly converted to transparent free‐standing films containing silver nanoparticles by copolymerization and an electron transfer reaction by radicals. The amount of radical initiator strongly influenced the size and number of silver nanoparticles formed within the polymer films. The formation of silver nanoparticles was confirmed by transmission electron microscopy (TEM) and characteristic UV absorbance spectra. Hydrophobic/hydrophilic microphase separation in the UAN/styrene solution was also confirmed by TEM and mechanical property measurements.

TEM image of poly(urethane‐co‐styrene) film containing silver nanoparticles.     

Improvement in Mechanical and Thermal Properties of Transparent Semi‐Aromatic Polyimide by Crosslinking

Both the formation of insoluble salt for aliphatic diamines and the poor reactivity for aliphatic dianhydrides result in semi‐aromatic polyimide (SAPI) with low molecular weight and, thereby, in highly brittle SAPI films in nature. To solve the above problems, a cyclic‐olefin copolymer synthesized from norbornene and maleic anhydride is used as the third monomer (crosslinking agent) to prepare the crosslinked SAPI (cSAPI) films. The relative viscosity of the precursor solution of cSAPI is increased with the loading of cyclic‐olefin copolymer, giving rise to the improvement in mechanical and thermal properties of cSAPI films. The tensile modulus, tensile strength, and elongation at break of cSAPI film with 5 wt% cyclic‐olefin copolymer are increased to 4.49 GPa, 137 MPa, and 14.9% from 3.57 GPa, 111 MPa, and 7.6%, respectively, compared to those of the baseline SAPI film. Meanwhile, the glass transition temperature of cSAPI films is increased to 282 from 270 °C of the SAPI film, which is advantageous to better meet the requirement for high‐temperature manufacturing processes such as lead‐free solder reflowing. In addition, all cSAPI films exhibit good optical transparency in the entire visible region.     

Improved Electro‐Optic Effect by Hyperbranched Chromophore Structures in Side‐Chain Polyimide

Hyperbranched structures of chromophores were developed to improve the nonlinearity of optical polymers. Macromolecules with 3‐[p‐(2′‐hydroxyethylmethylamino)styryl]‐1‐dicyanomethylene‐5,5‐dimethylcyclohex‐2‐ene (AIDC) were prepared using 3,5‐dihydroxyphenyl groups as building blocks. When the molecule was incorporated into a polyimide backbone (PI‐DAIDC101), a high electro‐optic coefficient was obtained, giving 32 pm · V^?1 at 1.55 μm. The nonlinearity is at least doubly enhanced in comparison with that of conventional side chain‐optical polyimides. This is mainly attributable to an increased polarizing efficiency derived from the chromophore structures.

The structure of the linear polyimide backbone (PI‐OH) and the chromophore‐attached optical polyimide (PI‐DAIDC101).