Formation of 7-nm-wide Line&Spaces in Half Pitch by 3 Dimensional Self-assembly of Nano-dots Using Sphere Type PS-PDMS

We have formed nanometer-wide lines & spaces by graphoepitaxy of sphere type polystyrene-poly dimethyl siloxane (PS-PDMS), with a molecular weight (MW) of 14.6 kg/mol., along electron-beam (EB)-drawn resist guide lines. We have 3-dimensionally ordered the sphere type PS-PDMS by controlling a thickness of the PS-PDMS along improved guide lines to form the line and space pattern. We obtained the thickness dependence on the pattern change such as nano-dot arrays and nano-line & space patterns. When the thickness increased to about +4 nm from the upper thickness for formation of the dot arrays, the line & space patterns have been formed with about 7 nm in line width and 14 nm in pitch.

Preparation by solution mixing and characterization of condensation type poly(dimethyl siloxane)/graphene nanoplatelets composites

The impact of the incorporation of graphene nanoplatelets (GN) on the properties of hydroxyl-terminated poly(dimethylsiloxane) (PDMS) matrices was investigated. The composites were prepared by solution mixing, using tetrahydrofuran (THF) as a solvent. Brookfield viscosimetry, implemented during the vulcanization process, revealed that GN increases the viscosity of the system, compared to pristine PDMS, proportionally to its concentration. X-ray diffraction patterns suggested an efficient dispersion of GN in the polysiloxane matrix. The D and G bands ratio (ID/IG) calculation, based on RAMAN spectra of GN/PDMS specimens, revealed more defects in graphene nanoplatelets when incorporated in the PDMS matrix. By differential scanning calorimetry (DSC), a marginal increase in crystallization, glass transition and melting temperatures of PDMS in GN/PDMS composites was observed. Improvement of the thermal stability of LMW PDMS composites, especially for higher GN concentrations (3 and 5 phr), was noticed by thermogravimetric analysis (TGA). Additionally, GN enhanced the tensile strength of composites, up to 73% for the 3 phr GN/LMW PDMS composite. A significant increase in the elongation at break was recorded, whereas no effect on the modulus of elasticity was recorded. The decrease in toluene-swelling, for the LMW PDMS matrix composites, was attributed to the increase in the tortuosity path because of the efficient dispersion of GN. A decrease in oxygen permeability of 55–65% and 44–58% was measured in membranes made of PDMS composites containing 0.5 phr and 1 phr GN, respectively. Dielectric relaxation spectroscopy (DRS) measurements recorded a significant increase in the conductivity of the higher graphene content composites.

Novel Polyimide-block-poly(dimethyl siloxane) copolymers: Effect of time on the synthesis and thermal properties

Polyimide-block-poly(dimethyl siloxane) copolymer was synthesized by a two-step process, initiated by coupling anhydride terminated poly(amic acid), AT-PAA with amino terminated poly(dimethyl siloxane), (NH2)2-PDMS to form poly(amic acid)-block-poly(dimethyl siloxane). The resulting copolymer is then thermally treated to produce polyimide-block-poly(dimethyl siloxane), PI-PDMS. Because of the high glass transition temperature, Tg of polyimide, it is usually cured at a high temperature of about 300°C for over 2.5 h. Copolymerization of polyimide with polysiloxane, reduces the imidization temperature while maintaining high thermomechanical properties. A series of instruments were used to monitor the progress of copolymerization. The time-based analysis of the product of copolymerization enables the optimization of the structure and properties of the copolymers. The chemical structure and composition of the copolymer were studied by Fourier Transform Infrared Spectroscopy, (FT-IR). The incorporation of PDMS blocks into the copolymer and the degree of imidization of the polyimide block increased with increasing reaction time. The change in the viscosity of the copolymerizing solution was monitored by simple shear viscometry conducted with the Brookfield Viscometer. The reported increase in solution viscosity with increasing copolymerization time is associated with increasing molecular weight of the copolymer. The intrinsic viscosity of the copolymer solution was measured as a function of copolymerization time and it was found that the intrinsic viscosity of the copolymer solution increased with increasing reaction time. The glass transition temperature (Tg) and the thermal stability of the copolymer were determined by differential scanning calorimetry, DSC and thermogravimetric analysis, and TGA, respectively. Between 25°C and 420°C, the copolymers synthesized in this study show two glass transition temperatures due to the polyimide, PI block at around 380°C and another peak associated with PDMS plasticized polyimide at about 290–300°C. The two Tg peaks observed in the DSC thermogram are believed to be indicative of the structure of a block copolymer. TGA analysis shows that the thermoxidative stability of the copolymers increased with increasing reaction time, due to the incorporation of increased amount of PDMS unit into the copolymer. The combination of increasing molecular weight of copolymer, higher degree of imidization of polyimide blocks and enhanced thermoxidative stability may translate into improved flame retardancy of copolymers. This suggested enhancement in flame retardancy in air atmosphere, is believed to be due the incorporated PDMS blocks, which can be converted into silica, SiO2, a recognized thermally stable material.

Electrochemical topological transformation of polysiloxanes

Coupling reactions between polymers are an important class of chemical modifications for changing, enhancing, and tuning the properties of polymeric materials. In particular, transformation of polymer topologies based on efficient, facile and less wasted coupling reactions remains a significant challenge. Here, we report coupling reactions based on electrochemical oxidation of 2,4,5-triphenylimidazole into a 2,4,5-triphenylimidazolyl radical and its spontaneous dimerization into hexaarylbiimidazole. Based on this chemistry, electrochemical topological transformation (ETT) and electrochemical chain extension have been realized with siloxane-based oligomers and polymers. Moreover, this approach enables one step ETT of star-shaped poly(dimethyl siloxane)s (PDMSs) into network PDMSs, running in an ionic liquid solvent and requiring no purification steps.

3D Simulation Modeling for the Electrical Conductivity of Carbon Nanotube Networks in Polymer Nanocomposites

In this paper, we developed a three-dimensional percolation model to investigate the effects of the concentration and morphology of CNTs (carbon nanotubes) on the electrical conductivity of the nanocomposites. In the model, we judged the connections between CNTs by range search algorithm based on KD-Tree structure. At the same time, DIJKSTRA-Melissa algorithm was applied to efficiently find all the conductive paths instead of finding conductive network in traditional methods. From the simulation results, CNTs with higher aspect ratio were easier to form the conductive network. In a certain range of CNT’s concentration, the relationship between the conductivity of the conductive network and the carbon nanotubes was basically consistent with the classical percolation theory. To verify our simulation model, the morphological, electrical properties of Carbon nanotubes (CNTs)/poly(dimethyl siloxane) (PDMS) nanocomposites with different aspect ratio (AR) of MWNTs were systematically studied. In conclusion, these unique advantageous properties could be exploited to suggest potential applications of artificial electronic skin.

Design and Displacement Analysis of Three different Cantilever based MEMS Piezoresistive Pressure Sensor with Polymer (PDMS/PMMA) Thin Flim

This paper mainly focuses on to get high displacement from polymer based piezoresistive cantilever for MEMS/NEMS pressure sensor applications. The displacement has been analyzed and compared with three different cantilever using PDMS (Poly dimethyl siloxane) and PMMA (Poly methyl methacrylate) materials. The p-type silicon piezoresistors connected the form based on wheat stone bridge to get high sensible pressure sensor with respect to low response. An according to get high displacement, obviously the other performance of parameters such as stress, strain gets high range. So, this analyzed cantilever structure used to design a pressure sensor with high sensitivity. The design and simulation are done by using COMSOL Multiphysics.