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PS Matrix (ps + matrix)
Selected AbstractsDirected Helical Growth: A Spring-Like Behavior of Chiral Block Copolymer with Helical Nanostructure Driven by Crystallization (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Mater. Crystalline helices (PLLA crystallization directed by helical confined microdomains) and crystalline cylinders (phase transformation of helical nano structures dictated by crystallization) are obtained by controlling the crystallization temperature of PLLA with respect to the glass transition temperature of PS in PS-PLLA block copolymers; this process is described by J.-W. Chiang et al. on page 448. A spring-like behavior of the PLLA helical nanostructures embedded in the PS matrix can be driven by crystallization, so as to dictate the transformation of the helices, resulting in crystalline cylinders that might represent a possible avenue for the design of switchable large-strain actuators. [source] Spontaneous Vertical Ordering and Pyrolytic Formation of Nanoscopic Ceramic Patterns from Poly(styrene- b -ferrocenylsilane),ADVANCED MATERIALS, Issue 4 2003K. Temple The rapid generation of nanopatterned surfaces using thin films of the amorphous diblock copolymer poly(styrene- b -ferrocenylethylmethylsilane) (PS- b -PFS) is reported. Spontaneous self-assembly into vertically oriented cylinders of PFS in a PS matrix is observed on a variety of substrates by spin or dip coating, irrespective of the substrate surface polarity. Pyrolysis of the films affords arrays of 20 nm Fe-containing ceramic nanoparticles, (see Figure, AFM, 4 ,m2 scan area). [source] Preparation and properties of plasticized starch/multiwalled carbon nanotubes compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007Xiaodong Cao Abstract In this work we have studied the utilization of multiwalled carbon nanotubes (MWCNTs) as filler-reinforcement to improve the performance of plasticized starch (PS). The PS/MWCNTs nanocomposites were successfully prepared by a simple method of solution casting and evaporation. The morphology, thermal behavior, and mechanical properties of the films were investigated by means of scanning electron microscopy, wide-angle X-ray diffraction, differential scanning calorimetry, and tensile testing. The results indicated that the MWCNTs dispersed homogeneously in the PS matrix and formed strong hydrogen bonding with PS molecules. Compared with the pure PS, the tensile strength and Young's modulus of the nanocomposites were enhanced significantly from 2.85 to 4.73 MPa and from 20.74 to 39.18 MPa with an increase in MWCNTs content from 0 to 3.0 wt %, respectively. The value of elongation at break of the nanocomposites was higher than that of PS and reached a maximum value as the MWCNTs content was at 1.0 wt %. Besides the improvement of mechanical properties, the incorporation of MWCNTs into the PS matrix also led to a decrease of water sensitivity of the PS-based materials. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Effect of an organic dicarboxylic acid salt on fractionated crystallization of polypropylene dropletsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Y. Jin Abstract The effect of a particulate nucleating agent on fractionated crystallization of polypropylene (PP) was studied. A novel method utilizing breakup of PP nanolayers was used to obtain a dispersion of PP droplets in a polystyrene (PS) matrix. An assembly with hundreds of PP nanolayers alternating with thicker PS layers was fabricated by layer-multiplying coextusion. The concentration of an organic dicarboxylic acid salt (HPN) nucleating agent in the coextruded PP nanolayers was varied up to 2 wt %. When the assembly was heated into the melt, interfacial driven breakup of the thin PP layers produced a dispersion of PP particles in a PS matrix. Analysis of optical microscope images and atomic force microscope images indicated that layer breakup produced a bimodal particle size distribution of submicron particles and large, micron-sized particles. Almost entirely submicron particles were obtained from breakup of 12 nm PP layers. The fraction of PP as submicron particles dropped dramatically as the PP nanolayer thickness increased to 40 nm. Only large, micron-sized particles were obtained from 200 nm PP nanolayers. The crystallization behavior of the particle dispersions was characterized by thermal analysis and wide angle X-ray diffraction. Only part of the PP was nucleated by HPN. It was found that HPN was not effective in nucleating the population of submicron particles. The particulate HPN was too large to be accommodated in the submicron PP particles. On the other hand, the amount of nucleated crystallization qualitatively paralleled the fraction of PP in the form of large, micron-sized particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Synthesis and self-assembly of polystyrene-grafted multiwalled carbon nanotubes with a hairy-rod nanostructureJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2006Yingkui Yang Abstract Polystyrene-grafted multiwalled carbon nanotubes (PS- g -MWNTs) with a hairy-rod nanostructure were synthesized by the in situ free-radical polymerization of styrene in the presence of multiwalled carbon nanotubes (MWNTs) terminated with vinyl groups. To quantitatively study the molecular weight and composition of polystyrene (PS) chains in PS- g -MWNTs, PS- g -MWNTs were fully defunctionalized by hydrolysis. The results showed that 1 of every 100 carbon atoms in MWNTs was functionalized at the tips and outer walls of the carbon nanotubes and grafted by PS with a weight-average molecular weight of 9800 g/mol; therefore, a uniform thin layer (ca. 8,10 nm) of a PS shell was formed on the outer wall of MWNTs. PS- g -MWNTs were soluble in dimethylformamide and tetrahydrofuran. The thermal stability and glass-transition temperature of PS in PS- g -MWNTs were obviously increased. Nanopins were formed on the glass substrates by the self-assembly of PS- g -MWNTs, and the dewetting effect between the glass substrate and PS chains covered MWNTs during the evaporation of the solution. Both the length and diameter of the nanopins increased with the solution concentration. When PS- g -MWNTs were compression-molded, MWNTs were dispersed uniformly in the PS matrix and formed good networks, such as circlelike and starlike structures, because of the entanglements of hairy PS chains on MWNTs. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3869,3881, 2006 [source] Nanocellular Foams of PS/PMMA Polymer BlendsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 1 2008Tetsuo Otsuka Abstract A nanocellular PS/PMMA polymer blend foam was prepared, where bubble nucleation was localized in the PMMA domains. The blend, which contains dispersed nanoscale PMMA islands, was prepared by polymerizing MMA monomers in a PS matrix to form highly dispersed PMMA domains in the PS matrix by diffusion mixing. The resulting blend was foamed with CO2 at room temperature. A higher depressurization rate at lower foaming temperature made the bubble diameter smaller and the bubble density larger, and a higher PS composition in the blend resulted in a larger bubble density. A void with 40,50 nm in average diameter and a pore density of 8.5,×,1014 cm,3 was obtained as for the finest nanocellular foams. [source] Structural and mechanical properties of polystyrene nanocomposites with 1D titanate nanostructures prepared by an extrusion processPOLYMER COMPOSITES, Issue 9 2009Polona Umek Polystyrene (PS) nanocomposites with titanate nanotubes and titanate nanoribbons were prepared by an extrusion process at 180°C. Nanocomposites with 1 wt% of nanofillers and pure PS that had also been exposed to the extrusion process were comparatively examined with scanning electron microscopy (SEM), electron dispersive X-ray spectrometry (EDS) mapping, solid state proton nuclear magnetic resonance measurements (1H NMR), tensile tests, and shear creep measurements. SEM images and EDS mapping analysis show that titanate nanoribbons homogeneously distribute at a micrometer length-scale in the PS matrix during the extrusion process. This is not the case for titanate nanotubes, which show a stronger tendency to form clusters. Solid state 1H NMR studies, however, proved that the nanocomposites are inhomogeneous at a nanometric scale where structural components with highly mobile PS molecules coexist with domains of rigid PS molecules. Differences in the 1H spin-lattice relaxation at and above the glass transition temperature Tg = 373 K suggest that nanofillers affect the thermodynamic properties of nanocomposite domains. Only a slight increase in mechanical tensile properties was observed in the case of the nanocomposite containing 1 wt% of titanate nanoribbons (TiNRs) probably reflecting a weak interaction between the polymer matrix and the nanofiller. Nevertheless, our results prove that the use of functionalized TiNRs may, in combination with the extrusion process, represent a very promising starting point for the preparation of TiNR nanocomposites at the industrial level. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Synthesis of sub-micrometer core,shell rubber particles with 1,2-azobisisobutyronitrile as initiator and deformation mechanisms of modified polystyrene under various conditionsPOLYMER INTERNATIONAL, Issue 10 2009Rujun Dai Abstract BACKGROUND: Sub-micrometer core-shell polybutadiene- graft -polystyrene (PB- g -PS) copolymers with various ratios of polybutadiene (PB) core to polystyrene (PS) shell were synthesized by emulsion grafting polymerization with 1,2-azobisisobutyronitrile (AIBN) as initiator. These graft copolymers were blended with PS to prepare PS/PB- g -PS with a rubber content of 20 wt%. The mechanical properties, morphologies of the core-shell rubber particles and deformation mechanisms under various conditions were investigated. RESULTS: Infrared spectroscopic analysis confirmed that PS could be grafted onto the PB rubber particles. The experimental results showed that a specimen with a ,cluster' dispersion state of rubber particles in the PS matrix displayed better mechanical properties. Transmission electron micrographs suggested that crazing only occurred from rubber particles and extended in a bridge-like manner to neighboring rubber particles parallel to the equatorial plane at a high speed for failure specimens, while the interaction between crazing and shear yielding stabilized the growing crazes at a low speed in tensile tests. CONCLUSION: AIBN can be used as an initiator in the graft polymerization of styrene onto PB. The dispersion of rubber particles in a ,cluster' state leads to better impact resistance. The deformation mechanism in impact tests was multi-crazing, and crazing and shear yielding absorbed the energy in tensile experiments. Copyright © 2009 Society of Chemical Industry [source] Thermal conductive PS/graphite compositesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2009Haoming Tu Abstract Polystyrene (PS) was compounded with graphite that possesses high thermal conductivity and layer structures, and the PS/graphite thermal conductive nano-composites were prepared. Thermal conductivity of PS improved remarkably in the presence of the graphite, and a much higher thermal conductivity of 1.95,W/m,K can be achieved for the composite with 34,vol% of colloidal graphite. The Maxwell-Eucken model and the Agari model were used to evaluate the thermal conductivity of the composites. For the purpose of improving the interfacial compatibility of PS/graphite, realizing the exfoliation and nano-dispersion of graphite in the PS matrix, three intercalation methods, including rolling intercalation, solvent intercalation, and pan milling intercalation, were applied to prepare the composites, and the morphologies, thermal conductivities, and mechanical properties of the composites were investigated. It should be noted that the one prepared by pan milling intercalation not only had excellent thermal conductivity but also much higher mechanical properties, resulting from a high degree of layer exfoliation of the graphite, the formation of the chain structure agglomerates of the graphite, and the creation of more conductive paths under the strong shear stress of pan milling. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||