Papers by Keyword: Block-Copolymer

Abstract: In order to find out optimum filler to increase manufacturability (extrudability) of composites based on ultra-high molecular weight polyethylene (UHMWPE) matrix as well as to develop polymer-polymeric composites with improved tribological characteristics, the structure, mechanical properties and wear resistance of UHMWPE mixtures with elasticizing block-copolymer PA-b-LLDPE (UHMWPE + PA-b-LLDPE) was investigated under dry sliding friction. Applied aspect of the study is related to the selection of commercially available fillers being compatible with UHMWPE for manufacturing anti-frictional extrudable nanocomposites. It is shown that as compared with pure UHMWPE mechanical properties (ultimate strength, value of elongation at failure) do not vary substantially, but the wear rate under dry sliding friction of polymeric composites UHMWPE + n wt.% PA-b-LLDPE is reduced only when block copolymer weight fraction is less than ≤ 5 wt.%. By the polymeric filling an important technological characteristic - specific pressure of extrusion (that is proportional to melt flow index) might be decreased. Permolecular structure and wear track surfaces of polymer-polymer composites UHMWPE + n wt.% PA-b-LLDPE was examined and numerically characterized.

Abstract: We demonstrate the structural reorganization of microdomain arrays toward the perpendicular orientation of lamellar morphology in high-molecular-weight PS-b-PMMA films using a combinational approach by solvent-vapor and sequential thermal annealing processes. Solvent annealing with a PMMA-selective acetone vapor induced a cylindrical morphology. However, the sequential thermal annealing of block copolymer (BCP) films led to structural reorganization to an equilibrium lamellar morphology, where the lamellar microdomains were oriented to normal to the film surface. This technique suggests an efficient route for directing orientation and structural reorganization of microdomain arrays in the thin films of high-molecular-weight BCP self-assembly.

Abstract: The aim of the study is to design wear-resistant and extrudable polymeric composites based on mixture of UHMWPE+PP with increased tribotechnical characteristics for the wide application in friction units of machine parts and mechanisms as well as using the polymeric resin developed for obtaining nanocomposites. Adding of block copolymer PP-b LLDPE to UHMWPE is motivated by the necessity to increase the adhesion between the incompatible polymeric components of the mixture. It is shown that wear intensity of the polymer-polymeric composites UHMWPE+n wt.% PP-b-LLDPE is reduced at filling UHMWPE by the block copolymer. In doing so, an important technological characteristic of UHMWPE specific extrusion pressure (proportional to the melt flow index) is improved (is lowered). Nanocomposites on the basis of the given matrix have shown wear resistance of 3-4 times higher in contrast with pure UHMWPE. Permolecular structure and wear track surfaces of nanocomposites on the basis of polymer-polymeric matrix (UHMWPE+10 wt.% PP-b-LLDPE) were investigated. The mechanism of the wear of nanocomposites is discussed.

Abstract: ZnO nanoparticles were synthesized by using N, N-dimethylformamide as solvent and poly(styrene-b-butadiene-b-styrene) SBS-OH as stablizer at 100°C through “in situ” reaction process. The optical properties and morphologies for the synthesized ZnO nanoparticles were measured through UV-Vis, PL and TEM methods. The results show that corona-embedded ZnO nanoparticles could be obtained by SBS-OH micelles in polar solvent DMF. The obtained ZnO nanoparticles could give an apparent quantum size confinement effects and PL results show that ZnO nanoparticles could give good luminescence properties.

Abstract: We investigated the fabrication of self-assembled nanodot array using poly (styrene)-poly (dimethyl-siloxane) (PS-PDMS) block copolymer and its transfer technique as a promising method to fabricate magnetic nanodot arrays for ultrahigh density recording. A carbon (C) layer with a high etch-resistance was especially adopted for magnetic nanodot fabrication. We fabricated PDMS nanodot using PS-PDMS block copolymer with a molecular mass of 11,700-2,900 g/mol. The nanodots were first transferred into silicon (Si) layer and then into C layer on Si substrate by carbon tetrafluoride (CF₄) and oxygen (O₂) reactive ion etching (RIE), respectively. We succeeded in fabricating C nanodots with a diameter of 10 nm and an average pitch of 20 nm.

Abstract: We investigated the possibility of ordering of 12 nm pitced self-assembled nanodots from block copolymer (BCP) improved by the guide pattern with low line edge roughness (LER) for patterned media. We found that LER of the line pattern (σ-value) was reduced by using high-resolution salty development for HSQ resist line pattern fabrication compared with conventional tetramethyl ammonium hydroxide (TMAH) developer. By adopting this development technique to guide pattern fabrication, we demonstrated 10 rows of ordered self-assembled BCP nanodot arrays with a size of 6 nm and a pitch of 12 nm (5 Tbit/in.²) between the guide patterns.

Abstract: Structural deformation during uniaxial drawing of polyethylene-block-polystyrene (PE-b-PS) copolymer film was analyzed by in-situ small angle X-ray scattering (SAXS) measurement. The PE-b-PS film was prepared by solution casting, followed by isothermally crystallizing from melt. The obtained film exhibits the characteristic bicontinuous crystalline/amorphous morphology. Initial stage of uniaxial drawing induces the orientation of such crystalline/amorphous phases, but these phase separation is destroyed in the latter stage. In contrast, solvent swelling treatment successfully induces the orientation of crystalline/amorphous phases with keeping the phase continuity.

Abstract: Quantum dots (QDs) have a great potential to be applied as a biosensor to detect cancer cells because of their properties such as high photoluminescence, photo stability, narrow peak of luminescence, etc. However, cadmium sulphide (CdS) quantum dots are toxic and hydrophobic, making it impossible to be applied into biomaterials. A template is needed to make CdS QDs nontoxic and hydrophilic. The optical properties of these QDs are needed to be protected. To achieve this purpose, the template for CdS QDs has been designed by capping CdS QDs with apo-ferritin shells before aligning them onto cylindrical perpendicular PS-b-P2VP template, with the aim of locating CdS QDs appropriately in sequence. A host-guest system can be developed.

Abstract: A new series of hydrophobic-hydrophilic multiblock sulfonated poly (arylene ether ketone)-b-poly (arylene ether ketone) copolymers were successfully synthesized and evaluated for use as proton exchange membranes (PEMs). The membrane properties of block copolymers including ion exchange capacities (IECs), water uptake and proton conductivities were characterized for the multiblock copolymers and compared with random sulfonated poly (arylene ether) s and other multiblock copolymer membranes at similar ion exchange capacity value. This series of multiblock copolymers showed moderate conductivities up to 0.063 S/cm at 80 °C with very low water uptake of 19%. Therefore, they are considered to be promising PEM materials for fuel cells.

Abstract: A new series of hydrophobic-hydrophilic multiblock copolymers derived from fluorine terminated poly (arylene ether ketone) as hydrophobic blocks and phenoxide terminated sulfonated poly (arylene ether sulfone) as hydrophilic blocks were successfully synthesized and evaluated for use as proton exchange membranes (PEMs). All the hydrophobic and hydrophilic oligomers were synthesized via molecular-weight controlled step growth polymerization of the monomers. ¹H NMR spectra were used as characterization tool to determine the telechelic oligomers molecular weight and multiblock copolymers structure. The morphologies of multiblock copolymers were investigated by transmission electron microscopy (TEM), which showed they had a clear microphase-separated structure between the hydrophilic domains and hydrophobic domains. All the sulfonated poly (arylene ether sulfone)-b-poly (arylene ether ketone) copolymers can easily be cast into tough membranes for applications in proton exchange membrane.