Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

Polymer nanocomposites based on functionalized carbon nanotubes

Polybenzoxazines-New high performance thermosetting resins : Synthesis and properties

This study aims at investigating package materials based on polymer matrix for microelectronics. The next generation package materials are expected to possess high heat dissipation capability in addition to low coefficient of thermal expansion (CTE) as the accumulated heat from high performance electronic devices should be removed for proper operation. In this study, various inorganic fillers including aluminum nitride (AlN), wollastonite, silicon carbide whisker (SiC) and boron nitride (BN) with different shape and size were used alone or in combination to prepare thermally conductive polymer composites. In case of AlN, titanate coupling agent was used for the surface treatment of fillers. The use of hybrid filler was found to be effective in increasing thermal conductivity of the composite probably due to the enhanced connectivity offered by structuring filler with high aspect ratio in hybrid filler. For given filler loading, the use of larger particle and surface treated filler resulted in composite materials with enhanced thermal conductivity. The surface treatment of filler also allowed producing the composites with lower CTE.

Enhanced thermal conductivity of polymer composites filled with hybrid filler

Effect of organoclay structure on nylon 6 nanocomposite morphology and properties

Comparisons of thermal properties between inorganic filler and acid-treated multiwall nanotube/polymer composites

The effect of molecular weight between crosslinks, Mc, on the fracture behavior of rubber-toughened epoxy adhesives was investigated and compared with the behavior of the bulk resins. In the liquid rubber-toughened bulk system, fracture energy increased with increasing Mc. However, in the liquid rubber-toughened adhesive system, with increasing Mc, the locus of joint fracture had a transition from cohesive failure, break in the bond layer, to interfacial failure, rupture of the bond layer from the surface of the substrate. Specimens fractured by cohesive failure exhibited larger fracture energies than those by interfacial failure. The occurrence of transition from cohesive to interfacial failure seemed to be caused by the increase in the ductility of matrix, the mismatch of elastic constant, and the agglomeration of rubber particles at the metal/epoxy interface. When core-shell rubber, which did not agglomerate at the interface, was used as a toughening agent, fracture energy increased with Mc. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 38–48, 2001

Effect of molecular weight between crosslinks on the fracture behavior of rubber-toughened epoxy adhesives

Multi-walled carbon nanotubes (MWNTs) pre-treated by concentrated mixed acid or oxidized at high temperature were melt mixed with poly(methyl methacrylate) (PMMA) using a twin screw extruder. The morphologies and electrical properties of the MWNT/PMMA composites were investigated. The thermally treated MWNTs (t-MWNTs) were well dispersed, whereas the acid treated MWNTs (a-MWNTs) were highly entangled, forming large-sized clusters. The resulting electrical properties of the composites were analyzed in terms of the carbon nanotube (CNT) dispersion. The experimental percolation threshold was estimated to be 3 wt% of t-MWNTs, but no percolation occurred at similar concentrations in the a-MWNT composites, due to the poor dispersion in the matrix.

/pdf/effect-of-carbon-nanotube-pre-treatment-on-dispersion-and-50flej0tik.pdf

Effect of Carbon Nanotube Pre-treatment on Dispersion and Electrical Properties of Melt Mixed Multi-Walled Carbon Nanotubes / Poly(methyl methacrylate) Composites

In the melt intercalation of cation-exchange clay, mixtures of montmorillonite and poly(styrene-co-acrylonitrile) (SAN) with various acrylonitrile contents were studied to examine the effect of specific interaction. When organic molecules with hydroxyl groups were used as intercalants for the clay, the amount of SAN penetrating the gallery of the layered structure of the clay and the corresponding increase in the gallery height occurred at a much higher rate because of the attractive specific interaction between acrylonitrile groups and polar groups on the clay surface. However, there was a limit to the increase in the gallery height, and the tendency for the gallery height to increase with the acrylonitrile group content disappeared when the acrylonitrile content was greater than 30 wt %, implying that excessive attractive interaction on the clay surfaces and polymer molecules glued the two adjacent silicate layers together; consequently, the increase in the gallery height could not be accomplished. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2430–2435, 2001

Specific interaction governing the melt intercalation of clay with poly(styrene‐co‐acrylonitrile) copolymers

For the poly(butylene terephthalate) (PBT)/poly(ethylene terephthalate) blend system, the addition of a barium sulfate (BaSO4) particle, the surface of which was modified with a titanate coupling agent, suppressed the transesterification reaction. The polyester chain ends, considered one of the main sites of transesterification reactions, were blocked through a chemical reaction with the surface hydroxyl groups of the BaSO4 particle; a block copolymer-like architecture was obtained with a BaSO4 linkage. The formation of the block copolymer-like structure for the polyesters stuck to the BaSO4 particle facilitated crystallization by providing a crystallization nucleus without a significant transesterification reaction, resulting in higher mechanical properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2589–2597, 2001

Park Min

Papers

Comparisons of thermal properties between inorganic filler and acid-treated multiwall nanotube/polymer composites

Effect of molecular weight between crosslinks on the fracture behavior of rubber-toughened epoxy adhesives

Effect of Carbon Nanotube Pre-treatment on Dispersion and Electrical Properties of Melt Mixed Multi-Walled Carbon Nanotubes / Poly(methyl methacrylate) Composites

Specific interaction governing the melt intercalation of clay with poly(styrene‐co‐acrylonitrile) copolymers

Transesterification reaction of the BaSO4‐filled PBT/poly(ethylene terephthalate) blend