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

Review: Raw Natural Fiber–Based Polymer Composites

Modification of epoxy resins with functional silanes, polysiloxanes, silsesquioxanes, silica and silicates

Polymer/polyhedral oligomeric silsesquioxane (POSS) nanocomposites: An overview of fire retardance

POSS are nano-sized stable 3-dimensional architectures which consist of alternate Si–O bonds to form cage structures with Si atoms as vertices. The mono- or multi-functional POSS could be prepared through modification of their reactive organic functional groups attached in the vertex positions. Depending on the structure and reactivity of those vertex groups, POSS are allowed to be introduced into virtually any existing polymer systems. This review paper summarizes the recent development on the preparation and properties of POSS-containing polymers. In addition, this review paper also gives an overview of the recent development in the area of a wide range of POSS-based composite systems for a variety of applications including fluorescence sensors, liquid crystals, photoresist materials, low dielectric constant materials, organic semiconductors, energy-related materials, drug and gene delivery systems, coating materials and special rubber materials.

Polyhedral oligomeric silsesquioxane-based hybrid materials and their applications

Polyhedral oligomeric silsesquioxane (POSS) viz; namely, Octa functional silsesquioxanes [octa amino (OAPS) and octa glycidyl (OG)] reinforced epoxy modified cyanate ester nanocomposites were prepa...

Synthesis and characterization of epoxy modified cyanate ester POSS nanocomposites

Octakis(dimethylsiloxypropylglycidylether)silsesquioxane (OG-POSS) was used as a reinforcing agent to prepare polybenzoxazine nanocomposites. Benzoxazine was synthesized using 1,1-bis(3-methyl-4-hydroxyphenyl)cyclohexane, paraformaldehyde and two distinctive aromatic diamines, namely 4,4′-diaminodiphenylmethane (DDM) and 4,4′-diaminodiphenylether (DDE) through Mannich condensation. Polybenzoxazine-POSS hybrid nanocomposites were prepared by ring opening polymerization via thermal curing using benzoxazine precursors and OG-POSS (up to 10 wt %). Thermogravimetric analysis indicate that the nanocomposites display improved thermal stability. Morphological characteristic was studied by scanning electron microscopy. The dispersion of POSS in polybenzoxazine and nanostructure of the composites were confirmed by confocal optical microscopy (COM), transmission electron microscopy (TEM) and atomic force microscopic (AFM) analysis.

Octakis(dimethylsiloxypropylglycidylether)silsesquioxane (OG-POSS) reinforced 1,1-bis(3-methyl-4-hydroxymethyl)cyclohexane based polybenzoxazine nanocomposites

In the present investigation, C4-ether-linked bismaleimide-toughened epoxy-reinforced alumina nanocomposites were formulated. The silane-functionalized nanoparticles are covalently connected to the matrix through the reaction between epoxide groups during curing, and as a consequence, the interfacial interaction between the alumina nanoparticle and matrix was enhanced. The Tg increased with the addition of alumina nanoparticles up to 5 wt% beyond which the Tg decreased due to phase segregation. The nanoindentation studies revealed that the hardness and the elastic modulus of the nanocomposites had increased with the filler concentration up to 5 wt% beyond which it showed a decreasing trend. The wear performance of the hybrid nanocomposite was significantly lower than those of the epoxy nanocomposite. The nanocomposites with 5 wt% Al2O3 showed greatest improvement in wear resistance compared to higher alumina concentration, and the key factor riding the wear resistance is due to positive rolling effect phenomenon.

Effect of Nanoalumina on the Tribology Performance of C4-Ether-Linked Bismaleimide-Toughened Epoxy Nanocomposites

Polyhedral oligomeric silsesquioxane (POSS)–siloxane-modified polyimide (PI) hybrid nanocomposites were prepared by the reaction of siloxane-modified polyamic acid (PAA) with octaaminophenylsilsesquioxane (OAPS). PAA was prepared by the reaction of 4,4-diaminodiphenylsulfone with pyromellitic dianhydride in N-methylpyrrolidone (NMP), followed by the reaction of PAA with bis(3-aminopropyl) polydimethylsiloxane to obtain siloxane-modified. The siloxane-modified PI was further blended with varying weight percentages of OAPS using NMP solution. The reactions occurred during the formation of hybrid nanocomposites were confirmed by Fourier transform infrared spectra. The siloxane-modified PI OAPS nanocomposites were characterized for their thermal properties using differential scanning calorimeter and by thermogravimetric analysis. Morphological studies of the nanocomposites indicate that the incorporation of siloxane moieties creates heterogeneous morphology. Data from thermal studies indicate that the incorpo...

Synthesis and characterization of polyhedral oligomeric silsesquioxane–siloxane-modified polyimide hybrid nanocomposites

1,1-bis (3-methyl-4-epoxyphenyl) cyclohexane (BMEPC) was synthesized from 1,1-bis (3-methyl-4-hydroxyphenyl) cyclohexane and 2-(chloromethyl) oxirane, and its structure was confirmed by Fourier transform infrared (FT-IR), 1H-, 13C-NMR and electron impact-mass spectrometry. Both diglycidyl ether of bisphenol-A (DGEBA) and tetraglycidyl diamine diphenyl methane (TGDDM) epoxy resins were toughened with BMEPC using 4,4′-diaminodiphenylmethane (DDM) as a curing agent. Epoxy and BMEPC-toughened epoxy systems were further modified with organophilic MMT (OMMT) clay. The chemical reactions involved between epoxy and DDM with OMMT was confirmed by FT-IR. OMMT clay-filled hybrid BMEPC-epoxy resin castings were characterized for their mechanical, thermal, thermo-mechanical and morphological properties. The values of Tg and heat distortion temperature of hybrid epoxy decreased with increasing incorporation of OMMT. The data obtained from thermal studies indicated that the incorporation of nano clay into BMEPC-modified...

A. Chandramohan

Papers

Synthesis and characterization of epoxy modified cyanate ester POSS nanocomposites

Octakis(dimethylsiloxypropylglycidylether)silsesquioxane (OG-POSS) reinforced 1,1-bis(3-methyl-4-hydroxymethyl)cyclohexane based polybenzoxazine nanocomposites

Effect of Nanoalumina on the Tribology Performance of C4-Ether-Linked Bismaleimide-Toughened Epoxy Nanocomposites

Synthesis and characterization of polyhedral oligomeric silsesquioxane–siloxane-modified polyimide hybrid nanocomposites

Synthesis and characterization of 1, 1-bis (3-methyl-4-epoxyphenyl) cyclohexane-toughened DGEBA and TGDDM organo clay hybrid nanocomposites