Organic/Inorganic Imide Nanocomposites from Aminophenylsilsesquioxanes

Abstract

We present here part of an ongoing study on structure-processing-property relationships in cubic silsesquioxane (cube) nanocomposites. Here, we focus on imide nanocomposites prepared from octaaminophenylsilsesquioxane (OAPS) as a model nanobuilding block for rigid, high-temperature hybrid nanocomposite materials. OAPS units are linked NH 2 vertex to NH 2 vertex by reaction with various dianhydrides to form three-dimensional nanocomposites. The architecture of the organic tethers between vertices can be manipulated to optimize processability, rigidity, and thermomechanical properties. Studies were initiated using an extreme tether structure with zero flexibility prepared by solvent casting and then curing mixtures of OAPS with pyromellitic dianhydride (PMDA) at 330 °C. The resulting materials are extremely brittle, making thermomechanical property measurements quite difficult. Tether rigidity, length, and cross-link densities were then modified using reactions of OAPS with oxydiphthalic anhydride (ODPA) and diluting with oxydianiline (ODA) to adjust nanocomposite stiffness. FTIR and DMA of the OAPS/ODPA/ODA nanocomposites suggest that cure temperatures of >500 °C are necessary for optimal imidization. However, increasing the cross-link density alone by increasing OAPS loading without curing at high temperatures also significantly improves thermomechanical stabilities. DMA, TGA, and nanoindentation measurements show that macroscopic relaxation is eliminated completely at OAPS loadings of >60 mol % providing 5% mass loss at temperatures >570 °C and compressive moduli of ≈3.8 GPa.

Synthesis and Characterization of a POSS-Maleimide Precursor for Hybrid Nanocomposites

“…In this context, hybridizing POSS derivatives with industrially valuable polymeric components can lead to new chemical feed stock technology for the development of interphased nanohybrid materials. There is already evidence to support the belief that modification of polymeric materials using derivatives of polyhedral oligomeric silsesquioxane (POSS) is expected to upgrade many of their useful properties namely thermal stability [3], oxidation resistance [4], resistance to atomic oxygen in low earth orbit [5,6] glass transition temperature [7], tensile strength [8], fracture toughness [9], abrasion resistance, dimensional stability, dielectric behaviour, optical properties and weather resistance [10][11][12].…”

Relationship between the dielectric and mechanical properties and the ratio of epoxy resin to hardener of the hybrid thermosetting polymers

“…In these materials the cubes of the cubic siloxane can be connected one another by organic components with known architecture and lengths of the order of 3-5 nm, forming composites with completely defined interfacial component between organic and inorganic phase. [19][20][21][22][23][24][25][26] Dieletric relaxation technique allows to study changes in ionic and dipolar mobilities of a thermoset material when it is subjected to an alternating electric field. [27][28][29][30][31][32][33][34][35][36][37] In dielectric analysis, the capacitance and conductance of a material can be measured as a function of time, temperature, and frequency.…”

Relationships between the curing conditions and some mechanical properties of hybrid thermosetting materials

“…[8][9][10][11][12][13][14][15][16][17][18] Methods of appropriately mixing two or more different materials, such as inorganic and organic, to obtain a new hybrid material with desirable features have been developed. [19][20][21][22][23] Polymerization of the hybrid epoxy resin studied in this work, which is a nanosized epoxy resin, can lead to nanocomposite materials. In these materials the cubes of the cubic siloxane can be connected one another by organic components with known architecture and lengths of the order of 3-5 nm, forming composites with a completely defined interfacial component between the organic and inorganic phase.…”

“…In these materials the cubes of the cubic siloxane can be connected one another by organic components with known architecture and lengths of the order of 3-5 nm, forming composites with a completely defined interfacial component between the organic and inorganic phase. [19][20][21][22][23] This hybrid epoxy resin can be classified as a polyhedral oligomeric silsesquioxane, where the cubic silica cores are "hard particles" rigid with 0.53 nm diameter and a spherical radius of 1-3 nm including the peripheral organic units. [14][15][16][17][18] It is known that different types of epoxy resins and curing conditions confer different characteristic properties.…”