In-Situ Generation of a Dispersion of POSS Crystalline Platelets in an Epoxy Matrix Induced by Polymerization

Abstract

The dispersion of intercalated/exfoliated clays in polymers imparts some desired properties to the neat matrix, such as a decrease in permeability due to geometrical effects and an increase in the fire resistance due to the inorganic character of the clay. However, processing is difficult mainly due to the high viscosities of the starting dispersions. In this article we explored the possibility of producing a dispersion of crystalline platelets in situ during polymerization, starting from homogeneous solutions. For this purpose, we replaced the clays with polyhedral oligomeric silsesquioxanes (POSS) because they can be dissolved in adequate polymer precursors and can be phase-separated in the course of polymerization. The aim was to find conditions where a crystal-liquid (C-L) phase separation could take place instead of a conventional L-L phase separation. The in-situ generation of POSS crystalline platelets can impart similar characteristics to those observed in clay-modified polymers (except for the nanoscopic size of thickness), with the advantage of a much easier processing. The selected formulation was based on glycidyloxypropyl-heptaisobutyl POSS dissolved in a stoichiometric mixture of diglycidyl ether of bisphenol A (DGEBA) and 4,4 0 -methylenebis(2,6diethylaniline) (MDEA). In a specific range of POSS concentrations and polymerization temperatures, a C-L phase separation was observed generating POSS crystalline platelets with sizes in the range of the micrometers. Following this primary phase separation, a dispersion of POSS-rich droplets was produced when the residual liquid phase entered the L-L immiscibility region. The final material exhibited a dual dispersion of POSS platelets and spherical POSS-rich domains uniformly dispersed in the matrix. A thermodynamic model enabled to provide an explanation of the experimental observations.

Mechanism of Particle Formation in Silver/Epoxy Nanocomposites Obtained through a Visible-Light-Assisted in Situ Synthesis

“…The conversion of epoxy groups was followed by measuring the height of the absorption band at 4530 cm −1 with respect to the height of a reference band at 4620 cm −1 . 31 2.3.3. Rheometry.…”

PDMS mixed‐matrix membranes with molecular fillers via reactive incorporation and their application for bio‐butanol recovery from aqueous solution

“…From the AFM phase image, it can be clearly seen the POSS dispersion phase from the PDMS continuous phase. It indicates that the aggregation of POSS molecules into particles [ 32 ] which are phase separated from the PDMS matrix in the POSS/PDMS at high POSS loading (>6 wt.%).…”

Self-assembly of nanoparticles employing polymerization-induced phase separation

“…For example, a POSS cube with 7 isobutyl groups and 1 glycidyloxypropyl group at its corners could be dissolved at high temperatures in epoxy precursors based on stoichiometric amounts of diglycidylether of bisphenol A (DGEBA) and 4,4' methylenebis(2,6-diethylaniline) 6 (MDEA) [3]. The morphologies arising from PIPS will depend on the composition of the blend and the polymerization temperature.…”

“…3). Cooling from the polymerization temperature generates crystallization of POSS inside the spherical domains as revealed from XRD spectra and differential scanning calorimetry (DSC) thermograms [3].…”

“…4). At advanced conversions the system enters the metastable L-L region and spherical domains coexisting with the crystalline platelets are also produced [3].…”