Siloxane- and Imide-modified Epoxy Resin Cured with Siloxane-containing Dianhydride

Mechanism of Morphology Development in HDGEBA/PAMS Hybrid Thermosets: Monte Carlo Simulation and LSCM Study

Reactive combinations of aliphatic epoxy resins and functional polysiloxanes form a class of hybrid thermosetting materials with properties that may come from both the organic and the inorganic phases. The two typically immiscible phases form a suspension whose morphology, composition, and thermal properties vary with curing time. The aim of this research was to elucidate the mechanism by which morphology changed with time and to simulate it through Metropolis-Monte Carlo. The selected system was hydrogenated epoxy (HDGEBA) and a synthetic polyaminosiloxane (PAMS). It was studied by DSC, FTnIR, gel point, viscometry, and in-situ laser scanning confocal microscopy. A mechanism for morphology generation was proposed and simulated, exploring a wide range of values of the "a priori" relevant variables. The essential features were captured by simulations with a reasonable agreement with experimental data. However, the complete process was more complex than the geometrical approach of the simulation. The main deviations that were found and qualitatively explained are: (i) the induction period on the rate of coalescence, and (ii) PAMS-rich domain average size increases faster than predictions.

Low Dielectric Poly(imide siloxane) Films Enabled by a Well-Defined Disiloxane-Linked Alkyl Diamine

This paper presents an efficient pathway to achieve the dielectric constant as low as 2.48 @ 25 °C, 1 MHz for nonporous poly(imide siloxane) films with mechanical and thermal robustness. A symmetric disiloxane-linked alkyl diamine, bis(aminopropyl)tetramethyldisiloxane (BATMS) with a well-defined molecular formula NH2CH2CH2CH2Si(CH3)2OSi(CH3)2CH2CH2CH2NH2, has been used to controllably reduce the dielectric constant of the polymer films by adjusting the loading of BATMS. The thermal stability of all the polymer films remains robust with T 5 and T 10 no less than 458 and 472 °C, respectively, while the glass-transition temperature decreases with increasing incorporation of flexible disiloxane-alkyl segments into a polymer backbone. There exists a consistent regularity between the thermal, optical, and dielectric properties with the loading amount of BATMS in the polymer films, inferring that the disiloxane-alkyl segments are homogeneously distributed in the polymer backbone. Charge-transfer complex inhibition of polymer films by disiloxane segments has been revealed by an enlarged d-spacing in wide-angle X-ray diffraction spectra and a blue shift in film fluorescence emission spectra. The combined low dielectric constant, robust mechanical and thermal stability, and improved hydrophobicity make the series of BATMS-resulting poly(imide siloxane) films promising candidates for sophisticated flexible microelectronic application.

Studies on synthesis and characterization of multi-walled carbon nanotube-reinforced polyimide nanocomposites based on a siloxane-modified anhydride

A novel series of multi-walled carbon nanotube (MWCNT) reinforced siloxane dianhydride based polyimide (PI) nanocomposites were designed and developed using in situ polymerization approach via thermal imidization. The polyamic acid obtained from the reaction of siloxane dianhydride and pyridine diamine/ p-phenylenediamine was then incorporated with varying percentages of MWCNTs, which then undergoes thermal imidization to form MWCNT-PI nanocomposites. The synthesized PIs were then characterized using analytical methods. From thermal analysis, it can be seen that the glass transition temperature increased significantly by incorporating acid functionalized MWCNTs into the PI matrix than that of neat PI. This is due to the constraint effect of MWCNTs as well as the reduction in the movement of polymer chains. It exhibits an increased dielectric constant with the increase in weight percentage of MWCNTs to PI matrix. No aggregation and homogeneous dispersion of MWCNTs throughout the PI matrix have been achieved as evidenced by scanning electron microscopy and transmission electron microscopy. The newly designed PI system is responsible for the significant improvement of dispersion, thus enhancing attractive flame retardancy and dielectric properties.