A reactive nanoparticle approach to organic-inorganic hybrid nanocomposites: Preparation and characterization.

摘要

Hybrid nanocomposite films were prepared by compression molding nanoparticles that possess a gelatin-rich shell layer and a titanium or aluminum oxide rich core. The nanoparticles were prepared by a reactive nanoparticle method that yields core-shell nanoparticles with a median diameter of 30 nm to 60 nm depending on the process variables. The metal oxide domains are formed via a sol-gel route using either aluminum or titanium alkoxide precursors. Depending on the process conditions, the compression molded films sometimes retain a core-shell structure, but TEM observations of the films also show metal oxide domains (below 5 nm) that were outside of the well-defined nanoparticles. The metal oxide domains were created using up to 50 wt% of the precursor, yielding up to 12.5 wt% and 14.0 wt% aluminum and titanium oxide respectively. The domains are well dispersed throughout the polymer matrix and possess good interfacial adhesion as demonstrated by substantial increases in Tg (up to 30°C) and Young's modulus (up to 0.45 GPa). Heating the films for 5 days at 50°C and at 200°C showed no changes in the size or distribution of the dispersed phase as observed by TEM. The films created in this fashion are highly flexible and transparent. The transparency, refractive index, and dielectric constant were measured for films containing titanium oxide (0.0-14.0 wt% of the oxide). The percent light transmission (at 800 nm) of these films was 90-95% of that of the polymer matrix, the refractive index (at 1543 nm) ranged from 1.5954 +/- 0.0094 to 1.7042 +/- 0.0009 (compared to 1.5272 +/- 0.0059 for the matrix) and the dielectric constant was 5.4 +/- 0.6 up to 12.0 +/- 0.1 compared to 5.1 +/- 0.3 for the matrix. This dissertation explores the effects of the processing conditions (reaction time, temperature, reactive precursor identity and amount, cure catalyst amount, and film treatment) on the physical properties of compression-molded films.