A diglycidyl ether resin and an amine hardener, both based on polyethylene glycol (PEG) were synthesized and utilized for preparing new epoxy thermosetting materials. Two popular monomers, i.e. diglycidyl ether of bisphenol A (DGEBA) and/or isophorone diamine (IPDA) were also utilized. Three transparent and rubber-like films were fabricated through one combinational and two non-combinational manners. In the combinational manner, diglycidyl ether of PEG (DGEPEG) and DGEBA with equal moles were cured with equal moles of amine-functionalized PEG (APEG) and IPDA. In the non-combinational manners, at one time, the PEG-based resin was cured with IPDA hardener, and at the other time, DGEBA resin was cured with PEG-based amine hardener. Stoichiometric amounts of epoxy resin and amine hardener were used in all of the curing processes. Three epoxy/silica nanocomposites with silica-loading of 5.0 wt%, and with the same epoxy matrices were also synthesized similarly. Silica nanoparticles were organically modified and amine-functionalized prior to use. The neat epoxy networks and their silica-loaded nanocomposites were characterized by FT-IR, and FE-SEM techniques. The structure and composition of the six networks obtained significantly affect their thermal, mechanical, and thermo-mechanical behaviors. These influencing factors were fully investigated by thermogravimetric analysis, tensile testing, and dynamic mechanical analysis.