A novel processing technique was introduced through which pre-gelled precursors (aka PRS) at different extents of polymerization were introduced into epoxy crosslinked systems. It was shown that the PRS-modified cure systems are more resistant to fracture than the corresponding control systems, and the toughness is enhanced with increasing the conversion level of the embedded PRS for the isomeric polymer networks. In addition, the T_g values of the isomeric systems shift to the higher temperatures for the PRS-modified samples with elevated PRS conversions. It was also shown that by adding an additional step to the processing of the epoxy systems, toughened isomeric systems with elevated T_gs attained without sacrificing essential mechanical properties such as Young's modulus, strength and failure strain.
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