This paper investigates what effect network heterogeneity has on the thermal and non-linear mechanical properties of epoxy based asymmetric double network glasses. Asymmetric Double Network epoxies were formulated using miscible stoichiometric blends of amines following a controlled three stage cure schedule. The widely different reactivities of the aromatic and aliphatic amines allows for sequential network formation leading to the development of Double Networks where the two networks are different both in terms of their backbone stiffness and crosslink density. This study involves correlating these complex network architectures with non-linear mechanical properties such as strain hardening modulus (G(R)) and important engineering properties such as fracture toughness, as compared to single network systems with the same glass transition. Initial results demonstrate that Asymmetric Double Network epoxies exhibit better combined high glass transition temperature and high fracture toughness when compared to their single network counterparts. This work further shows that the strain hardening response of amorphous glassy epoxies is not only dependent of the average crosslink density but it is sensitive to the details of the network architecture. (C) 2017 Published by Elsevier Ltd.