The objective of this work focuses on the study of epoxy network formation as a complex process that shows the relation between chemical reactions and physical processes. These examinations include the epoxy network structures formed and their influence on selected thermal properties. Therefore, structure and functionality variations as well as the molar ratio of the starting materials are important factors in order to understand the complex relations in those crosslinking systems. Noncrosslinkable chemical model compounds were used for adetailed understanding of occuring chemical reaction mechanisms, description of kinetic profiles for the occuring reactions, and analysis of the chemical structures formed in such networks. The use of different methods, e. g. Raman Spectroscopy, torque measurements, solgel analysis, ultrasonic measurements, measurement of shrinkage, DSC, and fluorescence probe technique opened the opportunity to describe the epoxy network formation process as a complex one, which is influenced by both chemical reactions and physical processes. The analysis of the epoxy network structure formed by several methods, i. e. sol gel analysis, FTIR-Spectroscopy in the middle and the NIR region, uniaxiale compression, torsion pendulum analysis, dynamical mechanical analysis, fluorescence probe technology, DSC, thermomechanical analysis, and polarization microscopy, give together a clear picture of the complex structure of such networks and its relation to physical properties, such as glass transition temperature and expansion coefficients. The different epoxy compounds (bisphenolA-diglycidylether, diglycidylaniline, diglycidylether of 4-hydroxyphenyl-4'-hydroxybenzoate,N,N,N',N'-tetraglycidyldiaminodiphenylmethane, and novolac epoxies based on bisphenol-Anovolacs) and comonomers (4,4'-diaminodiphenylmethane in absence of any accelerator or inpresence of imidazole as accelerator, bisphenol-A, 4-hydroxyphenyl-4'-hydroxybenzoate andbisphenol-A-novolacs) used for formation of amorphous networks show differences in the network formation process. Photoinduced cationic crosslinking of the diglycidylether of 4hydroxyphenyl-4'-hydroxybenzoate in its anisotropic phase results in networks with an ordered structure. On the other hand, amorphous networks without any order structure are formed when the crosslinking process occurs in the isotropic phase. The glass transition temperatures possess different numbers for the ordered and the amorphous networks. The ordered structure frozen by network formation is stable even in the high temperature region. Variation of the monomer structure and combination of different methods for investigation of network formation processes and network structure results in structure property relations of the synthesized epoxy networks, which are interesting for interdisciplinary cooperation between chemists, physicists, and material science engineers. The results of the theses help to optimize the properties of epoxies for special applications.