An attempt was made on the modification of the tetraglycidyl-4,4'-diaminodiphenyl methane/diaminodiphenyl sulfone (TGDDM/DDS) system to improve properties for several industrial applications. Epoxy resins [TGDDM and 1-glycidyloxy-4-methoxy phenol (GMP)] were synthesized in the laboratory. Also, a new cyanate ester and phenoxy polymer were synthesized and characterized by FTIR, H-1-/C-13-NMR, and thermal studies. GMP was added as a diluent and a new cyanate ester (DCDPT) was introduced to reduce the tight crosslinking density. Further, a new phenoxy polymer was added to improve the toughness property. A variety of neat resin casts using different compositions of the blends were made and their physical, chemical, thermal, and mechanical properties were evaluated to study the effect of GMP as a diluent, cyanate ester as a comonomer, and phenoxy polymer as a toughener. (C) 2003 Wiley Periodicals, Inc.