Poly(glycidyl azide) (PGA) networks were prepared by using Desmodur N-100 pluriisocyanate, isophorone diisocyanate (IPDI)/trimethylol propane (TMP), and hexamethylene diisocyanate (HMDI)/(TMP) reactive systems with various NCO/OH reactive group ratios. Swelling tests of these networks were carried out in tetrahydrofuran (THF) at room temperature. The number average molecular weight ((M) over bar(n)) and polymer solvent interaction parameter (chi(l)) of PGA in THF was determined by vapour pressure osmometry (VPO) to be 0.25 for the PGA-THF system at 45 degrees C. The average molecular weights between junction points (M-c) were calculated by using the Flory-Rehner equation. For the networks prepared by three different reaction systems, a linear change of M-c with sol content was observed. (C) 1997 Elsevier Science Ltd. All rights reserved.