Abstract Thermally induced curing of the precursor to the cross-linked polymer was studied with transmission electron microscopy. The cured polymer was observed to have micro-domain morphology. Analysis of the microscopic images resulted in the statistical size distributions of micro-domains described subsequently using principles of irreversible thermodynamics. The statistical distribution parameters were determined to change with the curing temperature. A correlation of micro-structural and macroscopic parameters (the mean size of micro-domains and the dynamic Young’s modulus), both varying during the precursor curing, was found and explained in terms of the kinetic concept of fracture.