Strain energy density is developed for a network of flexible chains with weak excluded-volume interactions between segments. Constitutive equations (involving three to four material constants) are derived for an incompressible network of self-repellent chains at finite strains. These relations are applied to study the elastic response of thermoplastic elastomers at uniaxial tension. Good agreement is demonstrated between experimental data and results of numerical simulation at uniaxial deformations with elongation ratios up to 1100%. (c) 2006 Elsevier Ltd. All rights reserved.