Supplement Number 1

The supplementary materials present: (i) the evolution of density ρ during heating for unstretched, uniaxially stretched, and biaxially stretched high‑entanglement‑density (HE) systems; (ii) the evolution of internal energy U during heating for unstretched, uniaxially stretched, and biaxially stretched systems with varying entanglement densities; (iii) the evolution of density ρ, internal energy U, and stress σₓ during uniaxial and biaxial stretch-relaxation for systems with different entanglement densities.

(iv) Evolution of the entanglement length Ne during uniaxial and biaxial stretch-relaxation for systems with different entanglement densities, and (v) The evolution of normalized density ρ/ρ0 during post stretch relaxation for each of the four independent runs in systems with different Ne under uniaxial and biaxial stretching. The green dotted line represents ρ/ρ0=1