How do soft nanoparticles affect temperature-induced nonlinearity of a UCST copolymer blend?

Temperature-induced nonlinearity of an upper critical solution temperature (UCST) copolymer blend and its nanocomposites containing 5 wt% mono-size soft nanoparticles (SNPs) were investigated. Mechanical and thermal energies contribution into the nonlinearity of UCST copolymer blend was 8.9 × 10³ Jm⁻³ and 2.2 × 10³ Jmol⁻¹, respectively. Addition of SNP did not change the system thermal-based nonlinearity, while altered its mechanical contribution at constant heating and solicitation conditions. It diminished to 0.4 × 10³ Jm⁻³ in the nanocomposite containing nano-size dispersion of aged SNPs. Micron-size agglomeration of the fresh SNPs in the nanocomposite; however, enhanced the required mechanical energy for nonlinearity to 4.1 × 10³ Jm⁻³. Short-time annealing of the nanocomposite with micron-size agglomerates reduced its mechanical energy part to 2.8 × 10³ Jm⁻³, while annealing extension maximized it at 9.3 × 10³ Jm⁻³. Heating rate increase amplified the thermal contribution into the nonlinearity at constant or reduced mechanical contribution. Finally, room-temperature annealing magnified the temperature-induced nonlinearity of the UCST copolymer blend at minimum mechanical contribution.