Figure 4.

(A) Frequency sweep master curve shifted at T₀ = 20 °C of HDI_C8DA. (B) Effect of brush length on the critical angular frequency (ω_cr) corresponding to the minimum of tanδ in the apparent plateau region (star markers). Effect of brush length on the molecular weight between entanglements (M_e) calculated by rubber elasticity theory (triangle markers). As the effect of enhanced tube dilution ω_cr shifts to higher frequencies increasing the brush length, M_e is unchanged since the distance among urethane linkages is unvaried for all the polymers analyzed. For brush length higher than 8, the time–temperature superposition (TTS) principle was not applicable. In the absence of brushes (HDI_BDO), TTS was not applicable. In both cases, the dependence of the shift factor on temperature severely deviated from the WLF law. Dashed lines point out the theoretical molecular weight between contiguous urethane units (dashed purple line) and the theoretical main-chain molecular weight corresponding to the occurrence of main-chain entanglements (dashed blue line).