S30 (ESI † ), the melt shear storage modulus of P5d at both temperatures showed an increasing trend over time, which indicated crosslinking and gel formation. 68 Such phenomenon was not observed for P3d and P4d at 160 °C, indicating the stability of both polymers under such processing conditions.
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The storage moduli ( E ′) at glassy plateau (25 °C) of P3a–d showed a decreasing trend as the increased length of alkylene unit (2009, 1969, 1777 and 1752 MPa, respectively), which was consistent with the trend reported for other indole-based polyesters with 1,3-disubstitution pattern. 50,58 The storage moduli ( E ′) at glassy plateau (25 °C) of P3a–d were higher than the corresponding values for the polyesters with 1,3-disubstitution pattern (P4a–d and P5a–d) under identical measurement conditions, but lower than the corresponding values of bottle-grade PET and PET-like copolyester AkestraTM (from Perstorp AB) under the same measurement conditions (∼3000 MPa). 58 3.3.