Extended Data Fig. 9: Infrared absorbance bands of P(VDF-TrFE) copolymers at around 1,290 cm−1 and 507 cm−1, measured at various temperatures.
From: Ferroelectric polymers exhibiting behaviour reminiscent of a morphotropic phase boundary
a–h, Infrared absorbance curves obtained during heating for copolymers with CVDF = 45 mol% (a, e), CVDF = 49 mol% (b, f), CVDF = 55 mol% (c, g) and CVDF = 65 mol% (d, h). i–p, Corresponding curves obtained during cooling for CVDF = 45 mol% (i, m), CVDF = 49 mol% (j, n), CVDF = 55 mol% (k, o) and CVDF = 65 mol% (l, p). ‘O’, ‘D’ and ‘PD’ represent the ordered, disordered and pseudo-disordered phases (Extended Data Fig. 1), respectively. For CVDF < 49 mol%, the characteristic bands that correspond to both the all-trans and 3/1-helical conformations shrink or expand uniformly upon heating (a, e) or cooling (i, m), implying no phase transition. For CVDF ≥ 49 mol%, two distinct regimes can be clearly resolved (as marked by grey arrows), signifying the presence of the order–disorder phase transition. Thermal hysteresis is negligible for 49 mol% ≤ CVDF ≤ 55 mol% (second-order phase transition), whereas substantial thermal hysteresis is observed for P(VDF-TrFE) with a VDF contant of 65 mol% (first-order phase transition).
