We have developed an advanced rheo-optical method, based on pulse-induced dynamic compression ATR step scan time-resolved-FT-IR spectroscopy. By inserting a massive weight between a film sample and a piezo electric actuator; a clear ring-down compression signal has been successfully detected according to inertial effect obtained from the film sample and massive weight. This rheo-optical method was named as Pulse-induced Dynamic Compression (PDC) method. PDC method detects nonlinear dynamic reorientational responses of electric dipole transition moments of given functional groups. In the present study, we have additionally equipped PDC with a heating apparatus on top of the massive weight to analyze nonlinear molecular dynamics of uncrystalized polyester under different temperature conditions. By monitoring the polyester's CO stretching (1718 cm−1), and ester CCO vibrational regions (1307−1225 cm−1), two types of dynamic responses were found under different temperatures: complex reversible positive responses, and relatively simple reversible negative dynamic responses. Difference between the CO and CCO functional groups is also found, suggesting that they exist in inhomogeneous surrounding environments. Further detailed study has been performed by using a DFT spectral simulation and 2D-IR analysis.