How Dipolar Side-Chains Influence Polymer Dynamics and the Glass Transition in Amorphous Copolymers

The influence of chemical functionalization on polymer dynamics was investigated in a series of P(THF-ran-ECH)-based copolymers containing side groups with different dipolar characters (–H, –CF3, –CN, and –NO2). Broadband dielectric spectroscopy (BDS), differential scanning calorimetry (DSC), time-of-flight (ToF), and neutron spin echo (NSE) spectroscopy were combined to probe molecular motions over a broad range of length- and timescales. Functionalization systematically modifies the dynamic response of the copolymers, leading to pronounced changes in cooperative segmental dynamics while preserving most localized motions. The α-relaxation progressively shifts toward slower timescales as more polar side groups are introduced, accompanied by higher glass transition temperatures and slower cooperative dynamics. Neutron scattering measurements reveal a clear separation between fast localized motions detected by ToF spectroscopy and slower collective segmental dynamics captured by NSE. The combined relaxation map obtained from dielectric and neutron techniques establishes direct correlations between the different dynamical regimes and demonstrates how chemical functionalization influences polymer mobility across multiple length- and timescales. These results provide insight into the relationship between chemical structure and polymer dynamics and offer design guidelines for functional polymers requiring controlled relaxation behavior.