New Insights into Segmental Packing, Chain Dynamics and Thermomechanical Performance of Aliphatic Polyurea Composites: Comparison between Silica Oxides and Titanium (III) Oxides

Polyurea (PU) is intrinsically reinforced by its microphase-separated morphology, giving its excellent mechanical properties. In this study, it is shown how a high-index PU formulation applies easy diffusion of hard segments into the soft phase of the PU matrix and tune its chain mobility. Moreover, the interaction of micro (>100 nm), nano (<100 nm) fillers with the microdomains and their thermomechanical properties are unraveled. Herein, nanosilica oxide (NS) and micro titanium (III) oxide (Ti2O3) are incorporated at low loadings into a solvent-free two-component aliphatic PU via insitu polymerization. While NS achieves an interfacial interaction with urea groups and forms a tight hard segmental packing, the large-sized Ti2O3 assembles the interconnected PU chain network, improving its crystallinity. Strong reinforcement by NS is noticed when tensile strength increased from 26 to 31 MPa and on the maximum thermal degradation temperature by 21 °C increment from the neat PU. In contrast, the soft segmental dynamics are triggered with the presence of Ti2O3 as indicated in the reduction in glass transition temperature and the 288% improvement in the storage modulus. This study provides an insightful perspective in designing robust PU composites, effective for myriad applications including strong and flexible films in circuit boards and photovoltaic (PV) cells.