Structure-property relationships of ferrocene functionalized segmented polyurethane

Abstract

In this report, non-hydrogen bonded, segmented polyurethane (SPU) of ferrocene functionalized polybutadiene diol has been synthesized and studied in depth to understand the role of ferrocene moiety in the structure-property relationship of SPU. Interactions among hard segments of SPU through the ferrocene moiety played a vital role in the separation of hard and soft segments. Ferrocene attached hydroxyl terminated polybutadiene (HTPB) diol was polymerized with isophorone diisocyanate followed by curing at 70 °C to obtain polyurethane (PU). Dynamic mechanical analysis (DMA) and an in-depth small angle X-ray scattering (SAXS) studies revealed the presence of a strong microphase separation between hard and soft segments which resulted in the formation of nano hard segment domain (HSD) in PU and thus yielded SPU. Though spectroscopic studies of SPU could not identify any hydrogen bonding between the PU chains but due to the presence of ferrocene moiety on the adjacent carbon of urethane group, favorable electrostatic interaction between the hard segments has been identified. This interaction was found to be the driving force for the formation of micrometer scale assemblies of nano HSD, as clearly seen in scanning electron microscopy, and the size of nano HSD assembly increases with increasing ferrocene content in the HTPB. This dependency confirming that the presence ferrocene functional moiety is responsible for formation of assembly of nano HSD which in turn enhanced tensile strength and aggregation induced emission intensity of the resulting SPU.