Synthesis and Characterization of Shape Memory Polyurethane/Conducting Polymer Blends and Their Nanocomposites

Abstract

Shape-memory polyurethanes (SMPUs) blends and nanocomposites with conducting polymers (CPs) have fascinated noteworthy considerations for both academic and industrial research due to their important and captivating applications. In the present study, four CPs namely polypyrrole (PPy), polyaniline (PAni), polythiophene (PTh) and poly(aniline-co-thiophene) (PAni-co-PTh) were prepared via chemical oxidative polymerization and used to synthesize the blends and nanocomposites with shape-memory polyurethane (SMPU). Polyurethane was prepared by addition polymerization using polyethylene oxide (PEO) and poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) (PPG-b-PEG-b-PPG) as soft segment, while 2,4-toluene diisocyanate (2,4-TDI) as hard segment. Four series of PU/CPs blend and composite films for each conducting polymer with the varying weight % of CP (0.1, 0.3, 0.5 and 1.0%) were fabricated. The structural characterization and morphology of the prepared samples was inspected by Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM), respectively. Mechanical, thermal, electrical and shape memory properties of the SMPU/CPs blends and nanocomposites were also investigated. Improved mechanical performances such as tensile strength and Young’s modulus of PU/CPs blends were observed with higher content of CPs, while nanocomposites showed decreasing trend with CPs owing to globular morphology, outcome of layered adsorption of CPs over multi-walled carbon nanotube (MWCNTs). Thermal stability was found to increase systematically with increasing CPs content in blend and composite films. Differential scanning calorimetric (DSC) scans indicated an increase in glass transition, melting and crystallization temperatures for blend samples with CPs loading (0.1-1.0 wt. %). While for nanocomposites, better DSC parameters were observed with 0.1% CPs content. All prepared samples followed the same trend with different CPs except PTh-based blends and composites which was due to the lack of interaction between PU segments and PTh chains. X-ray diffraction results also complimented the DSC studies. Moreover, the electrical conductivity of PU/CPs blends and nanocomposites was also found to be a function of CPs loadings. However, nanocomposites possessed higher conductivities values compared to their respective blends ascribed to the presence of thermally more stable and electrically conductive modified carbon nanotubes in composites. Remarkable recoverability of thermally triggered shape memory (SM) behavior was achieved for all prepared PU/CPs blends and nanocomposites.