An interesting correlation between initial loading and nature of wrapping of regioregular poly(3-hexylthiophene) (rrP3HT) on multiwalled carbon nanotube and their combined effect on dynamic- and thermomechanical properties in ternary system (thermoplastic polyurethane as matrix) is highlighted. Wrapping of rrP3HT on carbon nanotube (CNT) makes the hexyl side chains thermally nonequivalent and composites more stable. Dynamic- and thermomechanical analysis ascertained the miscibility (single Tg = 40 degrees C), large mechanical reinforcement, and improved storage modulus of nanocomposites in the presence of CNT compared to its blends. Two breaks at approximate to 100 and approximate to 40 degrees C for TPU-P3HT composites (PHs) and TPU-P3HT-MWCNT composites (PHCs) in the loss modulus vs. temperature plot indicates two different types of transitions in P3HT chains. Dimensional stability by expansion probe technique measures low coefficient of thermal expansion of PHCs compared to its blends. Softening property by penetration probe technique suggests that 2.5 wt % loading of P3HT exhibits lowest degree of penetration compared to other nanocomposites. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013