Fabrication of Nanostructured Poly(3-thiophene methyl acetate) within Poly(vinylidene fluoride) Matrix: New Physical and Conducting Properties

Abstract

Nanostructured poly(3-thiophene methyl acetate) (PTMA) within the poly(vinylidene fluoride) (PVDF) matrix is achieved by reactive blending technique under melt-cooled condition. The nanoparticles are almost spherical showing a minimum size with 5% (w/w) PTMA concentration (PTMA5), and they become agglomerated at > or = 25% (w/w) PTMA concentration. Different phase separation mechanisms are used to explain the above variation of nanoparticle size. The lower size nanophase in the PTMA5 blend is attributed to spinodal decomposition, while the larger size nanophases are produced from binodal decomposition. The TGA study indicates increasing thermal stability of PVDF in the nanoblends. DSC study shows increasing melting and crystallization temperature of the nanoblends; the former is due to the attractive forces of PTMA nanostructure, and the latter is for the nucleating effect of nanophase PTMA. The long distance, lamellar distance, and amorphous overlayer distance decrease to different extents. The pi-pi* transition band of UV-vis spectra shows a red shift with increasing PTMA concentration, but the photoluminescence spectra of the nanoblends show a blue shift. The former is attributed to intrachain aggregation of PTMA, while the latter is caused from "static excimer" formation at the ground state. PTMA1 and PTMA3 show approximately 8 times increase in PL intensity except PTMA5 where interconnectivity between the nanodomains makes the nonradiative decay similar to bulk PTMA. The temperature variation of conductivity indicates a conformational transition of PTMA chain with increasing temperature facilitating better charge transport. The I-V characteristic curves are really interesting; the nanoblends show a negative hysterisis, but PTMA5 shows a memory effect attributed to the electrical bistability originated from the interconnected nanophases arising from spinodal decomposition.