Nano-structured poly(3-hexyl thiophene) grafted on poly(vinylidene fluoride) via poly(glycidyl methacrylate)

Poly(vinylidene fluoride)-g-poly(glycidyl methacrylate)-g-poly(3-hexyl thiophene) (PGHT) co-polymer was synthesized using atom transfer radical polymerization (ATRP) of glycidyl methacrylate (GMA) on a poly(vinylidene fluoride) (PVDF) backbone in ethylene carbonate (EC), followed by the oxidative polymerization of 3-hexyl thiophene (3-HT) from the anchored thiophene unit in nitromethane. The poly(vinylidene fluoride)-g-poly(glycidyl methacrylate (PG) and PGHT graft co-polymers are characterized by H-1 NMR, FTIR and GPC analysis. The PG graft co-polymer exhibits an open spherulitic morphology which further worsens with increasing polymerization time. In PGHT, P3HT exhibits nanosphere morphology of diameter 2.9-5.5 nm that decreases with increased PG polymerization time. The lamellar structure of PVDF deteriorates with the progress of PG polymerization, however, upon further grafting with P3HT the lamellar structure of PVDF reappears. In the PG co-polymers PVDF exists in the a-polymorph but in PGHT, it transforms into the piezoelectric b-polymorph. Both the PG and PGHT graft co-polymers exhibit high thermal stability. The PVDF melting point in the PG co-polymers has decreased by 12-19 degrees. However, in PGHT the PVDF melting point remains the same and the P3HT melting point increases. In PGHT, the pi-pi* transition peak shows a small red shift emitting at 14-18 nm lower wavelength than that of pristine P3HT. The above spectral shift is attributed to the self organized structure of grafted P3HT chains in PGHT forming a nanosphere morphology. The dc conductivity of PGHT is lower than that of P3HT.