Effect of Regioregularity on the Semicrystalline Structure of Poly(3-hexylthiophene)

The melting behavior for a series of different regioregularity Poly(3-hexylthiophene-2,5-diyl) (P3HT) polymers was studied and the effect of regioregularity on limiting ultimate crystal lamellar thickness was found. P3HT samples of varying regioregularity but with similar number- and mass-averaged molar masses, polydispersity indices (PDI), and prepared by the same synthetic technique to minimize any other potential effects, were studied. Measurements on an oriented P3HT film of ≮96% regioregularity yields a crystal lamellar thickness of 9.1 nm, which also compares relatively well with the FCT model prediction for thickness 0.96 of 9.9 nm. Control of the crystal lamellar domain sizes through control of the regioregularity to specific levels might enable semiquantitative tailoring of the P3HT crystal domain size.