Nanoporous Poly(3-alkylthiophene) Thin Films Generated from Block Copolymer Templates

We report the synthesis and characterization of a new series of rod−coil block copolymers, regioregular poly(3-alkylthiophene)- b -polylactide (P3AT-PLA), where the alkyl chain in the polythiophene moiety is either 6 or 12 carbons in length. After utilizing a controlled polymerization technique to synthesize end-functionalized P3AT, these polymers were used as macroinitiators for the controlled ring-opening polymerization (ROP) of d, l -lactide. The block copolymers were characterized by 1 H NMR spectroscopy, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), wide-angle X-ray scattering (WAXS), ultraviolet−visible (UV−vis) spectroscopy, and atomic force microscopy (AFM). In thin films of these materials (ca. 35 nm thickness), microphase separated domains are formed while the crystallinity of the P3AT majority phase is maintained. Upon chemical etching of the PLA block, we observed a nanopitted film where the crystallinity of the P3AT phase remains; characteristic pits are on the order of 35 nm in diameter with depths of up to 10 nm. The increase in the exposed surface area of the semiconducting polymer (∼150% that of the planar film) could be useful in a variety of organic electronic applications.