Previous routes to polymers with mono-alkylated bithiophenes have proceeded through polymerization of monoalkyl-2,2'-bithiophene monomers through oxidative or AB-type cross-coupling polymerizations. The resulting polymer regiochemistry affects both the location and orientation of the polymer side-chains. In contrast, AABB-type cross-coupling polymerizations can control the location and in some cases the orientation of the side-chains. To study how this control can impact polymer properties, two poly(monodecyl-2,2'-bithiophene) polymers have been synthesized through Stille AABB-type polycondensations of 2,5-bis(trimethylstannyl) thiophene with different monomers. The alkyl side-chains are located on every other thiophene, but polymer 1 consists of both head-to-tail and head-to-head dyads, whereas polymer 2 is made up of only head-to-head dyads. H-1 NMR, C-13 NMR, and heteronuclear single quantum correlation spectroscopy are used to confirm and contrast the polymer regiochemistries. The physical properties of the two polymers are analyzed using UV-vis spectroscopy, differential scanning calorimetry, and grazing-incidence X-ray diffraction. Polymer 2 is found to display significantly more aggregation in solution than 1, and it displays different thermal properties. The film properties of polymers 1 and 2, however, are very similar, with nearly identical UV-vis profiles and d-spacing values as determined by grazing incidence X-ray diffraction. (C) 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 908-915