Polymer wrapped single-walled carbon nanotubes (SWNTs) have been demonstrated to be a very effi cient technique to obtain high purity semiconducting SWNT solutions. However, the extraction yield of this technique is low compared to other techniques. Poly-alkyl-thiophenes have been reported to show higher extraction yield compare to polyfl uorene derivatives. Here, the affi nity for semiconducting SWNTs of two polymers with a backbone containing didodecylthiophene units interspersed with N atoms is reported. It is demonstrated that one of the polymers, namely, poly(2,5-dimethylidynenitrilo-3,4-didodecylthienylene) (PAMDD), has very high semiconducting SWNT extraction yield compared to the poly(3,4-didodecylthienylene) azine (PAZDD). The dissimilar wrapping effi ciency of these two polymers for semiconducting SWNTs is attributed to the interplay between the affi nity for the nitrogen atoms of the highly polarizable walls of SWNTs and the mechanical fl exibility of the polymer backbones. Photoluminescence (PL) measurements demonstrate the presence of metallic tubes and SWNT bundles in the sample selected with PAZDD and higher purity of SWNT-PAMDD samples. The high purity of the semiconducting SWNTs selected by PAMDD is further demonstrated by the high performance of the solution-processed fi eld-effect transistors (FETs) fabricated using a blade coating technique, which exhibit hole mobilities up to 33.3 cm(2) V-1 s(-1) with on/off ratios of 10(6).