Spintronics offers a promising avenue for surpassing the performance and energy efficiency limits of conventional electronic devices. However, existing spintronic materials, including metals and doped conjugated polymers, face intrinsic stability and performance challenges. To address these limitations, we employed computational methods to investigate the electronic structure, spin transport properties, and crystallographic order of a stereoregular radical polymer. Computational simulations in different stereoregularities were utilized to model spin-spin interactions, charge delocalization, and long-range order within the polymer backbone. Crystallographic data analysis provided insights into the molecular packing of the monomer (M1) and the role of stereochemistry in controlling spin alignment. Our findings highlight how stereoselective polymerization enables persistent radicals in each repeat unit to support long-range spin transport without conventional doping. This computationally guided approach underscores the potential of stereoregular radical polymers as a novel platform for next-generation spintronic devices and quantum information processing. The computational results support the hypothesis that molecular-level alterations in polymer stereochemistry are critical for controlling spin-spin interactions and alignment. An additional file containing the crystal data, pre-reported and uploaded to CCDC (Cambridge Crystallographic Data Centre) is attached - composed by Cole C. Sorensen under the supervision of Frank A. Leibfarth. The original works of Data S1 and S2 were composed by Andrew Marquardt under the supervision of Brett M. Savoie.

Three trimers were analyzed using the Conformer-Rotamer Ensemble Sampling Tool (CREST) and GFN2-xTB semi-empirical potential. The trimers corresponded to the heterotactic (m,r), syndiotactic (r,r), and isotactic (m,m) triads that map to the atactic, syndiotactic, and atactic polymerization scenarios. The universal force field (UFF) in the OpenBabel quantum chemistry file conversion package was used to generate an initial optimized geometry from stereochemically-specific SMILES strings for each triad, which was then optimized using xTB before being subjected to conformational sampling via CREST using the most comprehensive default setting. The initial geometries and outputted conformers were analyzed to ensure no incorrect bond rearrangements or intramolecular radical dimerization had occurred. Separation and alignment analysis was performed on all conformations. Each triad has two pairs of nearest neighbors (i.e., the first and second radicals, and the second and third radicals) whose alignment and separation were parsed and reflected in the histograms. Conformer weights within the distributions were calculated via Boltzmann probabilities using the relative energy calculated by CREST for each conformer.

The alignment autocorrelation decay was calculated for each tacticity using the alignment data from the corresponding triads. A virtual polymerization was performed by Boltzmann sampling (i.e., selecting pairs of alignment angles based on the energy of the corresponding triad conformer) the triad statistics 250,000 times, producing a sequence of 500,000 pendant radical alignments. The alignment decay was calculated from these radical sequences using each radical as an independent origin and averaging the alignment dot products with respect to separation along the sequence. This procedure resulted in 499,900 (i.e., 500,000-100) decay curves that were averaged over to yield. The persistence length was reported as the separation after which the alignment fell to e^-1. A Jupyter notebook illustrating these calculations is distributed with this work.