Different Gelation and Self‐Sorting Properties of Two Isomeric Polyamides Owing to the Parallel versus Anti‐Parallel Alignment of Backbone Dipoles

Two isomeric bottlebrush polyamides P‐1 and A‐1 , with the same repeating monomer dipole units aligned along the polymer backbone in pseudo‐parallel and pseudo‐antiparallel fashion, respectively, were synthesized and characterized. Both polymers can form thermoreversible gels with aromatic solvents but P‐1 was found to show inferior gelation strength compared with that of A‐1 . Furthermore, despite their close structural resemblance, a 1:1 mixture of the P‐1 and A‐1 polymers was shown to exhibit self‐sorting in the gel state. Gel formation was found to be a kinetically trapped process through hydrogen bonding, π–π stacking interactions, and side chain interdigitation. The different gelation and self‐sorting properties can be explained by the local dipole–dipole interactions originating from the different modes of backbone dipole alignment. In single gel systems, the antiparallel‐aligned dipoles in A‐1 facilitated a more compact molecular packing owing to the enthalpically more favorable polymer chain association. On the other hand, the parallel‐aligned dipoles in P‐1 gave rise to a less stable head‐to‐head packing, which had difficulties to convert to the more stable head‐to‐tail packing in a kinetically trapped environment. In the mixed gel system, it is the unfavorable hetero‐polymer mismatch dipole–dipole interaction that inhibited the mixing of the A‐1 and P‐1 polymers and led to self‐sorting.