Self-assembled mesomorphic structure in complexes of branched poly(ethyleneimine) with octadecanoic acid

Self-assembled lamellar mesophases were observed in complexes (PEI(OA) x ) of branched poly(ethyleneimine) (PEI) with octadecanoic acid (OA). The packing mode of alkyl tails between neighboring PEI layers varies from interdigitation (x ≤ 1.02) to end-to-end (x ≥ 1.17). A fractional increase in the trans conformation of alkyl chains for PEI(OA) x with small x causes an increase in the lamellar spacing of alkyl tails. Macrophase separation of excess free OA from complexes occurs when x is larger than 1.64.