Cationic aliphatic ammonium polyionenes, specifically 12,12- and 6,12-ionenes, were synthesized using step-growth polymerization and aqueous-based size exclusion chromatography (SEC) coupled with multiangle laser light scattering (MALLS) revealed absolute molecular weight information. The chromatographic separation of cationic polyelectrolytes presents many additional challenges compared to SEC of nonassociating, neutral polymers. Therefore, an aqueous-based SEC-MALLS mobile phase composition was identified to separate these notoriously challenging polyelectrolytes in an effort to achieve absolute molecular weight analysis. Various solvent compositions were evaluated for their ability to solvate and reproducibly separate both 6,12- and 12,-12-ionenes. Dynamic light scattering (DLS) verified the absence of aggregation of polyionenes in preferred mobile phase compositions. The optimum solvent composition comprised a ternary mixture of 54/23/23 water/methanol/glacial acetic acid, 0.54 M NaOAc, at a pH of 4.0. Weight-average molecular weights for the synthesized ammonium 12,12-ionenes ranged from 11 000 to 40 000 g/mol, and ammonium 6,12-ionenes had weight-average molecular weights ranging from 19 000 to 49 900 g/mol. Mark−Houwink parameters were also determined for both the 12,12- and 6,12-ionenes in the optimum mobile phase using an online capillary viscometer.

Water-soluble 12,12-ammonium ionenes were prepared via the Menschutkin reaction from 1,12-dibromododecane and 1,12-bis(N,N-dimethylamino)dodecane. A stoichiometric imbalance of monomers controlled the final molecular weights of the polymers. The absolute molecular weights were determined for the first time using an online multiangle laser light scattering (MALLS) detector in aqueous size exclusion chromatography (SEC). Weight-average molecular weights ranged from 4300 to 20 900 g/mol. Relationships between weight-average molecular weight and mechanical properties were established for a series of 12,12-ammonium ionenes using both tensile testing and dynamic mechanical analysis (DMA). Tensile analysis of the higher molecular weight ionenes revealed an average tensile strength of 20 MPa and elongations ranging from 230 to 440%. Dissociation of ionic aggregates was observed at 85−88 °C in DMA experiments, and the glass transition temperatures increased with increasing molecular weight (61−88 °C). X-ray scattering revealed an amorphous polyethylene peak at ≈14 nm−1 and a sharp ionic group correlation peak at 4.38 nm−1. These correlations agreed well with the proposed macromolecular structure.