Macromolecular structure and film properties of enzymatically-engineered high molar mass dextrans
Résumé
New α(1 → 2) or α(1 → 3) branched dextrans with high molar masses and controlled architecture were synthesized using a dextransucrase and branching sucrases. Their molecular structure, solubility, conformation, film-forming ability, as well as their thermal and mechanical properties were determined. These new dextrans present structures with low densities from 9,500 to 14,000 g m−3 in H2O/DMSO medium, their molar mass, size and dispersity increase with increasing branching degree (weight-average molar mass up to 109 g mol−1 and radius of gyration around 500 nm). Dextrans exhibit a glass transition between 40.5 and 63.2 °C for water content varying from 12.2 to 14.1%. The effect of branching is mainly observed on the ability of dextran to crystallize. They have a good film-forming ability with a storage modulus which varies from 2 to 4 GPa within a relative humidity range of 10–50%.