Dimensional and conformational properties of pullulan tris(alkylcarbamate)s in tetrahydrofuran

Pullulan tris( n -butylcarbamate) (PTBC) and pullulan tris(ethylcarbamate) (PTEC) samples with different weight-average molar masses M w were prepared from pullulan samples with varying chain lengths. Size-exclusion chromatography equipped with multi-angle light scattering detectors (SEC-MALS), small-angle X-ray scattering (SAXS), and viscometry were performed on the samples in tetrahydrofuran (THF) at 25 °C to determine M w , form factor P ( q ), radius of gyration R g , second virial coefficient, and intrinsic viscosity [ η ]. Infrared absorption measurements were also conducted to investigate the intramolecular hydrogen bonding between the C O and NH groups on adjacent monomer units. The obtained P ( q ), R g , and [ η ] data were analyzed using the wormlike chain model with excluded volume effects, primarily to determine the contour length per monomer unit and the Kuhn segment length L K , a measure of chain stiffness. The latter parameter L K values were found to be 10 nm and 8 nm for PTBC and PTEC, respectively. The resulting chain stiffness was significantly lower than that of the corresponding amylose derivatives. Notably, PTBC and PTEC exhibited few intramolecular hydrogen bonding, in contrast to previously investigated amylose derivatives. This characteristic feature suggests that the free polar groups in pullulan derivatives could offer potential applications as macromolecular recognition materials. • Pullulan tris(alkylcarbamate)s (PTACs) behave as semiflexible polymers in THF. • PTACs in THF are more expanded compared to pullulan in aqueous media. • PTACs are more flexible than the corresponding amylose and cellulose derivatives. • PTACs exhibit only a few intramolecular hydrogen bonds in THF.