Evaluation of Mechanical Properties of Polysaccharide Films Prepared from Furcellaria Lumbricalis and Gigartina Skottsbergii Seaweeds by PF-QNM Technique

Films from Furcellaria lumbricalis (FL) and Gigartina skottsbergii (GS) seaweed extracts were prepared and their properties were investigated. According to NMR analysis of GS ultrasonic water (GSUW) extraction (1-3)-α-glycan 6-sulfate was isolated. The analogical treatment with carbonate-peroxide solution (GSUCP) resulted in a mixture of the same glycan and carrageenan hybrids µ-D6S and ν-D2S,6S observed for the first time in this study. The extraction of GS in boiling water under reflux (GSW) in comparison to FL (FLW), indicates that GSW consisted of the most complex mixture of α-, β-, κ-, ι-, θ-, ζ-carrageenans, (1-3)-α-glycan partially sulfated at C6, and µ-D6S and ν-D2S,6S hybrids. The analogical FLW extract contained α-, θ-, λ-, µ-, ν- and ζ-carrageenans and (1-3)-α-glycan partially sulphated at C6. SEC-MALS results indicate that molecular weight of chromatographic main peak (Mp) is decreasing: GSUCP (994 kg/mol) > GSUW (565 kg/mol) > FLW (498 kg/mol) > ι-carrageenan (264 kg/mol) > κ-carrageenan (174 kg/mol) > furcellaran (144 kg/mol) > GSW (78 kg/mol). Macromolecules conformation is varying from flexible random coil for κ-carrageenan to nearly compact spheres for ι-carrageenan. Furcellaran conformation is intermediate between κ-carrageenan and ι-carrageenan, specifically a little more compact than κ-carrageenan. XRD analysis confirmed no cellulose content in all prepared films. AFM and PF-QNM analysis showed relations between values of Rg and Mp and the values of surface roughness, reduced moduli, stiffness and adhesion.