Browsing by Subject "Molecular weight"

Now showing 1 - 2 of 2
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    Influence of starch composition and molecular weight on physicochemical properties of biodegradable films
    (MDPI, 2019-06-26) Domene López, Daniel; García Quesada, Juan Carlos; Martín Gullón, Ignacio; García Montalbán, Mercedes; Ingeniería Química
    Thermoplastic starch (TPS) films are considered one of the most promising alternatives for replacing synthetic polymers in the packaging field due to the starch biodegradability, low cost, and abundant availability. However, starch granule composition, expressed in terms of amylose content and phosphate monoesters, and molecular weight of starch clearly affects some film properties. In this contribution, biodegradable TPS films made from potato, corn, wheat, and rice starch were prepared using the casting technique. The effect of the grain structure of each starch on microstructure, transparency, hydration properties, crystallinity, and mechanical properties of the films, was evaluated. Potato starch films were the most transparent and corn starch films the most opaque. All the films had homogeneous internal structures-highly amorphous and with no pores, both of which point to a good starch gelatinization process. The maximum tensile strength (4.48-8.14 MPa), elongation at break (35.41-100.34%), and Young's modulus (116.42-294.98 MPa) of the TPS films were clearly influenced by the amylose content, molecular weight, and crystallinity of the film. In this respect, wheat and corn starch films, are the most resistant and least stretchable, while rice starch films are the most extensible but least resistant. These findings show that all the studied starches can be considered suitable for manufacturing resistant and flexible films with similar properties to those of synthetic low-density polyethylene (LDPE), by a simple and environmentally-friendly process.
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    Size-exclusion chromatography of macromolecules: a brief tutorial overview on fundamentals with computational tools for data analysis and determination of structural information
    (MDPI, 2025-02-22) Henández-Cifre, José Ginés; Collado-González, Mar; Díaz Baños, F. Guillermo; García de la Torre, José; Química Física; Ingeniería Química; Biología Celular e Histología
    Size-exclusion chromatography (SEC) is presently a widely used and very informative technique for the characterization of macromolecules in solution. Beyond the first implementations of SEC—which required cumbersome column calibrations and were mainly intended for the determination of molecular weights—the modern SEC approach involving multiple detectors (md-SEC) is based on solution properties such as intrinsic viscosity and light scattering. Thus, md-SEC enables the direct and more efficient determination of molecular weights, as well as the determination of relationships between property and molecular weight, which can be quite useful in structural studies. Here, we first present a review of the fundamental aspects of the dilute-solution properties of macromolecules—particularly the differential refractive index, intrinsic viscosity, and scattering-related properties—on which the various detectors involved in md-SEC are based. Then, we developed SECtools, a suite of public-domain, open-source computer programs, which allow for the full analysis of md-SEC chromatograms. These analyses range from just the recorded raw signals (mV) of the detectors to a full determination of molecular weight averages and distributions. The use of these programs is illustrated through experimental studies using various samples.