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Medronho, Bruno
Publications (6 of 6) Show all publications
Melro, E., Filipe, A., Sousa, D., Valente, A. J. M., Romano, A., Antunes, F. E. & Medronho, B. (2020). Dissolution of kraft lignin in alkaline solutions. International Journal of Biological Macromolecules, 148, 688-695
Open this publication in new window or tab >>Dissolution of kraft lignin in alkaline solutions
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2020 (English)In: International Journal of Biological Macromolecules, ISSN 0141-8130, E-ISSN 1879-0003, Vol. 148, p. 688-695Article in journal (Refereed) Published
Abstract [en]

Lignins are among the most abundant renewable resources on the planet. However, their application is limited by the lack of efficient dissolution and extraction methodologies. In this work, a systematic and quantitative analysis of the dissolution efficiency of different alkaline-based aqueous systems (i.e. lithium hydroxide, LiOH; sodium hydroxide, NaOH; potassium hydroxide, KOH; cuprammonium hydroxide, CuAOH; tetrapropylammonium hydroxide, TPAOH and tetrabutylammonium hydroxide, TBAOH) is reported, for the first time, for kraft lignin. Phase maps were determined for all systems and lignin solubility was found to decrease in the following order: LiOH > NaOH > KOH > CuAOH > TPAOH > TBAOH, thus suggesting that the size of the cation plays an important role on its solubility. The π∗ parameter has an opposite trend to the solubility, supporting the idea that cations of smaller size favor lignin solubility. Dissolution was observed to increase exponentially above pH 9–10 being the LiOH system the most efficient. The soluble and insoluble fractions of lignin in 0.1 M NaOH were collected and analyzed by several techniques. Overall, data suggests a greater amount of simple aromatic compounds, preferentially containing sulfur, in the soluble fraction while the insoluble fraction is very similar to the native kraft lignin.

Keywords
Alkaline solvents, Dissolution, Kraft lignin
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-38354 (URN)10.1016/j.ijbiomac.2020.01.153 (DOI)000522094600069 ()2-s2.0-85078177957 (Scopus ID)
Available from: 2020-02-03 Created: 2020-02-03 Last updated: 2020-04-16Bibliographically approved
Yang, J., Medronho, B., Lindman, B. & Norgren, M. (2020). Simple one pot preparation of chemical hydrogels from cellulose dissolved in cold LiOH/Urea. Polymers, 12(2), Article ID 373.
Open this publication in new window or tab >>Simple one pot preparation of chemical hydrogels from cellulose dissolved in cold LiOH/Urea
2020 (English)In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 12, no 2, article id 373Article in journal (Refereed) Published
Abstract [en]

In this work, non-derivatized cellulose pulp was dissolved in a cold alkali solution (LiOH/urea) and chemically cross-linked with methylenebisacrylamide (MBA) to form a robust hydrogel with superior water absorption properties. Different cellulose concentrations (i.e., 2, 3 and 4 wt%) and MBA/glucose molar ratios (i.e., 0.26, 0.53 and 1.05) were tested. The cellulose hydrogel cured at 60 °C for 30 min, with a MBA/glucose molar ratio of 1.05, exhibited the highest water swelling capacity absorbing ca. 220 g H2O/g dry hydrogel. Moreover, the data suggest that the cross-linking occurs via a basic Michael addition mechanism. This innovative procedure based on the direct dissolution of unmodified cellulose in LiOH/urea followed by MBA cross-linking provides a simple and fast approach to prepare chemically cross-linked non-derivatized high-molecular-weight cellulose hydrogels with superior water uptake capacity. 

Keywords
Cellulose hydrogel, LiOH/urea, Methylenebisacrylamide, Michael addition
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:miun:diva-38703 (URN)10.3390/polym12020373 (DOI)000519849800123 ()2-s2.0-85081242855 (Scopus ID)
Available from: 2020-03-25 Created: 2020-03-25 Last updated: 2020-05-29
From, M., Larsson, P. T., Andreasson, B., Medronho, B., Svanedal, I., Edlund, H. & Norgren, M. (2020). Tuning the properties of regenerated cellulose: Effects of polarity and water solubility of the coagulation medium. Carbohydrate Polymers, 236, Article ID 116068.
Open this publication in new window or tab >>Tuning the properties of regenerated cellulose: Effects of polarity and water solubility of the coagulation medium
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2020 (English)In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 236, article id 116068Article in journal (Refereed) Published
Abstract [en]

In this study, the effect of different alcohols and esters as a coagulation medium in the regeneration of cellulose dissolved in an aqueous LiOH-urea-based solvent was thoroughly investigated using various methods such as solid state NMR, X-ray diffraction, water contact angle, oxygen gas permeability, mechanical testing, and scanning electron microscopy. It was observed that several material properties of the regenerated cellulose films follow trends that correlate to the degree of cellulose II crystallinity, which is determined to be set by the miscibility of the coagulant medium (nonsolvent) and the aqueous alkali cellulose solvent rather than the nonsolvents’ polarity. This article provides an insight, thus creating a possibility to carefully tune and control the cellulose material properties when tailor-made for different applications. 

Keywords
Cellulose, Coagulation medium, Crystallinity, Polarity, Regeneration
National Category
Chemical Sciences
Identifiers
urn:nbn:se:miun:diva-38656 (URN)10.1016/j.carbpol.2020.116068 (DOI)000519306900074 ()2-s2.0-85080088394 (Scopus ID)
Available from: 2020-03-16 Created: 2020-03-16 Last updated: 2020-04-03Bibliographically approved
Magalhães, S., Alves, L., Medronho, B., Fonseca, A. C., Romano, A., Coelho, J. F. & Norgren, M. (2019). Brief overview on bio-based adhesives and sealants. Polymers, 11(10), Article ID 1685.
Open this publication in new window or tab >>Brief overview on bio-based adhesives and sealants
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2019 (English)In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 11, no 10, article id 1685Article in journal (Refereed) Published
Abstract [en]

Adhesives and sealants (AS) are materials with excellent properties, versatility, and simple curing mechanisms, being widely used in different areas ranging from the construction to the medical sectors. Due to the fast-growing demand for petroleum-based products and the consequent negative environmental impact, there is an increasing need to develop novel and more sustainable sources to obtain raw materials (monomers). This reality is particularly relevant for AS industries, which are generally dependent on non-sustainable fossil raw materials. In this respect, biopolymers, such as cellulose, starch, lignin, or proteins, emerge as important alternatives. Nevertheless, substantial improvements and developments are still required in order to simplify the synthetic routes, as well as to improve the biopolymer stability and performance of these new bio-based AS formulations. This environmentally friendly strategy will hopefully lead to the future partial or even total replacement of non-renewable petroleum-based feedstock. In this brief overview, the general features of typical AS are reviewed and critically discussed regarding their drawbacks and advantages. Moreover, the challenges faced by novel and more ecological alternatives, in particular lignocellulose-based solutions, are highlighted. 

Keywords
Adhesion, Adhesives, Cellulose, Lignin, Sealants, Silicone
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-37706 (URN)10.3390/polym11101685 (DOI)000495382700154 ()31618916 (PubMedID)2-s2.0-85074462579 (Scopus ID)
Available from: 2019-11-18 Created: 2019-11-18 Last updated: 2020-01-15Bibliographically approved
Costa, C., Medronho, B., Filipe, A., Mira, I., Lindman, B., Edlund, H. & Norgren, M. (2019). Emulsion formation and stabilization by biomolecules: The leading role of cellulose. Polymers, 11(10), Article ID 1570.
Open this publication in new window or tab >>Emulsion formation and stabilization by biomolecules: The leading role of cellulose
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2019 (English)In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 11, no 10, article id 1570Article in journal (Refereed) Published
Abstract [en]

Emulsion stabilization by native cellulose has been mainly hampered because of its insolubility in water. Chemical modification is normally needed to obtain water-soluble cellulose derivatives. These modified celluloses have been widely used for a range of applications by the food, cosmetic, pharmaceutic, paint and construction industries. In most cases, the modified celluloses are used as rheology modifiers (thickeners) or as emulsifying agents. In the last decade, the structural features of cellulose have been revisited, with particular focus on its structural anisotropy (amphiphilicity) and the molecular interactions leading to its resistance to dissolution. The amphiphilic behavior of native cellulose is evidenced by its capacity to adsorb at the interface between oil and aqueous solvent solutions, thus being capable of stabilizing emulsions. In this overview, the fundamentals of emulsion formation and stabilization by biomolecules are briefly revisited before different aspects around the emerging role of cellulose as emulsion stabilizer are addressed in detail. Particular focus is given to systems stabilized by native cellulose, either molecularly-dissolved or not (Pickering-like effect). 

Keywords
Adsorption, Amphiphilicity, Cellulose, Emulsion stability, Oil-water interface
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-37680 (URN)10.3390/polym11101570 (DOI)000495382700039 ()31561633 (PubMedID)2-s2.0-85073478887 (Scopus ID)
Available from: 2019-11-14 Created: 2019-11-14 Last updated: 2020-01-15Bibliographically approved
Medronho, B., Filipe, A., Napso, S., Khalfin, R. L., Pereira, R. F. P., De Zea Bermudez, V., . . . Cohen, Y. (2019). Silk Fibroin Dissolution in Tetrabutylammonium Hydroxide Aqueous Solution. Biomacromolecules, 20, 4107-4116
Open this publication in new window or tab >>Silk Fibroin Dissolution in Tetrabutylammonium Hydroxide Aqueous Solution
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2019 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 20, p. 4107-4116Article in journal (Refereed) Published
Abstract [en]

Bombyx mori L. silk fibroin (SF) is widely used in different areas due to its ability to form durable and resilient materials with notable mechanical properties. However, in some of these applications the dissolution of SF is required, and this is not often straightforward due to its inability to be dissolved in the majority of common solvents. This work reports a novel approach to dissolve SF using 40 wt % aqueous tetrabutylammonium hydroxide, TBAOH(aq), at mild temperature. A thorough rheological study combined with small-angle X-ray scattering is presented to correlate the SF state in solution with changes in the rheological parameters. The scattering data suggest that the SF conformation in TBAOH(aq) is close to a random coil, possibly having some compact domains linked with flexible random chains. The radius of gyration (Rg) and the molecular weight (Mw) were estimated to be ca. 17.5 nm and 450 kDa, respectively, which are in good agreement with previous works. Nevertheless, a lower Mw value was deduced from rheometry (i.e., 321 kDa) demonstrating a low degree of depolymerization during dissolution in comparison to other harsh processes. The transition from a dilute to a semidilute regime coincides with the estimated critical concentration and is marked by the presence of a shear-thinning behavior in the flow curves, violation of the empirical Cox-Merz rule, and an upward increase in the activation energy. This work paves the way toward the development of advanced high-tech SF-based materials. © 2019 American Chemical Society.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:miun:diva-37682 (URN)10.1021/acs.biomac.9b00946 (DOI)000496343800006 ()31573794 (PubMedID)2-s2.0-85073821543 (Scopus ID)
Available from: 2019-11-15 Created: 2019-11-15 Last updated: 2020-02-21Bibliographically approved
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