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19 pages, 4525 KiB

Open AccessArticle

Effects of Phenolics on the Physicochemical and Structural Properties of Collagen Hydrogel

by Sadia Munir, Wei Yue, Jinling Li, Xiaoyue Yu, Tianhao Ying, Ru Liu, Juan You, Shanbai Xiong and Yang Hu

Polymers 2023, 15(24), 4647; https://doi.org/10.3390/polym15244647 - 08 Dec 2023

Cited by 1 | Viewed by 979

Abstract

In the current era, the treatment of collagen hydrogels with natural phenolics for the improvement in physicochemical properties has been the subject of considerable attention. The present research aimed to fabricate collagen hydrogels cross-linked with gallic acid (GA) and ellagic acid (EA) at [...] Read more.

In the current era, the treatment of collagen hydrogels with natural phenolics for the improvement in physicochemical properties has been the subject of considerable attention. The present research aimed to fabricate collagen hydrogels cross-linked with gallic acid (GA) and ellagic acid (EA) at different concentrations depending on the collagen dry weight. The structural, enzymatic, thermal, morphological, and physical properties of the native collagen hydrogels were compared with those of the GA/EA cross-linked hydrogels. XRD and FTIR spectroscopic analyses confirmed the structural stability and reliability of the collagen after treatment with either GA or EA. The cross-linking also significantly contributed to the improvement in the storage modulus, of 435 Pa for 100% GA cross-linked hydrogels. The thermal stability was improved, as the highest residual weight of 43.8% was obtained for the hydrogels cross-linked with 50% GA in comparison with all the other hydrogels. The hydrogels immersed in 30%, 50%, and 100% concentrations of GA also showed improved swelling behavior and porosity, and the highest resistance to type 1 collagenase (76.56%), was obtained for 50% GA cross-linked collagen hydrogels. Moreover, GA 100% and EA 100% obtained the highest denaturation temperatures (Td) of 74.96 °C and 75.78 °C, respectively. In addition, SEM analysis was also carried out to check the surface morphology of the pristine collagen hydrogels and the cross-linked collagen hydrogels. The result showed that the hydrogels cross-linked with GA/EA were denser and more compact. However, the improved physicochemical properties were probably due to the formation of hydrogen bonds between the phenolic hydroxyl groups of GA and EA and the nitrogen atoms of the collagen backbone. The presence of inter- and intramolecular cross-links between collagen and GA or EA components and an increased density of intermolecular bonds suggest potential hydrogen bonding or hydrophobic interactions. Overall, the present study paves the way for further investigations in the field by providing valuable insights into the GA/EA interaction with collagen molecules. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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12 pages, 1058 KiB

Open AccessArticle

Construction and Characterization of Fitting Equations for a New Wheat Straw Pulping Method

by Xiaoli Liang, Shan Wei, Yanpeng Xu, Liang Yin, Ruiming Wang, Piwu Li and Kaiquan Liu

Polymers 2023, 15(24), 4637; https://doi.org/10.3390/polym15244637 - 07 Dec 2023

Cited by 1 | Viewed by 594

Abstract

The pretreatment of pulp with enzymes has been extensively studied in the laboratory. However, due to cost constraints, the application of enzymes in the pulp and paper industry is very limited. In this paper, an environment-friendly and efficient pulping method is proposed as [...] Read more.

The pretreatment of pulp with enzymes has been extensively studied in the laboratory. However, due to cost constraints, the application of enzymes in the pulp and paper industry is very limited. In this paper, an environment-friendly and efficient pulping method is proposed as an alternative to traditional pulping and papermaking methods. This new method overcomes the low efficiency and extreme pollution problems associated with traditional pulping methods. In addition, fitting equations for the new pulping method are constructed using data on enzyme treatments, which reflect the effect of enzymes and enable the realization of real-time control of the pulping process. The experimental results show that the efficiency of the pulping and papermaking process can be improved using biological enzymes, and the separation of cellulose can be facilitated using mixed enzymes, which have a better effect than single enzymes. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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12 pages, 2669 KiB

Open AccessArticle

Influence of Enzymatically Hydrophobized Hemp Protein on Morphology and Mechanical Properties of Bio-Based Polyurethane and Epoxy Foams

by Guillem Ferreres, Sílvia Pérez-Rafael, Angela Gala Morena, Tzanko Tzanov and Liudmyla Gryshchuk

Polymers 2023, 15(17), 3608; https://doi.org/10.3390/polym15173608 - 31 Aug 2023

Viewed by 995

Abstract

Biomass fillers offer the possibility to modify the mechanical properties of foams, increasing their cost-effectiveness and reducing their carbon footprint. In this study, bio-based PU (soft, open cells for the automotive sector) and epoxy (EP, hard, closed cells for construction applications) composite foams [...] Read more.

Biomass fillers offer the possibility to modify the mechanical properties of foams, increasing their cost-effectiveness and reducing their carbon footprint. In this study, bio-based PU (soft, open cells for the automotive sector) and epoxy (EP, hard, closed cells for construction applications) composite foams were prepared by adding pristine and laccase-mediated lauryl gallate-hydrophobized hemp protein particles as filler (HP and HHP, respectively). The fillers were able to modify the density, the mechanical properties and the morphology of the PU and EP foams. The addition of HP filler increases the density of PU foams up to 100% and significantly increases the σ values by 40% and Emod values. On the other hand, the inclusion of the HHP as filler in PU foams mostly results in reduced density, by almost 30%, and reduced σ values in comparison with reference and HP-filled foams. Independently from filler concentration and type, the biomass increased the Emod values for all foams relative to the reference. In the case of the EP foams, the tests were only conducted for the foams filled with HHP due to the poor compatibility of HP with the EP matrix. HHP decreased the density, compressive strength and Emod values of the composites. For both foams, the fillers increased the size of the cells, while reducing the amount of open cells of PU foams and the amount of closed cells for EP foams. Finally, both types of foams filled with HHP reduced the moisture uptake by 80 and 45%, respectively, indicating the successful hydrophobization of the composites. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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15 pages, 2358 KiB

Open AccessArticle

Synthesis and Characterisation of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)-b-poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Multi-Block Copolymers Produced Using Diisocyanate Chemistry

by Jingjing Mai, Steven Pratt, Bronwyn Laycock and Clement Matthew Chan

Polymers 2023, 15(15), 3257; https://doi.org/10.3390/polym15153257 - 31 Jul 2023

Cited by 2 | Viewed by 964

Abstract

Bacterially derived polyhydroxyalkanoates (PHAs) are attractive alternatives to commodity petroleum-derived plastics. The most common forms of the short chain length (scl-) PHAs, including poly(3-hydroxybutyrate) (P3HB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), are currently limited in application because they are relatively stiff and brittle. The [...] Read more.

Bacterially derived polyhydroxyalkanoates (PHAs) are attractive alternatives to commodity petroleum-derived plastics. The most common forms of the short chain length (scl-) PHAs, including poly(3-hydroxybutyrate) (P3HB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), are currently limited in application because they are relatively stiff and brittle. The synthesis of PHA-b-PHA block copolymers could enhance the physical properties of PHAs. Therefore, this work explores the synthesis of PHBV-b-PHBV using relatively high molecular weight hydroxy-functionalised PHBV starting materials, coupled using facile diisocyanate chemistry, delivering industrially relevant high-molecular-weight block copolymeric products. A two-step synthesis approach was compared with a one-step approach, both of which resulted in successful block copolymer production. However, the two-step synthesis was shown to be less effective in building molecular weight. Both synthetic approaches were affected by additional isocyanate reactions resulting in the formation of by-products such as allophanate and likely biuret groups, which delivered partial cross-linking and higher molecular weights in the resulting multi-block products, identified for the first time as likely and significant by-products in such reactions, affecting the product performance. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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19 pages, 5705 KiB

Open AccessArticle

In Situ Tensile Testing under High-Speed Optical Recording to Determine Hierarchical Damage Kinetics in Polymer Layers of Flax Fibre Elements

by Emmanuelle Richely, Johnny Beaugrand, Michel Coret, Christophe Binetruy, Pierre Ouagne, Alain Bourmaud and Sofiane Guessasma

Polymers 2023, 15(13), 2794; https://doi.org/10.3390/polym15132794 - 23 Jun 2023

Cited by 1 | Viewed by 1082

Abstract

This study aims at better understanding the damage and fracture kinetics in flax fibre elements at both the unitary and bundle scales, using an experimental setup allowing optical observation at high recording rate in the course of tensile loading. Defects and issues from [...] Read more.

This study aims at better understanding the damage and fracture kinetics in flax fibre elements at both the unitary and bundle scales, using an experimental setup allowing optical observation at high recording rate in the course of tensile loading. Defects and issues from flax unitary fibre extraction are quantitated using polarized light microscopy. Tensile loading is conducted according to a particular setup, adapted to fibres of 10 to 20 µm in diameter and 10 mm in length. Optical recording using a high-speed camera is performed during loading up to the failure at acquisition, with speed ranging from 108,000 to 270,000 frames per second. Crack initiation in polymer layers of fibre elements, propagation as well as damage mechanisms are captured. The results show different failure scenarios depending on the fibre element’s nature. In particular, fractured fibres underline either a fully transverse failure propagation or a combination of transverse and longitudinal cracking with different balances. Image recordings with high time resolution of down to 3.7 μs suggest an unstable system and transverse crack speed higher than 4 m/s and a slower propagation for longitudinal crack deviation. Failure propagation monitoring and fracture mechanism studies in individual natural fibre or bundles, using tensile load with optical observation, showed contrasted behaviour and the importance of the structural scale exanimated. This study can help in tailoring the eco-design of flax-based composites, in terms of toughness and mechanical performances, for both replacement of synthetic fibre materials and innovative composites with advanced properties. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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19 pages, 3651 KiB

Open AccessArticle

Melanin Nanoparticles Obtained from Preformed Recombinant Melanin by Bottom-Up and Top-Down Approaches

by Sergio Alcalá-Alcalá, José Eduardo Casarrubias-Anacleto, Maximiliano Mondragón-Guillén, Carlos Alberto Tavira-Montalvan, Marcos Bonilla-Hernández, Diana Lizbeth Gómez-Galicia, Guillermo Gosset and Angélica Meneses-Acosta

Polymers 2023, 15(10), 2381; https://doi.org/10.3390/polym15102381 - 19 May 2023

Cited by 1 | Viewed by 1779

Abstract

Melanin is an insoluble, amorphous polymer that forms planar sheets that aggregate naturally to create colloidal particles with several biological functions. Based on this, here, a preformed recombinant melanin (PRM) was utilized as the polymeric raw material to generate recombinant melanin nanoparticles (RMNPs). [...] Read more.

Melanin is an insoluble, amorphous polymer that forms planar sheets that aggregate naturally to create colloidal particles with several biological functions. Based on this, here, a preformed recombinant melanin (PRM) was utilized as the polymeric raw material to generate recombinant melanin nanoparticles (RMNPs). These nanoparticles were prepared using bottom-up (nanocrystallization—NC, and double emulsion–solvent evaporation—DE) and top-down (high-pressure homogenization—HP) manufacturing approaches. The particle size, Z-potential, identity, stability, morphology, and solid-state properties were evaluated. RMNP biocompatibility was determined in human embryogenic kidney (HEK293) and human epidermal keratinocyte (HEKn) cell lines. RMNPs prepared by NC reached a particle size of 245.9 ± 31.5 nm and a Z-potential of −20.2 ± 1.56 mV; 253.1 ± 30.6 nm and −39.2 ± 0.56 mV compared to that obtained by DE, as well as RMNPs of 302.2 ± 69.9 nm and −38.6 ± 2.25 mV using HP. Spherical and solid nanostructures in the bottom-up approaches were observed; however, they were an irregular shape with a wide size distribution when the HP method was applied. Infrared (IR) spectra showed no changes in the chemical structure of the melanin after the manufacturing process but did exhibit an amorphous crystal rearrangement according to calorimetric and PXRD analysis. All RMNPs presented long stability in an aqueous suspension and resistance to being sterilized by wet steam and ultraviolet (UV) radiation. Finally, cytotoxicity assays showed that RMNPs are safe up to 100 μg/mL. These findings open new possibilities for obtaining melanin nanoparticles with potential applications in drug delivery, tissue engineering, diagnosis, and sun protection, among others. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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18 pages, 10089 KiB

Open AccessArticle

Wood−Derived Polymers from Olefin−Functionalized Lignin and Ethyl Cellulose via Thiol–Ene Click Chemistry

by Rongrong An, Chengguo Liu, Jun Wang and Puyou Jia

Polymers 2023, 15(8), 1923; https://doi.org/10.3390/polym15081923 - 18 Apr 2023

Viewed by 1190

Abstract

Lignin and cellulose derivatives have vast potential to be applied in polymer materials. The preparation of cellulose and lignin derivatives through esterification modification is an important method to endow cellulose and lignin with good reactivity, processability and functionality. In this study, ethyl cellulose [...] Read more.

Lignin and cellulose derivatives have vast potential to be applied in polymer materials. The preparation of cellulose and lignin derivatives through esterification modification is an important method to endow cellulose and lignin with good reactivity, processability and functionality. In this study, ethyl cellulose and lignin are modified via esterification to prepare olefin−functionalized ethyl cellulose and lignin, which are further used to prepare cellulose and lignin cross−linker polymers via thiol–ene click chemistry. The results show that the olefin group concentration in olefin−functionalized ethyl cellulose and lignin reached 2.8096 mmol/g and 3.7000 mmol/g. The tensile stress at break of the cellulose cross−linked polymers reached 23.59 MPa. The gradual enhancement in mechanical properties is positively correlated with the olefin group concentration. The existence of ester groups in the cross−linked polymers and degradation products makes them more thermally stable. In addition, the microstructure and pyrolysis gas composition are also investigated in this paper. This research is of vast significance to the chemical modification and practical application of lignin and cellulose. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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16 pages, 2408 KiB

Open AccessEditor’s ChoiceArticle

Processing, Characterization and Disintegration Properties of Biopolymers Based on Mater-Bi^® and Ellagic Acid/Chitosan Coating

by Carolina Villegas, Sara Martínez, Alejandra Torres, Adrián Rojas, Rocío Araya, Abel Guarda and María José Galotto

Polymers 2023, 15(6), 1548; https://doi.org/10.3390/polym15061548 - 21 Mar 2023

Cited by 3 | Viewed by 2015

Abstract

Among the most promising synthetic biopolymers to replace conventional plastics in numerous applications is MaterBi^® (MB), a commercial biodegradable polymer based on modified starch and synthetic polymers. Actually, MB has important commercial applications as it shows interesting mechanical properties, thermal stability, processability [...] Read more.

Among the most promising synthetic biopolymers to replace conventional plastics in numerous applications is MaterBi^® (MB), a commercial biodegradable polymer based on modified starch and synthetic polymers. Actually, MB has important commercial applications as it shows interesting mechanical properties, thermal stability, processability and biodegradability. On the other hand, research has also focused on the incorporation of natural, efficient and low-cost active compounds into various materials with the aim of incorporating antimicrobial and/or antioxidant capacities into matrix polymers to extend the shelf life of foods. Among these is ellagic acid (EA), a polyphenolic compound abundant in some fruits, nuts and seeds, but also in agroforestry and industrial residues, which seems to be a promising biomolecule with interesting biological activities, including antioxidant activity, antibacterial activity and UV-barrier properties. The objective of this research is to develop a film based on commercial biopolymer Mater-Bi^® (MB) EF51L, incorporating active coating from chitosan with a natural active compound (EA) at two concentrations (2.5 and 5 wt.%). The formulations obtained complete characterization and were carried out in order to evaluate whether the incorporation of the coating significantly affects thermal, mechanical, structural, water-vapor barrier and disintegration properties. From the results, FTIR analysis yielded identification, through characteristic peaks, that the type of MB used is constituted by three polymers, namely PLA, TPS and PBAT. With respect to the mechanical properties, the values of tensile modulus and tensile strength of the MB-CHI film were between 15 and 23% lower than the values obtained for the MB film. The addition of 2.5 wt.% EA to the CHI layer did not generate changes in the mechanical properties of the system, whereas a 5 wt.% increase in ellagic acid improved the mechanical properties of the CHI film through the addition of natural phenolic compounds at high concentrations. Finally, the disintegration process was mainly affected by the PBAT biopolymer, causing the material to not disintegrate within the times indicated by ISO 20200. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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19 pages, 2743 KiB

Open AccessArticle

Ion-Induced Polysaccharide Gelation: Peculiarities of Alginate Egg-Box Association with Different Divalent Cations

by Anastasiya O. Makarova, Svetlana R. Derkach, Tahar Khair, Mariia A. Kazantseva, Yuriy F. Zuev and Olga S. Zueva

Polymers 2023, 15(5), 1243; https://doi.org/10.3390/polym15051243 - 28 Feb 2023

Cited by 17 | Viewed by 2823

Abstract

Structural aspects of polysaccharide hydrogels based on sodium alginate and divalent cations Ba²⁺, Ca²⁺, Sr²⁺, Cu²⁺, Zn²⁺, Ni²⁺ and Mn²⁺ was studied using data on hydrogel elemental composition and combinatorial analysis [...] Read more.

Structural aspects of polysaccharide hydrogels based on sodium alginate and divalent cations Ba²⁺, Ca²⁺, Sr²⁺, Cu²⁺, Zn²⁺, Ni²⁺ and Mn²⁺ was studied using data on hydrogel elemental composition and combinatorial analysis of the primary structure of alginate chains. It was shown that the elemental composition of hydrogels in the form of freezing dried microspheres gives information on the structure of junction zones in the polysaccharide hydrogel network, the degree of filling of egg-box cells by cations, the type and magnitude of the interaction of cations with alginate chains, the most preferred types of alginate egg-box cells for cation binding and the nature of alginate dimers binding in junction zones. It was ascertained that metal–alginate complexes have more complicated organization than was previously desired. It was revealed that in metal–alginate hydrogels, the number of cations of various metals per C12 block may be less than the limiting theoretical value equal to 1 for completely filled cells. In the case of alkaline earth metals and zinc, this number is equal to 0.3 for calcium, 0.6 for barium and zinc and 0.65–0.7 for strontium. We have determined that in the presence of transition metals copper, nickel and manganese, a structure similar to an egg-box is formed with completely filled cells. It was determined that in nickel–alginate and copper–alginate microspheres, the cross-linking of alginate chains and formation of ordered egg-box structures with completely filled cells are carried out by hydrated metal complexes with complicated composition. It was found that an additional characteristic of complex formation with manganese cations is the partial destruction of alginate chains. It has been established that the existence of unequal binding sites of metal ions with alginate chains can lead to the appearance of ordered secondary structures due to the physical sorption of metal ions and their compounds from the environment. It was shown that hydrogels based on calcium alginate are most promising for absorbent engineering in environmental and other modern technologies. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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20 pages, 3343 KiB

Open AccessEditor’s ChoiceArticle

Enzyme-Catalyzed Polymerization of Kraft Lignin from Eucalyptus globulus: Comparison of Bacterial and Fungal Laccases Efficacy

by Luisa García-Fuentevilla, Gabriela Domínguez, Raquel Martín-Sampedro, Manuel Hernández, María E. Arias, José I. Santos, David Ibarra and María E. Eugenio

Polymers 2023, 15(3), 513; https://doi.org/10.3390/polym15030513 - 18 Jan 2023

Cited by 2 | Viewed by 2207

Abstract

Kraft lignin, a side-stream from the pulp and paper industry, can be modified by laccases for the synthesis of high added-value products. This work aims to study different laccase sources, including a bacterial laccase from Streptomyces ipomoeae (SiLA) and a fungal laccase from [...] Read more.

Kraft lignin, a side-stream from the pulp and paper industry, can be modified by laccases for the synthesis of high added-value products. This work aims to study different laccase sources, including a bacterial laccase from Streptomyces ipomoeae (SiLA) and a fungal laccase from Myceliophthora thermophila (MtL), for kraft lignin polymerization. To study the influence of some variables in these processes, a central composite design (CCD) with two continuous variables (enzyme concentration and reaction time) and three levels for each variable was used. The prediction of the behavior of the output variables (phenolic content and molecular weight of lignins) were modelled by means of response surface methodology (RSM). Moreover, characterization of lignins was performed by Fourier-transform infrared (FTIR) spectroscopy and different nuclear magnetic resonance (NMR) spectroscopy techniques. In addition, antioxidant activity was also analyzed. Results showed that lignin polymerization (referring to polymerization as lower phenolic content and higher molecular weight) occurred by the action of both laccases. The enzyme concentration was the most influential variable in the lignin polymerization reaction within the range studied for SiLA laccase, while the most influential variable for MtL laccase was the reaction time. FTIR and NMR characterization analysis corroborated lignin polymerization results obtained from the RSM. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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16 pages, 4387 KiB

Open AccessArticle

Towards a Circular Economy: Study of the Mechanical, Thermal, and Electrical Properties of Recycled Polypropylene and Their Composite Materials

by Tongsai Jamnongkan, Nitchanan Intraramongkol, Wesarach Samoechip, Pranut Potiyaraj, Rattanaphol Mongkholrattanasit, Porntip Jamnongkan, Piyada Wongwachirakorn, Masataka Sugimoto, Hiroshi Ito and Chih-Feng Huang

Polymers 2022, 14(24), 5482; https://doi.org/10.3390/polym14245482 - 14 Dec 2022

Cited by 11 | Viewed by 3079

Abstract

This research focuses on the mechanical properties of polypropylene (PP) blended with recycled PP (rPP) at various concentrations. The rPP can be added at up to 40 wt% into the PP matrix without significantly affecting the mechanical properties. MFI of blended PP increased [...] Read more.

This research focuses on the mechanical properties of polypropylene (PP) blended with recycled PP (rPP) at various concentrations. The rPP can be added at up to 40 wt% into the PP matrix without significantly affecting the mechanical properties. MFI of blended PP increased with increasing rPP content. Modulus and tensile strength of PP slightly decreased with increased rPP content, while the elongation at break increased to up to 30.68% with a 40 wt% increase in rPP content. This is probably caused by the interfacial adhesion of PP and rPP during the blending process. The electrical conductivity of materials was improved by adding carbon black into the rPP matrices. It has a significant effect on the mechanical and electrical properties of the composites. Stress-strain curves of composites changed from ductile to brittle behaviors. This could be caused by the poor interfacial interaction between rPP and carbon black. FTIR spectra indicate that carbon black did not have any chemical reactions with the PP chains. The obtained composites exhibited good performance in the electrical properties tested. Finally, DSC results showed that rPP and carbon black could act as nucleating agents and thus increase the degree of crystallinity of PP. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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18 pages, 4287 KiB

Open AccessArticle

High-Pressure Depolymerization of Poly(lactic acid) (PLA) and Poly(3-hydroxybutyrate) (PHB) Using Bio-Based Solvents: A Way to Produce Alkyl Esters Which Can Be Modified to Polymerizable Monomers

by Vojtěch Jašek, Jan Fučík, Lucia Ivanová, Dominik Veselý, Silvestr Figalla, Ludmila Mravcova, Petr Sedlacek, Jozef Krajčovič and Radek Přikryl

Polymers 2022, 14(23), 5236; https://doi.org/10.3390/polym14235236 - 01 Dec 2022

Cited by 5 | Viewed by 2134

Abstract

The polyesters poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) used in various applications such as food packaging or 3D printing were depolymerized by biobased aliphatic alcohols—methanol and ethanol with the presence of para-toluenesulphonic acid (p-TSA) as a catalyst at a temperature [...] Read more.

The polyesters poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) used in various applications such as food packaging or 3D printing were depolymerized by biobased aliphatic alcohols—methanol and ethanol with the presence of para-toluenesulphonic acid (p-TSA) as a catalyst at a temperature of 151 °C. It was found that the fastest depolymerization is reached using methanol as anucleophile for the reaction with PLA, resulting in the value of reaction rate constant (k) of 0.0425 min⁻¹ and the yield of methyl lactate of 93.8% after 120 min. On the other hand, the value of constant k for the depolymerization of PHB in the presence of ethanol reached 0.0064 min⁻¹ and the yield of ethyl 3-hydroxybutyrate was of 76.0% after 240 min. A kinetics study of depolymerization was performed via LC–MS analysis of alkyl esters of lactic acid and 3-hydroxybutanoic acid. The structure confirmation of the products was performed via FT-IR, MS, ¹H NMR, and ¹³C NMR. Synthesized alkyl lactates and 3-hydroxybutyrates were modified into polymerizable molecules using methacrylic anhydride as a reactant and potassium 2-ethylhexanoate as a catalyst at a temperature of 80 °C. All alkyl esters were methacrylated for 24 h, guaranteeing the quantitative yield (which in all cases reached values equal to or of more than 98%). The methacrylation rate constants (k′) were calculated to compare the reaction kinetics of each alkyl ester. It was found that lactates reach afaster rate of reaction than 3-hydroxybutyrates. The value of k′ for themethacrylated methyl lactate reached 0.0885 dm³/(mol·min). Opposite to this result, methacrylated ethyl 3-hydroxybutyrate’s constant k′ was 0.0075 dm³/(mol·min). The reaction rate study was conducted by the GC-FID method and the structures were confirmed via FT-IR, MS, ¹H NMR, and ¹³C NMR. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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19 pages, 44063 KiB

Open AccessArticle

Novel Biocatalysts Based on Bromelain Immobilized on Functionalized Chitosans and Research on Their Structural Features

by Marina G. Holyavka, Svetlana S. Goncharova, Andrey V. Sorokin, Maria S. Lavlinskaya, Yulia A. Redko, Dzhigangir A. Faizullin, Diana R. Baidamshina, Yuriy F. Zuev, Maxim S. Kondratyev, Airat R. Kayumov and Valeriy G. Artyukhov

Polymers 2022, 14(23), 5110; https://doi.org/10.3390/polym14235110 - 24 Nov 2022

Cited by 5 | Viewed by 1363

Abstract

Enzyme immobilization on various carriers represents an effective approach to improve their stability, reusability, and even change their catalytic properties. Here, we show the mechanism of interaction of cysteine protease bromelain with the water-soluble derivatives of chitosan—carboxymethylchitosan, N-(2-hydroxypropyl)-3-trimethylammonium chitosan, chitosan sulfate, and [...] Read more.

Enzyme immobilization on various carriers represents an effective approach to improve their stability, reusability, and even change their catalytic properties. Here, we show the mechanism of interaction of cysteine protease bromelain with the water-soluble derivatives of chitosan—carboxymethylchitosan, N-(2-hydroxypropyl)-3-trimethylammonium chitosan, chitosan sulfate, and chitosan acetate—during immobilization and characterize the structural features and catalytic properties of obtained complexes. Chitosan sulfate and carboxymethylchitosan form the highest number of hydrogen bonds with bromelain in comparison with chitosan acetate and N-(2-hydroxypropyl)-3-trimethylammonium chitosan, leading to a higher yield of protein immobilization on chitosan sulfate and carboxymethylchitosan (up to 58 and 65%, respectively). In addition, all derivatives of chitosan studied in this work form hydrogen bonds with His158 located in the active site of bromelain (except N-(2-hydroxypropyl)-3-trimethylammonium chitosan), apparently explaining a significant decrease in the activity of biocatalysts. The N-(2-hydroxypropyl)-3-trimethylammonium chitosan displays only physical interactions with His158, thus possibly modulating the structure of the bromelain active site and leading to the hyperactivation of the enzyme, up to 208% of the total activity and 158% of the specific activity. The FTIR analysis revealed that interaction between N-(2-hydroxypropyl)-3-trimethylammonium chitosan and bromelain did not significantly change the enzyme structure. Perhaps this is due to the slowing down of aggregation and the autolysis processes during the complex formation of bromelain with a carrier, with a minimal modification of enzyme structure and its active site orientation. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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24 pages, 5772 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Bio-Based Electrospun Fibers from Chitosan Schiff Base and Polylactide and Their Cu²⁺ and Fe³⁺ Complexes: Preparation and Antibacterial and Anticancer Activities

by Milena Ignatova, Ina Anastasova, Nevena Manolova, Iliya Rashkov, Nadya Markova, Rositsa Kukeva, Radostina Stoyanova, Ani Georgieva and Reneta Toshkova

Polymers 2022, 14(22), 5002; https://doi.org/10.3390/polym14225002 - 18 Nov 2022

Cited by 6 | Viewed by 1721

Abstract

The Schiff base derivative (Ch-8Q) of chitosan (Ch) and 8-hydroxyquinoline-2-carboxaldehyde (8QCHO) was prepared and fibrous mats were obtained by the electrospinning of Ch-8Q/polylactide (PLA) blend solutions in trifluoroacetic acid (TFA). Complexes of the mats were prepared by immersing them in a solution of [...] Read more.

The Schiff base derivative (Ch-8Q) of chitosan (Ch) and 8-hydroxyquinoline-2-carboxaldehyde (8QCHO) was prepared and fibrous mats were obtained by the electrospinning of Ch-8Q/polylactide (PLA) blend solutions in trifluoroacetic acid (TFA). Complexes of the mats were prepared by immersing them in a solution of CuCl₂ or FeCl₃. Electron paramagnetic resonance (EPR) analysis was performed to examine the complexation of Cu²⁺(Fe³⁺) in the Ch-8Q/PLA mats complexes. The morphology of the novel materials and their surface chemical composition were studied by scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The performed microbiological screening demonstrated that in contrast to the neat PLA mats, the Ch-8Q-containing mats and their complexes were able to kill all S. aureus bacteria within 3 h of contact. These fibrous materials had efficiency in suppressing the adhesion of pathogenic bacteria S. aureus. In addition, Ch-8Q/PLA mats and their complexes exerted good anticancer efficacy in vitro against human cervical HeLa cells and human breast MCF-7 cells. The Ch-8Q-containing fibrous materials had no cytotoxicity against non-cancer BALB/c 3T3 mouse fibroblast cells. These properties render the prepared materials promising as wound dressings as well as for application in local cancer treatment. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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17 pages, 3476 KiB

Open AccessArticle

Cellulose in Secondary Xylem of Cactaceae: Crystalline Composition and Anatomical Distribution

by Agustín Maceda, Marcos Soto-Hernández and Teresa Terrazas

Polymers 2022, 14(22), 4840; https://doi.org/10.3390/polym14224840 - 10 Nov 2022

Cited by 5 | Viewed by 1387

Abstract

Cellulose is the main polymer that gives strength to the cell wall and is located in the primary and secondary cell walls of plants. In Cactaceae, there are no studies on the composition of cellulose. The objective of this work was to analyze [...] Read more.

Cellulose is the main polymer that gives strength to the cell wall and is located in the primary and secondary cell walls of plants. In Cactaceae, there are no studies on the composition of cellulose. The objective of this work was to analyze the crystallinity composition and anatomical distribution of cellulose in Cactaceae vascular tissue. Twenty-five species of Cactaceae were collected, dried, and milled. Cellulose was purified and analyzed with Fourier transform infrared spectroscopy, the crystallinity indexes were calculated, and statistical analyzes were performed. Stem sections were fixed, cut, and stained with safranin O/fast green, for observation with epifluorescence microscopy. The crystalline cellulose ratios had statistical differences between Echinocereus pectinatus and Coryphantha pallida. All cacti species presented a higher proportion of crystalline cellulose. The fluorescence emission of the cellulose was red in color and distributed in the primary wall of non-fibrous species; while in the fibrous species, the distribution was in the pits. The high percentages of crystalline cellulose may be related to its distribution in the non-lignified parenchyma and primary walls of tracheary elements with helical or annular thickenings of non-fibrous species, possibly offering structural rigidity and forming part of the defense system against pathogens. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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13 pages, 5327 KiB

Open AccessArticle

Silk Fibroin-g-Polyaniline Platform for the Design of Biocompatible-Electroactive Substrate

by Elsa Veronica Flores-Vela, Alain Salvador Conejo-Dávila, Claudia Alejandra Hernández-Escobar, Rocio Berenice Dominguez, David Chávez-Flores, Lillian V. Tapia-Lopez, Claudia Piñon-Balderrama, Anayansi Estrada-Monje, María Antonia Luna-Velasco, Velia Carolina Osuna and Erasto Armando Zaragoza-Contreras

Polymers 2022, 14(21), 4653; https://doi.org/10.3390/polym14214653 - 01 Nov 2022

Viewed by 1612

Abstract

The structural modification of biopolymers is a current strategy to develop materials with biomedical applications. Silk fibroin is a natural fiber derived from a protein produced by the silkworm (Bombyx mori) with biocompatible characteristics and excellent mechanical properties. This research reports [...] Read more.

The structural modification of biopolymers is a current strategy to develop materials with biomedical applications. Silk fibroin is a natural fiber derived from a protein produced by the silkworm (Bombyx mori) with biocompatible characteristics and excellent mechanical properties. This research reports the structural modification of silk fibroin by incorporating polyaniline chain grafts through a one-pot process (esterification reaction/oxidative polymerization). The structural characterization was achieved by ¹H-NMR and FT-IR. The morphology was studied by scanning electron microscopy and complemented with thermogravimetric analysis to understand the effect of the thermal stability at each step of the modification. Different fibroin silk (Fib): polyaniline (PAni) mass ratios were evaluated. From this evaluation, it was found that a Fib to PAni ratio of at least 1 to 0.5 is required to produce electroactive polyaniline, as observed by UV-vis and CV. Notably, all the fibroin-g-PAni systems present low cytotoxicity, making them promising systems for developing biocompatible electrochemical sensors. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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22 pages, 4650 KiB

Open AccessArticle

Lignin as a High-Value Bioaditive in 3D-DLP Printable Acrylic Resins and Polyaniline Conductive Composite

by Goretti Arias-Ferreiro, Aurora Lasagabáster-Latorre, Ana Ares-Pernas, Pablo Ligero, Sandra María García-Garabal, María Sonia Dopico-García and María-José Abad

Polymers 2022, 14(19), 4164; https://doi.org/10.3390/polym14194164 - 04 Oct 2022

Cited by 10 | Viewed by 2274

Abstract

With increasing environmental awareness, lignin will play a key role in the transition from the traditional materials industry towards sustainability and Industry 4.0, boosting the development of functional eco-friendly composites for future electronic devices. In this work, a detailed study of the effect [...] Read more.

With increasing environmental awareness, lignin will play a key role in the transition from the traditional materials industry towards sustainability and Industry 4.0, boosting the development of functional eco-friendly composites for future electronic devices. In this work, a detailed study of the effect of unmodified lignin on 3D printed light-curable acrylic composites was performed up to 4 wt.%. Lignin ratios below 3 wt.% could be easily and reproducibly printed on a digital light processing (DLP) printer, maintaining the flexibility and thermal stability of the pristine resin. These low lignin contents lead to 3D printed composites with smoother surfaces, improved hardness (Shore A increase ~5%), and higher wettability (contact angles decrease ~19.5%). Finally, 1 wt.% lignin was added into 3D printed acrylic resins containing 5 wt.% p-toluensulfonic doped polyaniline (pTSA-PANI). The lignin/pTSA-PANI/acrylic composite showed a clear improvement in the dispersion of the conductive filler, reducing the average surface roughness (R_a) by 61% and increasing the electrical conductivity by an order of magnitude (up to 10⁻⁶ S cm⁻¹) compared to lignin free PANI composites. Thus, incorporating organosolv lignin from wood industry wastes as raw material into 3D printed photocurable resins represents a simple, low-cost potential application for the design of novel high-valued, bio-based products. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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26 pages, 2635 KiB

Open AccessReview

The Role of Mucoadhesion and Mucopenetration in the Immune Response Induced by Polymer-Based Mucosal Adjuvants

by Nathaly Vasquez-Martínez, Daniel Guillen, Silvia Andrea Moreno-Mendieta, Sergio Sanchez and Romina Rodríguez-Sanoja

Polymers 2023, 15(7), 1615; https://doi.org/10.3390/polym15071615 - 24 Mar 2023

Cited by 6 | Viewed by 2953

Abstract

Mucus is a viscoelastic gel that acts as a protective barrier for epithelial surfaces. The mucosal vehicles and adjuvants need to pass through the mucus layer to make drugs and vaccine delivery by mucosal routes possible. The mucoadhesion of polymer particle adjuvants significantly [...] Read more.

Mucus is a viscoelastic gel that acts as a protective barrier for epithelial surfaces. The mucosal vehicles and adjuvants need to pass through the mucus layer to make drugs and vaccine delivery by mucosal routes possible. The mucoadhesion of polymer particle adjuvants significantly increases the contact time between vaccine formulations and the mucosa; then, the particles can penetrate the mucus layer and epithelium to reach mucosa-associated lymphoid tissues. This review presents the key findings that have aided in understanding mucoadhesion and mucopenetration while exploring the influence of physicochemical characteristics on mucus–polymer interactions. We describe polymer-based particles designed with mucoadhesive or mucopenetrating properties and discuss the impact of mucoadhesive polymers on local and systemic immune responses after mucosal immunization. In future research, more attention paid to the design and development of mucosal adjuvants could lead to more effective vaccines. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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21 pages, 2653 KiB

Open AccessReview

Chemical Structures, Properties, and Applications of Selected Crude Oil-Based and Bio-Based Polymers

by Piotr Koczoń, Bartłomiej Bartyzel, Anna Iuliano, Dorota Klensporf-Pawlik, Dorota Kowalska, Ewa Majewska, Katarzyna Tarnowska, Bartłomiej Zieniuk and Eliza Gruczyńska-Sękowska

Polymers 2022, 14(24), 5551; https://doi.org/10.3390/polym14245551 - 19 Dec 2022

Cited by 2 | Viewed by 3546

Abstract

The growing perspective of running out of crude oil followed by increasing prices for all crude oil-based materials, e.g., crude oil-based polymers, which have a huge number of practical applications but are usually neither biodegradable nor environmentally friendly, has resulted in searching for [...] Read more.

The growing perspective of running out of crude oil followed by increasing prices for all crude oil-based materials, e.g., crude oil-based polymers, which have a huge number of practical applications but are usually neither biodegradable nor environmentally friendly, has resulted in searching for their substitutes—namely, bio-based polymers. Currently, both these types of polymers are used in practice worldwide. Owing to the advantages and disadvantages occurring among plastics with different origin, in this current review data on selected popular crude oil-based and bio-based polymers has been collected in order to compare their practical applications resulting from their composition, chemical structure, and related physical and chemical properties. The main goal is to compare polymers in pairs, which have the same or similar practical applications, regardless of different origin and composition. It has been proven that many crude oil-based polymers can be effectively replaced by bio-based polymers without significant loss of properties that ensure practical applications. Additionally, biopolymers have higher potential than crude oil-based polymers in many modern applications. It is concluded that the future of polymers will belong to bio-based rather than crude oil-based polymers. Full article

(This article belongs to the Special Issue Development of Bio-Based Materials: Synthesis, Characterization, and Applications II)

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