Editorial

3 pages, 188 KiB

Open AccessEditorial

Special Issue “Natural Polymers and Biopolymers II”

by Sylvain Caillol

Molecules 2021, 26(1), 112; https://doi.org/10.3390/molecules26010112 - 29 Dec 2020

Cited by 17 | Viewed by 3083

BioPolymers could be either natural polymers (polymer naturally occurring in Nature, such as cellulose or starch…), or biobased polymers that are artificially synthesized from natural resources [...] Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

Research

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17 pages, 4855 KiB

Open AccessArticle

Biobased Polymers via Radical Homopolymerization and Copolymerization of a Series of Terpenoid-Derived Conjugated Dienes with exo-Methylene and 6-Membered Ring

by Takenori Nishida, Kotaro Satoh and Masami Kamigaito

Molecules 2020, 25(24), 5890; https://doi.org/10.3390/molecules25245890 - 12 Dec 2020

Cited by 14 | Viewed by 3036

Abstract

A series of exo-methylene 6-membered ring conjugated dienes, which are directly or indirectly obtained from terpenoids, such as β-phellandrene, carvone, piperitone, and verbenone, were radically polymerized. Although their radical homopolymerizations were very slow, radical copolymerizations proceeded well with various common vinyl monomers, [...] Read more.

A series of exo-methylene 6-membered ring conjugated dienes, which are directly or indirectly obtained from terpenoids, such as β-phellandrene, carvone, piperitone, and verbenone, were radically polymerized. Although their radical homopolymerizations were very slow, radical copolymerizations proceeded well with various common vinyl monomers, such as methyl acrylate (MA), acrylonitrile (AN), methyl methacrylate (MMA), and styrene (St), resulting in copolymers with comparable incorporation ratios of bio-based cyclic conjugated monomer units ranging from 40 to 60 mol% at a 1:1 feed ratio. The monomer reactivity ratios when using AN as a comonomer were close to 0, whereas those with St were approximately 0.5 to 1, indicating that these diene monomers can be considered electron-rich monomers. Reversible addition fragmentation chain-transfer (RAFT) copolymerizations with MA, AN, MMA, and St were all successful when using S-cumyl-S’-butyl trithiocarbonate (CBTC) as the RAFT agent resulting in copolymers with controlled molecular weights. The copolymers obtained with AN, MMA, or St showed glass transition temperatures (T_g) similar to those of common vinyl polymers (T_g ~ 100 °C), indicating that biobased cyclic structures were successfully incorporated into commodity polymers without losing good thermal properties. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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16 pages, 3589 KiB

Open AccessArticle

Biosourced All-Acrylic ABA Block Copolymers with Lactic Acid-Based Soft Phase

by Nabil Bensabeh, Ana Jiménez-Alesanco, Ilme Liblikas, Juan C. Ronda, Virginia Cádiz, Marina Galià, Lauri Vares, Olga Abián and Gerard Lligadas

Molecules 2020, 25(23), 5740; https://doi.org/10.3390/molecules25235740 - 05 Dec 2020

Cited by 9 | Viewed by 3249

Abstract

Lactic acid is one of the key biobased chemical building blocks, given its readily availability from sugars through fermentation and facile conversion into a range of important chemical intermediates and polymers. Herein, well-defined rubbery polymers derived from butyl lactate solvent were successfully prepared [...] Read more.

Lactic acid is one of the key biobased chemical building blocks, given its readily availability from sugars through fermentation and facile conversion into a range of important chemical intermediates and polymers. Herein, well-defined rubbery polymers derived from butyl lactate solvent were successfully prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization of the corresponding monomeric acrylic derivative. Good control over molecular weight and molecular weight distribution was achieved in bulk using either monofunctional or bifunctional trithiocarbonate-type chain transfer agents. Subsequently, poly(butyl lactate acrylate), with a relative low T_g (−20 °C), good thermal stability (5% wt. loss at 340 °C) and low toxicity was evaluated as a sustainable middle block in all-acrylic ABA copolymers using isosorbide and vanillin-derived glassy polyacrylates as representative end blocks. Thermal, morphological and mechanical properties of copolymers containing hard segment contents of <20 wt% were evaluated to demonstrate the suitability of rubbery poly(alkyl lactate) building blocks for developing functional sustainable materials. Noteworthy, 180° peel adhesion measurements showed that the synthesized biosourced all-acrylic ABA copolymers possess competitive performance when compared with commercial pressure-sensitive tapes. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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9 pages, 2763 KiB

Open AccessArticle

Silane Coupling Agent Modifies the Mechanical Properties of a Chitosan Microfiber

by Yuki Shirosaki, Toshinobu Okabayashi and Saki Yasutomi

Molecules 2020, 25(22), 5292; https://doi.org/10.3390/molecules25225292 - 13 Nov 2020

Cited by 2 | Viewed by 2312

Abstract

Chitosan microfibers are widely used in medical applications because they have favorable inherent properties. However, their mechanical properties require further improvement. In the present study, a trimethoxysilane aldehyde (TMSA) crosslinking agent was added to chitosan microfibers to improve their tensile strength. The chitosan [...] Read more.

Chitosan microfibers are widely used in medical applications because they have favorable inherent properties. However, their mechanical properties require further improvement. In the present study, a trimethoxysilane aldehyde (TMSA) crosslinking agent was added to chitosan microfibers to improve their tensile strength. The chitosan microfibers were prepared using a coagulation method. The tensile strength of the chitosan microfibers was improved by crosslinking them with TMSA, even when only a small amount was used (less than 1%). TMSA did not change the orientation of the chitosan molecules. Furthermore, aldehyde derived from TMSA did not remain, and siloxane units were formed in the microfibers. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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18 pages, 3432 KiB

Open AccessArticle

Curcumin-Loaded Bacterial Cellulose/Alginate/Gelatin as A Multifunctional Biopolymer Composite Film

by Nadda Chiaoprakobkij, Thapanar Suwanmajo, Neeracha Sanchavanakit and Muenduen Phisalaphong

Molecules 2020, 25(17), 3800; https://doi.org/10.3390/molecules25173800 - 21 Aug 2020

Cited by 47 | Viewed by 5277

Abstract

Multifunctional biopolymer composites comprising mechanically-disintegrated bacterial cellulose, alginate, gelatin and curcumin plasticized with glycerol were successfully fabricated through a simple, facile, cost-effective mechanical blending and casting method. SEM images indicate a well-distributed structure of the composites. The water contact angles existed in the [...] Read more.

Multifunctional biopolymer composites comprising mechanically-disintegrated bacterial cellulose, alginate, gelatin and curcumin plasticized with glycerol were successfully fabricated through a simple, facile, cost-effective mechanical blending and casting method. SEM images indicate a well-distributed structure of the composites. The water contact angles existed in the range of 50–70°. Measured water vapor permeability values were 300–800 g/m²/24 h, which were comparable with those of commercial dressing products. No release of curcumin from the films was observed during the immersion in PBS and artificial saliva, and the fluid uptakes were in the range of 100–700%. Films were stretchable and provided appropriate stiffness and enduring deformation. Hydrated films adhered firmly onto the skin. In vitro mucoadhesion time was found in the range of 0.5–6 h with porcine mucosa as model membrane under artificial saliva medium. The curcumin-loaded films had substantial antibacterial activity against E. coli and S. aureus. The films showed non-cytotoxicity to human keratinocytes and human gingival fibroblasts but exhibited potent anticancer activity in oral cancer cells. Therefore, these curcumin-loaded films showed their potential for use as leave-on skin applications. These versatile films can be further developed to achieve desirable characteristics for local topical patches for wound care, periodontitis and oral cancer treatment. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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17 pages, 4711 KiB

Open AccessArticle

Photoinduced Polymerization of Eugenol-Derived Methacrylates

by Samantha Molina-Gutiérrez, Sara Dalle Vacche, Alessandra Vitale, Vincent Ladmiral, Sylvain Caillol, Roberta Bongiovanni and Patrick Lacroix-Desmazes

Molecules 2020, 25(15), 3444; https://doi.org/10.3390/molecules25153444 - 29 Jul 2020

Cited by 25 | Viewed by 4473

Abstract

Biobased monomers have been used to replace their petroleum counterparts in the synthesis of polymers that are aimed at different applications. However, environmentally friendly polymerization processes are also essential to guarantee greener materials. Thus, photoinduced polymerization, which is low-energy consuming and solvent-free, rises [...] Read more.

Biobased monomers have been used to replace their petroleum counterparts in the synthesis of polymers that are aimed at different applications. However, environmentally friendly polymerization processes are also essential to guarantee greener materials. Thus, photoinduced polymerization, which is low-energy consuming and solvent-free, rises as a suitable option. In this work, eugenol-, isoeugenol-, and dihydroeugenol-derived methacrylates are employed in radical photopolymerization to produce biobased polymers. The polymerization is monitored in the absence and presence of a photoinitiator and under air or protected from air, using Real-Time Fourier Transform Infrared Spectroscopy. The polymerization rate of the methacrylate double bonds was affected by the presence and reactivity of the allyl and propenyl groups in the eugenol- and isoeugenol-derived methacrylates, respectively. These groups are involved in radical addition, degradative chain transfer, and termination reactions, yielding crosslinked polymers. The materials, in the form of films, are characterized by differential scanning calorimetry, thermogravimetric, and contact angle analyses. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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18 pages, 6838 KiB

Open AccessFeature PaperArticle

Adhesion and Stability of Nanocellulose Coatings on Flat Polymer Films and Textiles

by Raha Saremi, Nikolay Borodinov, Amine Mohamed Laradji, Suraj Sharma, Igor Luzinov and Sergiy Minko

Molecules 2020, 25(14), 3238; https://doi.org/10.3390/molecules25143238 - 16 Jul 2020

Cited by 21 | Viewed by 3663

Abstract

Renewable nanocellulose materials received increased attention owing to their small dimensions, high specific surface area, high mechanical characteristics, biocompatibility, and compostability. Nanocellulose coatings are among many interesting applications of these materials to functionalize different by composition and structure surfaces, including plastics, polymer coatings, [...] Read more.

Renewable nanocellulose materials received increased attention owing to their small dimensions, high specific surface area, high mechanical characteristics, biocompatibility, and compostability. Nanocellulose coatings are among many interesting applications of these materials to functionalize different by composition and structure surfaces, including plastics, polymer coatings, and textiles with broader applications from food packaging to smart textiles. Variations in porosity and thickness of nanocellulose coatings are used to adjust a load of functional molecules and particles into the coatings, their permeability, and filtration properties. Mechanical stability of nanocellulose coatings in a wet and dry state are critical characteristics for many applications. In this work, nanofibrillated and nanocrystalline cellulose coatings deposited on the surface of polymer films and textiles made of cellulose, polyester, and nylon are studied using atomic force microscopy, ellipsometry, and T-peel adhesion tests. Methods to improve coatings’ adhesion and stability using physical and chemical cross-linking with added polymers and polycarboxylic acids are analyzed in this study. The paper reports on the effect of the substrate structure and ability of nanocellulose particles to intercalate into the substrate on the coating adhesion. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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22 pages, 6366 KiB

Open AccessArticle

Tuning Lignin Characteristics by Fractionation: A Versatile Approach Based on Solvent Extraction and Membrane-Assisted Ultrafiltration

by Chiara Allegretti, Oussama Boumezgane, Letizia Rossato, Alberto Strini, Julien Troquet, Stefano Turri, Gianmarco Griffini and Paola D’Arrigo

Molecules 2020, 25(12), 2893; https://doi.org/10.3390/molecules25122893 - 23 Jun 2020

Cited by 13 | Viewed by 3245

Abstract

Technical lignins, typically obtained from the biorefining of lignocellulosic raw materials, represent a highly abundant natural aromatic feedstock with high potential in a sustainable economy scenario, especially considering the huge primary production volumes and the inherently renewable nature of this resource. One of [...] Read more.

Technical lignins, typically obtained from the biorefining of lignocellulosic raw materials, represent a highly abundant natural aromatic feedstock with high potential in a sustainable economy scenario, especially considering the huge primary production volumes and the inherently renewable nature of this resource. One of the main drawbacks in their full exploitation is their high variability and heterogeneity in terms of chemical composition and molecular weight distribution. Within this context, the availability of effective and robust fractionation processes represents a key requirement for the effective valorization of lignin. In the present work, a multistep fractionation of two different well known technical lignins obtained from two distinct delignification processes (soda vs. kraft pulping) was described. A comprehensive approach combining solvent extraction in organic or aqueous medium with membrane-assisted ultrafiltration was developed in order to maximize the process versatility. The obtained lignin fractions were thoroughly characterized in terms of their chemical, physical, thermal, and structural properties, highlighting the ability of the proposed approach to deliver consistent and reproducible fractions of well-controlled and predictable characteristics, irrespective of their biomass origin. The results of this study demonstrate the versatility and the reliability of this integrated multistep fractionation method, which can be easily adapted to different solvent media using the same ultrafiltration membrane set up, thereby enhancing the potential applicability of this approach in an industrial scale-up perspective for a large variety of starting raw lignins. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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20 pages, 6003 KiB

Open AccessFeature PaperArticle

Multiscale Structure of Starches Grafted with Hydrophobic Groups: A New Analytical Strategy

by Chloé Volant, Alexandre Gilet, Fatima Beddiaf, Marion Collinet-Fressancourt, Xavier Falourd, Nicolas Descamps, Vincent Wiatz, Hervé Bricout, Sébastien Tilloy, Eric Monflier, Claude Quettier, Ahmed Mazzah and Agnès Rolland-Sabaté

Molecules 2020, 25(12), 2827; https://doi.org/10.3390/molecules25122827 - 18 Jun 2020

Cited by 12 | Viewed by 3250

Abstract

Starch, an abundant and low-cost plant-based glucopolymer, has great potential to replace carbon-based polymers in various materials. In order to optimize its functional properties for bioplastics applications chemical groups need to be introduced on the free hydroxyl groups in a controlled manner, so [...] Read more.

Starch, an abundant and low-cost plant-based glucopolymer, has great potential to replace carbon-based polymers in various materials. In order to optimize its functional properties for bioplastics applications chemical groups need to be introduced on the free hydroxyl groups in a controlled manner, so an understanding of the resulting structure-properties relationships is therefore essential. The purpose of this work was to study the multiscale structure of highly-acetylated (degree of substitution, 0.4 < DS ≤ 3) and etherified starches by using an original combination of experimental strategies and methodologies. The molecular structure and substituents repartition were investigated by developing new sample preparation strategies for specific analysis including Asymmetrical Flow Field Flow Fractionation associated with Multiangle Laser Light Scattering, Nuclear Magnetic Resonance (NMR), Raman and Time of Flight Secondary Ion Mass spectroscopies. Molar mass decrease and specific ways of chain breakage due to modification were pointed out and are correlated to the amylose content. The amorphous structuration was revealed by solid-state NMR. This original broad analytical approach allowed for the first time a large characterization of highly-acetylated starches insoluble in aqueous solvents. This strategy, then applied to characterize etherified starches, opens the way to correlate the structure to the properties of such insoluble starch-based materials. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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27 pages, 2244 KiB

Open AccessArticle

Influence of Drainage on Peat Organic Matter: Implications for Development, Stability, and Transformation

by Lech W. Szajdak, Adam Jezierski, Kazimiera Wegner, Teresa Meysner and Marek Szczepański

Molecules 2020, 25(11), 2587; https://doi.org/10.3390/molecules25112587 - 02 Jun 2020

Cited by 24 | Viewed by 3437

Abstract

The agricultural use of peatlands, the stabilization of the substrate for building or road construction or for increasing the capacity of soil to support heavy machinery for industrial activities (peat and petroleum extraction), harvesting to provide peat for energy, and the growing media [...] Read more.

The agricultural use of peatlands, the stabilization of the substrate for building or road construction or for increasing the capacity of soil to support heavy machinery for industrial activities (peat and petroleum extraction), harvesting to provide peat for energy, and the growing media and initiation of chemical processes must be preceded by drainage. As a consequence of drainage, peat underwent an irreversible conversion into moorsh (secondary transformation of the peat). The object of the study was to investigate comparatively the organic matter composition and molecular structure of humic acids (HAs) in the raised bog, fen, and peat-moorsh soils developed in various compositions of botanical cover, peat-forming species, and oxic and anoxic conditions as a result of the oscillation of ground water during drainage as well as to evaluate the vulnerability of soil organic matter (SOM) to decomposition. Drainage was shown to be the principal factor causing the various chemical compositions and physicochemical properties of HAs. Large and significant differences in chemical composition of peat and the properties of HAs were found to be related to the degree of decomposition. The HAs from drained peatlands were less chemically mature. In contrast, the HAs from fen and raised bog were found to be more mature than that of the corresponding drained peatlands. The above findings showed the distinguishable structure of HAs within the soil profile created by the plant residue biodegradation and formed in both oxic and anoxic conditions. The analytical methods of thermal analysis together with the optical densities and paramagnetic behaviour are suitable and effective tools for studying structure–property relationships characterizing the origin and formation process of HAs in various environmental conditions. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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13 pages, 2851 KiB

Open AccessArticle

Cellulose Nanofibrils Filled Poly(Lactic Acid) Biocomposite Filament for FDM 3D Printing

by Qianqian Wang, Chencheng Ji, Lushan Sun, Jianzhong Sun and Jun Liu

Molecules 2020, 25(10), 2319; https://doi.org/10.3390/molecules25102319 - 15 May 2020

Cited by 59 | Viewed by 4944

Abstract

As direct digital manufacturing, 3D printing (3DP) technology provides new development directions and opportunities for the high-value utilization of a wide range of biological materials. Cellulose nanofibrils (CNF) and polylactic acid (PLA) biocomposite filaments for fused deposition modeling (FDM) 3DP were developed in [...] Read more.

As direct digital manufacturing, 3D printing (3DP) technology provides new development directions and opportunities for the high-value utilization of a wide range of biological materials. Cellulose nanofibrils (CNF) and polylactic acid (PLA) biocomposite filaments for fused deposition modeling (FDM) 3DP were developed in this study. Firstly, CNF was isolated by enzymatic hydrolysis combined with high-pressure homogenization. CNF/PLA filaments were then prepared by melt-extrusion of PLA as the matrix and CNF as the filler. Thermal stability, mechanical performance, and water absorption property of biocomposite filaments and 3D-printed objects were analyzed. Findings showed that CNF increased the thermal stability of the PLA/PEG600/CNF composite. Compared to unfilled PLA FDM filaments, the CNF filled PLA biocomposite filament showed an increase of 33% in tensile strength and 19% in elongation at break, suggesting better compatibility for desktop FDM 3DP. This study provided a new potential for the high-value utilization of CNF in 3DP in consumer product applications. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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12 pages, 3783 KiB

Open AccessArticle

Bio-Based Thermo-Reversible Aliphatic Polycarbonate Network

by Pierre-Luc Durand, Etienne Grau and Henri Cramail

Molecules 2020, 25(1), 74; https://doi.org/10.3390/molecules25010074 - 24 Dec 2019

Cited by 8 | Viewed by 3320

Abstract

Aliphatic polycarbonates represent an important class of materials with notable applications in the biomedical field. In this work, low Tg furan-functionalized bio-based aliphatic polycarbonates were cross-linked thanks to the Diels–Alder (DA) reaction with a bis-maleimide as the cross-linking agent. The thermo-reversible DA reaction [...] Read more.

Aliphatic polycarbonates represent an important class of materials with notable applications in the biomedical field. In this work, low Tg furan-functionalized bio-based aliphatic polycarbonates were cross-linked thanks to the Diels–Alder (DA) reaction with a bis-maleimide as the cross-linking agent. The thermo-reversible DA reaction allowed for the preparation of reversible cross-linked polycarbonate materials with tuneable properties as a function of the pendent furan content that was grafted on the polycarbonate backbone. The possibility to decrosslink the network around 70 °C could be an advantage for biomedical applications, despite the rather poor thermal stability of the furan-functionalized cross-linked polycarbonates. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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20 pages, 4259 KiB

Open AccessArticle

New Insight on the Study of the Kinetic of Biobased Polyurethanes Synthesis Based on Oleo-Chemistry

by Julien Peyrton, Clémence Chambaretaud and Luc Avérous

Molecules 2019, 24(23), 4332; https://doi.org/10.3390/molecules24234332 - 27 Nov 2019

Cited by 15 | Viewed by 3347

Abstract

Nowadays, polyols are basic chemicals for the synthesis of a large range of polymers, such as polyurethane foams (PUF), which are produced with several other compounds, such as polyisocyanates. During the last decades, the oleo-chemistry has developed several routes from glycerides to polyols [...] Read more.

Nowadays, polyols are basic chemicals for the synthesis of a large range of polymers, such as polyurethane foams (PUF), which are produced with several other compounds, such as polyisocyanates. During the last decades, the oleo-chemistry has developed several routes from glycerides to polyols for the polyurethanes (PU) industry to replace mainly conventional fossil-based polyols. A large range of biobased polyols can be now obtained by epoxidation of the double bonds and ring-opening (RO) of the subsequent epoxides with different chemical moieties. In preliminary studies, the RO kinetics of an epoxidized model molecule (methyl oleate) with ethanol and acetic acid were investigated. Subsequently, polyols that were derived from unsaturated triglycerides were explored in the frame of e.g., PUF formulations. Different associations were studied with different mono-alcohols derived from epoxidized and ring-opened methyl oleate while using several ring-openers to model such systems and for comparison purposes. Kinetic studies were realized with the pseudo-first-order principle, meaning that hydroxyls are in large excess when compared to the isocyanate groups. The rate of isocyanate consumption was found to be dependent on the moiety located in β-position of the reactive hydroxyl, following this specific order: tertiary amine >> ether > ester. The tertiary amine in β-position of the hydroxyl tremendously increases the reactivity toward isocyanate. Consequently, a biobased reactive polyurethane catalyst was synthesized from unsaturated glycerides. These approaches offer new insights regarding the replacement of current catalysts often harmful, pungent, and volatile used in PU and PUF industry, in order to revisit this chemistry. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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19 pages, 3712 KiB

Open AccessArticle

Synthesis of Resins Using Epoxies and Humins as Building Blocks: A Mechanistic Study Based on In-Situ FT-IR and NMR Spectroscopies

by Xavier Montané, Roxana Dinu and Alice Mija

Molecules 2019, 24(22), 4110; https://doi.org/10.3390/molecules24224110 - 14 Nov 2019

Cited by 13 | Viewed by 3720

Abstract

The combination of eco-respectful epoxy compounds with the humins, a by-product of biomass chemical conversion technologies, allow the obtention of materials with high added value. In this work, we propose a chemical connection study of humins with two aliphatic bis-epoxides through copolymerization reactions [...] Read more.

The combination of eco-respectful epoxy compounds with the humins, a by-product of biomass chemical conversion technologies, allow the obtention of materials with high added value. In this work, we propose a chemical connection study of humins with two aliphatic bis-epoxides through copolymerization reactions to synthesize sustainable, bio-based thermosets. The mechanism insights for the crosslinking between the epoxides and humins was proposed considering the different functionalities of the humins structure. Fourier Transform InfraRed (FT-IR), one dimensional (1D) and two-dimensional (2D) Nuclear Magnetic Resonance (NMR) spectroscopy techniques were used to build the proposed mechanism. By these techniques, the principal chain connections and the reactivity of all the components were highlighted in the synthesized networks. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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15 pages, 7012 KiB

Open AccessArticle

Photocuring of Epoxidized Cardanol for Biobased Composites with Microfibrillated Cellulose

by Sara Dalle Vacche, Alessandra Vitale and Roberta Bongiovanni

Molecules 2019, 24(21), 3858; https://doi.org/10.3390/molecules24213858 - 25 Oct 2019

Cited by 29 | Viewed by 3417

Abstract

Cardanol is a natural alkylphenolic compound derived from Cashew NutShell Liquid (CNSL), a non-food annually renewable raw material extracted from cashew nutshells. In the quest for sustainable materials, the curing of biobased monomers and prepolymers with environmentally friendly processes attracts increasing interest. Photopolymerization [...] Read more.

Cardanol is a natural alkylphenolic compound derived from Cashew NutShell Liquid (CNSL), a non-food annually renewable raw material extracted from cashew nutshells. In the quest for sustainable materials, the curing of biobased monomers and prepolymers with environmentally friendly processes attracts increasing interest. Photopolymerization is considered to be a green technology owing to low energy requirements, room temperature operation with high reaction rates, and absence of solvents. In this work, we study the photocuring of a commercially available epoxidized cardanol, and explore its use in combination with microfibrillated cellulose (MFC) for the fabrication of fully biobased composites. Wet MFC mats were prepared by filtration, and then impregnated with the resin. The impregnated mats were then irradiated with ultraviolet (UV) light. Fourier Transform InfraRed (FT-IR) spectroscopy was used to investigate the photocuring of the epoxidized cardanol, and of the composites. The thermomechanical properties of the composites were assessed by thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. We confirmed that fully cured composites could be obtained, although a high photoinitiator concentration was needed, possibly due to a side reaction of the photoinitiator with MFC. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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18 pages, 4519 KiB

Open AccessArticle

Synthesis of Pluri-Functional Amine Hardeners from Bio-Based Aromatic Aldehydes for Epoxy Amine Thermosets

by Anne-Sophie Mora, Russell Tayouo, Bernard Boutevin, Ghislain David and Sylvain Caillol

Molecules 2019, 24(18), 3285; https://doi.org/10.3390/molecules24183285 - 09 Sep 2019

Cited by 7 | Viewed by 4528

Abstract

Most of the current amine hardeners are petro-sourced and only a few studies have focused on the research of bio-based substitutes. Hence, in an eco-friendly context, our team proposed the design of bio-based amine monomers with aromatic structures. This work described the use [...] Read more.

Most of the current amine hardeners are petro-sourced and only a few studies have focused on the research of bio-based substitutes. Hence, in an eco-friendly context, our team proposed the design of bio-based amine monomers with aromatic structures. This work described the use of the reductive amination with imine intermediate in order to obtain bio-based pluri-functional amines exhibiting low viscosity. The effect of the nature of initial aldehyde reactant on the hardener properties was studied, as well as the reaction conditions. Then, these pluri-functional amines were added to petro-sourced (diglycidyl ether of bisphenol A, DGEBA) or bio-based (diglycidyl ether of vanillin alcohol, DGEVA) epoxy monomers to form thermosets by step growth polymerization. Due to their low viscosity, the epoxy-amine mixtures were easily homogenized and cured more rapidly compared to the use of more viscous hardeners (<0.6 Pa s at 22 °C). After curing, the thermo-mechanical properties of the epoxy thermosets were determined and compared. The isophthalatetetramine (IPTA) hardener, with a higher number of amine active H, led to thermosets with higher thermo-mechanical properties (glass transition temperatures (T_g and T_α) were around 95 °C for DGEBA-based thermosets against 60 °C for DGEVA-based thermosets) than materials from benzylamine (BDA) or furfurylamine (FDA) that contained less active hydrogens (T_g and T_α around 77 °C for DGEBA-based thermosets and T_g and T_α around 45 °C for DGEVA-based thermosets). By comparing to industrial hardener references, IPTA possesses six active hydrogens which obtain high cross-linked systems, similar to industrial references, and longer molecular length due to the presence of two alkyl chains, leading respectively to high mechanical strength with lower T_g. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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17 pages, 4258 KiB

Open AccessArticle

Synthesis and Characterization of a Bioartificial Polymeric System with Potential Antibacterial Activity: Chitosan-Polyvinyl Alcohol-Ampicillin

by Andres Bernal-Ballen, Jorge Lopez-Garcia, Martha-Andrea Merchan-Merchan and Marian Lehocky

Molecules 2018, 23(12), 3109; https://doi.org/10.3390/molecules23123109 - 28 Nov 2018

Cited by 16 | Viewed by 3571

Abstract

Bio-artificial polymeric systems are a new class of polymeric constituents based on blends of synthetic and natural polymers, designed with the purpose of producing new materials that exhibit enhanced properties with respect to the individual components. In this frame, a combination of polyvinyl [...] Read more.

Bio-artificial polymeric systems are a new class of polymeric constituents based on blends of synthetic and natural polymers, designed with the purpose of producing new materials that exhibit enhanced properties with respect to the individual components. In this frame, a combination of polyvinyl alcohol (PVA) and chitosan, blended with a widely used antibiotic, sodium ampicillin, has been developed showing a moderate behavior in terms of antibacterial properties. Thus, aqueous solutions of PVA at 1 wt.% were mixed with acid solutions of chitosan at 1 wt.%, followed by adding ampicillin ranging from 0.3 to 1.0 wt.% related to the total amount of the polymers. The prepared bio-artificial polymeric system was characterized by FTIR, SEM, DSC, contact angle measurements, antibacterial activity against Staphylococcus aureus and Escherichia coli and antibiotic release studies. The statistical significance of the antibacterial activity was determined using a multifactorial analysis of variance with ρ < 0.05 (ANOVA). The characterization techniques did not show alterations in the ampicillin structure and the interactions with polymers were limited to intermolecular forces. Therefore, the antibiotic was efficiently released from the matrix and its antibacterial activity was preserved. The system disclosed moderate antibacterial activity against bacterial strains without adding a high antibiotic concentration. The findings of this study suggest that the system may be effective against healthcare-associated infections, a promising view in the design of novel antimicrobial biomaterials potentially suitable for tissue engineering applications. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers)

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16 pages, 3609 KiB

Open AccessFeature PaperArticle

Limonene-Based Epoxy: Anhydride Thermoset Reaction Study

by Guillaume Couture, Lérys Granado, Florent Fanget, Bernard Boutevin and Sylvain Caillol

Molecules 2018, 23(11), 2739; https://doi.org/10.3390/molecules23112739 - 23 Oct 2018

Cited by 27 | Viewed by 5542

Abstract

The development of epoxy thermosets from renewable resources is of paramount importance in a sustainable development context. In this paper, a novel bio-based epoxy monomer derived from limonene was synthesized without epichlorohydrine and characterized. In fact, this paper depicts the synthesis of bis-limonene [...] Read more.

The development of epoxy thermosets from renewable resources is of paramount importance in a sustainable development context. In this paper, a novel bio-based epoxy monomer derived from limonene was synthesized without epichlorohydrine and characterized. In fact, this paper depicts the synthesis of bis-limonene oxide (bis-LO). However, intern epoxy rings generally exhibit a poor reactivity and allow reaction with anhydride. Therefore, we used a reaction model with hexahydro-4-methylphthalic anhydride to compare reactivity of terminal and interepoxy functions. We also studied the influence of methyl group on intern epoxy functions. Furthermore, the influence of epoxy:anhydride stoichiometry and initiator amount was studied. These studies allow to propose an optimized formulation of bis-LO. Finally, a bis-LO-based thermoset was obtained and characterized. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers)

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18 pages, 6797 KiB

Open AccessArticle

Synthesis and Characterization of Poly(Vinyl Alcohol)-Chitosan-Hydroxyapatite Scaffolds: A Promising Alternative for Bone Tissue Regeneration

by Sergio Pineda-Castillo, Andrés Bernal-Ballén, Cristian Bernal-López, Hugo Segura-Puello, Diana Nieto-Mosquera, Andrea Villamil-Ballesteros, Diana Muñoz-Forero and Lukas Munster

Molecules 2018, 23(10), 2414; https://doi.org/10.3390/molecules23102414 - 20 Sep 2018

Cited by 29 | Viewed by 4756

Abstract

Scaffolds can be considered as one of the most promising treatments for bone tissue regeneration. Herein, blends of chitosan, poly(vinyl alcohol), and hydroxyapatite in different ratios were used to synthesize scaffolds via freeze-drying. Mechanical tests, FTIR, swelling and solubility degree, DSC, morphology, and [...] Read more.

Scaffolds can be considered as one of the most promising treatments for bone tissue regeneration. Herein, blends of chitosan, poly(vinyl alcohol), and hydroxyapatite in different ratios were used to synthesize scaffolds via freeze-drying. Mechanical tests, FTIR, swelling and solubility degree, DSC, morphology, and cell viability were used as characterization techniques. Statistical significance of the experiments was determined using a two-way analysis of variance (ANOVA) with p < 0.05. Crosslinked and plasticized scaffolds absorbed five times more water than non-crosslinked and plasticized ones, which is an indicator of better hydrophilic features, as well as adequate resistance to water without detriment of the swelling potential. Indeed, the tested mechanical properties were notably higher for samples which were undergone to crosslinking and plasticized process. The presence of chitosan is determinant in pore formation and distribution which is an imperative for cell communication. Uniform pore size with diameters ranging from 142 to 519 µm were obtained, a range that has been described as optimal for bone tissue regeneration. Moreover, cytotoxicity was considered as negligible in the tested conditions, and viability indicates that the material might have potential as a bone regeneration system. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers)

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17 pages, 3176 KiB

Open AccessFeature PaperArticle

Enzymatic Synthesis of Amino Acids Endcapped Polycaprolactone: A Green Route Towards Functional Polyesters

by Stéphane W. Duchiron, Eric Pollet, Sébastien Givry and Luc Avérous

Molecules 2018, 23(2), 290; https://doi.org/10.3390/molecules23020290 - 30 Jan 2018

Cited by 10 | Viewed by 5716

Abstract

ε-caprolactone (CL) has been enzymatically polymerized using α-amino acids based on sulfur (methionine and cysteine) as (co-)initiators and immobilized lipase B of Candida antarctica (CALB) as biocatalyst. In-depth characterizations allowed determining the corresponding involved mechanisms and the polymers thermal properties. Two synthetic strategies [...] Read more.

ε-caprolactone (CL) has been enzymatically polymerized using α-amino acids based on sulfur (methionine and cysteine) as (co-)initiators and immobilized lipase B of Candida antarctica (CALB) as biocatalyst. In-depth characterizations allowed determining the corresponding involved mechanisms and the polymers thermal properties. Two synthetic strategies were tested, a first one with direct polymerization of CL with the native amino acids and a second one involving the use of an amino acid with protected functional groups. The first route showed that mainly polycaprolactone (PCL) homopolymer could be obtained and highlighted the lack of reactivity of the unmodified amino acids due to poor solubility and affinity with the lipase active site. The second strategy based on protected cysteine showed higher monomer conversion, with the amino acids acting as (co-)initiators, but their insertion along the PCL chains remained limited to chain endcapping. These results thus showed the possibility to synthesize enzymatically polycaprolactone-based chains bearing amino acids units. Such cysteine endcapped PCL materials could then find application in the biomedical field. Indeed, subsequent functionalization of these polyesters with drugs or bioactive molecules can be obtained, by derivatization of the amino acids, after removal of the protecting group. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers)

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2031 KiB

Open AccessArticle

Characterization of Non-Derivatized Cellulose Samples by Size Exclusion Chromatography in Tetrabutylammonium Fluoride/Dimethylsulfoxide (TBAF/DMSO)

by Jérémy Rebière, Antoine Rouilly, Vanessa Durrieu and Frédéric Violleau

Molecules 2017, 22(11), 1985; https://doi.org/10.3390/molecules22111985 - 16 Nov 2017

Cited by 6 | Viewed by 4830

Abstract

This paper deals with the use of tetrabutylammonium fluoride/dimethylsulfoxide (TBAF/DMSO) to characterize the molar mass distribution of non-derivatized cellulosic samples by size exclusion chromatography (SEC). Different cellulose samples with various average degree of polymerization (DP) were first solubilized in this solvent system, with [...] Read more.

This paper deals with the use of tetrabutylammonium fluoride/dimethylsulfoxide (TBAF/DMSO) to characterize the molar mass distribution of non-derivatized cellulosic samples by size exclusion chromatography (SEC). Different cellulose samples with various average degree of polymerization (DP) were first solubilized in this solvent system, with increasing TBAF rates, and then analyzed by SEC coupled to a refractive index detector (RID), using DMSO as mobile phase. The Molar Masses (MM) obtained by conventional calibration were then discussed and compared with suppliers’ data and MM determined by viscosimetry measurements. By this non-classic method, molar mass of low DP samples (Avicel^® and cotton fibers) have been determined. For high DP samples (α-cellulose and Vitacel^®), dissolution with TBAF concentration of 10 mg/mL involved elution of cellulose aggregates in the exclusion volume, related to an incomplete dissolution or the dilution of TBAF molecules in elution solvent, preventing the correct evaluation of their molar mass. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers)

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7926 KiB

Open AccessArticle

Characteristics of Multifunctional, Eco-Friendly Lignin-Al₂O₃ Hybrid Fillers and Their Influence on the Properties of Composites for Abrasive Tools

by Łukasz Klapiszewski, Artur Jamrozik, Beata Strzemiecka, Iwona Koltsov, Bartłomiej Borek, Danuta Matykiewicz, Adam Voelkel and Teofil Jesionowski

Molecules 2017, 22(11), 1920; https://doi.org/10.3390/molecules22111920 - 07 Nov 2017

Cited by 24 | Viewed by 4836

Abstract

The main aim of the present study was the preparation and comprehensive characterization of innovative additives to abrasive materials based on functional, pro-ecological lignin-alumina hybrid fillers. The behavior of lignin, alumina and lignin-Al₂O₃ hybrids in a resin matrix was explained [...] Read more.

The main aim of the present study was the preparation and comprehensive characterization of innovative additives to abrasive materials based on functional, pro-ecological lignin-alumina hybrid fillers. The behavior of lignin, alumina and lignin-Al₂O₃ hybrids in a resin matrix was explained on the basis of their surface and application properties determined by inverse gas chromatography, the degree of adhesion/cohesion between components, thermomechanical and rheological properties. On the basis of the presented results, a hypothetical mechanism of interactions between lignin and Al₂O₃ as well as between lignin-Al₂O₃ hybrids and phenolic resins was proposed. It was concluded that lignin compounds can provide new, promising properties for a phenolic binder combining the good properties of this biopolymer as a plasticizer and of alumina as a filler improving mechanical and thermal properties. The use of such materials may be relatively non-complicated and efficient way to improve the performance of bonded abrasive tools. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers)

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1869 KiB

Open AccessArticle

Single Actin Bundle Rheology

by Dan Strehle, Paul Mollenkopf, Martin Glaser, Tom Golde, Carsten Schuldt, Josef A. Käs and Jörg Schnauß

Molecules 2017, 22(10), 1804; https://doi.org/10.3390/molecules22101804 - 24 Oct 2017

Cited by 11 | Viewed by 4625

Abstract

Bundled actin structures play an essential role in the mechanical response of the actin cytoskeleton in eukaryotic cells. Although responsible for crucial cellular processes, they are rarely investigated in comparison to single filaments and isotropic networks. Presenting a highly anisotropic structure, the determination [...] Read more.

Bundled actin structures play an essential role in the mechanical response of the actin cytoskeleton in eukaryotic cells. Although responsible for crucial cellular processes, they are rarely investigated in comparison to single filaments and isotropic networks. Presenting a highly anisotropic structure, the determination of the mechanical properties of individual bundles was previously achieved through passive approaches observing bending deformations induced by thermal fluctuations. We present a new method to determine the bending stiffness of individual bundles, by measuring the decay of an actively induced oscillation. This approach allows us to systematically test anisotropic, bundled structures. Our experiments revealed that thin, depletion force-induced bundles behave as semiflexible polymers and obey the theoretical predictions determined by the wormlike chain model. Thickening an individual bundle by merging it with other bundles enabled us to study effects that are solely based on the number of involved filaments. These thicker bundles showed a frequency-dependent bending stiffness, a behavior that is inconsistent with the predictions of the wormlike chain model. We attribute this effect to internal processes and give a possible explanation with regard to the wormlike bundle theory. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers)

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2912 KiB

Open AccessArticle

Development, Optimization and In Vitro/In Vivo Characterization of Collagen-Dextran Spongious Wound Dressings Loaded with Flufenamic Acid

by Mihaela Violeta Ghica, Mădălina Georgiana Albu Kaya, Cristina-Elena Dinu-Pîrvu, Dumitru Lupuleasa and Denisa Ioana Udeanu

Molecules 2017, 22(9), 1552; https://doi.org/10.3390/molecules22091552 - 15 Sep 2017

Cited by 42 | Viewed by 6219

Abstract

The aim of this study was the development and optimization of some topical collagen-dextran sponges with flufenamic acid, designed to be potential dressings for burn wounds healing. The sponges were obtained by lyophilization of hydrogels based on type I fibrillar collagen gel extracted [...] Read more.

The aim of this study was the development and optimization of some topical collagen-dextran sponges with flufenamic acid, designed to be potential dressings for burn wounds healing. The sponges were obtained by lyophilization of hydrogels based on type I fibrillar collagen gel extracted from calf hide, dextran and flufenamic acid, crosslinked and un-crosslinked, and designed according to a 3-factor, 3-level Box-Behnken experimental design. The sponges showed good fluid uptake ability quantified by a high swelling ratio. The flufenamic acid release profiles from sponges presented two stages—burst effect resulting in a rapid inflammation reduction, and gradual delivery ensuring the anti-inflammatory effect over a longer burn healing period. The resistance to enzymatic degradation was monitored through a weight loss parameter. The optimization of the sponge formulations was performed based on an experimental design technique combined with response surface methodology, followed by the Taguchi approach to select those formulations that are the least affected by the noise factors. The treatment of experimentally induced burns on animals with selected sponges accelerated the wound healing process and promoted a faster regeneration of the affected epithelial tissues compared to the control group. The results generated by the complex sponge characterization indicate that these formulations could be successfully used for burn dressing applications. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers)

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6335 KiB

Open AccessArticle

Phase Behaviour and Miscibility Studies of Collagen/Silk Fibroin Macromolecular System in Dilute Solutions and Solid State

by Ima Ghaeli, Mariana A. De Moraes, Marisa M. Beppu, Katarzyna Lewandowska, Alina Sionkowska, Frederico Ferreira-da-Silva, Maria P. Ferraz and Fernando J. Monteiro

Molecules 2017, 22(8), 1368; https://doi.org/10.3390/molecules22081368 - 18 Aug 2017

Cited by 23 | Viewed by 6173

Abstract

Miscibility is an important issue in biopolymer blends for analysis of the behavior of polymer pairs through the detection of phase separation and improvement of the mechanical and physical properties of the blend. This study presents the formulation of a stable and one-phase [...] Read more.

Miscibility is an important issue in biopolymer blends for analysis of the behavior of polymer pairs through the detection of phase separation and improvement of the mechanical and physical properties of the blend. This study presents the formulation of a stable and one-phase mixture of collagen and regenerated silk fibroin (RSF), with the highest miscibility ratio between these two macromolecules, through inducing electrostatic interactions, using salt ions. For this aim, a ternary phase diagram was experimentally built for the mixtures, based on observations of phase behavior of blend solutions with various ratios. The miscibility behavior of the blend solutions in the miscible zones of the phase diagram was confirmed quantitatively by viscosimetric measurements. Assessing the effects of biopolymer mixing ratio and salt ions, before and after dialysis of blend solutions, revealed the importance of ion-specific interactions in the formation of coacervate-based materials containing collagen and RSF blends that can be used in pharmaceutical, drug delivery, and biomedical applications. Moreover, the conformational change of silk fibroin from random coil to beta sheet, in solution and in the final solid films, was detected by circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR), respectively. Scanning electron microscopy (SEM) exhibited alterations of surface morphology for the biocomposite films with different ratios. Surface contact angle measurement illustrated different hydrophobic properties for the blended film surfaces. Differential scanning calorimetry (DSC) showed that the formation of the beta sheet structure of silk fibroin enhances the thermal stability of the final blend films. Therefore, the novel method presented in this study resulted in the formation of biocomposite films whose physico-chemical properties can be tuned by silk fibroin conformational changes by applying different component mixing ratios. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers)

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3883 KiB

Open AccessArticle

Polyurethane Foams for Thermal Insulation Uses Produced from Castor Oil and Crude Glycerol Biopolyols

by Camila S. Carriço, Thaís Fraga, Vagner E. Carvalho and Vânya M. D. Pasa

Molecules 2017, 22(7), 1091; https://doi.org/10.3390/molecules22071091 - 02 Jul 2017

Cited by 49 | Viewed by 9760

Abstract

Rigid polyurethane foams were synthesized using a renewable polyol from the simple physical mixture of castor oil and crude glycerol. The effect of the catalyst (DBTDL) content and blowing agents in the foams’ properties were evaluated. The use of physical blowing agents (cyclopentane [...] Read more.

Rigid polyurethane foams were synthesized using a renewable polyol from the simple physical mixture of castor oil and crude glycerol. The effect of the catalyst (DBTDL) content and blowing agents in the foams’ properties were evaluated. The use of physical blowing agents (cyclopentane and n-pentane) allowed foams with smaller cells to be obtained in comparison with the foams produced with a chemical blowing agent (water). The increase of the water content caused a decrease in density, thermal conductivity, compressive strength, and Young’s modulus, which indicates that the increment of CO₂ production contributes to the formation of larger cells. Higher amounts of catalyst in the foam formulations caused a slight density decrease and a small increase of thermal conductivity, compressive strength, and Young’s modulus values. These green foams presented properties that indicate a great potential to be used as thermal insulation: density (23–41 kg·m⁻³), thermal conductivity (0.0128–0.0207 W·m⁻¹·K⁻¹), compressive strength (45–188 kPa), and Young’s modulus (3–28 kPa). These biofoams are also environmentally friendly polymers and can aggregate revenue to the biodiesel industry, contributing to a reduction in fuel prices. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers)

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19 pages, 5350 KiB

Open AccessFeature PaperReview

Non-Conventional Features of Plant Oil-Based Acrylic Monomers in Emulsion Polymerization

by Ananiy Kohut, Stanislav Voronov, Zoriana Demchuk, Vasylyna Kirianchuk, Kyle Kingsley, Oleg Shevchuk, Sylvain Caillol and Andriy Voronov

Molecules 2020, 25(13), 2990; https://doi.org/10.3390/molecules25132990 - 30 Jun 2020

Cited by 12 | Viewed by 3356

Abstract

In recent years, polymer chemistry has experienced an intensive development of a new field regarding the synthesis of aliphatic and aromatic biobased monomers obtained from renewable plant sources. A one-step process for the synthesis of new vinyl monomers by the reaction of direct [...] Read more.

In recent years, polymer chemistry has experienced an intensive development of a new field regarding the synthesis of aliphatic and aromatic biobased monomers obtained from renewable plant sources. A one-step process for the synthesis of new vinyl monomers by the reaction of direct transesterification of plant oil triglycerides with N-(hydroxyethyl)acrylamide has been recently invented to yield plant oil-based monomers (POBMs). The features of the POBM chemical structure, containing both a polar (hydrophilic) fragment capable of electrostatic interactions, and hydrophobic acyl fatty acid moieties (C₁₅-C₁₇) capable of van der Waals interactions, ensures the participation of the POBMs fragments of polymers in intermolecular interactions before and during polymerization. The use of the POBMs with different unsaturations in copolymerization reactions with conventional vinyl monomers allows for obtaining copolymers with enhanced hydrophobicity, provides a mechanism of internal plasticization and control of crosslinking degree. Synthesized latexes and latex polymers are promising candidates for the formation of hydrophobic polymer coatings with controlled physical and mechanical properties through the targeted control of the content of different POBM units with different degrees of unsaturation in the latex polymers. Full article

(This article belongs to the Special Issue Natural Polymers and Biopolymers II)

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