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Advances in Biodegradable Polymers
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Advances in Biodegradable Polymers

A topical collection in Macromol (ISSN 2673-6209).

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Editor

Prof. Dr. Dimitrios Bikiaris

E-Mail Website
Guest Editor
Laboratory of Chemistry and Technology of Polymers and Colors, Department of Chemistry, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece
Interests: synthesis and characterization of polyesters; development of biobased polymers; biodegradable polymers; polymer composites and nanocomposites; synthesis and characterization of copolymers; polymer blends; recycling of polymers with various techniques; enzymatic hydrolysis studies; modification of natural polymers; polymers for wastewater treatment pollutant removal; polymers for tissue engineering and drug delivery applications; drug–polymer solid dispersions; drug targeting; drug nanoencapsulation and microencapsulation
Special Issues, Collections and Topics in MDPI journals

Topical Collection Information

Dear Colleagues,

Biodegradable polymers are polymers that can be subjected to significant changes in their chemical structure under certain environmental conditions in a relatively short time via natural biological processes, like the action of micro-organisms (mainly bacteria and fungi) resulting in a progressive reduction of their molecular weight and alteration of their physical properties. The mechanisms of biodegradable polymers include enzymatic degradation, hydrolysis and the combination of them, and is a surface or bulk erosion procedure. Enzymes are acting as biocatalysts. The process of biodegradation can be divided into three stages: biodeterioration, biofragmentation, and assimilation, leading to harmless and simple products (mainly CO2 and H2O after completely biodegradation), thus reducing the need to create a disposal system that causes harm to thr environment. The biodegradation rate depends either on external factors like temperature, oxygen, water and light or on internal ones, such as the chemical structure of polymers, their molecular weight, degree of crystallinity and hydrophilicity.

Biodegradable polymers are divided into two main categories: (a) Natural polymers obtained from natural resources during the growth cycles of all organisms, that are generally non-toxic and abundant, such as polysaccharides (chitosan, starch, cellulose, dextran, etc.), and proteins (collagen, fibrin, albumin, etc.), and (b) synthetic biodegradable polymers prepared by ring opening polymerization of cyclic esters and/or by melt polycondensation procedure, including aliphatic polyesters like poly(lactic  acid), poly(glycolic acid), poly(ε-caprolactone), poly(butylene succinate) and others, such as polyanhydrides, polyphosphazenes, polyurethanes, poly(hydroxy alkanoates) produced by microogranisms etc. This class of polymers bears many advantages compared to non-degradable polymers. They are readily and abundantly available (especially natural polymers), comparatively inexpensive, they can be modified to obtain semi-synthetic forms with new properties, whereas synthetic biodegradable polymers can be shortly degraded into nontoxic products. 

In recent years, due to the major environmental problems caused by the use of non-degradable polymers, biodegradable polymers have been increasingly gaining great interest. Biodegradable polyesters can be prepared naturally or by monomers derived from renewable sources. Natural polymers are completely biodegradable within a very short time, which is their key advantage, and they have high molecular weight. Aliphatic polyesters have also many benefits, being completely compostable or biodegradable, with no additional CO2 emissions after their complete biodegradation. The lattest are thermoplastic materials, completely recyclable and can be used in several applications like food packaging, single-use items, 3D printing, waste water treatment, cosmetics, drug delivery, biomedicine, tissue engineering, surgery, etc.

The aim of this Special Issue is to highlight the progress and fundamental aspects of the synthesis, characterization, properties, and applications of biodegrable polymers, as well as their copolymers, composites, and nanocomposites in several scientific fields. Scientific works and mostly short reviews are warmly welcome. 

Prof. Dr. Dimitrios Bikiaris
Guest Editor

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Keywords

  • Biodegradable polymers
  • Compostable polymers
  • Natural polymers
  • Polysaccharides
  • Proteins
  • Aliphatic polyesters
  • Mechanical properties
  • Thermal properties

Published Papers (20 papers)

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2024

Jump to: 2023, 2022, 2021

20 pages, 1569 KiB  
Review
Polysaccharides and Composite Adsorbents in the Spotlight for Effective Agrochemical Residue Removal from Water
by Mónica Ortiz-Martínez, Brenda Restori-Corona, Luis Hernández-García and Diana Alonso-Segura
Macromol 2024, 4(4), 785-804; https://doi.org/10.3390/macromol4040047 - 6 Nov 2024
Viewed by 1195
Abstract
Agrochemical residues, including pesticides and herbicides, pose significant environmental and health risks when present in water sources. Conventional water treatment methods often fall short in effectively removing these persistent pollutants, necessitating innovative solutions. This review explores the use of polysaccharides and composite adsorbents [...] Read more.
Agrochemical residues, including pesticides and herbicides, pose significant environmental and health risks when present in water sources. Conventional water treatment methods often fall short in effectively removing these persistent pollutants, necessitating innovative solutions. This review explores the use of polysaccharides and composite adsorbents as sustainable alternatives for agrochemical residue removal from water. Biopolymers such as chitosan, alginate, and cellulose are highlighted for their biodegradability, biocompatibility, and ability to be functionalized for enhanced adsorption performance. Recent advances in the development of composite materials incorporating nanomaterials, such as graphene, oxide, and metal oxides, have shown significant promise in enhancing the efficiency and selectivity of agrochemical adsorption. The review also addresses the fundamental mechanism of adsorption, such as electrostatic interactions, hydrogen bonding, and hydrophobic forces, that contribute to the effectiveness of these materials. Challenges associated with scalability, regeneration, and real-world applications are discussed, as well as future opportunities for integrating emerging technologies like 3D printing and machine learning into adsorbent design. Overall, polysaccharides and composites offer a promising pathway toward achieving efficient and sustainable agrochemical residue removal, with ongoing research needed to overcome current limitations and optimize their practical application in water treatment. Full article
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13 pages, 2596 KiB  
Article
Near-Surface Reconfiguration of Biopolymer Blends by Mechanical Embossment: Creation of Friction-Reduced Foils
by Hang Liu, Markus Kiefel, Nova Reichel, Jochen Hofmann, Tobias Walcher, Wadim Schulz, Katharina Weber and Joachim Albrecht
Macromol 2024, 4(4), 772-784; https://doi.org/10.3390/macromol4040046 - 5 Nov 2024
Viewed by 2384
Abstract
Biopolymer blends of polylactic acid (PLA) and polybutylene adipate-co-terephthalate (PBAT) are extruded into flexible monolayer films. These blends are excellent candidates for the realization of environmentally friendly packaging applications. A necessary pre-requisite for that are appropriate tribological properties under mechanical contact. Reasonable wear [...] Read more.
Biopolymer blends of polylactic acid (PLA) and polybutylene adipate-co-terephthalate (PBAT) are extruded into flexible monolayer films. These blends are excellent candidates for the realization of environmentally friendly packaging applications. A necessary pre-requisite for that are appropriate tribological properties under mechanical contact. Reasonable wear resistance allows good protection of packed goods, and low friction forces reduce difficulties in stacking. In this research, mechanical embossment under high loads at room temperature was used for the modification of polymer surfaces to exhibit a significant friction reduction under dry conditions. The results particularly show a systematic decrease in the coefficient of friction for biopolymer blends containing 30 wt% and 40 wt% PBAT. FTIR was used to analyze the change in surface composition after mechanical embossing. A sophisticated FTIR calibration method revealed that the blend with 30 wt% PBAT shows a modified distribution of PBAT and PLA at the surface due to mechanical embossment. This leads to a controlled and long-lasting modification of the surface properties without a substantial change in the chemical composition of the polymer in bulk. Without the use of additional coatings, biodegradable packaging foils with improved characteristics are accessible. Full article
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15 pages, 2939 KiB  
Article
Four-Ingredient Blends of Poly(lactic acid) with Cottonseed Oil and Meal for Biocomposite Utilization
by Zhongqi He, Huai N. Cheng, Catrina V. Ford, Sunghyun Nam, Chanel Fortier, Michael Santiago Cintron, Ocen Modesto Olanya and Joseph Uknalis
Macromol 2024, 4(4), 708-722; https://doi.org/10.3390/macromol4040042 - 1 Oct 2024
Viewed by 841
Abstract
The development and characterization of agricultural byproduct-based biocomposites are an important part of green chemistry. In this work, four-ingredient blends were formulated with the melt blending method. The set of composites (named as CSO series) was made with poly(lactic acid) (PLA) as the [...] Read more.
The development and characterization of agricultural byproduct-based biocomposites are an important part of green chemistry. In this work, four-ingredient blends were formulated with the melt blending method. The set of composites (named as CSO series) was made with poly(lactic acid) (PLA) as the major matrix, washed cottonseed meal (WCSM) as a filler, cottonseed oil (CSO) as a compatibilizer, and glycerol (GLY) as a plasticizer. The morphological analysis showed the homogenous dispersion of the cottonseed byproducts into the PLA matrix to some extent. The thermogravimetric analysis revealed that thermal stability was impacted by the ingredient’s addition. The functional group analysis of the sample and simulation by Fourier transform infrared spectra confirmed the chemical interactions of PLA with WCSM in the blend products. CSO was most likely subjected to physical blending into the products. The mechanical strengths of those composites were affected by the ratios of PLA-CSO. Generally, the tensile strengths were in the range of 0.74–2.1 MPa, which indicate its suitability for low-strength biodegradable plant container development. The blend products had a lower water absorption during the water soaking test. This work shows the feasibility of incorporating cottonseed WCSM and CSO into a PLA composite for sustainable agricultural applications. Full article
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19 pages, 9180 KiB  
Article
In-Situ Grown Nanohydroxyapatite on Graphene Oxide Nanoscrolls for Modulated Physicochemical Properties of Poly (Caprolactone) Composites
by Lillian Tsitsi Mambiri, Gabrielle Broussard, Ja’Caleb Smith and Dilip Depan
Macromol 2024, 4(2), 285-303; https://doi.org/10.3390/macromol4020017 - 11 May 2024
Viewed by 831
Abstract
Polymer composites with exceptional bioactivity and controlled in vitro degradation are crucial in tissue engineering. A promising approach involves combining graphene oxide nanoscrolls (GONSs) and nanohydroxyapatite (nHA) with polycaprolactone (PCL). The synergy of these components enables the mineralization of nHA within GONSs through [...] Read more.
Polymer composites with exceptional bioactivity and controlled in vitro degradation are crucial in tissue engineering. A promising approach involves combining graphene oxide nanoscrolls (GONSs) and nanohydroxyapatite (nHA) with polycaprolactone (PCL). The synergy of these components enables the mineralization of nHA within GONSs through a two-step process: first, oxygen-containing anionic groups in the GONSs anchor Ca2+ ions, followed by the formation of dispersed nHA through chelation with CaHPO42− via electrovalent bonding. A thermal analysis of the scaffolds’ morphology and microstructure was conducted via DSC and SEM imaging. Its enhanced physical properties are attributed to interactions between PCL and nHA–GONSs, as confirmed by an FTIR analysis showing strong interfacial bonding. Enzymatic degradation studies demonstrated reduced weight loss in PCL–nHA–GONS composites over 21 days, highlighting GONSs’ role in enhancing dimensional stability and reinforcement. An EDS analysis post-degradation revealed increased Ca2+ deposition on scaffolds with nHA–GONSs, indicating improved biopolymer–bioceramic interaction facilitated by the GONSs’ scrolled structure. This research offers a straightforward yet effective method for functionalizing GONSs with biologically beneficial nHA, potentially advancing graphene-based biomaterial development. Full article
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2023

Jump to: 2024, 2022, 2021

30 pages, 6958 KiB  
Review
Oxo-Additives for Polyolefin Degradation: Kinetics and Mechanism
by Eldar A. Mamin, Petr V. Pantyukhov and Anatoly A. Olkhov
Macromol 2023, 3(3), 477-506; https://doi.org/10.3390/macromol3030029 - 24 Jul 2023
Cited by 3 | Viewed by 2938
Abstract
This review considers the recent investigations in the scope of biodegradability of synthetic polymers, spanning polyethylene (PE), polypropylene (PP), and their corresponding composites, with a focus on the influence of oxo-additives (mostly transition metal salts). The types of oxo-additives and the mechanisms of [...] Read more.
This review considers the recent investigations in the scope of biodegradability of synthetic polymers, spanning polyethylene (PE), polypropylene (PP), and their corresponding composites, with a focus on the influence of oxo-additives (mostly transition metal salts). The types of oxo-additives and the mechanisms of oxidation acceleration are discussed. Furthermore, the influence of oxo-additives on both physicochemical and biological stages of degradation is evaluated (laboratory and field experiments with microorganisms/fungi action) with recent standards suggested for degradation estimation. Comparisons of the metal salts are given with respect to catalysis, as well as the synergetic influence of additives. The additives presented on the commercial market are also discussed. Full article
10 pages, 2300 KiB  
Article
Reaction of Bacterial Poly-3-Hydroxybutyrate with Thionyl Chloride in the Presence of Zinc Chloride, and the Preparation of Chlorine-Containing Oligomers
by Anatoly Nikolayevich Boyandin
Macromol 2023, 3(3), 421-430; https://doi.org/10.3390/macromol3030025 - 2 Jul 2023
Viewed by 1626
Abstract
The degradation patterns of bacterial poly-3-hydroxybutyrate (PHB) in chloroform solution under the action of thionyl chloride in the presence of zinc chloride were studied. When 2.5.mol of zinc chloride and 100 mmol of thionyl chloride were introduced into the solution of 25 mmol [...] Read more.
The degradation patterns of bacterial poly-3-hydroxybutyrate (PHB) in chloroform solution under the action of thionyl chloride in the presence of zinc chloride were studied. When 2.5.mol of zinc chloride and 100 mmol of thionyl chloride were introduced into the solution of 25 mmol PHB, a decrease in the molecular weight of the polymer was observed. During the reaction, a relatively rapid decrease in the molecular weight of the polymer was noted in the first hour of the experiment; thus, the values of the weight-average molecular weight decreased from 840 kDa to 483, 167, 58.6, and 16.7 kDa after 1, 5, 24, and 96 h of the experiment, respectively. The polydispersity also gradually decreased from 2.69 at the beginning to 1.92 at the end of the experiment. Oligomers of PHB containing 3-chlorobutyric acid and 3-hydroxybutyryl chloride residues at the O and C ends of the polymer chain, respectively, were obtained. The results confirm the ability of thionyl chloride to interact with aliphatic esters in the presence of zinc compounds, and demonstrate the possibility of using this reaction to produce oligomeric derivatives of polyesters bearing chloralkyl and acid chloride functional groups. Full article
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11 pages, 2465 KiB  
Article
PLA Films Containing Montmorillonite Nanoclay–Citronella Essential Oil Hybrids for Potential Active Film Formulation
by Rafaela R. Ferreira, Marilia C. Farina, Anderson Maia and Rondes F. S. Torin
Macromol 2023, 3(2), 200-210; https://doi.org/10.3390/macromol3020012 - 8 May 2023
Cited by 5 | Viewed by 2128
Abstract
This work evaluated the synergistic effect of citronella essential oil (Ct) and montmorillonite (MMT) (called hybrid compound) incorporated in Poly(lactic acid) (PLA) films at different concentrations (3, 10, 15, and 20 wt%). PLA films were characterized using X-ray diffraction, SEM, TGA, and DSC [...] Read more.
This work evaluated the synergistic effect of citronella essential oil (Ct) and montmorillonite (MMT) (called hybrid compound) incorporated in Poly(lactic acid) (PLA) films at different concentrations (3, 10, 15, and 20 wt%). PLA films were characterized using X-ray diffraction, SEM, TGA, and DSC considering their mechanical properties and essential oil migration. XRD analysis showed the effective interaction between MMT and oil. Thermal analysis, SEM, and mechanical tests were essential to understand the saturation point of the PLA composites. Samples with 15% and 20% of Ct showed a crystallinity reduction of 0.5% compared to samples with 3% and 10% of Ct. PLA/MMT–Ct showed a reduction in tensile strength of the order of 16 and 24, correlated to 15% and 20% of the Ct content, respectively, compared to PLA/MMT–Ct3%. Migration tests showed fast oil delivery correlated with high oil concentration, as evidenced using the PLA/MMT–Ct20% sample results, which showed an estimated release of 50% in the first 150 h due to system saturation, and the remaining being released in the last 350 h. Therefore, the migration tests provide an effective Ct concentration range promising for application with active packaging due to the intrinsic antimicrobial properties of Ct. Full article
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12 pages, 1228 KiB  
Perspective
Perspectives of Polymers in Forensic Analysis
by Ana M. Díez-Pascual
Macromol 2023, 3(2), 108-119; https://doi.org/10.3390/macromol3020008 - 10 Apr 2023
Cited by 2 | Viewed by 2890
Abstract
Polymeric materials have recently attracted a lot of attention due to their potential applications in many fields, ranging from biomedicine, the food industry and environmental monitoring to electronic, energy storage and sensing devices. Their versatility, functionalization capability, chemical/physical stability, reusability, long shelf-life, as [...] Read more.
Polymeric materials have recently attracted a lot of attention due to their potential applications in many fields, ranging from biomedicine, the food industry and environmental monitoring to electronic, energy storage and sensing devices. Their versatility, functionalization capability, chemical/physical stability, reusability, long shelf-life, as well as good mechanical and thermal properties, also make them idoneous candidates for use in forensic sciences, which deal with the investigation of crimes, finding relations between evidence and criminals. In particular, molecularly imprinted polymers (MIPs), designed based on the principle of generating template-specific polymeric cavities fitted to the target molecules in the presence of selected chemicals via non-covalent or covalent interactions, are highly suitable for forensic analysis. In addition, their combination with other compounds such as carbon nanomaterials can provide composites with improved properties to be used in the analysis of illicit drugs, doping substances, biological agents, toxins and so forth. In this article, recent applications of polymeric materials in the field of forensic analysis are discussed. The goal is to summarize their current uses and put forth a projection of their potential as promising alternatives for standard competitors. Full article
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2022

Jump to: 2024, 2023, 2021

27 pages, 5625 KiB  
Review
Active Agents Incorporated in Polymeric Substrates to Enhance Antibacterial and Antioxidant Properties in Food Packaging Applications
by Johan Stanley, Athira John, Klementina Pušnik Črešnar, Lidija Fras Zemljič, Dimitra A. Lambropoulou and Dimitrios N. Bikiaris
Macromol 2023, 3(1), 1-27; https://doi.org/10.3390/macromol3010001 - 23 Dec 2022
Cited by 24 | Viewed by 5841
Abstract
Active packaging has played a significant role in consumers’ health and green environment over the years. Synthetic polymers, such as poly(ethylene terephthalate) (PET), polyethylene (PE), polypropylene (PP), polystyrene, poly(vinyl chloride) (PVC), polycarbonate (PC), poly(lactic acid) (PLA), etc., and naturally derived ones, such as [...] Read more.
Active packaging has played a significant role in consumers’ health and green environment over the years. Synthetic polymers, such as poly(ethylene terephthalate) (PET), polyethylene (PE), polypropylene (PP), polystyrene, poly(vinyl chloride) (PVC), polycarbonate (PC), poly(lactic acid) (PLA), etc., and naturally derived ones, such as cellulose, starch, chitosan, etc., are extensively used as packaging materials due to their broad range of desired properties (transparence, processability, gas barrier properties, mechanical strength, etc.). In recent years, the food packaging field has been challenged to deliver food products free from microbes that cause health hazards. However, most of the used polymers lack such properties. Owing to this, active agents such as antimicrobial agents and antioxidants have been broadly used as potential additives in food packaging substrates, to increase the shelf life, the quality and the safety of food products. Both synthetic active agents, such as Ag, Cu, ZnO, TiO2, nanoclays, and natural active agents, such as essential oils, catechin, curcumin, tannin, gallic acid, etc., exhibit a broad spectrum of antimicrobial and antioxidant effects, while restricting the growth of harmful microbes. Various bulk processing techniques have been developed over the years to produce appropriate food packaging products and to add active agents on polymer matrices or on their surface. Among these techniques, extrusion molding is the most used method for mass production of food packaging with incorporated active agents into polymer substrates, while injection molding, thermoforming, blow molding, electrospinning, etc., are used to a lower extent. This review intends to study the antimicrobial and antioxidant effects of various active agents incorporated into polymeric substrates and their bulk processing technologies involved in the field of food packaging. Full article
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15 pages, 3148 KiB  
Article
Influencing the Shape Recovery and Thermomechanical Properties of 3DP PLA Using Smart Textile and Boehmite Alumina and Thermochromic Dye Modifiers
by Dimakatso Makwakwa, Mpho Phillip Motloung, Vincent Ojijo, Jayita Bandyopadhyay and Suprakas Sinha Ray
Macromol 2022, 2(3), 485-499; https://doi.org/10.3390/macromol2030030 - 18 Sep 2022
Cited by 5 | Viewed by 2201
Abstract
The technology of 4DP utilizes shape memory materials (SMMs). Among the SMMs, SMP is the material that has potential and is ideal for this technology. However, due to their restrictions, fillers are incorporated to produce a novel shape memory polymer composite (SMPC). The [...] Read more.
The technology of 4DP utilizes shape memory materials (SMMs). Among the SMMs, SMP is the material that has potential and is ideal for this technology. However, due to their restrictions, fillers are incorporated to produce a novel shape memory polymer composite (SMPC). The objective of the present work was to investigate how the modification of PLA via the incorporation of boehmite alumina and thermochromic dye, and the use of 3DP on polyester fabric to make smart material textiles (SMT), influenced the shape-memory properties of printed objects. SMPCs with 3 wt% BA particles were prepared by means of the fused deposition modelling (FDM) process, with heat used as an actuation. It was demonstrated that sample thickness and the method of PLA modification affected the shape recovery of 3D-printed objects. All neat PLA samples recovered their angle fully for all thicknesses, while modified PLA incorporated with BA particles and dye recovered its initial angle fully at 1 mm thickness and showed less recovery for 1.5- and 2 mm-thicknesses. The 1 mm-thick sample was then chosen for printing onto the textile material for all samples. When printed onto the fabric, the neat PLA and SMPCs recovered their initial shapes fully, while samples with the dye added into the PLA and SMPC did not recover their initial shape fully due to the presence of the dye, which hindered the movement of the polymer chains. SEM revealed good layer bonding for the SMPCs compared to the neat PLA, which led to improved mechanical properties. The thermal stability of PLA was improved by the BA particles; furthermore, the dye and BA particles nucleated the crystallization of PLA, resulting in an enhanced storage modulus. Overall, a biodegradable 3D-printed object of 1 mm in thickness with improved thermal and mechanical properties was produced, with and without the use of the textile. Full article
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23 pages, 7093 KiB  
Review
Removal of Heavy Metal Ions from Wastewaters by Using Chitosan/Poly(Vinyl Alcohol) Adsorbents: A Review
by Dimitrios G. Trikkaliotis, Nina Maria Ainali, Athanasia K. Tolkou, Athanasios C. Mitropoulos, Dimitra A. Lambropoulou, Dimitrios N. Bikiaris and George Z. Kyzas
Macromol 2022, 2(3), 403-425; https://doi.org/10.3390/macromol2030026 - 6 Aug 2022
Cited by 26 | Viewed by 4721
Abstract
Through epistemic efforts in water remediation, numerous sorbents have emerged as either low-cost or more expensive. This review article describes the properties, functions and modifications of cost-effective sorbents based on chitosan and poly(vinyl alcohol) blends for aqueous solutions treatment from heavy metals. Interesting [...] Read more.
Through epistemic efforts in water remediation, numerous sorbents have emerged as either low-cost or more expensive. This review article describes the properties, functions and modifications of cost-effective sorbents based on chitosan and poly(vinyl alcohol) blends for aqueous solutions treatment from heavy metals. Interesting synthesis routes have been reported for the production of membranes, beads, foams and mats, while the kinetic and thermodynamic studies provide spherical knowledge of the system. Tables with the adsorbent’s capacity and enthalpy change are included, while indicative images from the synthesis and characterization techniques of the adsorbents are presented. Full article
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12 pages, 1495 KiB  
Article
The Stability Consequences Promoted by Doping Metallic Atoms on the Degradation of Poly (ε-Caprolactone)
by Traian Zaharescu, Tunde Borbath, Marius Mariș, Istvan Borbath and Mihaela Mariș
Macromol 2022, 2(3), 391-402; https://doi.org/10.3390/macromol2030025 - 5 Aug 2022
Cited by 2 | Viewed by 1594
Abstract
The stability of polymer materials is essentially determined by the molecular structure and the presence of additives and impurities. When a polymer substrate is subjected to vigorous damage by an energetic treatment, the molecular scission generates fragments, which may be oxidized by the [...] Read more.
The stability of polymer materials is essentially determined by the molecular structure and the presence of additives and impurities. When a polymer substrate is subjected to vigorous damage by an energetic treatment, the molecular scission generates fragments, which may be oxidized by the diffused oxygen. The traces of oxide catalysts that may be accidentally incorporated into the polymer materials initiate a faster oxidation that influences the material durability. This study presents the behavior of poly (ε-caprolactone) (PCL) loaded with 2 wt% PbZrO3 previously doped with foreign atoms (Cr, Nd, Mg, Mn, Ti) at the concentration of 0.1 mol%. The investigation procedure, chemiluminescence, reveals the acceleration of the degradation of PCL. The contribution of the metallic traces existing in the structure of PbTiO3 powder is characterized by the activation energies (Ea) involved in the propagation of oxidation. The free radicals are involved in a faster oxidation, when the polymer substrate is heated at superior rates. The comparison of the oxidation levels at the extended period of heating and irradiation indicates the sustained activities of metallic traces acting in oxide powder fillers, especially at temperatures exceeding 150 °C. The essential considerations on material strength against oxidation are presented. Full article
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13 pages, 1046 KiB  
Article
Rheological and Stability Evaluation of Emulsions Containing Fenugreek Galactomannan—Xanthan Gum Mixtures: Effect of Microwave and Ultrasound Treatments
by Rasoul Niknam, Mohammad Reza Soudi and Mohammad Mousavi
Macromol 2022, 2(3), 361-373; https://doi.org/10.3390/macromol2030023 - 1 Aug 2022
Cited by 7 | Viewed by 2578
Abstract
The effects of treating two biopolymers (Trigonella foenum—graceum galactomannan and xanthan gum mixtures) with microwaves and ultrasound on the rheological aspects of O/W emulsions were investigated. The data obtained from steady shear flow were fitted with various models and the best were [...] Read more.
The effects of treating two biopolymers (Trigonella foenum—graceum galactomannan and xanthan gum mixtures) with microwaves and ultrasound on the rheological aspects of O/W emulsions were investigated. The data obtained from steady shear flow were fitted with various models and the best were chosen due to the values of R2 and RMSE. The oscillatory shear rheology data demonstrated that the emulsions not treated with microwaves or ultrasound had viscous-like behavior and treated samples demonstrated weak gel behavior. The values obtained for various rheological parameters (especially apparent viscosity, storage modulus and loss modulus) indicated that fenugreek galactomannan had more impact on the rheological aspects of emulsions in comparison with xanthan gum. In addition, the synergistic interaction between two biopolymers, particularly in samples treated with ultrasound, resulted in better rheological aspects which could be affiliated with the strong bonds between the hydrocolloids. By treating the samples with microwaves and ultrasound, the emulsion stability values of the samples (especially those with a high ratio of galactomannan) significantly increased, which might be connected with various parameters, especially viscosity. Full article
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15 pages, 3431 KiB  
Review
Advances in Alkylated Chitosan and Its Applications for Hemostasis
by Huiyang Jin and Zhengke Wang
Macromol 2022, 2(3), 346-360; https://doi.org/10.3390/macromol2030022 - 27 Jul 2022
Cited by 22 | Viewed by 3760
Abstract
Chitosan, a natural polysaccharide, has been widely used as a biomaterial, especially for hemostasis. However, hemostatic materials processed from pure chitosan have limited hemostatic effect and are extremely unstable in some cases; chemical modification is therefore needed to improve the hemostatic properties of [...] Read more.
Chitosan, a natural polysaccharide, has been widely used as a biomaterial, especially for hemostasis. However, hemostatic materials processed from pure chitosan have limited hemostatic effect and are extremely unstable in some cases; chemical modification is therefore needed to improve the hemostatic properties of chitosan. Through chemical reactions with hydroxyl and amino groups in chitosan macromolecules, such as alkylation, carboxylation, quaternization, etc., different groups can be introduced into the repeating units. Moreover, the introduction of different substituents can endow chitosan with more functions. For example, the introduction of long alkyl chains can improve its hydrophobic property, and greatly improve its hemostatic property. However, there is still no review of alkylated chitosan for hemostasis. Therefore, we introduce in detail several methods (direct alkylation, reductive alkylation and acylation reaction) for preparing alkylated chitosan and its applications for hemostasis. Full article
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22 pages, 6624 KiB  
Article
Biodegradable Films from Kefiran-Based Cryogel Systems
by Stylianos Exarhopoulos, Athanasios Goulas and Georgia Dimitreli
Macromol 2022, 2(3), 324-345; https://doi.org/10.3390/macromol2030021 - 13 Jul 2022
Cited by 6 | Viewed by 2162
Abstract
Kefiran, which was isolated from kefir grains, was used for the fabrication of cryogel-films in the presence of plasticizers, such as glycerol and sorbitol. Varying concentration ratios of the exopolysaccharide/plasticizer system were employed in the process of the cryogel-film formulation and their effect [...] Read more.
Kefiran, which was isolated from kefir grains, was used for the fabrication of cryogel-films in the presence of plasticizers, such as glycerol and sorbitol. Varying concentration ratios of the exopolysaccharide/plasticizer system were employed in the process of the cryogel-film formulation and their effect on the physical (film thickness, moisture content, and solubility) and the mechanical (tensile strength and elongation at break) properties of the films was monitored. Kefiran-film vapor adsorption isotherms were calculated, and a thermal analysis of the samples was also performed. The structural characteristics of the cryogel-films were observed using confocal laser scanning microscopy. The cryo-treatment, alongside the plasticizer addition, affected the physical and mechanical properties of the kefiran films, as well as their morphology. Increasing kefiran concentration resulted in increasing the film thickness, the moisture content, and the tensile strength, while decreased their solubility and their elongation at break. Kefiran-film adsorption isotherms were affected by the cryo-treatment, the kefiran concentration, and the plasticizer use and concentration. The thermal analysis of the kefiran films showed thermal stability. The presence of the plasticizers and their increment concentration resulted in decreasing the glass transition and the melting temperatures. The cryo-treatment and the presence of plasticizers resulted in the films appearing smoother. Glycerol proved to affect more than the sorbitol–water vapor adsorption and the morphology of kefiran films. Full article
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11 pages, 1817 KiB  
Article
Poly(L-lactide) Epimerization and Chain Scission in the Presence of Organic Bases
by Julie Meimoun, Audrey Favrelle-Huret, Julien De Winter and Philippe Zinck
Macromol 2022, 2(2), 236-246; https://doi.org/10.3390/macromol2020016 - 15 Jun 2022
Cited by 4 | Viewed by 3164
Abstract
Organocatalysis for polymer chemistry has become a subject of significant interest in the last two decades. In this contribution, we have studied the evolution of the microstructure of poly(L-lactide) in solution in toluene at 105 °C in the presence of various organocatalysts. Weak [...] Read more.
Organocatalysis for polymer chemistry has become a subject of significant interest in the last two decades. In this contribution, we have studied the evolution of the microstructure of poly(L-lactide) in solution in toluene at 105 °C in the presence of various organocatalysts. Weak bases such as triethylamine and DMAP (4-dimethylaminopyridine) lead to a low extent of epimerization and a chain scission reaction. The DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) amidine induces in turn important extents of both epimerization (up to 37% D-stereoisomer formation) and chain scission. This has been tentatively attributed to a nucleophilic mechanism. Cinchona alkaloids lead to only a modest amount of epimerization. Phosphazene bases are in turn rather active, especially for high catalytic loadings (>1 mol %). The chain scission observed in this case is proposed to occur via a base-catalyzed hydrolysis mechanism. Finally, it is shown that combining an organic base with an acid can lead to a synergistic effect regarding notably the chain scission reaction. Full article
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28 pages, 2344 KiB  
Review
Enzymatic Polymerization as a Green Approach to Synthesizing Bio-Based Polyesters
by Christina I. Gkountela and Stamatina N. Vouyiouka
Macromol 2022, 2(1), 30-57; https://doi.org/10.3390/macromol2010003 - 24 Jan 2022
Cited by 23 | Viewed by 5940
Abstract
Given the fossil fuel crisis and the steady consumption of finite resources, the use of green polymers is becoming necessary. However, the term “green” describes materials that present green properties (such as biological origin and/or biodegradability) and are produced via sustainable processes conducted [...] Read more.
Given the fossil fuel crisis and the steady consumption of finite resources, the use of green polymers is becoming necessary. However, the term “green” describes materials that present green properties (such as biological origin and/or biodegradability) and are produced via sustainable processes conducted under mild conditions and not requiring the use of chemical catalysts, toxic solvents or reagents. Truly green materials must combine these characteristics; consequently, enzymatically synthesized bio-based and/or biodegradable polymers can be characterized as truly green. The present review focuses on the most promising, commercially available aliphatic and alipharomatic polyesters that can be synthesized enzymatically. In particular, the recent developments in the enzymatic polymerization of PLA and PBS and alipharomatic furan-based polyesters (e.g., PBF) are herein analyzed. Based on this analysis, it can be concluded that important steps have been taken toward synthesizing sustainably green polymers. Still, it is necessary to evaluate the applied methods regarding their capability to be used on an industrial scale. Full article
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2021

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33 pages, 9246 KiB  
Review
Insights into Biodegradable Polymer-Supported Titanium Dioxide Photocatalysts for Environmental Remediation
by Nina Maria Ainali, Dimitrios Kalaronis, Eleni Evgenidou, Dimitrios N. Bikiaris and Dimitra A. Lambropoulou
Macromol 2021, 1(3), 201-233; https://doi.org/10.3390/macromol1030015 - 2 Aug 2021
Cited by 35 | Viewed by 5622
Abstract
During the past two decades, immobilization of titanium dioxide (TiO2), a well-known photocatalyst, on several polymeric substrates has extensively gained ground since it limits the need of post-treatment separation stages. Taking into account the numerous substrates tested for supporting TiO2 [...] Read more.
During the past two decades, immobilization of titanium dioxide (TiO2), a well-known photocatalyst, on several polymeric substrates has extensively gained ground since it limits the need of post-treatment separation stages. Taking into account the numerous substrates tested for supporting TiO2 photocatalysts, the use of biodegradable polymer seems a hopeful option owing to its considerable merits, including the flexible nature, low price, chemical inertness, mechanical stability and wide feasibility. The present review places its emphasis on recently published research articles (2011–2021) and exhibits the most innovative studies facilitating the eco-friendly biodegradable polymers to fabricate polymer-based photocatalysts, while the preparation details, photocatalytic performance and reuse of the TiO2/polymer photocatalysts is also debated. The biodegradable polymers examined herein comprise of chitosan (CS), cellulose, alginate, starch, poly(lactid acid) (PLA), polycaprolactone (PCL) and poly(lactide-co-glycolide) (PLGA), while an emphasis on the synthetical pathway (dip-coating, electrospinning, etc.) of the photocatalysts is provided. Full article
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25 pages, 6054 KiB  
Review
Chitosan Adsorbent Derivatives for Pharmaceuticals Removal from Effluents: A Review
by Efstathios V. Liakos, Maria Lazaridou, Georgia Michailidou, Ioanna Koumentakou, Dimitra A. Lambropoulou, Dimitrios N. Bikiaris and George Z. Kyzas
Macromol 2021, 1(2), 130-154; https://doi.org/10.3390/macromol1020011 - 11 May 2021
Cited by 34 | Viewed by 6019
Abstract
Chitin is mentioned as the second most abundant and important natural biopolymer in worldwide scale. The main sources for the extraction and exploitation of this natural polysaccharide polymer are crabs and shrimps. Chitosan (poly-β-(1 → 4)-2-amino-2-deoxy-d-glucose) is the most important derivative of chitin and can [...] Read more.
Chitin is mentioned as the second most abundant and important natural biopolymer in worldwide scale. The main sources for the extraction and exploitation of this natural polysaccharide polymer are crabs and shrimps. Chitosan (poly-β-(1 → 4)-2-amino-2-deoxy-d-glucose) is the most important derivative of chitin and can be used in a wide variety of applications including cosmetics, pharmaceutical and biomedical applications, food, etc., giving this substance high value-added applications. Moreover, chitosan has applications in adsorption because it contains amino and hydroxyl groups in its molecules, and can thus contribute to many possible adsorption interactions between chitosan and pollutants (pharmaceuticals/drugs, metals, phenols, pesticides, etc.). However, it must be noted that one of the most important techniques of decontamination is considered to be adsorption because it is simple, low-cost, and fast. This review emphasizes on recently published research papers (2013–2021) and briefly describes the chemical modifications of chitosan (grafting, cross-linking, etc.), for the adsorption of a variety of emerging contaminants from aqueous solutions, and characterization results. Finally, tables are depicted from selected chitosan synthetic routes and the pH effects are discussed, along with the best-fitting isotherm and kinetic models. Full article
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9 pages, 6802 KiB  
Article
Effect of Cyanuric Acid as an Efficient Nucleating Agent on the Crystallization of Novel Biodegradable Branched Poly(Ethylene Succinate)
by Kangjing Zhang and Zhaobin Qiu
Macromol 2021, 1(2), 112-120; https://doi.org/10.3390/macromol1020009 - 7 Apr 2021
Cited by 3 | Viewed by 2980
Abstract
Novel biodegradable branched poly(ethylene succinate) (b-PES) composites, i.e., nucleated b-PES samples, were prepared by incorporating low loadings of cyanuric acid (CA) through a solution and casting method to enhance the crystallization rate. As an efficient nucleating agent, CA could remarkably increase the nonisothermal [...] Read more.
Novel biodegradable branched poly(ethylene succinate) (b-PES) composites, i.e., nucleated b-PES samples, were prepared by incorporating low loadings of cyanuric acid (CA) through a solution and casting method to enhance the crystallization rate. As an efficient nucleating agent, CA could remarkably increase the nonisothermal melt crystallization peak temperature, shorten the crystallization half-time, accelerate the overall isothermal melt crystallization, and enhance the nucleation density of b-PES spherulites in the composites. Despite the addition of CA, the crystallization mechanism and crystal structure of b-PES remained unchanged. A possible epitaxial crystallization mechanism may account for the nucleation of b-PES crystals induced by CA. Full article
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