New multi-block copolyester of 2,5-furandicarboxylic acid containing PEG-like sequences to form flexible and degradable films for sustainable packaging

Synthesis of Biobased Poly(butylene Furandicarboxylate) Containing Polysulfone with Excellent Thermal Resistance Properties

A synthetic biopolymer derived from furandicarboxylic acid monomer and hydroxyethyl-terminated poly(ether sulfone) is presented. The synthesis involves 4,4'-dichlorodiphenyl sulfone and 4,4-dihydroxydiphenyl sulfone, resulting in poly(butylene furandicarboxylate)-poly(ether sulfone) copolyesters (PBFES) through melt polycondensation with titanium-catalyzed polymerization. This facile method yields segmented polyesters incorporating polysulfone, creating a versatile group of high-temperature thermoplastics with adjustable thermomechanical properties. The PBFES copolyesters demonstrate an impressive tensile modulus of 2830 MPa and a tensile strength of 84 MPa for PBFES55. Additionally, the poly(ether sulfone) unit imparts a relatively high glass transition temperature (Tg), ranging from 36.6 °C for poly(butylene 2,5-furandicarboxylate) to 112.3 °C for PBFES62. Moreover, the complete amorphous film of PBFES exhibits excellent transparency and solvent resistance, making it suitable for applications, such as food packaging materials.

On the Selective Enzymatic Recycling of Poly(pentamethylene 2,5-furanoate)/Poly(lactic acid) Blends and Multiblock Copolymers

Among novel renewable furanoate-based polyesters, poly(pentamethylene 2,5-furandicarboxylate) (PPeF) shows outstanding gas barrier properties and high flexibility. PPeF blending/copolymerization with another well-known bio-based polymer, poly(lactic acid) (PLA), leads to considerably better mechanical and gas barrier properties of the latter, making it suitable for flexible food packaging applications. In this work, enzymatic depolymerization of PLA/PPeF blends with different compositions (1, 3, 5, 20, 30, and 50 wt % PPeF) and a PLA-PPeF block copolymer (50 wt % PPeF) by cutinase 1 from Thermobifida cellulositilytica (Thc_Cut1) was investigated as a possible recycling strategy. Based on quantification of weight loss and high-performance liquid chromatography (HPLC) analysis of released molecules, faster hydrolysis was seen for PLA/PPeF blends with increasing PPeF content when compared to neat PLA, while the block copolymer (P(LA50PeF50)) was significantly less susceptible to hydrolysis. Surface morphology analysis (via scanning electron microscopy), Fourier transform infrared spectroscopy, and NMR analysis confirmed preferential hydrolysis of the PPeF component. Through crystallization, 2,5-furandicarboxylic acid was selectively recovered from the depolymerized films and used for the resynthesis of the PPeF homopolymer, demonstrating the potential of enzymes for novel recycling concepts. The possibility of selective recovery of 2,5-furandicarboxylic acid from the completely depolymerized films with a 75% yield could bring further evidence of the high value of these materials, both in the form of blends and copolymers, for a sustainable whole packaging life cycle, where PPeF is potentially enzymatically recycled and PLA is mechanically recycled.

New Random Aromatic/Aliphatic Copolymers of 2,5-Furandicarboxylic and Camphoric Acids with Tunable Mechanical Properties and Exceptional Gas Barrier Capability for Sustainable Mono-Layered Food Packaging

High molecular weight, fully biobased random copolymers of 2,5-furandicarboxylic acid (2,5-FDCA) containing different amounts of (1R, 3S)-(+)-Camphoric Acid (CA) have been successfully synthesized by two-stage melt polycondensation and compression molding in the form of films. The synthesized copolyesters have been first subjected to molecular characterization by nuclear magnetic resonance spectroscopy and gel-permeation chromatography. Afterward, the samples have been characterized from a thermal and structural point of view by means of differential scanning calorimetry, thermogravimetric analysis, and wide-angle X-ray scattering, respectively. Mechanical and barrier properties to oxygen and carbon dioxide were also tested. The results obtained revealed that chemical modification permitted a modulation of the abovementioned properties depending on the amount of camphoric co-units present in the copolymers. The outstanding functional properties promoted by camphor moieties addition could be associated with improved interchain interactions (π-π ring stacking and hydrogen bonds).

Biobased and Compostable Multiblock Copolymer of Poly(l-lactic acid) Containing 2,5-Furandicarboxylic Acid for Sustainable Food Packaging: The Role of Parent Homopolymers in the Composting Kinetics and Mechanism

In the last years, the exponential growth in the demand of petroleum-based plastic materials, besides the extreme exploitation of nonrenewable resources, lead to the mismanagement of their disposal and to serious ecological issues related to their dispersion in the environment. Among the possible practical solutions, the design of biobased and biodegradable polymers represents one of the most innovative challenges. In such a context, the eco-design of an aromatic-aliphatic multiblock copolymer based on poly(lactic acid) and containing 2,5-furandicarboxylic acid was carried out with the aim of improving the properties of poly(l-lactic acid) for sustainable packaging applications. The synthetic method followed a novel top-down approach, starting from industrial high-molecular-weight poly(l-lactic acid) (PLLA), which was reacted with 1,5-pentanediol to get hydroxyl-terminated PLLA and then chain-extended with hydroxyl-terminated poly(pentamethylene furanoate) (PPeF-OH). The final copolymer, called P(LLA50PeF50)-CE, was subjected to molecular, structural, and thermal characterization. Tensile and gas permeability tests were also carried out. According to the results obtained, PLLA thermal stability was improved, being the range of processing temperatures widened, and its stiffness and brittleness were decreased, making the new material suitable for the realization of films for flexible packaging. The oxygen permeability of PLLA was decreased by 40% and a similar improvement was measured also for carbon dioxide. P(LLA50PeF50)-CE was found to be completely biodegraded within 60 days of composting treatment. In terms of mechanism, the blocks of PPeF and PLLA were demonstrated to undergo surface erosion and bulk hydrolysis, respectively. In terms of kinetics, PPeF blocks degraded slower than PLLA ones.

Recent advances in the development of green furan ring-containing polymeric materials based on renewable plant biomass

Fossil resources are rapidly depleting, forcing researchers in various fields of chemistry and materials science to switch to the use of renewable sources and the development of corresponding technologies. In this regard, the field of sustainable materials science is experiencing an extraordinary surge of interest in recent times due to the significant advances made in the development of new polymers with desired and controllable properties. This review summarizes important scientific reports in recent times dedicated to the synthesis, construction and computational studies of novel sustainable polymeric materials containing unchanged (pseudo)aromatic furan cores in their structure. Linear polymers for thermoplastics, branched polymers for thermosets and other crosslinked materials are emerging materials to highlight. Various polymer blends and composites based on sustainable polyfurans are also considered as pathways to achieve high-value-added products.

Bio-based and one-day compostable poly(diethylene 2,5-furanoate) for sustainable flexible food packaging: Effect of ether-oxygen atom insertion on the final properties

In the present work, the effect of ether oxygen atom introduction in a furan ring-containing polymer has been evaluated. Solvent-free polycondensation process permitted the preparation of high molecular weight poly(diethylene 2,5-furandicarboxylate) (PDEF), by reacting the dimethyl ester of 2,5-furandicarboxylic acid with diethylene glycol. After molecular and thermal characterization, PDEF mechanical response and gas barrier properties to O₂ and CO₂, measured at different temperatures and humidity, were studied and compared with those of poly(butylene 2,5-furandicarboxylate) (PBF) and poly(pentamethylene 2,5-furanoate) (PPeF) previously determined. Both PDEF and PPeF films were amorphous, differently from PBF one. Glass transition temperature of PDEF (24 °C) is between those of PBF (39 °C) and PPeF (13 °C). As concerns mechanical response, PDEF is more flexible (elastic modulus [E] = 673 MPa) than PBF (E = 1290 MPa) but stiffer than PPeF (E = 9 MPa). Moreover, PDEF is the most thermally stable (temperature of maximum degradation rate being 418 for PDEF, 407 for PBF and 414 °C for PPeF) and hydrophilic (water contact angle being 74° for PDEF, 90° for PBF and 93° for PPeF), with gas barrier performances very similar to those of PPeF (O₂ and CO₂ transmission rate being 0.0022 and 0.0018 for PDEF and, 0.0016 and 0.0014 cm³ cm/m² d atm for PPeF). Lab scale composting experiments indicated that PDEF and PPeF were compostable, the former degrading faster, in just one day. The results obtained are explained on the basis of the high electronegativity of ether oxygen atom with respect to the carbon one, and the consequent increase of dipoles along the macromolecule.

Poly(butylene 2,4-furanoate), an Added Member to the Class of Smart Furan-Based Polyesters for Sustainable Packaging: Structural Isomerism as a Key to Tune the Final Properties

High-molecular-weight poly(butylene 2,4-furanoate) (2,4-PBF), an isomer of well-known poly(butylene 2,5-furanoate) (2,5-PBF), was synthesized through an eco-friendly solvent-free polycondensation process and processed in the form of an amorphous film by compression molding. Molecular characterization was carried out by NMR spectroscopy and GPC analysis, confirming the chemical structure and high polymerization degree. Thermal analyses evidenced a reduction of both glass-to-rubber transition and melting temperatures, as well as a detriment of crystallization capability, for 2,4-PBF with respect to 2,5-PBF. Nevertheless, it was possible to induce crystal phase formation by annealing treatment. Wide-angle X-ray scattering revealed that the crystal lattices developed in the two isomers are distinct from each other. The different isomerism affects also the thermal stability, being 2,4-PBF more thermally inert than 2,5-PBF. Functional properties, such as wettability, mechanical response, and gas barrier capability, were tested on both amorphous and semicrystalline 2,4-PBF films and compared with those of 2,5-PBF. Reduced hydrophilicity was determined for 2,4-isomer, in line with its lower average dipole moment, suggesting better chemical resistance to hydrolysis. Stress-strain tests have evidenced the higher flexibility and toughness of 2,4-PBF with respect to those of 2,5-PBF and the possibility of improving its mechanical resistance by annealing. Finally, the different isomerism deeply affects the gas barrier performance, being the O₂- and CO₂-transmission rates of 2,4-PBF 50 and 110 times lower, respectively, than those of 2,5-PBF. The gas barrier properties turned out to be outstanding under a dry atmosphere as well as in humid conditions, suggesting the presence of interchain hydrogen bonds. The gas blocking capability decreases after annealing because of the presence of disclination associated with the formation of crystals.

Bio-Polyethylene (Bio-PE), Bio-Polypropylene (Bio-PP) and Bio-Poly(ethylene terephthalate) (Bio-PET): Recent Developments in Bio-Based Polymers Analogous to Petroleum-Derived Ones for Packaging and Engineering Applications

In recent year, there has been increasing concern about the growing amount of plastic waste coming from daily life. Different kinds of synthetic plastics are currently used for an extensive range of needs, but in order to reduce the impact of petroleum-based plastics and material waste, considerable attention has been focused on "green" plastics. In this paper, we present a broad review on the advances in the research and development of bio-based polymers analogous to petroleum-derived ones. The main interest for the development of bio-based materials is the strong public concern about waste, pollution and carbon footprint. The sustainability of those polymers, for general and specific applications, is driven by the great progress in the processing technologies that refine biomass feedstocks in order to obtain bio-based monomers that are used as building blocks. At the same time, thanks to the industrial progress, it is possible to obtain more versatile and specific chemical structures in order to synthetize polymers with ad-hoc tailored properties and functionalities, with engineering applications that include packaging but also durable and electronic goods. In particular, three types of polymers were described in this review: Bio-polyethylene (Bio-PE), bio-polypropylene (Bio-PP) and Bio-poly(ethylene terephthalate) (Bio-PET). The recent advances in their development in terms of processing technologies, product development and applications, as well as their advantages and disadvantages, are reported.

Bio-Polyethylene (Bio-PE), Bio-Polypropylene (Bio-PP) and Bio-Poly(ethylene terephthalate) (Bio-PET): Recent Developments in Bio-Based Polymers Analogous to Petroleum-Derived Ones for Packaging and Engineering Applications

In recent year, there has been increasing concern about the growing amount of plastic waste coming from daily life. Different kinds of synthetic plastics are currently used for an extensive range of needs, but in order to reduce the impact of petroleum-based plastics and material waste, considerable attention has been focused on "green" plastics. In this paper, we present a broad review on the advances in the research and development of bio-based polymers analogous to petroleum-derived ones. The main interest for the development of bio-based materials is the strong public concern about waste, pollution and carbon footprint. The sustainability of those polymers, for general and specific applications, is driven by the great progress in the processing technologies that refine biomass feedstocks in order to obtain bio-based monomers that are used as building blocks. At the same time, thanks to the industrial progress, it is possible to obtain more versatile and specific chemical structures in order to synthetize polymers with ad-hoc tailored properties and functionalities, with engineering applications that include packaging but also durable and electronic goods. In particular, three types of polymers were described in this review: Bio-polyethylene (Bio-PE), bio-polypropylene (Bio-PP) and Bio-poly(ethylene terephthalate) (Bio-PET). The recent advances in their development in terms of processing technologies, product development and applications, as well as their advantages and disadvantages, are reported.

Fully Biobased Superpolymers of 2,5-Furandicarboxylic Acid with Different Functional Properties: From Rigid to Flexible, High Performant Packaging Materials

In the present paper, four fully biobased homopolyesters of 2,5-furandicarboxylic acid (2,5-FDCA) with a high molecular weight have been successfully synthesized by two-stage melt polycondensation, starting from the dimethyl ester of 2,5-FDCA and glycols of different lengths (the number of methylene groups ranged from 3 to 6). The synthesized polyesters have been first subjected to an accurate molecular characterization by NMR and gel-permeation chromatography. Afterward, the samples have been successfully processed into free-standing thin films (thickness comprised between 150 to 180 μm) by compression molding. Such films have been characterized from the structural (by wide-angle X-ray scattering and small-angle X-ray scattering), thermal (by differential scanning calorimetry and thermogravimetric analysis), mechanical (by tensile test), and gas barrier (by permeability measurements) point of view. The glycol subunit length was revealed to be the key parameter in determining the kind and fraction of ordered phases developed by the sample during compression molding and subsequent cooling. After storage at room temperature for one month, only the homopolymers containing the glycol subunit with an even number of -CH2- groups (poly(butylene 2,5-furanoate) (PBF) and poly(hexamethylene 2,5-furanoate) (PHF)) were able to develop a three-dimensional ordered crystalline phase in addition to the amorphous one, the other two appearing completely amorphous (poly(propylene 2,5-furanoate (PPF) and poly(pentamethylene 2,5-furanoate) (PPeF)). From X-ray scattering experiments using synchrotron radiation, it was possible to evidence a third phase characterized by a lower degree of order (one- or two-dimensional), called a mesophase, in all the samples under study, its fraction being strictly related to the glycol subunit length: PPeF was found to be the sample with the highest fraction of mesophase followed by PHF. Such a mesophase, together with the amorphous and the eventually present crystalline phase, significantly impacted the mechanical and barrier properties, these last being particularly outstanding for PPeF, the polyester with the highest fraction of mesophase among those synthesized in the present work.