Search

Biodegradation of polyesters driven by enzymes is considered as one of the most effective way of degradation of these materials, as a way to control plastics accumulation in the environment. In this study, we present two different strategies to tune the enzymatic degradation of PBS films triggered by a lipase from Pseudomonas cepacia. Firstly, the kinetics of enzymatic degradation of PBS films was regulated by applying multilayer coats of polysaccharide alginate and chitosan (Alg/Chi) films. Secondly, self-degradable PBS films were prepared by embedding lipase-filled alginate particles. For comparison purposes, a detailed enzymatic degradation study of neat PBS films exposed to a lipase from P. cepacia in solution was made to determine the main experimental parameters influencing their degradation in solution. The results showed that an increase in enzyme concentration increased the degradation extent and rate of neat PBS films. At a fixed enzyme concentration, stirring of the solution containing the enzyme and the PBS also increased the biodegradation rate. In the case of the PBS films coated with a different number of Alg/Chi layers by spray-assisted LbL and subjected to enzymatic degradation experiments in solution, the extent of degradation was found to be dependent on the number of protective coating layers. Therefore, the Alg/Chi biobased coating constitutes an effective barrier to the diffusion of the lipase, thus proving its effectiveness in modulating the enzymatic activity as a function of coating thickness. In the case of self-degradable PBS containing lipase-embedded alginate beads (employed to protect the enzyme during high-temperature processing), only limited biodegradation was observed as the amount of encapsulated enzyme employed was too small. Nonetheless, these results are promising, as the enzymatic activity –indicative of the degradation capacity of the enzyme– determined for all these samples was about 2 orders of magnitude lower than that of p

Biodegradation of polyesters driven by enzymes is considered as one of the most effective way of degradation of these materials, as a way to control plastics accumulation in the environment. In this study, we present two different strategies to tune the enzymatic degradation of PBS films triggered by a lipase from Pseudomonas cepacia. Firstly, the kinetics of enzymatic degradation of PBS films was regulated by applying multilayer coats of polysaccharide alginate and chitosan (Alg/Chi) films. Secondly, self-degradable PBS films were prepared by embedding lipase-filled alginate particles. For comparison purposes, a detailed enzymatic degradation study of neat PBS films exposed to a lipase from P. cepacia in solution was made to determine the main experimental parameters influencing their degradation in solution. The results showed that an increase in enzyme concentration increased the degradation extent and rate of neat PBS films. At a fixed enzyme concentration, stirring of the solution containing the enzyme and the PBS also increased the biodegradation rate. In the case of the PBS films coated with a different number of Alg/Chi layers by spray-assisted LbL and subjected to enzymatic degradation experiments in solution, the extent of degradation was found to be dependent on the number of protective coating layers. Therefore, the Alg/Chi biobased coating constitutes an effective barrier to the diffusion of the lipase, thus proving its effectiveness in modulating the enzymatic activity as a function of coating thickness. In the case of self-degradable PBS containing lipase-embedded alginate beads (employed to protect the enzyme during high-temperature processing), only limited biodegradation was observed as the amount of encapsulated enzyme employed was too small. Nonetheless, these results are promising, as the enzymatic activity –indicative of the degradation capacity of the enzyme– determined for all these samples was about 2 orders of magnitude lower than that of p

Isodimorphic behavior is determined by partial inclusion of comonomer segments within the crystalline structure and arises from the comparatively similar repeating chain units of the parental homopolymers. Isodimorphic random copolymers are able to crystallize irrespective of their composition and exhibit a pseudo-eutectic behavior when their melting point values are plotted as a function of comonomer content. At the pseudo-eutectic point or region, two crystalline phases can coexist. On the right-hand and the left-hand side of the pseudo-eutectic point or region, only one single crystalline phase can form which is very similar to the crystalline structures of the parent homopolymers. This article aims to study the synthesis method, structure, crystallization behavior and mechanical properties of isodimorphic random PBS-ran-PCL copolyesters. Moreover, this study provides a comprehensive analysis of our main recent results on PBS-ran-PCL random copolyesters with three different molecular weights. The results show that the comonomer composition and crystallization conditions are the major factors responsible for the crystalline morphology, crystallization kinetics and mechanical performance of isodimorphic random copolyesters. Our studies demonstrate that in the pseudo-eutectic region, where both crystalline phases can coexist, the crystallization conditions determine the crystalline phase or phases of the copolymer. The relationships between the comonomer composition and mechanical properties are also addressed in this work.

[EN] Monomers obtained from renewable feedstocks have emerged as a sustainable alternative to petroleum derived polymers. One of the biomass derived polyesters that has recently been gaining attention as an alternative to petrochemical polyethylene terephtalate (PET) for food and beverage packaging applications is poly(ethylene furanoate) (PEF). However, similar to PET, PEF is not biodegradable or compostable and its end-of-life options must be thus considered to avoid contributing to the accumulation of plastic waste. In this manuscript, PEF films were first produced using thermo-compression, an industrially relevant processing method, and their thermal, mechanical, and barrier properties were determined and compared to those of PET and other biopolyesters to ascertain their suitability for food packaging. Thereafter, the chemical glycolysis of PEF film waste was investigated using a sustainable and thermally stable acid-base organocatalyst. After succesfully deconstructing PEF into bis(2-hydroxyethyl)-furan-2,5-dicarboxylate (BHEF), the obtained BHEF diester was used to resynthesize PEF using the same catalyst to generate a new biopolyester with similar thermal properties to the virgin one in a closed-loop cycle.

[EN] Monomers obtained from renewable feedstocks have emerged as a sustainable alternative to petroleum derived polymers. One of the biomass derived polyesters that has recently been gaining attention as an alternative to petrochemical polyethylene terephtalate (PET) for food and beverage packaging applications is poly(ethylene furanoate) (PEF). However, similar to PET, PEF is not biodegradable or compostable and its end-of-life options must be thus considered to avoid contributing to the accumulation of plastic waste. In this manuscript, PEF films were first produced using thermo-compression, an industrially relevant processing method, and their thermal, mechanical, and barrier properties were determined and compared to those of PET and other biopolyesters to ascertain their suitability for food packaging. Thereafter, the chemical glycolysis of PEF film waste was investigated using a sustainable and thermally stable acid-base organocatalyst. After succesfully deconstructing PEF into bis(2-hydroxyethyl)-furan-2,5-dicarboxylate (BHEF), the obtained BHEF diester was used to resynthesize PEF using the same catalyst to generate a new biopolyester with similar thermal properties to the virgin one in a closed-loop cycle.

Isodimorphic behavior is determined by partial inclusion of comonomer segments within the crystalline structure and arises from the comparatively similar repeating chain units of the parental homopolymers. Isodimorphic random copolymers are able to crystallize irrespective of their composition and exhibit a pseudo-eutectic behavior when their melting point values are plotted as a function of comonomer content. At the pseudo-eutectic point or region, two crystalline phases can coexist. On the right-hand and the left-hand side of the pseudo-eutectic point or region, only one single crystalline phase can form which is very similar to the crystalline structures of the parent homopolymers. This article aims to study the synthesis method, structure, crystallization behavior and mechanical properties of isodimorphic random PBS-ran-PCL copolyesters. Moreover, this study provides a comprehensive analysis of our main recent results on PBS-ran-PCL random copolyesters with three different molecular weights. The results show that the comonomer composition and crystallization conditions are the major factors responsible for the crystalline morphology, crystallization kinetics and mechanical performance of isodimorphic random copolyesters. Our studies demonstrate that in the pseudo-eutectic region, where both crystalline phases can coexist, the crystallization conditions determine the crystalline phase or phases of the copolymer. The relationships between the comonomer composition and mechanical properties are also addressed in this work.

Isodimorphic behavior is determined by partial inclusion of comonomer segments within the crystalline structure and arises from the comparatively similar repeating chain units of the parental homopolymers. Isodimorphic random copolymers are able to crystallize irrespective of their composition and exhibit a pseudo-eutectic behavior when their melting point values are plotted as a function of comonomer content. At the pseudo-eutectic point or region, two crystalline phases can coexist. On the right-hand and the left-hand side of the pseudo-eutectic point or region, only one single crystalline phase can form which is very similar to the crystalline structures of the parent homopolymers. This article aims to study the synthesis method, structure, crystallization behavior and mechanical properties of isodimorphic random PBS-ran-PCL copolyesters. Moreover, this study provides a comprehensive analysis of our main recent results on PBS-ran-PCL random copolyesters with three different molecular weights. The results show that the comonomer composition and crystallization conditions are the major factors responsible for the crystalline morphology, crystallization kinetics and mechanical performance of isodimorphic random copolyesters. Our studies demonstrate that in the pseudo-eutectic region, where both crystalline phases can coexist, the crystallization conditions determine the crystalline phase or phases of the copolymer. The relationships between the comonomer composition and mechanical properties are also addressed in this work.

Monomers obtained from renewable feedstocks have emerged as a sustainable alternative to petroleum derived polymers. One of the biomass derived polyesters that has recently been gaining attention as an alternative to petrochemical polyethylene terephtalate (PET) for food and beverage packaging applications is poly(ethylene furanoate) (PEF). However, similar to PET, PEF is not biodegradable or compostable and its end-of-life options must be thus considered to avoid contributing to the accumulation of plastic waste. In this manuscript, PEF films were first produced using thermo-compression, an industrially relevant processing method, and their thermal, mechanical, and barrier properties were determined and compared to those of PET and other biopolyesters to ascertain their suitability for food packaging. Thereafter, the chemical glycolysis of PEF film waste was investigated using a sustainable and thermally stable acid–base organocatalyst. After succesfully deconstructing PEF into bis(2-hydroxyethyl)-furan-2,5-dicarboxylate (BHEF), the obtained BHEF diester was used to resynthesize PEF using the same catalyst to generate a new biopolyester with similar thermal properties to the virgin one in a closed-loop cycle.

Two series of partially biobased ABA triblock copolyesters were successfully prepared by ring-opening polymerization (ROP) of L-lactide initiated by two telechelic polyester polyols using an organic catalyst. B blocks were made of telechelic poly(hexamethylene terephthalate) (PHT) and poly(hexamethylene 2,5- furandicarboxylate) (PHF), respectively, with average molar masses of around 3500 g mol-1 and A blocks were made of poly(lactic acid)s (PLA) of different block lengths. For each series, four copolymers with different PHT/PLA and PHF/PLA compositions were prepared by varying the feed molar ratios. The triblock structure of the obtained copolymers was ascertained by 13C NMR, which confirms that the organic catalyst employed does not promote transesterification reactions at the low temperatures used for the reaction. All copolyesters were thermally stable under inert atmosphere up to around 300 °C. For all synthesized copolyesters, the PLA blocks were unable to crystallize, mainly due to racemization reactions taking place during L-lactide ROP. Both, PHT and PHF blocks were able to crystallize and their thermal and structural properties (Tm, Tc, Xc and lamellar thickness) were independent on PLA content until its concentration was very high and topological restrictions difficulted crystallization. According to SAXS, most copolymers were found to be miscible in the melt. Both PLA-b-PHT-b-PLA or PLA-b-PHF-b-PLA triblock copolymers showed a single Tg indicating that the components are miscible in the amorphous state.

Two series of partially biobased ABA triblock copolyesters were successfully prepared by ring-opening polymerization (ROP) of L-lactide initiated by two telechelic polyester polyols using an organic catalyst. B blocks were made of telechelic poly(hexamethylene terephthalate) (PHT) and poly(hexamethylene 2,5- furandicarboxylate) (PHF), respectively, with average molar masses of around 3500 g mol-1 and A blocks were made of poly(lactic acid)s (PLA) of different block lengths. For each series, four copolymers with different PHT/PLA and PHF/PLA compositions were prepared by varying the feed molar ratios. The triblock structure of the obtained copolymers was ascertained by 13C NMR, which confirms that the organic catalyst employed does not promote transesterification reactions at the low temperatures used for the reaction. All copolyesters were thermally stable under inert atmosphere up to around 300 °C. For all synthesized copolyesters, the PLA blocks were unable to crystallize, mainly due to racemization reactions taking place during L-lactide ROP. Both, PHT and PHF blocks were able to crystallize and their thermal and structural properties (Tm, Tc, Xc and lamellar thickness) were independent on PLA content until its concentration was very high and topological restrictions difficulted crystallization. According to SAXS, most copolymers were found to be miscible in the melt. Both PLA-b-PHT-b-PLA or PLA-b-PHF-b-PLA triblock copolymers showed a single Tg indicating that the components are miscible in the amorphous state.

Two series of partially biobased ABA triblock copolyesters were successfully prepared by ring-opening polymerization (ROP) of L-lactide initiated by two telechelic polyester polyols using an organic catalyst. B blocks were made of telechelic poly(hexamethylene terephthalate) (PHT) and poly(hexamethylene 2,5- furandicarboxylate) (PHF), respectively, with average molar masses of around 3500 g mol-1 and A blocks were made of poly(lactic acid)s (PLA) of different block lengths. For each series, four copolymers with different PHT/PLA and PHF/PLA compositions were prepared by varying the feed molar ratios. The triblock structure of the obtained copolymers was ascertained by 13C NMR, which confirms that the organic catalyst employed does not promote transesterification reactions at the low temperatures used for the reaction. All copolyesters were thermally stable under inert atmosphere up to around 300 °C. For all synthesized copolyesters, the PLA blocks were unable to crystallize, mainly due to racemization reactions taking place during L-lactide ROP. Both, PHT and PHF blocks were able to crystallize and their thermal and structural properties (Tm, Tc, Xc and lamellar thickness) were independent on PLA content until its concentration was very high and topological restrictions difficulted crystallization. According to SAXS, most copolymers were found to be miscible in the melt. Both PLA-b-PHT-b-PLA or PLA-b-PHF-b-PLA triblock copolymers showed a single Tg indicating that the components are miscible in the amorphous state.

The capacity of redox D-mannitol-based polyurethanes to modulate the glutathione response under physiological conditions, as well as their effectiveness for sustained and site-specific drug release in the gastrointestinal tract (GIT), have been demonstrated in previous studies. Based on those promising results, our attention has now been drawn towards hydrolytic degradation processes at 37 °C and different pH values, from acidic to basic conditions, as in the GIT. For that, two sets of branched and linear D-mannitol-based polyurethanes containing disulfide bonds have been synthesized, which has been possible depending on the starting D-mannitol-derived monomer. Thus 3,4-O-isopropylidene-D-mannitol, having two secondary hydroxyl groups in addition to the two primary hydroxyl groups, afforded polyurethanes with a certain degree of branching. In contrast, 2,4:3,5-di-O-isopropylidene-D-mannitol and 2,3:4,5-di-O-isopropylidene-D-mannitol, lacking secondary hydroxyl groups, led to linear polyurethanes. Removal of the O-isopropylidene protecting groups resulted in more-hydrophilic materials. As in glutathione-mediated degradation, the branched polyurethanes presented enhanced degradation under physiological conditions, proportional to the content of D-mannitol, whereas linear polyurethanes were degraded slowly, and pH 8 and 10 were required.

The capacity of redox D-mannitol-based polyurethanes to modulate the glutathione response under physiological conditions, as well as their effectiveness for sustained and site-specific drug release in the gastrointestinal tract (GIT), have been demonstrated in previous studies. Based on those promising results, our attention has now been drawn towards hydrolytic degradation processes at 37 °C and different pH values, from acidic to basic conditions, as in the GIT. For that, two sets of branched and linear D-mannitol-based polyurethanes containing disulfide bonds have been synthesized, which has been possible depending on the starting D-mannitol-derived monomer. Thus 3,4-O-isopropylidene-D-mannitol, having two secondary hydroxyl groups in addition to the two primary hydroxyl groups, afforded polyurethanes with a certain degree of branching. In contrast, 2,4:3,5-di-O-isopropylidene-D-mannitol and 2,3:4,5-di-O-isopropylidene-D-mannitol, lacking secondary hydroxyl groups, led to linear polyurethanes. Removal of the O-isopropylidene protecting groups resulted in more-hydrophilic materials. As in glutathione-mediated degradation, the branched polyurethanes presented enhanced degradation under physiological conditions, proportional to the content of D-mannitol, whereas linear polyurethanes were degraded slowly, and pH 8 and 10 were required.

The capacity of redox D-mannitol-based polyurethanes to modulate the glutathione response under physiological conditions, as well as their effectiveness for sustained and site-specific drug release in the gastrointestinal tract (GIT), have been demonstrated in previous studies. Based on those promising results, our attention has now been drawn towards hydrolytic degradation processes at 37 °C and different pH values, from acidic to basic conditions, as in the GIT. For that, two sets of branched and linear D-mannitol-based polyurethanes containing disulfide bonds have been synthesized, which has been possible depending on the starting D-mannitol-derived monomer. Thus 3,4-O-isopropylidene-D-mannitol, having two secondary hydroxyl groups in addition to the two primary hydroxyl groups, afforded polyurethanes with a certain degree of branching. In contrast, 2,4:3,5-di-O-isopropylidene-D-mannitol and 2,3:4,5-di-O-isopropylidene-D-mannitol, lacking secondary hydroxyl groups, led to linear polyurethanes. Removal of the O-isopropylidene protecting groups resulted in more-hydrophilic materials. As in glutathione-mediated degradation, the branched polyurethanes presented enhanced degradation under physiological conditions, proportional to the content of D-mannitol, whereas linear polyurethanes were degraded slowly, and pH 8 and 10 were required.

The capacity of redox D-mannitol-based polyurethanes to modulate the glutathione response under physiological conditions, as well as their effectiveness for sustained and site-specific drug release in the gastrointestinal tract (GIT), have been demonstrated in previous studies. Based on those promising results, our attention has now been drawn towards hydrolytic degradation processes at 37 °C and different pH values, from acidic to basic conditions, as in the GIT. For that, two sets of branched and linear D-mannitol-based polyurethanes containing disulfide bonds have been synthesized, which has been possible depending on the starting D-mannitol-derived monomer. Thus 3,4-O-isopropylidene-D-mannitol, having two secondary hydroxyl groups in addition to the two primary hydroxyl groups, afforded polyurethanes with a certain degree of branching. In contrast, 2,4:3,5-di-O-isopropylidene-D-mannitol and 2,3:4,5-di-O-isopropylidene-D-mannitol, lacking secondary hydroxyl groups, led to linear polyurethanes. Removal of the O-isopropylidene protecting groups resulted in more-hydrophilic materials. As in glutathione-mediated degradation, the branched polyurethanes presented enhanced degradation under physiological conditions, proportional to the content of D-mannitol, whereas linear polyurethanes were degraded slowly, and pH 8 and 10 were required.

Poly(hexamethylene terephthalate) (PHT)/carbon nanotubes (CNT) nanocomposites containing 1% and 3% (w/w) of filler were prepared by two procedures: in situ ring-opening polymerization of hexamethylene terephthalate cyclic oligomers in the presence of CNT and melt blending of PHT/CNT mixtures. Arc discharge multiwalled carbon nanotubes, both pristine (MWCNT) and hydroxyl functionalized (MWCNT-OH), were used. The objective was to evaluate the effect of preparation procedure, nanotube side-wall functionalization and amount of nanotube loaded on properties of PHT. All nanocomposites showed an efficient distribution of the carbon nanotubes within the PHT matrix but interfacial adhesion and reinforcement effect was dependent on both functionalization and nanotubes loading. Significant differences in thermal stability and mechanical properties ascribable to functionalization and processing were observed among the prepared nanocomposites. All the prepared nanocomposites showed enhanced crystallizability due to CNT nucleating effects although changes in melting and glass transition temperatures were not significant.