George Z. Papageorgiou

Sustainable, eco-friendly polyesters synthesized from renewable resources: preparation and thermal characteristics of poly(dimethyl-propylene furanoate)

Poly(2,2-dimethyl-1,3-propylene furanoate) (PDMPF), an interesting sustainable biobased polyester based on 2,5-furan dicarboxylic acid (FDCA), was synthesized by applying the two-stage melt polycondensation method. The polyester exhibited a melting temperature of Tm = 198 °C and a glass transition temperature of Tg = 68 °C. Multiple melting was observed for the samples crystallized isothermally at temperatures ranging from 160 to 175 °C. Extensive recrystallization was evidenced by modulated temperature differential scanning calorimetry (MDSC) during heating. The equilibrium melting temperature was found to be and the enthalpy of fusion of the pure crystalline polymer was ΔHf = 133 J g−1. The crystallization rates were analyzed according to the secondary nucleation theory, and a relatively large nucleation constant Kg was obtained, representing the rigidity of the macromolecular chains. Large spherulites were observed during isothermal crystallization tests with the aid of polarized light optical microscopy (PLOM). The polyester showed significant stability during the thermal degradation tests. Finally, the degradation mechanism was investigated by employing a pyrolyzer–gas chromatography–mass spectroscopy (Py-GC-MS) system.

Synthesis, properties and thermal behavior of poly(decylene-2,5-furanoate): a biobased polyester from 2,5-furan dicarboxylic acid

In the present study, an interesting, eco-friendly polyester, poly(decylene-2,5-furanoate) (PDeF) was synthesized from 2,5-furan dicarboxylic acid with a variation of the well-known two-step melt polycondensation method. The crystallization and melting behavior of PDeF, was evaluated with different calorimetric methods; conventional, fast and temperature modulated scanning calorimetry. The results showed that PDeF is a fast crystallizing polyester, with a glass transition close to 1 °C and an equilibrium melting temperature equal to 129.8 °C. Various crystallization temperatures and rates were employed in order to evaluate in detail the thermal characteristics of PDeF. Isothermal and non-isothermal crystallization kinetics were also investigated by means of Avrami, Lauritzen–Hoffman theories and model-free kinetics. The structural features of PDeF were also studied by X-ray diffraction (XRD) and nuclear magnetic resonance (1H-NMR) while the size and density of spherulites was observed by polarized optical microscopy (POM) after crystallization in a wide range of temperatures. Finally, from tensile testing it was realized that PDeF has similar mechanical properties like tensile strength and Youngs modulus to that of low density polyethylene (LDPE).

Biobased poly(ethylene furanoate-co-ethylene succinate) copolyesters: solid state structure, melting point depression and biodegradability

Poly(ethylene furanoate) (PEF) is a fully bio-based polyester with unique gas barrier properties, considered an alternative to poly(ethylene terephthalate) (PET) in food packaging applications. However, it is not biodegradable. For this reason, copolymerization with an aliphatic succinic acid monomer was investigated. The respective poly(ethylene furanoate-co-ethylene succinate) (PEFSu) copolymers were prepared via melt polycondensation from 2,5-dimethylfuran-dicarboxylate, succinic acid and ethylene glycol at different ratios. 1HNMR spectroscopy showed the copolymers are random. The crystallization and melting of the copolymers were thoroughly evaluated. Isodimorphic cocrystallization was concluded from both the WAXD patterns and the minimum in the plots of melting temperature versus composition. The pseudo-eutectic melting point corresponded to an ethylene succinate content of about 30 mol%. The enzymatic hydrolysis tests using Rhizopus delemar and Pseudomonas cepacia lipase revealed that the copolymers with up to 50 mol% ES units show measurable weight loss rates. For higher ES content, the copolymers showed fast hydrolysis.

Controlled release formulations of risperidone antipsychotic drug in novel aliphatic polyester carriers: Data analysis and modelling

In the present study a series of biodegradable and biocompatible poly(ε-caprolactone)/poly(propylene glutarate) (PCL/PPGlu) polymer blends were investigated as controlled release carriers of Risperidone drug (RISP), appropriate for transdermal drug delivery. The PCL/PPGlu carriers were prepared in different weight ratios. Miscibility studies of blends were evaluated through differential scanning calorimetry (DSC) and X-ray diffractometry (XRD). Hydrolysis studies were performed at 37°C using a phosphate buffered saline solution. The prepared blends have been used for the preparation of RISP patches via solvent evaporation method, containing 5, 10 and 15wt% RISP. These formulations were characterized using FT-IR spectroscopy, DSC and WAXD in order to evaluate interactions taking place between polymer matrix and drug, as well as the dispersion and the physical state of the drug inside the polymer matrix. In vitro drug release studies were performed using as dissolution medium phosphate buffered saline simulating body fluids. It was found that in all cases controlled release formulations were obtained, while the RISP release varies due to the properties of the used polymer blend and the different levels of drug loading. Artificial Neural Networks (ANNs) were used for dissolution behaviour modelling showing increased correlation efficacy compared to Multi-Linear-Regression (MLR).

Effect of catalyst type on molecular weight increase and coloration of poly(ethylene furanoate) biobased polyester during melt polycondensation

In this work, the effect of the catalysts tetrabutyl titanate(IV) (TBT), titanium(IV) isopropoxide (TIS), tin(II) 2-ethylhexanoate (TEH) and dibutyltin(IV) oxide (DBTO) on the synthesis of poly(ethylene furanoate) (PEF) was studied during a two-stage melt polycondensation process. In all reactions, 2,5-dimethylfuran-dicarboxylate (DMFD) and ethylene glycol (EG) in 1u2006:u20062 molar ratios, and 400 ppm of catalyst were used. The rate of the transesterification reaction (first stage) was evaluated by measuring the volume of the distilled methanol and for the polycondensation reaction (second stage) by the increase of intrinsic viscosity. For the first stage, all catalysts had a similar effect to methanol distillation, except for TEH which was found to be the slowest catalyst, while for the second stage TIS and TBT were found to be the most effective catalysts, followed by DBTO and TEH, which again had the lowest reactivity. Coloration of the prepared polyesters was measured using the L*a*b* colour space system and was found to be dependent on catalyst type and melt polycondensation time, with titanate catalysts yielding the highest coloration. White coloured polyesters can be obtained after dissolution in trifluroacetic acid and chloroform mixture, and precipitation in methanol. Decomposition by-products formed throughout the different processes were identified in solution and elucidated by using liquid chromatography high resolution mass spectrometry (LC-HRMS). Similar decomposition products were detected in all chromatographs and therefore concentration in samples prepared with titanate catalysts might be the cause of the higher colour intensity of these samples.

Effect of surface functionalization of halloysite nanotubes on synthesis and thermal properties of poly( ε -caprolactone)

In this work, halloysite nanotubes (HNTs) and functionalized HNTs–APTES (aminopropyltriethoxysilane) in concentrations 0.5, 1 and 2.5xa0wt% were used as nanofillers in the synthesis of poly(ε-caprolactone) (PCL) nanocomposites via the in situ ring-opening polymerization of ε-caprolactone (CL). The successful functionalization of HNTs was confirmed with X-ray photoelectron spectroscopy. The effects of HNTs and HNTs–APTES on the polymerization procedure and on the thermal properties of PCL were studied in detail. It was found that both nanofillers reduced the

Production of bio-based 2,5-furan dicarboxylate polyesters: Recent progress and critical aspects in their synthesis and thermal properties

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Furan-based polyesters from renewable resources: Crystallization and thermal degradation behavior of poly(hexamethylene 2,5-furan-dicarboxylate)

M¯n values of the resulting nanocomposites, with the unfunctionalized one reducing it in a higher extent, while SEM micrographs indicated satisfactory dispersion in the PCL matrix. The crystallization study under isothermal and dynamic conditions revealed the nucleating effect of the nanotubes. The functionalization of nanotubes enabled even faster rates and attributed higher nucleation activity as a result of better dispersion and the formation of a strong interface between the filler and the matrix. An in-depth kinetic analysis was performed based on the data from crystallization procedures. PLOM images confirmed the effectiveness of both fillers as heterogeneous nucleation agents. Finally, from TGA analysis, it was found that HNTs did not affect the thermal stability of PCL while for HNTs–APTES, a small decrease in Tmax was observed, of about 5xa0°C for all filler contents.