Zoe Terzopoulou

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.

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.

Amino-Functionalized Multiwalled Carbon Nanotubes Lead to Successful Ring-Opening Polymerization of Poly(ε-caprolactone): Enhanced Interfacial Bonding and Optimized Mechanical Properties.

In this work, the synthesis, structural characteristics, interfacial bonding, and mechanical properties of poly(ε-caprolactone) (PCL) nanocomposites with small amounts (0.5, 1.0, and 2.5 wt %) of amino-functionalized multiwalled carbon nanotubes (f-MWCNTs) prepared by ring-opening polymerization (ROP) are reported. This method allows the creation of a covalent-bonding zone on the surface of nanotubes, which leads to efficient debundling and therefore satisfactory dispersion and effective load transfer in the nanocomposites. The high covalent grafting extent combined with the higher crystallinity provide the basis for a significant enhancement of the mechanical properties, which was detected in the composites with up to 1 wt % f-MWCNTs. Increasing filler concentration encourages intrinsic aggregation forces, which allow only minor grafting efficiency and poorer dispersion and hence inferior mechanical performance. f-MWCNTs also cause a significant improvement on the polymerization reaction of PCL. Indeed, the in situ polymerization kinetics studies reveal a significant decrease in the reaction temperature, by a factor of 30-40 °C, combined with accelerated the reaction kinetics during initiation and propagation and a drastically reduced effective activation energy.

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 1 : 2 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.

Use of mesoporous cellular foam (MCF) in preparation of polymeric microspheres for long acting injectable release formulations of paliperidone antipsychotic drug

Graphical abstract Figure. No caption available. ABSTRACT In this study, high surface area mesoporous silica foam with cellular pore morphology (MCF) was used for injectable delivery of paliperidone, an antipsychotic drug used in patients suffering from bipolar disorder. The aim was to enhance paliperidone solubility and simultaneously to prepare long active intractable microspheres. For this reason paliperidone was first loaded in MCF silica, and the whole system was further encapsulated into PLA and PLGA 75/25 w/w copolymer in the form of microspheres. It was found that paliperidone, after its adsorption into MCF, was transformed in its amorphous state, thus leading to enhanced in vitro dissolution profile. Furthermore, incorporation of the drug‐loaded MCF to polymeric microparticles (PLA and PLGA) prolonged the release time of paliperidone from 10 to 15 days.