Sofia Marceneiro

Phosphonium-based ionic liquids as modifiers for biomedical grade poly(vinyl chloride).

This work reports and discusses the influence of four phosphonium-based ionic liquids (PhILs), namely trihexyl(tetradecyl) phosphonium dicyanamide, [P(6,6,6,14)][dca]; trihexyl(tetradecyl) phosphonium bis(trifluoromethylsulfonyl)imide, [P(6,6,6,14)][Tf(2)N]; tetrabutyl phosphonium bromide, [P(4,4,4,4)][Br]; and tetrabutyl phosphonium chloride, [P(4,4,4,4)][Cl], on some of the chemical, physical and biological properties of a biomedical-grade suspension of poly(vinyl chloride) (PVC). The main goal of this work was to evaluate the capacity of these PhILs to modify some of the properties of neat PVC, in particular those that may allow their use as potential alternatives to traditional phthalate-based plasticizers in PVC biomedical applications. PVC films having different PhIL compositions (0, 5, 10 and 20 wt.%) were prepared (by solvent film casting) and characterised by Fourier transform infrared, thermogravimetric analysis, differential scanning calorimetry, dynamical mechanical thermal analysis, scanning electron microscopy/energy-dispersive X-ray/electron probe microanalysis, X-ray diffraction, transmittance, permeability towards oxygen and carbon dioxide, thermal degradation, contact angle measurement, water and vapour uptake, leachability and biocompatibility (haemolytic potential, thrombogenicity and cytotoxicity). A conventional organic plasticizer (di-isononyl phthalate) was used for comparison purposes. The results obtained showed that it was possible to change the neat PVC hydrophobicity, and consequently its water uptake capacity and plasticizer leachability, just by changing the PhIL employed and its composition. It was also possible to significantly change the thermal and mechanical properties of PVC films by choosing appropriate PhIL cation/anion combinations. However, a specific PhIL may not always be capable of simultaneously keeping and/or improving both physical properties. In addition, ionic halide salts were found to promote PVC dehydrochlorination. Finally, none of the prepared materials presented toxicity against Caco-2 cells, though pure [P(6,6,6,14)][dca] decreased HepG2 cells viability. Moreover, PVC films with [P(6,6,6,14)][dca] and [P(4,4,4,4)][Cl] were found to be haemolytic and thus these PhILs must be avoided as PVC modifiers if biomedical applications are envisaged. In conclusion, from all the PhILs tested, [P(6,6,6,14)][Tf(2)N] showed the most promising results regarding blood compatibility, leaching and permeability to gases of PVC films. The results presented are a strong indicator that adequate PhILs may be successfully employed as PVC multi-functional plasticizers for a wide range of potential applications, including those in the biomedical field.

Phosphonium ionic liquids as greener electrolytes for poly(vinyl chloride)-based ionic conducting polymers

Ionic liquid based ion-conducting polymers have been prepared and characterized by loading poly(vinyl chloride) (PVC) with one of two phosphonium-based ionic liquids (PhILs) (trihexyl(tetradecyl) phosphonium bis(trifluoromethylsulfonyl)imide, [P14,6,6,6][Tf2N] and trihexyl(tetradecyl) phosphonium chloride, [P14,6,6,6][Cl]) and a commonly used PVC plasticizer (di-isononyl phthalate, DINP). Different proportions of each charged (PhILs) and non-charged (DINP) additive were used to evaluate the influence of PhIL ionicity on the ionic conductivity of the PVC-based electrolyte and to study the effect of the thermomechanical properties of PVC on the diffusivity of ionic charges in between PVC molecular chains, and consequently on the electrochemical properties of the polymer. Films were characterized for their chemical, morphological, thermomechanical and electrical properties. The results show that both PhIL ionicity and PhIL–PVC compatibility play a major role in decreasing the electrical resistivity of PVC films. The lowest film resistivity (0.4 kΩ cm), corresponding to an estimated electrical conductivity of ∼2.4 μS cm−1, was observed for PVC films loaded with the highest tested amount of [P14,6,6,6][Tf2N] (45 wt% of PhIL at fixed DINP composition, 9 wt%). These films were also stable at temperatures up to 200 °C without using any further PVC thermal stabilizer. The polymer electrolytes presented in this work may be used as platforms to produce soft, safer and cost-effective ion-conducting materials by using non-volatile and electrochemically stable PhILs as liquid electrolytes incorporated into a cheap, stable and versatile polymer such as PVC.

Effects of Poly(vinyl chloride) Morphological Properties on the Rheology/Aging of Plastisols and on the Thermal/Leaching Properties of Films Formulated Using Nonconventional Plasticizers

The efficiency of poly(vinyl chloride) (PVC) plasticization depends predominantly on the strength of PVC–plasticizer interactions, which ultimately depends not only on the intrinsic physicochemical properties of the plasticizer but also those of the polymer. The aim of this work was to study the influence of the morphological properties of different PVC grades (two emulsion (with different K values) and one microsuspension grades) and of nonconventional greener plasticizers on the rheological/aging properties of PVC-based plastisols and on the thermal and plasticizer leaching properties of films obtained from those plastisols. Commercially available castor oil based CITROFOL AHII and GRINDSTED SOFT-N-SAFE were employed as plasticizers, and the phosphonium-based ionic liquid (trihexyl(tetradecyl)phosphonium bistriflamide ([P6,6,6,14][Tf2N]) as a coplasticizer. Plastisols formulated with the conventional plasticizer di-isodecyl phthalate (DIDP) were also prepared for comparison. Obtained results showed that...