Polymer Blends Based on 1-Hexadecyl-3-methyl Imidazolium 1,3-Dimethyl 5-Sulfoisophthalate Ionic Liquid: Thermo-Mechanical, Surface Morphology and Antibacterial Properties.

In this study, antibacterial polymer blends based on Polyvinyl Chloride (PVC) and Polystyrene-Ethylene-Butylene-Styrene (SEBS), loaded with the ionic liquid (IL) 1-hexadecyl-3-methyl imidazolium 1,3-dimethyl 5-sulfoisophthalate (HdmimDMSIP) at three different concentrations (1%, 5%, and 10%), were produced. The IL/blends were characterized by their thermo-mechanical properties, surface morphology, and wettability. IL release from the blends was also evaluated. The agar diffusion method was used to test the antibacterial activity of the blends against Staphylococcus epidermidis and Escherichia coli. Results from thermal analyses showed compatibility between the IL and the PVC matrix, while phase separation in the SEBS/IL blends was observed. These results were confirmed using PY-GC MS data. SEM analyses highlighted abundant IL deposition on PVC blend film surfaces containing the IL at 5-10% concentrations, whereas the SEBS blend film surfaces showed irregular structures similar to islands of different sizes. Data on water contact angle proved that the loading of the IL into both polymer matrices induced higher wettability of the blends' surfaces, mostly in the SEBS films. The mechanical analyses evidenced a lowering of Young's Modulus, Tensile Stress, and Strain at Break in the SEBS blends, according to IL concentration. The PVC/IL blends showed a similar trend, but with an increase in the Strain at Break as IL concentration in the blends increased. Both PVC/IL and SEBS/IL blends displayed the best performance against Staphylococcus epidermidis, being active at low concentration (1%), whereas the antimicrobial activity against Escherichia coli was lower than that of S. epidermidis. Release data highlighted an IL dose-dependent release. These results are promising for a versatile use of these antimicrobial polymers in a variety of fields.

Thermo-mechanical, antimicrobial and biocompatible properties of PVC blends based on imidazolium ionic liquids.

The aim of this study was the development of antimicrobial polyvinylchloride (PVC) blends loaded with 0.1-10% (w/w) of the ILs 1-hexadecyl-3-methylimidazolium 1,3-dimethyl 5-sulfoisophthalate (HdmimDMSIP) and 1-octyloximethyl-3-methylimidazolium hexafluorophosphate (OOMmimPF6). The synthetized ILs were characterized by 1HNMR, MALDI-TOF, DSC and TGA. PVC/ILs films were obtained by solvent casting.Thermal and mechanical properties (tensile stress TS and elongation at break EB), morphology by SEM, surface wettability, antimicrobial activity, cytotoxicity and ILs release in sterile water from PVC/ILs film blends were determined. Results demonstrated that the presence of both ILs in PVC formulation slightly affected thermal and mechanical properties of blends. The loading of both ILs into PVC matrix made PVC/ILs films hydrophilic, especially at the highest concentration of HdmimDMSIP. The PVC/ILs blends displayed antibacterial activity up to ILs lowest concentrations (0.1-0.5%). The inhibition of Escherichia coli growth was lower than that showed toward Staphylococcus epidermidis. The addition of 10% ILs concentration resulted excessive as demonstrated by accumulation of ILs on film surfaces (SEM) and ILs high release from PVC/ILs blends during the first day of water immersion. Biocompatibility studies highlighted that the addition of low amounts of both ILs into PVC matrix is not cytotoxic for mouse fibroblast cells (L929), supporting their potential use for biomedical porposes.

End-group rearrangements in poly(propylene sulfide) matrix-assisted laser desorption/ionization time-of-flight analysis. Experimental evidence and possible mechanisms.

RATIONALE: Polysulfides [poly(1,2-alkylene sulfides)] are oxidation-responsive polymers that are finding application in drug release and biomaterials. The precise knowledge of their macromolecular characteristics is of the essence in view of their application to biological systems. METHODS: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with and without silver trifluoroacetate was used to characterize a series of polymers with increasing molecular weight in the range 1000-4000 g/mol and with low polydispersity (<1.12). RESULTS: Well-resolved peaks and accurate mass-measured values were obtained using a 2-(4-hydroxyphenylazo)benzoic acid (HABA) matrix, but significant fragmentations took place in the absence of silver as a cationizing reagent. Elimination reactions appeared to occur at terminal groups and limited depolymerization could be recorded. Interestingly, the most common fragmentation pathway seemed to be based on an as-yet-unreported process of hydrogen transfer requiring the presence both of ester groups and of thioethers. CONCLUSIONS: The use of an appropriate cationizing reagent (silver trifluoroacetate) appeared to suppress end-group eliminations; we hypothesize that this action is based on the involvement of the terminal groups in silver chelation.

Matrix-assisted laser desorption/ionization time-of-flight investigation of Nylon 6 and Nylon 66 thermo-oxidation products.

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) was used to determine the structure of the molecules produced in the thermo-oxidative degradation of Nylon 6 and Nylon 66, at 180 degrees C and 250 degrees C in air. The MALDI spectra of the thermo-oxidized nylons provide information on the structure and end groups of the oligomers produced in the oxidation process. Our results show that the thermo-oxidation of both Ny6 and Ny66 proceeds through a hydrogen abstraction and subsequent formation of hydroperoxide intermediates. The latter decompose, yielding oligomers containing aldehydes, amides and methyl terminal groups. The aldehydes undergo further oxidation to produce carboxylic end groups. The formation of cyclopentanone terminal groups is also observed in the case of Nylon 66. Oligomers with structures deriving from Norrish-type degradation processes were not detected here for either Ny6 or Ny66.