Rosane Ligabue

Rationalizing the role of the anion in CO2 capture and conversion using imidazolium-based ionic liquid modified mesoporous silica

Covalently supported ionic liquids in mesoporous materials were prepared by grafting 1-methyl-3-(3-trimethoxysylilpropyl)imidazolium chloride in MCM-41. Subsequently, the [Cl−] anion was changed to [BF4−], [PF6−] or [Tf2N−]. These materials that present an advantageous combination of the properties of mesoporous solid materials and ionic liquids were evaluated for CO2 sorption as well as catalysts for CO2 conversion into cyclic carbonate using propylene oxide. The material with the [Cl−] anion had the best performance for both CO2 sorption and conversion. A CO2 sorption of 11 w/w% on the adsorbent was achieved and the cycloaddition reaction exhibited a conversion of 67% with 82% selectivity with the catalyst remaining active after 5 cycles, proving that the same sorbent/catalyst setup can be used for both CO2 capture and conversion. Based on the experimental data and electronic-structure numerical simulations, we have hypothesized two major reasons why chloride out performs other anions when adsorbed on MCM-41 unlike unsupported ionic liquids.

Syntheses and characterization of new poly(ionic liquid)s designed for CO2 capture

A series of new poly(ionic liquid)s-p(IL)s based on polyurethane structures were synthesized and characterized and their behavior evaluated in CO2 sorption tests under different pressures. The synthesized materials were characterized according to structure, composition, and thermal stability, by techniques such as FTIR, 1H-NMR, TGA and DSC. The CO2 sorption measurements were carried out in a Magnetic Suspension Balance-PTGA and proved that the change of the components of the polymer chain directly indicates the sorption behavior. The best performance for CO2 sorption (75.7 mol% at 20 bar) was achieved with the p(IL) PUA-02a obtained from HDI and PTMG-2000 with [bmim]+ as a counter-ion. The synthesized p(IL)s presenting nitrogenated and polyether structures into the backbone allied to imidazolium counter-cations proved to be worthy of note in the CO2 sorption besides being based on poly(urethane) a versatile and low-cost material. The results also highlighted the good performance of PUA-02 when compared with traditional solvents used in pre-combustion process, as well as the p(IL)s described in the literature.

Optically transparent membrane based on bacterial cellulose/polycaprolactone

Optically transparent membranes from bacterial cellulose (BC)/polycaprolactone (PCL) have been prepared by impregnation of PCL acetone solution into dried BC membranes. UV-Vis measurements showed an increase on transparency in BC/PCL membrane when compared with pristine BC. The good transparency of the BC/PCL can be related to the presence of BC nanofibers associated with deposit of PCL nano-sized spherulites which are smaller than the wavelength of visible light and practically free of light scattering. XRD results show that cellulose type I structure is preserved inside the BC/PCL membrane, while the mechanical properties suggested indicated that PCL acts as a plasticizer for the BC membrane. The novel BC/PCL membrane could be used for preparation of fully biocompatible flexible display and biodegradable food packaging.

A New Approach to CO2 Capture and Conversion Using Imidazolium Based-Ionic Liquids as Sorbent and Catalyst

Although the carbon capture and storage (CCS) technologies are receiving great attention for mitigation of greenhouse gas effect, the increasing costs and energy penalties associated to its implementation are still major drawbacks. However, the use of CO2 as a C1 building block in organic synthesis can be very attractive for the design of environmentally friendly processes. In this work, we have studied both the CO2 sorption and catalytic activities of some imidazolium based ionic liquids (ILs) for cyclic carbonate synthesis. The work demonstrates that the presence of a nucleophilic group in the catalytic system can enhance its performance by the use of an IL with a halide anion or by mixing a halide co-catalyst with ILs. The latter approach allowed to obtain an effective system for CO2 capture constituted by a fluorinated IL plus ZnBr2 that performs cyclic carbonate synthesis with 90% yield and 82% of selectivity.

Human alveolar bone-derived cell-culture behaviour on biodegradable poly(L-lactic Acid).

Poly(L-lactic acid) (PLA) is a polymer of great technological interest, whose excellent mechanical properties, thermal plasticity and bioresorbability render it potentially useful for environmental applications, as a biodegradable plastic and as a biocompatible material in biomedicine. The interactions between an implant material surface and host cells play central roles in the integration, biological performance and clinical success of implanted biomedical devices. Osteoblasts from human alveolar bone were chosen to investigate the cell behaviour when in contact with PLA discs. Cell morphology and adhesion through osteopontin (OPN) and fibronectin (FN) expression were evaluated in the initial osteogenesis, as well as cell proliferation, alkaline phosphatase activity and bone nodule formation. It was shown that the polymer favoured cell attachment. Cell proliferation increased until 21 days but in a smaller rate when compared to the control group. On the other hand, ALP activity and bone mineralization were not enhanced by the polymer. It is suggested that this polymer favours cell adhesion in the early osteogenesis in vitro, but it does not enhance differentiation and mineralization.

Preparation and properties of aromatic polyester/TiO2 nanocomposites from polyethylene terephthalate

The development of polyester based materials with enhanced properties as well as the use of post- consumer plastics as raw material has been an increasing market demand. This work aims the synthesis and characterization of aromatic polyesters/titanium dioxide nanocomposites from PET and using TiO2 (0, 1, 3 and 5% w/w) as filler by in situ polymerization. The results obtained by DSC, XRD and FTIR analyzes evidenced an interaction between the OH groups on the TiO2 surface with the ester groups of the polymer leading to decrease of the polymer crystallinity and of hydrophilicity. By SEM images was possible to note a homogeneous distribution of the filler into polymer matrix with 1%w/w TiO2 (average particle size of 199 nm), however for larger amounts of filler (3 and 5% TiO2) revealed the aggregates formation. The results showed an improvement of thermal properties and hardness of the nanocomposites containing TiO2 nanoparticles compared to pristine polyester.

Lower purity dimer acid based polyamides used as hot melt adhesives: synthesis and properties

Hot melt polyamides exhibit high adhesive strength. The polyamides synthesized from dimer fatty acids and diamines can present low crystallinity and a broad range of melting temperatures. In this work, polyamides with different compositions of dimer fatty acids, piperazine, ethylenediamine, sebacic acid and stearic acid and different content of secondary diamine (piperazine) and primary diamine (ethylenediamine) were synthesized. Polyamides with higher purity of dimer acids showed greater molecular weight, adhesion performance and a better mechanical resistance evaluated in stress/strain test. Softening point increased with increase in monomers content. By differential scanning calorimetry analysis, it was observed that polyamides with low percentage of monomer content show only one narrow melting peak in 100 °C. The increase in the acids monomer content leads to a larger temperature range of melting peak. The use of dimer fatty acid with a low content of monomers (up to 6%) in the polyamides synthesis promotes the formation of hot melt adhesives with good adhesion performances. The lowest monomer content leads to an increase in molecular weight, viscosity and mechanical properties of polyamide. Increase in the content of primary amines in polyamides increases crystallinity, viscosity and mechanical properties due to the higher number of hydrogen bonds formed by amide groups.

Potencial uso de serpentinito no armazenamento mineral do CO2

Rising anthropogenic CO2 emissions are considered a major contributor to the greenhouse effect. There are several options for reducing atmospheric CO2 levels, and among these alternatives, Carbon Capture and Storage (CCS) has been identified as an effective and promising approach. This work investigated the feasibility of using serpentinite as a vehicle for carbon storage presenting a source-sink match. The main results of the work confirmed that serpentinite is appropriate for the carbonation process due to the high concentration of Mg in its composition.

Dispositivos poliméricos cardiovasculares: comportamento termomecânico e viabilidade celular

In recent decades new synthetic materials have been developed with adequate biofunctionality and biocompatibility to become a biomaterial. Biostable polymers have widespread use in the biomedical field, and many advances in polymeric biomaterials have been made in the search for improvements to cardiovascular implants. Currently, the most commonly used synthetic materials for the production of vascular grafts are PTFE and PET, due to their chemical stability after implant. In this work, a study of the thermal and mechanical properties of the commercial devices based on PET and PTFE is reported, as well as their cytotoxicity in mouse fibroblast cells, 3T3- NIH, through tests for the evaluation of cell viability (MTT test and VN). These materials showed high thermal stability (over 300 ° C), even after 270 days in vitro degradation and elastic behavior (maximal strain value of 186±22% by PET and 65±19% by PTFE). Cell viability by VN and MTT of PTFE device was more than 80%, thus, classified as non-cytotoxic. For PET device, VN test showed no cytotoxic effect, however the results obtained by MTT indicated that it causes alteration of mitochondrial function, independent of dose and time measured.

Hybrid Pu/Synthetic Talc/Organic Clay Ternary Nanocomposites: Thermal, Mechanical and Morphological Properties

Polyurethane (PU) nanocomposites filled with inorganic particles, aiming at the improvement of mechanical and thermal properties, are well known. Unlike previous work we describe here the combination of two fillers, synthetic talc (silico-metallic mineral particles-SSMMP) with distinct hydrothermal processes (SSMMP 7 h and 24 h) and organically-modified commercial clay (SPR), aiming towards development of new polyurethane ternary nanocomposites by in situ polymerisation. Fillers were added 3 wt.% of the mass of pristine polymer, with a ranging of weight proportions (75:25/25:75) of SSMMP and SPR. Results were compared to those for nanocomposites containing pure SSMMP and SPR fillers. Dispersion degrees and filler interactions with the polyurethane matrix were followed by FTIR, XRD, SEM, TEM and AFM techniques. Results showed that the fillers presented a good dispersion and were exfoliated/ well dispersed in the polyurethane matrix. Thermal and mechanical properties of nanocomposites were evaluated in comparison to the binary nanocomposites (PU/SSMMP 7 h, PU/SSMMP 24 h and PU/ SPR). All nanocomposites presented superior values of Youngs modulus to that of pristine PU. Results evidenced that the blend of SSMMP and SPR fillers is an interesting strategy to improve thermal and mechanical properties of nanocomposites.