Effect of filler content on morphology and physical-chemical characteristics of poly(vinylidene fluoride)/NaY-zeolite filled membranes

Poly(vinylidene fluoride) electrospun membranes have been prepared with different NaY zeolite contents up to 32%wt. Inclusion of zeolites induces an increase of average fiber size from ~200 nm in the pure polymer up to ~500 nm in the composite with 16%wt zeolite content. For higher filler contents, a wider distribution of fibers occurs leading to a broader size distributions between the previous fiber size values. Hydrophobicity of the membranes increases from ~115º water contact angle to ~128º with the addition of the filler and is independent on filler content, indicating a wrapping of the zeolite by the polymer. The water contact angle further increases with fiber alignment up to ~137º. Electrospun membranes are formed with ~80 % of the polymer crystalline phase in the electroactive  phase, independently on the electrospinning processing conditions or filler content. Viability of MC3T3-E1 cells on the composite membranes after 72 h of cell culture indicates the suitability of the membranes for tissue engineering applications.

Effect of neutralization and cross-linking on the thermal degradation of chitosan electrospun membranes

Thermal degradation of as electrospun chitosan membranes and samples subsequently treated with ethanol and cross-linked with glutaraldehyde (GA) have been studied by thermogravimetry (TG) coupled with an infrared spectrometer (FTIR). The influence of the electrospinning process and cross-linking in the electrospun chitosan thermal stability was evaluated. Up to three degradation steps were observed in the TG data, corresponding to water dehydration reaction at temperatures below 100 ºC, loss of side groups formed between the amine groups of chitosan and trifluoroacetic acid between 150 – 270 ºC and chitosan thermal degradation that starts around 250 ºC and goes up to 400 ºC. The Kissinger model was employed to evaluate the activation energies of the electrospun membranes during isothermal experiments and revealed that thermal degradation activation energy increases for the samples processed by electrospinning and subsequent neutralization and cross-linking treatments with respect to the neat chitosan powder.

Partidos políticos e direito de oposição a Pirro

Art. 114º da Constituição da República Portuguesa: “1. Os partidos políticos participam nos órgãos baseados no sufrágio universal e directo, de acordo com a sua representatividade eleitoral. 2. É reconhecido às minorias o direito de oposição democrática, nos termos da Constituição e da lei. 3. Os partidos políticos representados na Assembleia da República e que não façam parte do Governo gozam, designadamente, do direito de serem informados regular e directamente pelo Governo sobre o andamento dos principais assuntos de interesse público, de igual direito gozando os partidos políticos representados nas Assembleias Legislativas das regiões autónomas e em quaisquer outras assembleias designadas por eleição directa relativamente aos correspondentes executivos de que não façam parte.”. § Article 114 of the Constitution of the Portuguese Republic. "1. Political parties shall participate in organs based on direct and universal suffrage, according to their electoral representation. 2. It is recognized minorities the right to democratic opposition, under the Constitution and the law. 3. Political parties represented in Parliament and not forming part of the Government shall, in particular, the right to be informed regularly and directly by the Government on the progress of the main matters of public interest, equal rights enjoying the political parties represented in Legislative Assemblies of the autonomous regions and any other assemblies formed through direct elections with respect to the corresponding executives who are not part. ".