Semi-interpenetrating polymer networks based on crosslinked poly(N-isopropyl acrylamide) and methylcellulose prepared by frontal polymerization

In this work, semi-interpenetrating gels of poly(N-isopropyl acrylamide) and methylcellulose were successfully synthesized by using the Frontal Polymerization (FP) technique. The gels were obtained in the presence of dimethyl sulfoxide and trihexyltetradecylphosphonium persulfate, as polymerization solvent and radical initiator, respectively, hence avoiding the formation of bubbles during polymerization. Then, some of the gels containing dimethyl sulfoxide were thoroughly washed with water, hence obtaining the corresponding hydrogels. The effects of the ratio between poly(N-isopropyl acrylamide) and methylcellulose, the amount of crosslinker and solvent medium (i.e. dimethyl sulfoxide and water) were thoroughly studied, assessing the influence of temperature and velocity of FP fronts on the glass transition temperature values (dried samples), on the swelling behavior and on the dynamic-mechanical properties (gels swollen both in water and dimethyl sulfoxide)

Preparation and characterization of polymeric nanocomposites containing exfoliated tungstenite at high concentrations

For the first time, ultrasonication was exploited for obtaining tungstenite nanoparticles directly into a monomer (tetraethyleneglycol diacrylate) to be eventually polymerized without any further manipulation. The resulting liquid dispersions were characterized by Raman, transmission electron and scanning electron microscopies. Eventually, they were directly used for preparing nanocomposites containing a relatively large amount of exfoliated tungstenite. Differential scanning calorimetry and thermogravimetric analyses were performed in order to assess the effect of the presence of the exfoliated nanofiller on the thermal features of the polymer matrix: a clear improvement of the thermal and thermo-oxidative stability was observed. At variance, the effect of the exfoliated tungstenite on the glass transition temperature of the polymer matrix was negligible. Furthermore, the mechanical behavior of the obtained nanocomposites was evaluated by means of flexural and shore A hardness tests: the exfoliated nanofiller turned out to exert a strong reinforcing effect on the polymer matrix even at very low concentratio