The phase behavior of blends of poly(dimethylsiloxane) and the eutectic mixture of liquid crystals E7 is investigated. Experimental phase diagrams are established by polarized optical microscopy for two systems with widely different polymer molecular weig

The variations of the heat capacity ΔCp=[Cpl−Cpg]T=Tg at the glass transition, and the value of the fragility index m were determined for two melamine formaldehyde resins by calorimetric investigations. These values characterise respectively the thermodynamic aspect and the kinetic aspect of the Angell “Strong–Fragile” concept. For resins cured with a neutral pH, the 3D network formed is made of massive molecular units connected together by small length chains, and the values are ΔCp=0.13 J K−1 g−1 and m=143. For acid pH curing conditions, the 3D network is made of only massive molecular units connected together and we obtain ΔCp=0.12 J K−1 g−1 and m=35. By comparing our results with the results of the literature concerning three-dimensional networks and inorganic polymers, we are able to conclude that the relaxation occurs in these systems mainly by movements involving triazine rings.