Study of a Polydimethylsiloxane (PDMS) Elastomer Generated by γ Irradiation: Correlation Between Properties (Thermal and Mechanical) and Structure (Crosslink Density Value)

The present study investigates the structural modification of polydimethylsiloxane (PDMS) with a molecular weight of 35 kDa, using varying high doses of gamma irradiation. Elastomeric structures with different crosslinked density values were obtained as a function of the gamma irradiation dose (250, 300, 350 and 400 kGy). The structural characterization of the obtained elastomers was performed by employing Fourier Transform Infrared, Si-29 Magic Angle Spinning Nuclear Magnetic Resonance and X-Ray Diffraction (FTIR, Si-29 MAS NMR and XRD), showing integration with the polymer chains by siloxane crosslinks (Type-Y) and methylene crosslinks (Type-H). The mechanical and thermal characterizations were carried out by employing dynamical-mechanical analysis (DMA) and modulated differential scanning calorimetry (MDSC). The results showed an important correlation between the thermo-mechanical behavior and the irradiation dose. The thermal stability, analyzed by a thermo-gravimetric analysis (TGA), exhibited interesting behavior that suggested a direct correlation between the decomposition temperature and the structure generated by the gamma irradiation. These results suggest that the obtained elastomers could potentially be considered shape changing materials (SCM).