Synthesis and characterization of poly (dimethylsiloxane-urethane) elastomers: Effect of hard segments of polyurethane on morphological and mechanical properties

A series of poly(dimethylsiloxane-urethane) elastomers based on hexamethylenediisocyanate, toluenediisocyanate, or 4,4′- methylenediphenyldiisocyanate hard segment and polydimethylsiloxane (PDMS) soft segment were synthesized. In this study, a new type of soft-segmented PDMS crosslinker was synthesized by hydrosilylation reaction of 2-allyloxyethanol with polyhydromethylsiloxane, using Karstedt's catalyst. The synthesized soft-segmented crosslinker was characterized by FT-IR, ¹H, and ¹³C NMR spectroscopic techniques. The mechanical and thermal properties of elastomers were characterized using tensile testing, thermogravimetric analysis, differential scanning calorimetry (DSC), and dynamical mechanical analysis measurements. The molecular structure of poly(dimethylsiloxane-urethane) membranes was characterized by ATR-FTIR spectroscopic techniques. Infrared spectra indicated the formation of urethane/urea aggregates and hydrogen bonding between the hard and soft domains. Better mechanical and thermal properties of the elastomers were observed. The restriction of chain mobility has been shown by the formation of hydrogen bonding in the soft and hard segment domains, resulting in the increase in the glass-transition temperature of soft segments. DSC analysis indicates the phase separation of the hard and soft domains. The storage modulus (E') of the elastomers was increasing with increase in the number of urethane connections between the hard and soft segments.