Effects of the Structures of End Groups of Pendant Polydimethylsiloxane Attached to a Polyurethane Copolymer on the Low Temperature Toughness

End groups with different structures were grafted to polyurethane (PU) using poly(dimethylsiloxane) (PDMS) as a spacer. The low-temperature toughness of the PUs was tested at -30 degrees C, and the structure selectivities of the end groups for low-temperature toughness were compared. The PDMS functioned as a flexible linker that connected the end groups to the PUs. The tensile strength of the PU generally improved despite the grafting of PDMS and end groups. The conventional shape recovery ratio at 45 degrees C remained greater than 90%, regardless of the content and structure of PDMS and the end group. The PU that contained an adamantyl group (cubic) or a naphthyl group (planar rectangle) showed instant recovery, even at -30 degrees C, but the PU that contained a phenyl (planar square) or phenoxyphenyl (bent squares) group required warming to 0 degrees C for a similar degree of recovery but showed improvement over a linear PU without any end group. The characteristic structure of the end group was responsible for the selective low-temperature toughness. The low-temperature toughness results and the thermal and mechanical properties of the PUs are discussed. (C) 2014 Society of Plastics Engineers