Substrate chemistry regulates the surface phase separation of polyurethane films

The effect of substrate chemistry on surface phase separation of polyurethane films were investigated by using self-assembled monolayer (SAM) with chemically different modifications, i.e. hydroxy (–OH) and methyl (–CH3) end groups. Results showed that hydrophilic (–OH) and hydrophobic end groups (–CH3) could respectively promote the aggregation of hard and soft segments at polyurethane–substrate interface, which further regulates the phase separation of polyurethane surface that contacts the substrate. The aggregation of hard segments tended to enhance the surface smoothness of polyurethane films, especially on hydrophilic substrates with hydroxy modification. Further analysis of tensile testing revealed that the regulation of surface phase separation had no effect on the shape memory effect of polyurethane films. These findings suggest that the chemical properties of the substrates could regulate the phase separation and may provide some guidance on the design of specific polyurethane with desired morpho...