In multiphase systems, monolayer films of amphiphilic molecules act to stabilize fluid-fluid interfaces by modifying interfacial tension and imparting surface viscoelasticity. For typical surfactants, the compressional or dilational rheological properties play a larger role than surface shear properties, however, the role of shear becomes significant for polymeric layers. In this work, we study the equilibrium and interfacial shear properties of a block copolymer layer at various air-liquid and liquid-liquid interfaces. Interestingly, interfacial flows of these monolayers in 2D microchannels can result in long equilibration times as a result of the large surface viscosities.