FACTORS AFFECTING THE HEIGHT AND PHASE IMAGES IN TAPPING MODE ATOMIC-FORCE MICROSCOPY - STUDY OF PHASE-SEPARATED POLYMER BLENDS OF POLY(ETHENE-CO-STYRENE) AND POLY(2,6-DIMETHYL-1,4-PHENYLENE OXIDE)

Blends of two polymers, poly(ethene-co-styrene) (PES) and poly(2,6-dim ethyl-1,4-phenylene oxide) (PPO), were examined with tapping mode atom ic force microscopy (AFM) using various values of the driving amplitud e A(0) and set-point amplitude ratio r(sp) = A(sp)/A(0), where A(sp) i s the set-point amplitude. In height and phase images of PPO/PES blend samples, the relative contrast of chemically different regions depend s sensitively on the r(sp) and A(0) values. As the tip-sample force is increased from small to large, both phase and height images of PPO/PE S blend samples can undergo a contrast reversal twice. This makes it d ifficult to assign the features of height and phase images to differen t chemical components without performing additional experiments. Phase and height images were interpreted by analyzing several factors that affect the dependence of phase shift and amplitude damping on r(sp) an d A(0).