topographic (left) and phase (right) images of a 80:20 PMMA-PB blend sample before annealing topographic (left) and phase (right) images of a 20:80 PMMA-PB blend sample before annealing
topographic (left) and phase (right) images of a 80:20 PMMA-PB blend sample after annealing topographic (left) and phase (right) images of a 20:80 PMMA-PB blend sample after annealing

Above, four sets of topographic (left) and phase (right) images are shown for an 80:20 PMMA-PB blend (image sets on the left) and a 20:80 PMMA-PB blend (image sets on the right). Prior to annealing (top image sets), both the surface chemical properties and the surface mechanical properties of the PMMA and PB regions were quite different. After annealing (bottom image sets), the two polymers had similar mechanical properties, glass transition temperatures, and polarities due to oxidation of the PB. Consequently, the phase image contrast (see right hand image of each of the 4 image sets) between the phase-separated regions of the blend samples is large before annealing and negligible after annealing. Nanoindentation was also utilized to follow changes in the relative stiffness of the phase-separated regions and to determine what regions of the samples were rich in PMMA and what regions were rich in PB.

Reference: D. Raghavan, M. VanLandingham, X. Gu, and T. Nguyen, Charactization of heterogeneous regions in polymer systems using tapping mode and force mode atomic force microscopy, Langmuir 16(24) (2000) 9448-9459.

This study was done in collaboration with Dr. Xiaohong Gu and Professor Dharmaraj Raghavan of the Howard University Department of Chemistry.

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