Combined AFM/Raman Studies of Heterogeneous Polymer Materials
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Combined AFM/Raman Studies of Heterogeneous Polymer Materials Marko Surtchev1, Mark Wall2 and Sergei Magonov1 1
NT-MDT Development Inc., 7910 S. Kyrene Rd, Tempe, AZ 85284, USA
2
Thermo Fisher Scientific, Madison, WI 53711, USA
ABSTRACT Compositional imaging of several immiscible polymer blends was examined with the combination of AFM-based mechanical and electric modes with chemically-specific Raman mapping. Results showed that these methods substantially complement each other in comprehensive characterization of surface morphology by helping to identify a composition of top surface and sub-surface materials in polymer heterogeneous systems.
INTRODUCTION Recognition of individual components and visualization of their distribution in heterogeneous polymer materials is the important application of Atomic Force Microscopy (AFM), and it can be achieved in different modes. AFM-based compositional imaging of complex materials rely on a specific shape and dimensions of individual constituents and differences in their local mechanical, electric and thermal properties. The AFM images of microphase separation of block copolymers, polymer blends and composites are well documented [1]. However, such identification of the individual components is primarily indirect and has definite limitations. The development of the combined instruments, in which AFM measurements are performed simultaneously with spectroscopic imaging [2], offers the direct and specific insight into the chemical nature of the constituents of complex materials. Currently, combined AFM/Raman instruments are more common and commercially available compared to the emerging AFM/IR devices. In some cases high-spatial resolution is claimed using tip-enhanced Raman mapping [3]. The AFM/Raman studies of several polymer blends, which are described below, were undertaken to explore the advanced capabilities for compositional imaging offered by combining these methods. The use of local spectral information is the essential step towards comprehensive analysis of heterogeneous polymer systems, and the spectroscopic imaging complements the mapping of local electric and mechanical properties. The experimental data, which was obtained on the polymer blends, strongly supports this approach. The important issues of such hyphenated studies such as lateral and depth resolution will be revealed and discussed. EXPERIMENTAL DETAILS A combination of AFM and Raman confocal microscopes was realized by integrating a modified NTEGRA microscope (NT-MDT) with Raman microscope DXR (ThermoFischer). Green (532 nm) and red (633 nm) laser sources were applied in the experiments. The sample
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illumination and collection of Raman scattering were performed in upright configuration. The use of NTEGRA microscope provides researchers with the most complete set o
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