Nanoscale chemical analysis of polymeric materials can be rapidly obtained by integrating a tunable infrared source with an Atomic Force Microscope (AFM), a technique referred to as AFM-IR. The AFM-IR technique makes use of a pulsed IR laser to induce a expansion of a sample due to absorption of the incident IR illumination. This rapid expansion causes the AFM cantilever to oscillate. Using the detection system of the AFM, the amplitude can be measured and has been shown to have direct correlation to the local absorption coefficient of the sample in proximity to the AFM probe. The pulsed IR source can tune over a broad range of the mid IR (900 – 3600 cm<sup>-1</sup>) producing a spectrum which matches well with spectra from transmission FTIR.<br/>In addition to the chemical information, the technique can also provide simultaneous mechanical information about the sample. This is accomplished by analyzing the frequency of the oscillation of the cantilever generated by the pulsed IR light, in a mode called Contact Resonance AFM. The contact resonance of an AFM cantilever has been shown to correlate well with the storage modulus of the sample. The pulsed light produces a clean excitation of the cantilever allowing a more accurate measurement of the contact resonance frequency as well as inducing oscillation of a number of modes of the cantilever providing for measurements over a broad range of sample stiffness.<br/>The AFM-IR technique has been used to analyze a broad range of polymeric materials. Recent applications that demonstrate the benefit of the nanoscale chemical measurements, in addition to the simultaneous multimodal analysis will be discussed.

Nanoscale chemical, mechanical and thermal analysis of polymers using AFM-IR

249th National Meeting (2015)

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