Nanoscale Infrared Spectroscopy

Correlative Nanoscale Chemical and Property Analysis of Polymers

Photothermal AFM-IR spectroscopy solutions for polymeric materials

Photothermal AFM-IR Spectroscopy Solutions for Polymeric Materials

Photothermal AFM-IR spectroscopy combines the high spatial resolution of atomic force microscopy (AFM) with the chemical identification capability of infrared (IR) spectroscopy to allow for the chemical characterization of samples in nanoscale detail.

The operating principle for photothermal AFM-IR can be explained in just three simple steps:

  1. An IR laser pulse arrives on the sample surface under the tip
  2. The sample absorbs the IR pulse, causing it to heat up and expand, thus applying a mechanical force on the AFM probe
  3. The magnitude of this force is proportional to the absorption coefficient and can be used to generate an IR spectrum

AFM-IR spectra can be interpreted just like Fourier-transform infrared spectroscopy (FTIR) spectra. Leveraging this ease of nanoscale chemical identification and combining it with correlated mechanical measurements on the AFM provides a valuable solution for polymer research. 

Correlate Local Chemical Information with Structure and Properties

Polymeric materials tend to have a lot of nanoscale variation, even in homopolymers. Thus, it is often vital to understand the nanoscale relationship between local chemistry, structure, and properties.

Many polymer researchers investigate these nanoscale chemistry-structure-property relationships to:

  • Improve existing polymer manufacturing processes
  • Develop next-gen polymeric materials

Photothermal AFM-IR can provide nanoscale chemical information with highly resolved IR spectra. Paired with standard and emerging AFM techniques, this chemical identification capability can be correlated with topographical and property data, supporting both materials development and process improvement research.

Correlated imaging on Polycarbonate/acrylonitrile butadiene styrene (PC-ABS), a material commonly used in 3D printing: (a) Topography; (b) IR absorption at 1766 cm-1; (PC), (c) IR absorption at 1450 cm-1; (ABS), (d) Modulus (0-20 GPa scale); (e) AFM-IR spectra on PC & ABS; (f) Master curve acquired in AFM-based Dynamic Mechanical Analysis (nDMA). Scan size is 2.5x2.5 µm.

Compare Common Polymer Characterization Techniques

Bruker’s photothermal AFM-IR platforms can non-destructively measure chemical inhomogeneity on the scale of a few nanometers while also offering the most correlative AFM modes for further localized properties, such as modulus, adhesion, melting point, work-function and more.

Table comparing common chemical analysis techniques.

Discover Localized FTIR at the Nanoscale

IR spectroscopic analysis is essential for chemical ID in polymer research. With AFM-IR, researchers can take advantage of the ease and versatility of FTIR characterization without being limited to a resolution of tens of microns. Though the measurement mechanism differs between FTIR and AFM-IR, the data collection and analysis processes are analogous.

The absorption coefficient is the property measured by FTIR and correlated with AFM-IR; as such, AFM-IR spectra can be interpreted just like FTIR spectra. Analysis of AFM-IR data can even be completed using established spectral libraries like Wiley’s KnowItAll.

Spectra obtained on a 300 nm polystyrene film with FTIR and nanoscale AFM-IR illustrating 1:1 match.

Broaden AFM Functionality to Include Chemical Information

Atomic force microscopy (AFM) is a nanoscale metrology and imaging technique that can evaluate:

  • Surface structure
  • Material properties (e.g., mechanical, electrical, magnetic, thermal)
  •  Coupled properties (e.g., electrochemical or piezoelectric)

By leveraging the tip-sample interaction required for AFM, photothermal AFM-IR extends the capabilities of AFM to include chemical identification. Adding AFM-IR to the AFM modes toolbox enables advanced polymers research in many fields, including:

  • Bioplastics
  • Microplastics
  • Medical-grade plastics
  • Food packaging
  • Tire manufacturing
  • Adhesives manufacturing
Correlated imaging of nanoscale chemical, mechanical and electrical properties on Polystyrene / Low Density Polyethylene:
(a) Topography; (b) IR absorption at 1493 cm-1; (c) IR absorption at 1464 cm-1; (d) AFM-IR spectra; (e) Surface Potential; (f) Capacitive/Dielectric; (g) Adhesion; and (h) Modulus.

Understand and Improve Existing Polymer Processes

Bruker’s Photothermal AFM-IR technology and correlative imaging further helps understand and expand on existing materials and polymer processes by:

  • Forming a more thorough understanding of localized chemistry
  • Suggesting processing changes that ultimately lead to improved material performance
  • Assisting to develop, improve and reverse-engineer key processes (e.g. medical-grade plastics, food packaging, tires, adhesives, biodegradable plastics, and more)


Pictured: Correlated imaging on styrene-butadiene rubber-a synthetic rubber widely used for automobile tires-with carbon black fillers

Topography imaging on styrene-butadiene rubber
(Left) Modulus image (1-12 GPa scale); (Right) IR ratio map of IR absorption at 910 cm-1 (butadiene) & 1601 cm-1 (styrene).
(Left) Modulus image (1-12 GPa scale); (Right) IR ratio map of IR absorption at 910 cm-1 (butadiene) & 1601 cm-1 (styrene).

Develop the Next Generation of Polymers

Bruker’s AFM-IR technology, enhanced by correlative mechanical imaging can be effectively used to develop next-generation polymeric materials. Bruker’s technology can:

  • Help understand nanoscale bonding and fully explore the structure-function relationship of polymeric materials
  • Show local variations in chemistry and crystallinity and reveal their effects on mechanical properties
  • Discriminate between surface and bulk behavior for the study of advanced polymers
  • Characterize future biopolymers and optimize their production
  • Map the chemical segregation of materials with unprecedented lateral resolution
  • Provide quantitative modulus mapping of nanoscale polymer phases
  • Correlate nanoscale viscoeleastic analysis, including construction of a time-temperature superposition (or master curve) with AFM-nDMA
AFM-IR of Polystyrene-polymethyl methacrylate (PS-PMMA) block copolymer: (a) Topography; (b) IR absorption at 1730 cm-1 (PMMA); (c ) IR at 1493 cm-1 (Polystyrene); and (d) corresponding AFM-IR spectra.

“The AFM-IR solves a longstanding need in polymeric materials development for chemical analysis at the nanoscale. By doing it with an AFM, it simultaneously addresses one of the most important missing capabilities of the scanning probe microscopy platform – lack of chemical specificity, thus enabling the further growth of the AFM technique in new applications and markets. We are now able to ‘see’ the chemistry in the morphology.”

– Dr. Greg Meyers, R&D Fellow, Dow Chemical

Explore Related Resources

Bruker's suite of nanoIR systems deliver true, model free nanoscale FTIR spectra for a wide range of polymers. For more information, see our Dimension IconIR, nanoIR3, and nanoIR3-s systems, or contact us to receive personalized support based on your experimental requirements.

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Our All-In-One Solution for Polymer Research

We have designed an IconIR solution specifically to address key needs in polymer research and engineering. This solution includes the following standard set of capabilities and is additionally configurable to meet nearly any material challenge:

  • IconIR with a laser to cover the fingerprint region of organic materials
  • Peakforce QNM for quantitative, high-accuracy measurements of local material mechanical properties
  • AFM-nDMA for full correlative viscoelastic mapping, providing results that directly match those from bulk DMA

Contact us or download the datasheet for more information about the Dimension IconIR polymer research package.

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