  AFM is a technique widely applied in the nanoscale characterisation of
polymers and their surface properties. With nano-FTIR and IR-sSNOM imaging an
optical dimension is added to this technique that allows for straightforward
high resolution characterisation and spectroscopy of polymers. As the volume
sampled by these near-field techniques depends mostly on the radius of the
cantilever tip, typically 10 nm, it is orders of magnitude smaller than in
conventional techniques. Nevertheless, comparability of nano-FTIR near-field
spectra and data from macroscopic methods has been shown. Some relevant
polymers such as polystyrene however, prove to be more difficult to detect than
others. Furthermore, the small sampled volume suggests lower signal quality of
nano-FTIR data and proof of its suitability for a reliable library search
identification is lacking. To evaluate the techniques especially towards
automatic and higher throughput identification of nanoscale polymers, for
example in blends or environmental samples, we examined domain distributions in
a PS-LDPE film and spectral responses of foils of the most relevant commercial
polymers. We demonstrate the successful library search identification of all
samples with nano-FTIR data measured in less than seven minutes/spectrum. We
discuss aspects affecting the accuracy of the identification and show that
already the small spectral range of 1700-1300 cm$^{-1}$ leads to similar
success in differentiating between polymer types with near-field data as with
conventional far-field FTIR spectroscopy.
