Polyhydroxyalkanotes (PHAs) polymers have attracted much attention as a potential green chemistry alternative to petrochemical based polymers. PHAs are produced by a variety of bacteria and can be harvested for potential use as biodegradable and biocompatible products. Much work has gone into understanding and controlling the crystallinity of these materials in order to improve the engineering properties, such as incorporating co-polymer segments or tweaking processing conditions to influence the crystallization process.
A new report, published in the journal Macromolecules by researchers at the University of Delaware, reports on the discovery of beta-form crystalline domains forming simultaneously with the more common alpha-form crystalline domains under certain electrospinning conditions. Infrared spectra taken from mats of fibers using bulk FTIR techniques suggests two forms, but ultra-high spatial resolution, single fiber spectra show much improved resolution of the two crystalline forms when not subject to averaging effects of sampling many fibers in various orientations.
Single fiber spectra can only be achieved using the AFM-IR technique. In this work, an Anasys Instruments nanoIR2 spectrometer provided both AFM imaging and AFM-IR spectroscopy results. X-ray diffraction results provide an objective confirmation of the IR spectra band shifts resulting from different processing procedures. Future work can extend the application of AFM-IR to map out the spatial distribution of nano-domains within single fibers.