title: Rapid visualization of macromolecular orientation by discrete frequency mid-infrared spectroscopic imaging.
abstract: Infrared (IR) spectroscopic imaging has been used to measure the composition and orientation of polymeric systems for decades. IR microscopy can provide detailed views of microscopic regions, allowing the observation of both morphology and molecular properties of a sample, but involves a trade-off between the spatial extent and details of molecular content. Here we describe an approximately two orders of magnitude faster approach to measure the spherulitic structure and molecular orientation in large semi-crystalline polymer samples compared to extant Fourier transform infrared (FT-IR) spectroscopic imaging. This discrete frequency approach utilizes individual narrowband emission lines of a quantum cascade laser (QCL) source to spectrally image large areas rapidly. The inherent polarization of the laser beam is employed to measure orientation, enabling calculation of Hermans in-plane orientation function along with molecular chain angles distribution.
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. rxb@illinois.edu.
authors.forename: Tomasz P
authors.initials: TP
authors.lastname: Wrobel
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. rxb@illinois.edu and Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Prabuddha
authors.initials: P
authors.lastname: Mukherjee
authors.affiliation: Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. rxb@illinois.edu and Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA and Departments of Chemical & Biomolecular Engineering, Electrical & Computer Engineering, Mechanical Science & Engineering and Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Rohit
authors.initials: R
authors.lastname: Bhargava