The Martin Group has a diverse set of research capabilities related to materials synthesis and fabrication, and characterization of materials properties such as structure and molecular transport. These are facilitated by instrumentation in the Martin Group laboratories as well as at university and outside research facilities.
Structure and Properties of Materials
X-ray Scattering – including grazing-angle incidence X-ray diffraction (GIXD), wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS). We use these techniques to determine material structure, both at equilibrium and during material processing. Facilities for WAXD (Bruker D2-Phaser) and SAXS (Bruker N8-Horizon) are available in our labs. We also have made extensive use of synchrotron X-ray user facilities including SSRL, NSLS, and APS.
Microscopy – Optical microscopy (including temperature control, polarized light, and fluorescence) are available in our labs. Electron Microscopy (SEM and TEM) are also commonly employed using VT’s NCFL user facility. We also have expertise in examining surface morphology and modulus in thin films via atomic force microscopy (AFM.)
Spectroscopy – We have made use of a variety of spectroscopic techniques to understand material behavior, particularly X-ray Photoelectron Spectroscopy (XPS – in NCFL), NMR, and FTIR (including attenuated total reflectance IR), and UV-VIS. These provide information about both surface and bulk material chemistry and structure.
Rheology – We make extensive use of rheology (i.e. dynamic mechanical analysis) to understand the development of structure during processing and at equilibrium. We primarily employ a TA instruments AR-G2 rheometer for these studies.
Surface Science – our group makes use of a variety of techniques to probe surface structure and interactions, including spectroscopy, AFM, and contact angle goniometry (via a KSV contact angle goniometer located in our lab.)
Molecular Transport and Membrane Separations
Isothermal Gravimetry – used to determine both the equilibrium sorption behavior and sorption kinetics of gases in various materials (e.g. polymers, zeolites, MOFs.) Data can be fitted to various models to extract thermodynamic parameters as well as mass transport information. These measurements are performed using a Hiden Isochema IGA 003 isothermal gravimetric analyzer located in our lab. We have also made use of a dissipative quartz crystal microbalance (QCM-D) to examine sorption in liquid environments.
Membrane Permeability – we have access to a variety of membrane permeation systems in our laboratory, depending on the desired separation system (i.e. gas, liquid, RO, enantiomeric):
- Single gas permeation – based on pressure increase with respect to time.
- Mixed gas permeation – using an inert sweep gas on the downstream side with automatic sampling and analysis via a Shimadzu gas chromatograph.
- Liquid phase permeation – permeation of dissolved solutes in a liquid through porous and non-porous membranes. Analysis via UV-Vis or other spectroscopic techniques.
- Enantiomeric Separations – liquid phase permeation with enantiomeric excess determined via a combination of HPLC and circular dichroism.
- Reverse Osmosis (RO) desalination – evaluation of water flux and salt rejection in flat RO membranes at high trans-membrane pressures.
Synthesis and Fabrication of Materials
Organic Synthesis – our group is equipped for the synthesis of both small molecules (i.e. surfactants, liquid crystals, monomers) and polymeric materials.
Thin Films – we have experience with the fabrication of nanometer to micrometer scale thin film fabrication including: Langmuir-Bodgett (LB) film deposition (NIMA LB trough), self-assembled monolayers (SAMs), spin-coated polymer films (Laurell instruments), and doctor-blade coated polymer films.
Membranes – Our group has developed and fabricated a number of novel membrane materials for different applications. These include:
- Liquid crystalline porous and non-porous membranes for enantioselective separations.
- Amino-acid functionalized enantioselective membranes.
- Cross-linked liquid crystal polymer membranes for gas separations.
- Functionalized carbon nanotube (CNT) membranes for RO water purification.