Bowman Lab

Gel Permeation Chromatography (GPC)

Gel permeation chromatography (GPC) is performed on a TOSOH EcoSEC system, run in DMSO for optimal solubility of otherwise intractable polymers. The EcoSEC is capable of measuring the molecular weight of polymers from 100 to 100K g/mol. Two detectors measure refractive index and UV absorbance at any wavelength from 200-400 nm.

Sample data from GPC indicating retention times for two polymers (blue and gray) and their conjugate (red). Shorter retention times indicate higher molecular weight, demonstrating the successful reaction linking the polymers.

 

Liquid Chromatography/Mass Spectroscopy (LC/MS)

The Agilent 1100 series liquid chromatography/mass spectroscopy (LC/MS ) with parallel evaporative light scattering detector (ELSD) separates mixtures and analyzes compounds ranging in weight from 100 to 2500 g/mol. This instrument is particularly useful in determining the identity of products from complex reactions including oligiomerizations.

Thermogravimetric Analyzer (TGA)

Thermogravimetric analysis (TGA, Perkin Elmer Pyris 1) is typically used to measure mass loss due to thermal decomposition within a sample. Because different chemical bonds dissociate at different temperatures, the change in mass as a function of temperature can yield many insights on the chemical nature of a material. This has been particularly useful in measuring the efficiency of surface grafting or coupling reaction on inorganic particles.

Sample data showing the changing mass of particles as a function of temperature. Decreasing mass indicates thermal decomposition at given temperatures.

Chipwriter

Microarray Reader

The microarray spotter (BioRad VersArray Chipwriter Pro), in combination with the microarray reader (Agilent Microarray Scanner), allows parallel analysis of large numbers of chemical reactions. The spotter produces a glass or silica chip with an array of spots of various compounds by contact-based pin printing. The chip can then be entirely exposed to one treatment or each spot may be subjected to unique treatments by subsequent spotting. The microarray reader can measure two channels of fluorescence for every spot on a chip simultaneously.

Fourier Transform Infrared (FTIR) Spectrometer with horizontal sample stage

Nicolet 6700 Fourier Transform Infrared (FTIR) spectrometer with the horizontal sample stage allows real time analysis of reactions. A port for a light guide lets the user collect data while simultaneously performing UV and reactions catalyzed by visible light. A heating stage is also available for thermally triggered reactions.

Sample data from FTIR shows conversion as a function of time for photoinitiated reaction with various contaminant.

Dynamic Mechanical Analyzer (DMA)

Dynamic mechanical analysis of mechanical properties (e.g. tensile modulus) of materials under oscillating deformation and as a function of temperature is used to determine the transitions of states of soft materials (e.g., at what temperature does a soft polymer become hard and glassy).

Sample data from the DMA shows the elastic modulus as a function of temperature and the peak
in tan δ indicating a transition from glassy to rubbery.

Rheometer

Like the DMA, the rheometer (TA Ares) can measure the mechanical properties of materials under oscillating strains. The rheometer, however, is more suited to liquids and viscoelastic solids (e.g., elastomers and gels). The rheometer measures the viscosity and shear modulus of materials in parallel plate and cone and plate configurations. The instrument is equipped with a Peltier temperature controller plate and a quartz plate that allows the sample to be irradiated with visible or UV light so that the developing mechanical properties of light-cured materials can be observed. A fiber optic apparatus that connects to an adjacent spectrometer also allows simultaneous FTIR monitoring of the reaction.

Sample data from rheometer showing the development of elastic modulus as a function of time during photocuring of highly reactive monomers (squares), moderately reactive monomers (circles), and poorly reactive monomers (triangles).

For more information about these facilities, contact Christopher Bowman.

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