Size-Exclusion Chromatography (SEC)/Gel Permeation (GPC) is a technique that separates macromolecules (polymers) based on their hydrodynamic size in solution. The relative molecular weight (molar mass) of an unknown polymer can be determined by calibrating the GPC column set by injecting a series of narrow polymer standards, and subsequently comparing elution volumes. If the GPC system uses advanced detectors such as a light-scattering detector, calibration of the detector itself will provide the absolute measurement of molecular weight.
Liquid Chromatography Time of Flight Tandem Mass Spectrometry (LC-MS), like conventional HPLC, separates molecules based on the affinity to the stationary phase of the column. Following separation in the LC column, the resolved sample enters the mass spectrometer which provides an accurate molar mass measurement for each molecule and/or fragment.
Fourier-Transform Infrared Spectroscopy (FT-IR) is a spectroscopic technique used to identify the presence or absence of certain functional groups on a material by measuring the resonance of covalent bond frequencies. These functional groups include carbonyl, hydroxyl, carboxyl, aliphatic, amine, amide, alkenes, and more.
Nuclear Magnetic Resonance Spectroscopy (NMR) provides a detailed description of the chemical structure of a molecule by identifying the quantity and chemical environment of a predetermined atom such as hydrogen or carbon. The most popular technique is 1H-NMR, which measures the atomic resonance of protons, and thus can elucidate the complete chemical structure of any organic molecule containing hydrogen. 13C-NMR measures carbon-13 resonance and 2D-NMR provides a more thorough investigation in order to determine structural characteristics.
Differential Scanning Calorimetry (DSC) measures thermal properties by applying heat to a polymer, and measuring the resultant response and heat capacity. DSC provides the glassy transition temperature (Tg), melting temperature (Tm), and crystallization temperature (Tc), all key properties of polymeric materials.
Thermogravimetric Analysis (TGA), like DSC, is also a thermal analytical technique, but it can heat the sample until complete combustion. TGA has the potential to measure polymer purity (by vaporizing all solvents), moisture content, volatiles content, thermal stability, and decomposition kinetics
Dynamic Light Scattering (DLS) is a physical characterization technique used to measure the average size of nanoparticles suspended in solution by irradiating with a laser and measuring the Brownian motion of the particles in solution through scattered light. This technique may also measure the zeta potential (charge) of a colloid, which is an indirect measurement of its stability in solution.
X-Ray Diffraction (XRD) is a technique used for phase identification of a crystalline material and can provide information on unit cell dimensions. The analyzed material is finely ground, homogenized, and average bulk composition is determined. It provides the average crystallite size and the ratio of crystalline vs amorphous phases in a polymer.
Dilute Solution Viscometry (DSV) used to measure a polymer’s intrinsic viscosity which is a measure of the change in solvent viscosity by the presence of polymer solutes in specific solvents and temperatures. Based on the measured intrinsic viscosity of a polymer, the viscosity average molecular weight and hydrodynamic radius of polymers can be also be calculated.
Scanning Electron Microscopy (SEM) is a technique that produces detailed, high-resolution images of a sample by emitting a focused electron beam at the surface of the sample. The electrons interact with the atoms of the sample and thus provide surface topography information and the size and surface shape of any present nanoparticles.
X-ray photoelectron spectroscopy (XPS), also known as Electron Spectroscopy for Chemical Analysis (ESCA), is a surface-sensitive quantitative spectroscopic technique that measures the elemental composition, empirical formula, chemical state, and electronic state of the elements that exist within a material. The material can be a powder or a film deposited on a substrate. In a typical XPS experiment, a material is irradiated with a beam of X-rays and the resulting kinetic energy and number of electrons that escape from the top surface layer (usually 1 to 10 nm) of the material are detected. The emitted photoelectron has a characteristic kinetic energy (KE), which can be converted to the binding energy (BE) of the electron by the following equation:
KE = hʋ – BE – Φ
Where Φ is work function of the instrument.
The characteristic binding energies for each element are known and are used to identify the elements present on the surface of the sample.