Molar Mass and Dispersity
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Molar mass: weight of one mole of polymer molecules; most common types are the number-average (Mn), weight-average (Mw) and z-average (Mz)
Dispersity: ratio of the weight-average molar mass to the number-average molar mass |
GPC: entire molar mass distribution but requires comparison with standard material
SLS: absolute value for Mw
DLS: diffusion coefficient and hydrodynamic radius
Mass spectroscopy: structure and molar mass
MALDI-TOF: for high molecular weight compounds; give distribution of travel times with heavier species taking longer travel through the detector |
Different measurement techniques: may yield different values important to have general idea of the molar mass range & be aware of the measurement technique
With Boolean operators molar mass ranges and measurement techniques should be included in the search string construction
Sources: listing of scattering factors in Section VII of Polymer Handbook1 & Polymer Data Handbook2 (compiles molar mass by name within polymer classes and types) |
| Spectral Analysis |
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IR: absorption of infrared radiation by chemical bonds; for identification of substances by measuring characteristic frequencies associated with specific molecular motions; different types: FT-IR or ATR-IR for surface characterization
Raman Spectroscopy: frequency change of inelastically scattered light; to measure specific chemical bond energy properties and to detect morphological changes; can be employed in different environments
NMR: measures radiation absorption relative to reference compound |
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| X-ray diffraction and scattering Analysis |
To elucidate crystalline and semicrystalline phases in polymers |
X-ray diffraction: scattering pattern; size of unit cell can be calculated
WAXS: measure spacing between individual chains in ordered regions to calculate degree of crystallinity and density
SAXS: information about larger molecular structure, crystal thickness and periodicity |
Sources: Crystallographic data in International Tables of Crystallography (ITC), WebCSD (further explanation in physical properties and spectra) and in Section V of Polymer Handbook1 & Polymer Data Handbook2 |
| Glass Transition (Tg) and melting (Tm) temperatures |
Types of thermophysical properties available for any polymer will depend on its structure (polymers can have the same chemical structure, but different physical structures depending on their formation and processing conditions)
Tg: for highly regular structure no variation by measurement method; amorphous polymers will only display glass transition temperature; Semi-crystalline or crystalline polymers may exhibit Tg and Tm
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XRD: to determine crystallinity of polymers
DSC: to measure crystallinity as well as glass and melting transitions, and heat capacityl; main experimental parameter is rate of change in the heating element and should be noted |
Sources: In Section V of the Polymer Handbook1, in the Polymer Data Handbook2 and in Section 13 of the CRC Handbook of Chemistry and Physics4
Attention should be paid to the method by which the value was determined |
| Decomposition temperature |
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TGA: measures mass loss as function of temperature; experiments can be carried out at different heating rates in various gaseous environment |
Heating rates and gaseous environment should be included for searching
Sources: In Section II of the Polymer Handbook1, |
| Polymer Solubility and Miscibility |
Implications for many experimental applications, including synthesis and characterization |
Solubility is directly related to polymer solution phase behavior in terms of upper critical solution temperatures (UCST) and lower critical solution temperatures (LCST) |
Sources: list of common solvents in Section III of the Polymer Handbook1 and in Section 13 of the CRC Handbook of Chemistry and Physics4
UCST & LCST: CRC Handbook of Chemistry and Physics4, p. 13-26 – 13-43 |
| Viscoelastic behavior |
Mechanical properties of polymers are related to the time temperature superposition (TTS) principle = properties measured at high rate are equivalent to properties measured at low temperature and vice versa (at low temperature there is thermal energy to effect molecular rearrangement and at high rate rates there is less time) |
Static testing: mechanical properties of relevance include tensile modulus, compressive modulus, shear modulus, ultimate tensile strength and Poisson’s rate; temperature of measurement is vital as properties can change drastically
Dynamic testing: mechanical properties such as storage modulus, loss modulus, tan delta and dynamic viscosity; specific to temperature, frequency of measurement and intrinsic polymer properties; can also vary by instrumentation used; experimental condition (temperature, shearing rate and frequency/frequency spectrum should be noted) |
For searching keep in mind TTS principle and be aware of the conditions under which reported values are obtained (temperature & rate of testing)
Sources: mechanical property for polymers in Section V of the Polymer Handbook1, in the Polymer Data Handbook2 (more easily navigable by polymer name than by property value)and in Section 13 of the CRC Handbook of Chemistry and Physics4 |
