【Basic Knowledge of Glossary Explanations for “Polymers and Materials”-015】Glossary explanations related to polymers
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This post was last edited by ljtjbx on 2015-8-9 10:06. 1. Huggins parameter: Reflects the change in interaction energy when a polymer mixes with a solvent. 2. Relative molecular weight distribution width index: It refers to the average square of the differences between each molecular weight in the sample and the average molecular weight. 3. High-elastic deformation: The process by which molecular chains gradually stretch through segmental movement; the degree of deformation is much greater than that in normal elastic deformation, and the deformation is proportional to time in an exponential manner. 4. Mechanical loss: If the change in deformation lags behind the change in stress, work is consumed in each cyclic change; this is known as mechanical loss. 5. Swelling phenomenon: The phenomenon in which a solvent penetrates into the interior of a polymer, causing its volume to increase.
What is the relationship between the index of relative molecular mass distribution width and the impact on the performance of the corresponding product? Everyone can discuss it
Learn *it first! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !
Flory-Huggins parameter: The Flory-Huggins interaction parameter. Transliteration: Huggins parameter
It’s such complicated stuff; I can’t understand any of it! ! Flory-Huggins interaction parameter. The parameter characterizing the interaction between the polymer and the solvent is denoted by X1. In the quasi-lattice theory of polymer solutions, it is assumed that each solvent molecule has the same size as each polymer chain segment, and that each chain segment or solvent molecule can have several neighbors. In this case, the interaction energy when each solvent molecule is in full contact with a polymer segment is approximately equal to z△e. The ratio of this quantity to the thermal motion energy kT is X1; X1 = z△e/kT, and X1 is a dimensionless quantity that does not depend on the solution concentration. It also has the following relationship with the difference in solubility parameters of the two components in the polymer solution: X1 = (δ1 – δ2)^2V1/RT, where V1 is the partial molar volume of the solvent and R is the gas constant. X1 can be determined from the relative vapor pressure or osmotic pressure of the solution; it is a measure of the thermodynamic affinity between the solvent and the polymer ； Therefore, △e includes not only the mixing heat △H1 but also the non-conformational mixing entropy, △S1. And X1 should consist of two parts: X1 = XH + HS. XH=△H1/RTΦ22, XS=-△S1F/RΦ22 (where F represents non-conformationality); here, △H1 is the enthalpy of mixing, and △S1F is the entropy of mixing due to non-conformationality. The smaller X1, the better the solvent ； The X1 value for extremely poor solvents can be greater than 1, while the value for extremely good solvents can be negative.
So this Huggins parameter reflects the change in interaction energy when a polymer mixes with a solvent. One only knows its function; the true meaning needs to be understood. By the way: What are the methods for determining Huggins parameters?
The HUGGINS parameter can be determined by the following methods: dilute solution viscosity method, membrane osmotic pressure method, light scattering method, and swelling method.