polidispersitat o polidispersió? 

Altres

El mot polidispersitat, derivat de l’adjectiu polidispers (usat per descriure l’estructura dels polímers) està format per la forma prefixada poli- i el nom dispersitat. Aquest nom no està recollit en cap diccionari de referència en català, perquè es tracta d’un creació lèxica recent feta en el camp de la ciència. En un document de la IUPAC publicat el 2009, titulat Dispersity in polymer science (IUPAC Recommendations 2009), es diu el següent:

A dimensionless ratio of two average values of a property is widely used in polymer science as a characteristic of the dispersion, or spread, of the distribution of values of that property in a sample of polymer. In particular, the ratios […] are quantities commonly used to characterize the dispersions of distributions of molar masses and degrees of polymerization, respectively. However, they do not have satisfactory names and the present recommendation seeks to rectify this situation.
[…] are both often erroneously called “polydispersity index”, although they are not indices and the term “polydispersity” is not a defined quantity. In addition, a polymer sample composed of a single macromolecular species should be called a “uniform polymer” and a polymer sample composed of macromolecular species of differing molar masses a “non-uniform polymer” [1]. It is preferable if such polymer samples are not called “monodisperse polymer” and “polydisperse polymer”, respectively [1]. “Monodisperse” is a self-contradictory term, and “polydisperse” is tautologous.
The names proposed in this recommendation for […], are “molar-mass dispersity” and “degree-of-polymerization dispersity”, respectively, with “relative-molecular-mass dispersity” and “molecular-weight dispersity” proposed as synonyms for molar-mass dispersity. “Dispersity” is a new word, coined to denote a measure of the dispersion of macromolecular species in a sample of polymer. The suffix “-ity” or “-ty” is described in dictionaries [2] as one used to form nouns describing quality, state of being or condition. In a scientific context, “-ity” is generally used to form nouns denoting the quality of a particular property, e.g., density, conductivity, resistivity, opacity, etc., in which the “quality” has a numerical value. Hence, “dispersity” is an appropriate word to describe a numerical attribute of the dispersion of a distribution.
The term “dispersity” is here limited to describing the dispersions of distributions of molar masses (or relative molecular masses, or molecular weights) and degrees of polymerization. With the use of suitable adjectives, it can easily be applied to distributions of other properties of samples of polymeric (and non-polymeric) materials, giving, for example, diffusion-coefficient dispersity and particle-diameter dispersity. Further applications and developments of the term will be the subject of future work. The immediate aim is to recommend satisfactory and widely acceptable names for […]. The general symbol Đ, pronounced “D-stroke”, is introduced for dispersity to avoid confusion with the conventional use of D for diffusion coefficient.

 En el fragment ombrejat en groc podem veure la justificació formal i conceptual per a la creació del nou mot. Com que el català també disposa d’aquest mateix recurs derivatiu, amb el sufix -itat, que té el mateix valor semàntic, podem fer un calc del procés formatiu i obtindrem dispersitat

 

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