Etude des volumes specifiques partiels de polystyrenes-modeles—Influence de la masse moleculaire et de la nature des groupements terminaux

It is well known that the apparent specific volume η₂ of a polymer may be expressed by the following relationship: $\text{η}{}_2\text{= η}{}_{\mathrm{m}}\text{+ K/}\text{M}{}_{\mathrm{n}}$ where M?_n is the number-average molecular weight of the polymer, η_m the specific volume of the infinite polymer, and K a constant. We have shown that this relationship is valid for low molecular weight polystyrenes ($\text{M}{}_{\mathrm{n}}\text{< 4·10}{}^4$) with different end-groups, independently of the nature of the solvent. The K values (and variations with the solvent and with the nature of the end-groups) may be predicted through simple calculations proposed here. We conclude that η_m does not represent the specific volume of the infinite polymer, since we observe a rapid decrease of η₂ for increasing M (when $\text{M}{}_{\mathrm{n}}\text{< 4·10}{}^4$). The decrease is much greater than expected from the relationship $\text{η}{}_2\text{= ? (1/}\text{M}\text{)}$.