Isotactic poly‐pentene‐1: Polymorphism and some physical properties

Abstract

Abstract Preliminary results of a physical study of highly isotactic poly‐pentene‐1 are here reported. This polymer, although crystallizable to a high degree, can be fractionated by a normal fractional precipitation technique. This is due to its capacity of giving metastable solutions in bad solvents, and therefore a liquid‐liquid separation, owing probably to its relatively low crystallization rate. Fractions were thus prepared for further experiments. Isotactic poly‐pentene‐1 is found to be able to crystallize into two modifications: modification 2, so far known, having melting temperature at 80°C.; and the apparently more stable modification 1, with a melting temperature regularly affected by molecular weight, but exceptionally dependent on crystallization temperature. Its maximum melting temperature is estimated, although in a non definite way to be around 130°C. X‐rays diffraction diagram and volumetric and dilatometric data of the two pure modifications are given. The volume‐temperature relationship of the amorphous isotactic phase is eventually drawn from experimental data and three dilatometric isophasic transitions are individualized at −52°, −10° and +13°C.