Pressure-induced structural change of intermediate-range order in poly(4-methyl-1-pentene) melt

Abstract

High-pressure in situ x-ray diffraction and specific-volume measurements on isotactic poly(4-methyl-1-pentene) melt have uncovered abrupt changes in the pressure dependence of microscopic structure as well as that of macroscopic density. The first sharp diffraction peak of the polymer melt, which is related to the intermediate-range order and is explained as resulting from the correlations between main chains, is suppressed at pressures less than 1 kbar. These changes in intermediate-range order show similarities to those seen in liquid-liquid or amorphous-amorphous transitions in simpler small molecule based systems, suggesting that this kind of phenomenon may occur in a wide range of materials.

Probing the different spatial scales of Kel F-800 polymeric glass under pressure

“…The so-called polymerization (or van der Waals) peak represents real space distances consistent with the expected inter-backbone distances16 and so is the analogous feature of the FSDP peak. Hence, hereafter we will refer to this as FSDP for either network or polymer glasses.…”

Melting temperatures and possible precursor plastic phases of CCl4and GeI4as a function of pressure

“…In their x-ray diffraction study of pressure-induced structural changes of intermediate-range order in poly(4-methyl-1-pentene) (P4MP1) melts, Chiba et al [9] found that the first sharp diffraction peak (FSDP) intensity I(FSDP) decreased with pressure. Additionally, the ratio of I (FSDP) to the intensity of the second peak also decreased sharply under pressure.…”

“…Thus, a decrease in I(FSDP) points a disordering of these backbone-backbone correlations and a shift to higher momentum transfers. This led Chiba et al [9] to construct a model of polymer chains such that the polymer backbones were separated by void spaces filled with the polymer side chains. At low pressures, the void space between the backbone chains is quite large and consequently the resulting loose structure is highly compressible.…”

Crystallography Under Extreme Conditions: State of the Art and Perspectives

“…Combination of in situ synchrotron X-ray absorption techniques and molecular dynamics simulations were used to determine the density range of primitive lunar melts at pressures equivalent to those in the lunar interior (4.5 GPa and 1800 K) (Van Kan Parker et al, 2012): these extreme conditions were generated with tiny samples heated thanks to high electric current while squashing them in a press (figure 6); knowing the attenuation of the synchrotron X-ray beam through both the solid and molten parts of the sample, the density at high pressure and high temperature could be measured. High pressure in situ X-ray diffraction and specific volume measurements on isotactic poly(4-methyl-1-pentene) melt have uncovered abrupt changes in the pressure dependence of microscopic structure as well as that of macroscopic density (Chiba et al, 2012). It was proved another time that pressure has an essential role in the production and control of superconductivity (Sun et al, 2012): it is reported that in the superconducting iron chalcogenides, a second superconducting phase suddenly re-emerges at a critical temperature Tc reaching 48.0 K and above 11.5 GPa, after the Tc drops from the first maximum of 32 K at 1 GPa.…”