Structurally different amorphous solids of isotactic poly(4-methyl-1-pentene) and an apparently press-working-induced amorphization

We have done press working of isotactic poly(4-methyl-1-pentene) (P4MP1) and carried out X-ray diffraction measurements of the pressed sheet at atmospheric pressure. The result shows an apparently pressure-induced amorphization, although the result will be partly due to the pressure gradient in the sample in the compression process. Separately from this measurement, we quenched the melted state of this polymer at atmospheric pressure and obtained an amorphous solid, and measured its X-ray diffraction at room temperature. Although the diffraction spectrum of this amorphous sample partially contained crystalline Bragg peaks, we found a difference between the diffraction spectra of quenched and pressed amorphous samples at the first peak height, which mirrors the difference between the diffraction spectra of low-density and high-density melt of the same polymer. We also suggest from the diffraction results that the crystalline state at room temperature contains high-density amorphous parts rather than low-density amorphous parts.