Structure and properties of polybutylene crystallized from the glassy state. I. X-ray scattering, DSC, and torsion pendulum

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Abstract
Isotactic polybutene (PB) can be quenched into a completely glassy state by quenching molten films into a solid-liquid mixture of isopentane, Freon, or ethanol. The crystallization of PB from the glass form was studied by x-ray scattering, differential scanning calorimetry (DSC), and dynamic mechanical spectroscopy (torsion pendulum). As for crystallization from the melt, PB crystallizes from the glass into a tetragonal crystal structure (Form II) at ca. 0°C, depending on sample thickness, and then transforms to the twinned hexagonal structure (Form I) upon aging at room temperature. In the presence of isopentane, PB crystallizes partially from the glass into the untwinned hexagonal (Form 1′) structure at ca. -70°C; the rest of the sample starts to transform to tetragonal structure at ca. -30°C and nearly completes crystallization at ca. 0°C. The exact temperatures of both transformations depend on the amount of isopentane present and sample thickness. Upon aging at room temperature the tetragonal structure converts to the twinned hexagonal structure even faster than in the absence of isopentane. Dynamic mechanical experiments show the presence of two relaxation-like peaks for the ultraquenched samples: Tr (L) = -27°C and Tr (U) = -15°C. X-ray diffraction, DSC, and torsion pendulum experiments show that PB crystallizes from the glass at Tr (U).

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