Crystal Growth of Isotactic Poly(butene-1) in the Melt. I. Kinetic Roughening

Abstract

ABSTRACT:The morphology, lateral growth rate and long spacings of isotactic poly(butene-1) (it-PB1) have been investigated for crystallization from the melt over a wide range of crystallization temperature from 50 to 111.9 C. The morphology of it-PB1 crystals is rounded shape at crystallization temperatures lower than 85 C, while lamellar single crystals possess faceted morphology at higher crystallization temperatures; the kinetic roughening transition occurs around 85 C. The nucleation and growth mechanism for crystallization does not work below 85 C, since the growth face is rough. However, the growth rate and the long spacings show the supercooling dependence derived from the nucleation and growth mechanism; the nucleation theory seems still to work even for rough surface growth. Crystallization of polymers has been investigated through morphology, growth rate and lamellar thickness. The growth rate observed at a crystallization temperature, T, is known to be well described by the following equationwhere G 0 and K are constants, U is the 'activation' energy for polymer diffusion, R ¼ kN A , (k is the Boltzmann constant and N A is Avogadro's number)m is the equilibrium melting temperature). The first exponential factor is the VogelFulcher factor for viscosity and the second exponential factor is the surface kinetic factor.According to the nucleation theory 1 by Hoffman et al., the secondary two-dimensional nucleation rate i is given by the following equation:

Lamellar crystal thickness transition of melt-crystallized isotactic polybutene-1 observed by small-angle X-ray scattering

“…In our previous work, we determined the kinetic roughening temperature to be around 358.2 K (Yamashita et al, 2004). This is not in agreement with the observed temperature of the thickness transition, 338.2 K. However, we also observed (100) sector boundaries in kinetically roughened crystals at 358.2 K. The existence of sector boundaries indicates that the crystals have a considerable fraction of (100) folding even in the kinetically roughened state.…”

“…it-PB1 tetragonal crystals have a facetted morphology indicative of flat growth fronts on the molecular scale at lower ÁT, while they present a rounded morphology with a kinetically roughened growth front on the molecular scale (Yamashita et al, 2004(Yamashita et al, , 2007. In facetted crystals of the tetragonal phase, the chain folding direction is restricted to that parallel to the (100) growth front within each (100) sector since step propagation occurs along the (100) growth front during the crystallization process.…”

Trigonal–Tetragonal Crystal Phase Island Structure of isotactic Polybutene-1

“…Island shaped structures of flat-on planar crystals encapsulated within larger crystals were observed. The larger crystals are spherulites of the tetragonal phase, which have already been reported to grow from the melt in previous literature [1][2][3]9].…”

Directional Entropy of Chain Folding Detected in Chain Folding Free Energies? Crystal Thickness Transition of isotactic Polybutene-1 Tetragonal Phase

“…In 2004, we determined the kinetic roughening temperature to be around 85 C. 11,12 This is higher than the observed temperature of thickness transition, 65…”