Two-step crystal nucleation kinetics: Solution of the master equation

The effect of local chain stiffness on oligomer crystallization from a melt

“…For example, several research groups modelled crystallization of a united-atom model of PE and found evidence that supports the single-step transition described by CNT, including a cylindrical critical nucleus and a lack of nematic ordering before crystallization [20][21][22][23][24][25]. On the other hand, other researchers have observed nematic ordering in simulations of n-alkanes and PE [26,27] and a non-cylindrically shaped nucleus, providing evidence for a two-step transition [3,[26][27][28][29][30][31]. Simulations of flow-induced crystallization of PE also provide evidence that chain orientation plays a role in nucleation [32][33][34].…”

“…Despite decades of study, the mechanism by which a crystal first nucleates in a polymer melt remains controversial [2]. The conventional theory, Classical Nucleation Theory (CNT), treats the transition between polymer melt and a crystal nucleus as a single-step transition [3]. However, for the most widely studied case of polyethylene (PE) crystallization, there are numerous experimental observations of mesoscale precursors prior to crystal formation [4][5][6][7][8][9][10][11][12].…”

The effect of local chain stiffness on the mechanism of crystal nucleation in an oligomer melt

“…[16][17][18][19][20][21] By contrast, several other researchers have observed nematic ordering in simulations of n-alkanes and PE, 22,23 and a non-cylindrically shaped nucleus, providing evidence for a two-step transition. 2,[22][23][24][25][26][27] Additionally, simulations of flowinduced crystallization of PE also provides evidence that chain orientation plays a role in nucleation. [28][29][30] A careful comparison of these simulations reveals two potentially significant sources of disagreement.…”

“…We studied models with rigid-rod and harmonic bonding potentials with a bond length scale l 0 , and with hard-bead and soft repulsive (Weeks-Chandler-Anderson, WCA) non-bonded potentials characterized by the parameter σ. 2 We selected the latter to ensure that the bead diameter a = l 0 , to ensure that crystallization is possible. 64,65 Further details relating to the polymer models are provided in the SI.…”

“…1 The conventional theory, Classical Nucleation Theory (CNT), treats the transition between polymer melt and crystal as a single-step transition. 2 However, for the most widely studied case of polyethylene (PE) crystallization, there are numerous experimental observations of mesoscale precursors prior to crystal formation contrary to the predictions of CNT. [3][4][5][6][7][8][9][10][11] Subsequently, as shown in Fig.…”