While the apparently negligible impact of heat release on the structural details of early-stage PE nuclei may seem unexpected based on results for small-molecule crystallization, there are two important distinctions between the polymer and smallmolecule scenarios. First, when part of a chain starts to be incorporated into a growing nucleus, the heat released from its crystallization can be transported along the chain's backbone away from the nucleus. Such long-range intramolecular heat transport is not possible in the case of small molecules. Second, small molecule reorganization is facile compared to the slow reptation processes governing the chains in entangled PE melts, such as those considered in this study. The end-to-end vector correlation function for the n-C 720 H 1442 chains decays slowly in the nucleation simulations, even compared to a n-C 720 H 1442 melt at 500 K (see Fig. ). Even on the microsecond timescale, the polymer chains in the nucleation simulations can only marginally relax. Consequently, compared to the small-molecule case, it is difficult for heat to remain localized on the timescales that would be required to impact polymer nucleation. and 2) some qualitative comparisons of order parameter behavior. In contrast, other work on PE nucleation describes substantial polymer reconfiguration as crystallization proceeds. This other work considered: 1) polymer crystallization from dilute solutions, if not the infinitely dilute regime, 2) crystallization in response to flow, and/or 3) molecules sufficiently small that entanglement effects were effectively nonexistent or negligible. The two sets of contrasting results highlight that the molecular-level details of polymer crystal nucleation depend substantially on system conditions, and that there are multiple regimes for polymer crystal nucleation. In turn, the results presented herein indicate that insights from previous work are not necessarily applicable to high-driving force, long-chain (entangled) conditions.