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In this paper we study the critical properties of the Heisenberg spin-1/2model on a comb lattice --- a 1D backbone decorated with finite 1D chains --the teeth. We address the problem numerically by a comb tensor network thatduplicates the geometry of a lattice. We observe a fundamental difference betweenthe states on a comb with even and odd number of sites per tooth, whichresembles an even-odd effect in spin-1/2 ladders. The comb with odd teeth isalways critical, not only along the teeth, but also along the backbone, whichleads to a competition between two critical regimes in orthogonal directions.In addition, we show that in a weak-backbone limit the excitation energy scales as1/(NL), and not as 1/N or 1/L typical for 1D systems. For even teeth in theweak backbone limit the system corresponds to a collection of decoupledcritical chains of length L, while in the strong backbone limit, one spin from eachtooth forms the backbone, so the effective length of a critical toothis one site shorter, L-1. Surprisingly, these two regimes are connected via astate where a critical chain spans over two nearest neighbor teeth, with an effectivelength 2L.
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Kinetic Monte Carlo Tool for Kinetic Modeling of Linear Step‐Growth Polymerization: Insight into Recycling of Polyurethanes
Abstract A kinetic Monte Carlo model of polyurethane polymerization which explicitly tracks the polymer sequences is developed and shared. This model is benchmarked against theoretical and experimental polyurethane data and used to investigate the effect on oligomer distributions of unequal reactivity of the first and second isocyanate to react. The reverse reactions using thermodynamic consistency are then added to the framework, and analogous to the addition polymerization concept of ceiling temperature, equilibrium chain length distributions at various temperatures are calculated. For a mixture of three monomers AA, BB, and CC, where BB and CC do not react with one another, are present in stoichiometric proportions, and have different enthalpies of reaction with AA, an odd‐even effect emerges. Odd length chains are more likely than even length chains for temperatures at which BB and CC have significantly different equilibrium conversions. The concept of ceiling temperature that is typically cited for addition polymers is extended here to provide a measure of conditions under which depolymerization for recycling is favored.
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- Award ID(s):
- 1743748
- PAR ID:
- 10446962
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Macromolecular Theory and Simulations
- Volume:
- 31
- Issue:
- 2
- ISSN:
- 1022-1344
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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