Coil-globule transition for regular, random, and specially designed copolymers: Monte Carlo simulation and self-consistent field theory

Abstract

The coil-globule transition has been studied for A-B copolymer chains both by means of lattice Monte Carlo (MC) simulations using bond fluctuation algorithm and by a numerical self-consistent-field (SCF) method. Copolymer chains of fixed length with A and B monomeric units with regular, random, and specially designed (proteinlike) primary sequences have been investigated. The dependence of the transition temperature on the AB sequence has been analyzed. A proteinlike copolymer is more stable than a copolymer with statistically random sequence. The transition is more sharp for random copolymers. It is found that there exists a temperature below which the chain appears to be in the lowest energy state (ground state). Both for random and proteinlike sequences and for regular copolymers with a relatively long repeating block, a molten globule regime is found between the ground state temperature and the transition temperature. For regular block copolymers the transition temperature increases with block size. Qualitatively, the results from both methods are in agreement. Differences between the methods result from approximations in the SCF theory and equilibration problems in MC simulations. The two methods are thus complementary.

Coil‐Globule Collapse in Flexible Macromolecules

“…Co-polymeric chains of fixed length with A and B monomeric units with regular, random, and designated primary sequences are investigated. [103] The two computational techniques give qualitatively similar results for the coil-globule transition of AB copolymers. [103] In principle, the MC technique is more exact, but in practice, computational restrictions impede the theoretical advantages.…”

“…[103] The two computational techniques give qualitatively similar results for the coil-globule transition of AB copolymers. [103] In principle, the MC technique is more exact, but in practice, computational restrictions impede the theoretical advantages. This is particularly true when information is needed for a compact globule.…”

“…[94] Recently, the coil-globule transition of A-B copolymer chains was studied by the following two methods: a lattice Monte Carlo (MC) simulations using a bond fluctuation model and a numerical self-consistent field (SCF) approach. [103] In this contribution, detailed information was provided for the motivation for using both of these methods. Co-polymeric chains of fixed length with A and B monomeric units with regular, random, and designated primary sequences are investigated.…”

“…On the other hand, the SCF computations, while not elaborate, are not capable of investigating individual conformations. [103] The authors found that the transition temperature is roughly an exponential function of the block length in a regular copolymer. The cooperativity of the transition is high for regular block copolymer molecules, but lower for the random and protein-like sequences because of the polydispersity of block length.…”

“…The cooperativity of the transition is high for regular block copolymer molecules, but lower for the random and protein-like sequences because of the polydispersity of block length. [103] However, the globular state for proteinlike sequences is more stable than that for statistical random copolymers. No comparison was made with experiments carried out on copolymers.…”