A coarse-grained model for PCL: conformation, self-assembly of MePEG-b-PCL amphiphilic diblock copolymers

MARTINI coarse‐grained model for poly‐ε‐caprolactone in acetone‐water mixtures

“…At this threshold acetone concentration in the mixture, a sharper globule-to-coil transition is detected for the single PCL chain in solution, with respect to the atomistic profile. This trend was also observed in previous CG simulations of polymer in binary mixtures, [64,66] but it does not agree with our previous atomistic simulation results where, however, the model could still undergo unphysical de-mixing. Since the latter is still related to a narrow acetone molar fraction range, and since such a phenomenon has been shown here to not take place at the CG level, the developed CG model can be considered robust and consistent with the proposed procedure.…”

“…They also detected that the stepwise transition observed for a single CG chain becomes less sharp for polymer brushes. Raman et al [64] observed the same behaviour at x A = 0.50 for single CG PCL chains in acetone-water mixtures, by using the MARTINI force field with a polarizable water model. However, in the results presented here it is not possible to detect a proper stepwise transition, [67] despite fact that the CG profile turns out to be much steeper than the atomistic one.…”

“…The parameters for the bonded potentials, reported in Equations (2) and (3), are r b = 0.415 nm, θ 0 = 170 (P 2 -C α -P 2 ) θ 0 = 129 (C α -P 2 -C α ) and the force constants K b = 5000 kJ/mol nm −2 and K θ = 50 kJ/mol, since it was already demonstrated that this set of values can correctly reproduce the atomistic distributions. [64] The energy minimization was carried out by means of the steepest descent algorithm. The system was equilibrated with a leap-frog algorithm for 1 ns-2 ns using a Berendsen thermostat and a combination of Berendsen and Parrinello-Rahman barostats (T = 300 K and P = 1 bar).…”

“…This trade-off procedure starts from the default MARTINI nonbonded intrachain parameters that, however, were shown in a previous attempt to lead to unphysical trends of the radius of gyration (it decreases at increasing chain lengths) at medium acetone molar fraction. [64] For this reason, they represent a starting point and, consequently, suitable modifications need to be done.…”

Morphology and ion diffusion in PEDOT:Tos. A coarse grained molecular dynamics simulation

“…63,64 In earlier work, a validation of the Martini CG model was based on the calculation of the free energy and a comparison with AA MD simulations and available experimental results. [35][36][37] In subsequent work, other physical and chemical quantities such as the mass density, 37,40,45,65,66 the dielectric constant, 42 the radius of gyration, 40,42,65,67,68 film morphology 37 and the diffusion coefficient 40 were used to validate the CG model. In the present work for the validation of our CG model of PEDOT, we focus at the formation of p-p stacking between PEDOT chains, the number of chains in crystallites, the mass density and the SASA, and compare the CG results with corresponding AA simulations as well as with experimental values (where available).…”