Abstract
In a previous work, we described a multi-scale protocol for the simulation of the conformation and dynamics of macromolecules that was applied to dendrimer molecules proving its predictive capability by comparison with experimental data. That scheme is now employed in order to predict conformational properties (radius of gyration) and overall hydrodynamic properties (translational diffusion and intrinsic viscosity) of hyperbranched molecules in dilute solution. For that purpose, we use a very simple coarse-grained bead-and-spring model whose parameters are not adjusted against experimental properties but they are obtained from previous atomic-level (Langevin) simulations of small fragments of real hyperbranched polymers. In addition, we devise a method to generate structures with different degree of branching. The Monte Carlo simulation technique was used to generate the set conformations of the coarse-grained model. In spite of the difficulties of reproducing experimental data of highly polydisperse entities (in terms of both molecular weight and topology) without using adjustable parameters, the results of this paper show that the proposed methodology allows for qualitative predictions of the behavior of such complex systems and lead us to conclude that, after some improvement, acceptable quantitative predictions can be achieved.
Highlights
Dendritic polymers are highly branched macromolecules which can be classified into three categories according to their degree of structural control: random hyperbranched polymers, dendrigraft polymers, and dendrimers [1]
We have simulated for each case (PAMAM, PCS3, PCS11 and polydimethyl 5-(4-hydroxybutoxy)isophthalate (PDHBI)), coarse-grained models containing from N = 50 to
It must be remarked that the topological variability may be insufficient since the parameter p is fixed (p = 0.425) what produces only small variations in degree of branching” (DB)
Summary
Dendritic polymers are highly branched macromolecules which can be classified into three categories according to their degree of structural control: random hyperbranched polymers, dendrigraft polymers, and dendrimers [1]. The irregular branching issue that appears both in real dendrimers due to defects and in truly random hyperbranched polymers (the topic of this work) can be addressed with the aid of computer simulation. In this regard, simulation techniques like Monte. There are several topological indices like the “Wiener index” [11] or the so-called “degree of branching” (DB) [12] that have been used to represent the degree of branching of hyperbranched polymers The latter is the most commonly employed index and takes values between 0 and 1 so that 0 corresponds to a linear chain and 1 corresponds to a whole branched chain (i.e., a chain with the maximum possible number of branches emerging from every node). That theory, which predicts successfully some experimental data, is based on defining some phenomenological functions whereas our simulation methodology tries to be more general by using atomic features of the polymers to predict any solution property
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