Effects of topology and size on statics and dynamics of complexes of hyperbranched polymers with linear polyelectrolytes

Abstract

Brownian dynamics simulations with explicit hydrodynamic interactions have been employed to study generic effects of size and topology in noncovalent ͑Coulombic-driven͒ complexes formed by irregular-shaped hyperbranched polymers and linear polyelectrolytes. The behavior of the complexes was explored in detail in terms of static and dynamic properties, both in local and in the entire complex scale. The results were compared to previous studies on perfect dendrimers and other hyperbranched molecules where available. It was found that both molecular weight and structure may impart significant changes to key factors known to be associated with the ability of these systems to take part in relevant nanoscale applications.

Shear-induced effects in hyperbranched-linear polyelectrolyte complexes

“…The HP constituents bear different sizes and extremely different branching structures allowing the assessment of the effects of molecular weight and topology on their response under shear flow. As it was demonstrated in our previous work where their equilibrium properties were examined, 34,38 complexes formed by HPs that are characterized by a dense branching pattern throughout the structure exhibit properties similar to those of systems formed by perfect dendritic analogs; this similarity allows them to be considered as cost-effective alternatives in relevant applications. On the other hand, complexes formed by the more open-in-structure, peripherally branched HPs exhibited remarkable differences from the former, both in static and in dynamic properties.…”

“…Differences, however, have been detected when the HP constituent was characterized by a more "open" structure bearing the dendritic branching units close to the periphery. 34,38 For all complexes, however, it was found that either in terms of conformational characteristics or in terms of global dynamics, the behavior of the linear chains was altered compared to their neutral counterparts, particularly when the size of the HP molecule was increased.…”

“…Since the main effect of electrostatic interactions is expected when the Debye length exceeds the complexes' size, we have adopted a sufficiently large value of r D = k −1 = 8.96l which corresponds to low aqueous salt concentration, 17 as was used in past studies in charged dendrimer systems 42 and in complexes with linear polyelectrolytes. 34,36 For complexes like the ones studied in this work, where the HP charge is fully compensated by the charge of the linear chain, counterion condensation is expected to be only of minor importance, and therefore the presence of counterions is not taken into account. The SHAKE algorithm with relative tolerance of 2 ϫ 10 −6 is used to maintain a fixed bond length.…”

“…where r ij is the distance between ith and jth beads, LJ = 0.3k B T and = 0.8l as in our previous work 34 are the characteristic energy and length parameters, and r cut is the cutoff distance ͑r cut = 2.5 ͒. The attractive interactions between charged beads in Eq.…”

“…26,33 The mechanisms involved in the manifestation of static and dynamic properties in noncovalent complexes between hyperbranched molecules and linear polyelectrolytes in equilibrium have been investigated in detail by means of computer simulations. [34][35][36][37] In neutral complexes ͑i.e., where the total charge of the LP equals in magnitude to that of the HP molecule͒ comprised by HPs bearing a perfect or almosta͒ Author to whom correspondence should be addressed. Electronic mail: karatas@eng.auth.gr.…”