Dendrimer‐Based Polyion Complex Vesicles: Loops Make Loose

Abstract

Associations of amphiphiles assume their various morphologies according to the so-called packing parameter under thermodynamic control. However, one may raise the question of whether polymers can always relax fast enough to obey thermodynamic control, and how this may be checked. Here, a case of polyion complex (PIC) assemblies where the morphology appears to be subject to kinetic control is discussed. Poly (ethylene oxide)-b-(styrene sulfonate) block copolymers are combined with cationic PAMAM dendrimers of various generations (2-7). The PEO-PSS diblocks, and the corresponding PSS-PEO-PSS triblocks should have nearly identical packing parameters, but surprisingly creat different assemblies, namely core-shell micelles and vesicles, respectively. Moreover, the micelles are very stable against added salt, whereas the vesicles are not only much more sensitive to added salt, but also appear to exchange matter on relevant time scales. The small and largely quenched early-stage precursor complexes are responsible for the morphological and dynamic differences, implying that kinetic control may also be a way to obtain particles with well-defined and useful properties. The exciting new finding that triblocks produce more "active" vesicles will hopefully trigger the exploration of more pathways, and so learn how to tune PICsomes toward specific applications.

Rational Polyelectrolyte Design Enables Multifunctional Polyion Complex Vesicles

“…27,28 Particularly, the triblock copolymer facilities PEO loop formation upon complexation, which is favorable to construct lamellar structures. 29 The designed combination integrates the benefits of both triblock and coordination polymers, which dominate lamellar structure and functionality, respectively. We start with investigating the co-assembly and formation of PIC vesicles, followed by manipulating the charged block length of a triblock copolymer, the metal−ligand combination, and the structure of coordination polymers, and exposing their effects on vesicle structure and functionalities.…”

“…This control leads to coordination polymers with modulated structures and functionalities, which enables fabrication of multifunctional PIC vesicles. For the other building block, the charged–neutral diblock copolymer was substituted by a cationic–neutral–cationic triblock copolymer, which displays distinctive regulation of both the co-assembly and structure properties. , Particularly, the triblock copolymer facilities PEO loop formation upon complexation, which is favorable to construct lamellar structures . The designed combination integrates the benefits of both triblock and coordination polymers, which dominate lamellar structure and functionality, respectively.…”