Functional Columnar Liquid Crystalline Phases From Ionic Complexes of Dendronized Polymers and Sulfate Alkyl Tails

Abstract

Summary:We describe how cationic dendronized polymers of generations 1, and 2 and anionic monoalkyl tails can be combined by supramolecular ionic complexation into comb-like liquid crystalline polymers. The final structures in bulk of these supramolecular complexes were studied by differential scanning calorimetry (DSC), cross-polarized optical microscopy (CPOM), small angle x-rays scattering (SAXS) and transmission electron microscopy (TEM). The combination of these techniques allowed elucidating (i) that these complexes exhibit thermotropic behaviour, (ii) that various liquid crystalline structures in the 3-5 nm length scale can be obtained such as columnar rectangular, columnar tetragonal, columnar hexagonal and lamellar, depending both on alkyl tail length and polymer generation, (iii) that although the alkyl tails represent the majority phase in the columnar phases, they form the cylindric domains, and the dendronized polymers occupy the continuous domains. Therefore, upon selective cleavage of the alkyl tails in the columnar phases, the present self-assembly approach may constitute an efficient strategy towards the formation of porous organic matrices with ultra-dense pore size in the range of 2 to 4 nm.

Controlling Hierarchical Self-Assembly in Supramolecular Tailed-Dendron Systems

“…Exploiting the supramolecular noncovalent binding between the dendrons and alkyl tails, their confinement within cylinders and the temperature-responsiveness of the linear polymer emanating from the focal point of the dendrons (the polymer used in the present system has a lower critical solubility temperature LCST of 25°C) shall enable the design of new materials for templating responsive molecular filters and membranes similar to those described by Nykanen et al 50 The present systems could additionally offer a controllable pore size and lattice by simply removing the ionically bound surfactants. 27 Finally, the orderorder transitions observed at moderate temperatures could also be exploited to induce sudden temperature-driven changes in materials properties, making these systems a very appealing candidate for new applications. Chemical structures for the complexes used in the present work.…”

“…In each case, upon addition of the polymer, the solutions became turbid, indicating the formation of stoichiometric complexes, 11 as we have already observed and characterized in our previous studies on dendritic polyelectrolytes-counter-charged surfactants ionic complexes. [25][26][27] Complexes were collected after centrifugation and removal of the water and then dried at 50°C for 1 day under low vacuum. The annealing of the samples was performed under high vacuum (<10 -7 mBar) at temperatures above the glass transition of the G2-PMeDEG polymers and maintained systematically between the melting temperature of the alkyl tails and the orderdisorder transition of the complexes (determined by SAXS measurements at different temperatures).…”

“…26 These exciting results open new routes to the design of porous nanotemplates if the surfactants restricted within the columns in the hexagonal or rectangular packing can be removed by exploiting their noncovalent bindings to the dendrons. 27 To understand to which extent this "inverted" self-assembly scheme is maintained and to control the resulting structural properties of the nanotemplates, we have used the same secondgeneration dendron as in ref 26 but with a polymer chain emanating out of the focal point. The polymerization degree of this polymer chain and thus its volume fraction can be maintained as a tunable parameter.…”

Novel Phase Morphologies in a Microphase-Separated Dendritic Polymer Melt

“…In addition, the phase sequence predicted by our model (Dis f Rec f Sq f L 2 ) with fixed f B is consistent with available experimental results. [22][23][24][25] All transitions in the phase diagram in Figure 2b are first order with the exception of one, which is drawn with a dashed line. This is the Sq to Rec transition, which is a continuous transition, and will be discussed in more detail below.…”

Redox-active mesomorphic complexes from the ionic self-assembly of cationic polyferrocenylsilane polyelectrolytes and anionic surfactants

“…As a result of their facile synthesis, structural versatility, and potential applications, polyelectrolyte-surfactant complexes have been of intense interest over the last decade. [1][2][3][4][5][6][7][8] Central to this theme is the technique of Ionic Self-Assembly (ISA), a powerful tool that utilizes molecular building blocks (or tectons), such as ionic surfactants and oppositely charged polyelectrolytes, to form new nanostructures and functional materials. 9 Usually, ionic binding of the surfactant molecules to the oppositely charged polyelectrolyte is characterized by cooperativity and is initiated at the critical aggregation concentration (CAC), a few orders of magnitude below the critical micelle concentration (CMC) of the surfactant itself.…”