Comblike Liquid-Crystalline Polymers from Ionic Complexation of Dendronized Polymers and Lipids

Abstract

This work describes the self-assembly behavior, the structure, the state, and phase diagrams of comblike liquid-crystalline polymers obtained by supramolecular ionic complexation of cationic dendronized polymers (PG1-PG3) and anionic sulfonated lipid surfactants. In order to characterize the influence of both the polymer and the surfactant on the microphase separation of these complexes, dendronized polymers with generation 1 e n e 3, carrying 2 n positive charges per monomer, were complexed with a stoichiometric amount of anionic sodium alkyl monosulfate surfactants with hydrocarbon chain of C 8 , C 12 , C 14 , and C 18 lengths. Supramolecular complexes were obtained in water, and the complexation process was monitored by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance. After drying and thermal annealing under high vacuum, the complexes showed thermotropic liquid-crystalline behavior as demonstrated by both cross-polarized optical microscopy and differential scanning calorimetry. Small-angle X-ray scattering allowed determining the respective lattice parameters and type of structures for all the complexes considered. Depending on both generation and lipid chain length, amorphous isotropic fluid, columnar rectangular, columnar hexagonal, columnar tetragonal, and lamellar phases were observed, each characterized by a specific order-disorder transition temperature (T ODT ).

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

“…These findings, which are in agreement with previously reported FTIR and NMR analysis, [13,14] allow a straightforward evaluation of the volume fraction of alkyl tails and dendronized polymers in final complexes, as soon as the densities of the individual components are measured.…”

“…First (PG1) and second (PG2) generation cationic dendronized polymers synthesized as described previously [13,14] were selected to form comb-like ionic supramolecular complexes as depicted in Figure 1. Complexation was realized in water solutions maintained at pH ¼ 3-4.…”

“…More recently, other types of macromolecular polyelectrolytes have been explored such as dendrimers [11,12] and dendronized polymers, [13,14] leading to richer polymorphism compared to previous systems. In particular it has been shown that for these classes of highly branched systems can form columnar phases of various lattices such as rectangular hexagonal and lamellar types.…”

Hierarchical self-organization in polyelectrolyte-surfactant complexes based on heteroarm star block copolyampholytes

“…choice of non-covalent bonding type(s), side-groups, and macromolecular template chemistry and architecture). 6 Regarding this last choice, much recent work has focused on complexes involving macromolecular templates with even more complicated architectures, such as dendrimers, 14,15 hyperbranched polymers, 16 dendronized polymers, [17][18][19] and rod-coil block copolymers. [20][21][22] Nandan et al have recently reported hierarchically organized materials formed by complexation of amphiphilic surfactants with heteroarm star (HAS) and block-arm star (BAS) polymers composed of polystyrene (PS) and poly(2-vinylpyridine) (PVP).…”

Thermotropic Ionic Liquid Crystals via Self-Assembly of Cationic Hyperbranched Polypeptides and Anionic Surfactants

“…10,11 The hydrogen-bonding strategy has been applied mostly to linear homopolymers and block copolymers to design macromolecular templates in which the polymer backbone acts as a hydrogenbonding acceptor and surfactants act as hydrogen-bonding donors so that hairy comblike polymers are formed in which the segregation between the surfactant and the polymer backbone leads to the final morphology. 12 In the case of ionic complexation, various polyelectrolyte architectures have been considered, such as linear, hyperbranched, dendritic, and dendronized polymers, 8,13,14,15 while hydrocarbon-based surfactants and rigid rods have been the mostly investigated classes of ionic surfactants. 16,17 The resulting polyelectrolyte-surfactant complexes have been shown to microphase segregate into liquid crystalline mesophases, analogous to those obtained in systems where the mesogenic units are covalently attached to macromolecules.…”