Philic and Phobic Segregation in Liquid-Crystal Ionic Dendrimers: An Enthalpy-Entropy Competition

Instituto de Ciencia de Materiales de Aragón-CSIC, Universidad de Zaragoza, Plaza San Francisco s/n, 50009-Zaragoza, Spain.
Angewandte Chemie International Edition (Impact Factor: 11.34). 03/2010; 49(11):1990-4. DOI: 10.1002/anie.200905654
Source: PubMed
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper reviews our recent research with regard to bulk self-assemblers based on well-defined branched building blocks. Branched molecules/polymers have been known to show different physical properties from conventional linear-shaped polymers. As well as thermal and solution properties, structural modification into branched building blocks also has a significant influence on self-assembling behavior in the bulk states, including solid and liquid crystalline (LC) phases. As a branched component, dendrons/dendrimers with well-defined structures can be ideal candidates for the construction of advanced self-assemblers. Recently, we worked on new assembling systems such as dendron-coils, block codendrimers and discotic LC molecules. In the design, we used aliphatic polyether dendrons in most cases and poly(benzyl ether) dendrons in part. Their bulk assembling and thermal properties were found to be distinct from conventional linear block copolymers and they were dependent upon their chain architectures. To self-assemble into ordered nanostructures, the hybrid assembers were designed to have incompatible blocks, for example, hydrophilic and hydrophobic parts. Furthermore, in some cases an ionic complexation was carried out to maximize the immiscibility between the two different blocks. This review describes the molecular manipulations to engineer the nanoassemblies in bulk and also the ionic transportation properties depending on the assembling morphology.
    Polymer Journal 03/2012; 44(6):475-489. DOI:10.1038/pj.2012.31 · 1.55 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The self-assembly behaviour both in the bulk and water of a series of amphiphilic dendrimers constituted by second generation PAMAM ionically functionalized with different amounts of myristic acid is shown here. The number of acids in the dendrimer determines the liquid-crystal properties and the structural parameters of their supramolecular organization. Most of them present mesomorphism, organizing in a smectic A mesophase, with a layer spacing decreasing when increasing the number of acids. All these dendrimers form well-defined nanoobjects in water. Micelles and broken lamellae have been found for compounds with low acid contents. In contrast, dendrimers with higher fatty acid contents self-assemble forming nanospheres with a lamellar nanostructure. All compounds are able to trap the hydrophobic molecule 9,10-diphenylanthracene independent of the acid contents. Interestingly, the trapped hydrophobic molecule dominates the self-assembly trend of the dendrimers with low acid contents and thus different nanoobjects are found after the encapsulation.
    Soft Matter 12/2013; 10(2):281-9. DOI:10.1039/c3sm52393d · 4.15 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Two novel families of dendrimers have been synthesized by hydrogen bonding between a triazine moiety (M), as an electron-transporting central core, and three peripheral dendrons of generations 1 and 2 derived from bis(hydroxymethyl)propionic acid (bis-MPA). The dendrons contain both carbazole-based groups as hole-transporting moieties and promesogenic units derived from 5-[4-(4-butoxybenzoyloxy)phenyloxy]pentanoic acid (family A) or cholesteryl hemisuccinate (family B) (in a 1:3 ratio). The formation of the complexes was confirmed by IR and NMR data. All synthesized complexes displayed mesogenic properties and their liquid crystalline properties have been investigated by means of differential scanning calorimetry (DSC), polarized optical microscopy (POM) and X-ray diffractometry (XRD). Complexes derived from CzAn dendrons (family A) exhibit nematic mesomorphism whereas complexes derived from CzBn dendrons (family B) exhibit a smectic A phase. The electrochemical behavior of the dendritic complexes was investigated by cyclic voltammetry (CV) and the dendrimers show irreversible or quasi-reversible electrochemical behavior in the range 0.0–2.0 V at a scan rate of 100 mV s−1. The UV-vis absorption and emission properties of the compounds and the photoconductive properties of the dendrons and dendrimers have also been investigated.
    10/2013; 1(44). DOI:10.1039/C3TC31390E