Remarkable Stabilization of Self-Assembled Organogels by Polymerization

Loos, Maaike de; Esch, Jan H. van; Stokroos, I.; Kellogg, Richard M.; Feringa, Bernard; Stokroos,

doi:10.1021/ja972899z

Cited by 261 publications

(131 citation statements)

References 17 publications

Supporting

Mentioning

124

Contrasting

Unclassified

Order By: Relevance

“…Photopolymerization of selfassembled fibers is an effective method to produce stable gels. [22][23][24][25][26][27][28][29] The enhancement of the thermal stability and durability of the self-assembled LC gels is essential for practical applications.…”

Section: Resultsmentioning

confidence: 99%

Liquid-crystalline gels exhibiting electrooptical light scattering properties: fibrous polymerized network of a lysine-based gelator having acrylate moieties

Eimura

Yoshio

Shoji

et al. 2012

Polym J

View full text Add to dashboard Cite

New liquid-crystalline (LC) gels composed of a lysine-based bisurea derivative having terminal acrylate moieties and a nematic liquid crystal, 4-cyano-4 0 -pentylbiphenyl, have been prepared to develop light-scattering electrooptical materials. Randomly dispersed networks of the polymerizable fibers are obtained by self-assembly of the lysine derivative through the formation of hydrogen bonds in the isotropic phase of the nematic LC molecule. After the isotropic-nematic transition of the LC molecule occurs at 35 1C on cooling, light-scattering nematic LC gels are formed because of the formation of microphase-separated structures of fibrous solids and the liquid crystal. The fibrous structures are fixed by photopolymerization, leading to the enhancement of thermal stability. The polymerized LC gels exhibit electrooptical switching between light-scattering and transparent states with lower driving voltages than the non-polymerized LC gels. The threshold voltages of the LC gels based on the polymerizable lysine gelator are also lower than those of the LC gels containing a non-polymerizable lysine gelator. Polymer Journal (2012) 44, 594-599; doi:10.1038/pj.2012.21; published online 21 March 2012Keywords: electrooptical properties; gel; gelator; hydrogen bond; liquid crystal; photopolymerization; self-assembly INTRODUCTION Liquid crystals have been widely used as electrooptical materials because their molecular alignment can be controlled by external electric fields. 1 Their electrooptical switching properties can be tuned by the incorporation of self-assembled fibers, 2-10 organic and inorganic particles, 11,12 and dendrimers 13 into liquid crystals as well as the encapsulation or phase separation of liquid crystals in polymer matrices. 14-16 Liquid-crystalline (LC) physical gels are formed by fibrous self-assembly of small amounts of gelators (0.2-5.0 wt%) in liquid crystals. [2][3][4][5][6][7][8][9][10] In these materials, the liquid crystals and the fibrous aggregates of the gelators form microphase-separated structures. The efficient electrooptical switching and the induction of light-scattering electrooptical effects of nematic liquid crystals were achieved by the formation of finely dispersed fibers of gelators in liquid crystals. [5][6][7][8][9] The electrooptical properties of the LC physical gels were examined for twisted nematic 5,6 and light-scattering modes. 7 To enhance thermal stability of the anisotropic gels, a new type of light-scattering LC gel has been developed by self-assembly of an L-valine-based gelator having methacryloyl moieties and a room temperature nematic liquid crystal. 10 The gelator formed randomly aligned fibrous aggregates through the formation of intermolecular hydrogen bonds in the isotropic phase of LC molecules. Photopolymerization of the gelator forming the self-assembled

show abstract

Section: Resultsmentioning

confidence: 99%

Liquid-crystalline gels exhibiting electrooptical light scattering properties: fibrous polymerized network of a lysine-based gelator having acrylate moieties

Eimura

Yoshio

Shoji

et al. 2012

Polym J

View full text Add to dashboard Cite

show abstract

“…Such IR shifts indicate Fig.1. IR spectra of gelators 1 in (a) toluene (10 mg/mL, gel state) and CHCl 3 (10 mg/mL, solution) at 25 °C. the presence of the intermolecular hydrogen bonding interaction.…”

Section: Highlight Major Self-assembling Interactions Of Organogelatorsmentioning

confidence: 99%

“…[1][2][3][4][5] Spectroscopic techniques such as nuclear magnetic resonance (NMR), infra-red (IR), fluorescence emission and circular dichroism (CD) are commonly employed with the aim at elucidating the detailed structure of supramolecular gels. A widely accepted mechanism of gelation is the spontaneous self-assembly of individual molecules into fibers and subsequent entanglement of these fibres into fibrous networks, including solvents in the interstices.…”

mentioning

confidence: 99%

Self-Organization of Gelator Molecules Inside an Organogel

Pham

Brosse²,

Frochot

et al. 2007

3rd France-Russia Seminar

View full text Add to dashboard Cite

Low-molecular-weight organic gelling agents are currently subject of increasing attention, not only Introduction Low-molecular-weight organic gelling agents are currently subject of increasing attention, not only because of the numerous applications of gels, but also because understanding the detailed structural information of molecular assemblies is important for the rational design of those materials. [1][2][3][4][5] Spectroscopic techniques such as nuclear magnetic resonance (NMR), infra-red (IR), fluorescence emission and circular dichroism (CD) are commonly employed with the aim at elucidating the detailed structure of supramolecular gels. A widely accepted mechanism of gelation is the spontaneous self-assembly of individual molecules into fibers and subsequent entanglement of these fibres into fibrous networks, including solvents in the interstices. The driving force for the self-assembly of molecules into fibres are non-covalent forces 1 such as hydrogen bonding, π-π stacking, van der Waals interactions, solvophobic interaction etc. In a preliminary communication, we described a new family of (S)-aminoacid type gelators obtained via an easy and inexpensive way. 6 These novel gelling agents are very easily prepared from cheap starting materials and allowed many structural variations of the side chain. In order to go deeply into the organogelation phenomenon, we point out in this paper the self-assembling behaviour of gelator 1 (see chart 1) which bears a fluorescent chromophore (a naphthalimide moiety) through IR, NMR, fluorescence spectroscopy and molecular simulation. Highly oriented network structures were observed at gel state and disappeared in isotropic solution.

show abstract

“…Based on the design principles described in the previous section, we successfully prepared a new polymerizable bis-urea gelator 35, which is capable of gelating a many different organic solvents [68]. On the other hand, the bis-amide derivative does not gel any of the solvents investigated, indicating that the stronger hydrogen bonding urea groups are essential for gelation.…”

Section: Figure 29mentioning

confidence: 99%