Planar-bilayer activities of linear oligoester bolaamphiphiles

• Jonathan K. W. Chui,
• Thomas M. Fyles and
• Horace Luong

Beilstein J. Org. Chem. 2011, 7, 1562–1569, doi:10.3762/bjoc.7.184

• events indistinguishable from channels are possible [26]. It was recently reported that an applied potential can effect lipid phase transitions [27], one consequence of which is the creation of voltage-dependent lipid ion channels at the phase-transition temperature. Pure diphytanoyl phosphatidylcholine

Amphiphilic dendritic peptides: Synthesis and behavior as an organogelator and liquid crystal

• Baoxiang Gao,
• Hongxia Li,
• Defang Xia,
• Sufang Sun and
• Xinwu Ba

Beilstein J. Org. Chem. 2011, 7, 198–203, doi:10.3762/bjoc.7.26

• showed three phase transitions at 15 °C, 25 °C and 40 °C, which are attributed to phase transitions of recrystallization and crystal to isotropic melt. G2 only showed a phase transitions at 71 °C, which is attributed to the phase transition of crystal to isotropic melt. DSC analysis of G3 showed phase

Exceptionally small supramolecular hydrogelators based on aromatic–aromatic interactions

• Junfeng Shi,
• Yuan Gao,
• Zhimou Yang and
• Bing Xu

Beilstein J. Org. Chem. 2011, 7, 167–172, doi:10.3762/bjoc.7.23

• by compounds 1, 3, 4 and 6, respectively) are thermally and pH reversible. For example, heating the gel formed by 0.3 wt % of compound 1 in water to 56 °C or changing its pH from 6.6 to 9.0 leads to a gel–sol phase transition. The gel forms again after restoring the previous conditions, and this

Differences between β-Ala and Gly-Gly in the design of amino acids-based hydrogels

• Andreea Pasc,
• Firmin Obounou Akong,
• Sedat Cosgun and
• Christine Gérardin

Beilstein J. Org. Chem. 2010, 6, 973–977, doi:10.3762/bjoc.6.109

• surfactant molecule, 2 × 3.4 nm (calculated using MOPAC method, CS Chem Office). Upon heating, the intensity of the peak decreased drastically which can be attributed to a phase transition between 50 and 60 °C. The phase transition temperature was in agreement with the one observed by the dropping ball

Towards racemizable chiral organogelators

• Jian Bin Lin,
• Debarshi Dasgupta,
• Seda Cantekin and
• Albertus P. H. J. Schenning

Beilstein J. Org. Chem. 2010, 6, 960–965, doi:10.3762/bjoc.6.107

• concentration (CGC) was detected by the failure of the whole mass to flow when the vial was turned upside down. The CGC value was 2.3 mM for R-3, which means that R-3 can immobilize approximately 2700 molecules of octane per gelator molecule. The gel is thermoreversible, indicating that the first order phase

• transition is associated with gel melting and/or gel formation. When the racemate (R-3 = S-3 = 2.5 mM) was heated and cooled to room temperature, precipitation was observed (Figure 2b). The morphology of the organogel was further characterized by field emission scanning electron microscopy (FESEM) as well as

Hybrid biofunctional nanostructures as stimuli-responsive catalytic systems

• Gernot U. Marten,
• Thorsten Gelbrich and
• Annette M. Schmidt

Beilstein J. Org. Chem. 2010, 6, 922–931, doi:10.3762/bjoc.6.98

• at magnetic fractions of μ(Fe3O4) = 0.5 mass % and higher. In this temperature range, we observe a slight deviation from the expected logarithmic deceleration of the heating rate (Figure 4b). We attribute the deviation to the heat consumption caused by the phase transition process. Enzyme

Novel multi-responsive P2VP-block-PNIPAAm block copolymers via nitroxide-mediated radical polymerization

• Cathrin Corten,
• Katja Kretschmer and
• Dirk Kuckling

Beilstein J. Org. Chem. 2010, 6, 756–765, doi:10.3762/bjoc.6.89

• calorimetry (DSC). Block copolymers showed pH- and temperature-responsive solubility in aqueous media. By increasing the P2VP content, the phase transition temperature shifted to lower temperatures (e.g. 26 °C for P2VP114-block-PNIPAAm180). Depending on the resulting block length, temperature and pH value of

• systems [4], as well as chemo-mechanical actuators [5], e.g., in valves where their characteristics have been studied extensively by a large range of methods [6][7]. One of the most intensively studied polymers in this field is poly(N-isopropylacrylamide) (PNIPAAm), which exhibits a sharp phase transition

• . Due to the hydrophobic character of P2VP, the resulting polymers possessed lower phase transition temperatures compared to pure PNIPAAm [42]. With increase of the 2VP/NIPAAm ratio within the block copolymers, the critical temperature dropped to 26.3 °C. Although all polymers showed a temperature

Symmetry breaking and structure of a mixture of nematic liquid crystals and anisotropic nanoparticles

• Marjan Krasna,
• Matej Cvetko and
• Milan Ambrožič

Beilstein J. Org. Chem. 2010, 6, No. 74, doi:10.3762/bjoc.6.74

• mechanism [8][9] which was originally introduced to explain the formation of topological defects in the early universe following the big bang [8]. For the latter purposes, we summarize main features of this universal mechanism for the case of the isotropic–nematic (I–N) phase transition. In the I–N quench

• interaction energy with respect to all the spins. Therefore, we neglect thermal fluctuations. Consequently, our approach is sensible, deep in the nematic LC phase region, i.e. well below the isotropic–nematic phase transition. In order to satisfy the normalization of the spin vectors, = 1, the “operational

Self-assembled ordered structures in thin films of HAT5 discotic liquid crystal

• Piero Morales,
• Jan Lagerwall,
• Paolo Vacca,
• Sabine Laschat and
• Giusy Scalia

Beilstein J. Org. Chem. 2010, 6, No. 51, doi:10.3762/bjoc.6.51

• dimensions comparable to the ones constituting the thicker rope, not in aggregates but lying separately on the substrate as can be seen in Figure 4. These thinner fibers can also be very long, at least tens of micrometers. The phase transition behavior in the thin spin-coated films could be studied in the

• thick linear structures as these were observable by optical microscopy. Interestingly, this revealed a drastic difference from the drop-cast sample. In the ropes of the spin-coated film no phase transition was detected upon heating from room temperature up to 129 °C, when the material became isotropic

Competition between local disordering and global ordering fields in nematic liquid crystals

• Matej Cvetko,
• Milan Ambrožič and
• Samo Kralj

Beilstein J. Org. Chem. 2010, 6, No. 2, doi:10.3762/bjoc.6.2

• ]. Studies so far have mainly focused on structural and phase behavior [8][9][10][11][12][13][14][15][16][17][18]. It has been shown that the isotropic nematic phase transition is typically replaced by the paranematic–nematic (PN–N) phase transition. The transition temperature in most cases decreases with

• in the numerical approach section. We have neglected the role of thermal fluctuations and consider configurations at zero temperature. In case of nematic ordering in liquid crystals such assumption is sensible deep in the nematic phase (i.e. well below the isotropic-nematic LC phase transition

Low temperature enantiotropic nematic phases from V-shaped, shape-persistent molecules

• Matthias Lehmann and
• Jens Seltmann

Beilstein J. Org. Chem. 2009, 5, No. 73, doi:10.3762/bjoc.5.73

• length on the phase transition temperatures. Only with the heptyl chains do the transition temperatures decrease significantly. A closer look at transition enthalpies and entropies reveal very small values for 3a and 3b (ΔH = 0.1 kJ·mol−1; ΔS = 0.2 J·K−1·mol−1). Entropy values approaching zero, i.e

• revealed positive optical anisotropy, thus the molecules’ long axes are aligned perpendicular to the glass substrate. The black texture between the crossed polarisers at all rotation angles of the sample indicates the uniaxial nature right after the phase transition, further confirmed by the conoscopic

Molecular length distribution and the formation of smectic phases

• Nadia Kapernaum,
• C. Scott Hartley,
• Jeffrey C. Roberts,
• Robert P. Lemieux and
• Frank Giesselmann

Beilstein J. Org. Chem. 2009, 5, No. 65, doi:10.3762/bjoc.5.65

• % PhP14 in 2PhP, respectively. The reduced layer spacing (calculated from the measured layer spacing divided by the layer spacing of the SmA phase) is plotted vs the temperature difference T−Tc relative to the phase transition temperature from SmA to SmC. The pure compound 2PhP shows a ‘common’ behaviour

• of the longer molecules reduces the SmC-tilt stepwise until only a SmA phase is left. This system thus shows a concentration induced SmC to SmA phase transition and therefore opens the possibility to design SmC phases with very small tilt angles [9]. These tilt angles are in good agreement with the

• phase transition to SmA. These quite counterintuitive results are of general interest for the understanding of the structure and dynamics of smectic phases. Several theoretical approaches have been made to predict the behaviour of bidisperse mixtures [14][15][16][17][18]. They analyzed the stability of

Influence of spacer chain lengths and polar terminal groups on the mesomorphic properties of tethered 5-phenylpyrimidines

• Gundula F. Starkulla,
• Elisabeth Kapatsina,
• Angelika Baro,
• Frank Giesselmann,
• Stefan Tussetschläger,
• Martin Kaller and
• Sabine Laschat

Beilstein J. Org. Chem. 2009, 5, No. 63, doi:10.3762/bjoc.5.63

• . Synthesis of compounds 6 and 7. Phase transition temperatures [°C] and enthalpies [kJ/mol] of compounds 3.a Phase transition temperatures [°C] and enthalpies [kJ/mol] of compounds 4.a Phase transition temperatures [°C] and enthalpies [kJ/mol] of compounds 6.a Supporting Information Supporting information

Coaxial electrospinning of liquid crystal-containing poly(vinylpyrrolidone) microfibres

• Eva Enz,
• Ute Baumeister and
• Jan Lagerwall

Beilstein J. Org. Chem. 2009, 5, No. 58, doi:10.3762/bjoc.5.58

• field strength variations on the inner diameter is in fact almost negligible, which would explain that we found no influence on the phase transition temperatures, which are the same for all samples shown and whose values fit to the results shown in Figure 5 with corresponding LC flow rate. Since our

• along the fibre axis in contrast to our experimental results. Possible explanations of this discrepancy might be either that the significant stretching during the electrospinning process leads to a shear induced phase transition to the nematic phase, causing a rearrangement of the molecules, or that the

Saddle-shaped tetraphenylenes with peripheral gallic esters displaying columnar mesophases

• Eugen Wuckert,
• Constanze Hägele,
• Frank Giesselmann,
• Angelika Baro and
• Sabine Laschat

Beilstein J. Org. Chem. 2009, 5, No. 57, doi:10.3762/bjoc.5.57

• function of the chain lengths n. The differences between the clearing temperatures Tcl [°C] of tetraphenylenes 2 and the melting points Tmalk of the n-alkanes exhibit an almost normal odd-even effect without any inversion of the alteration. Synthesis of tetraphenylenes 2. Phase transition temperatures [°C

A convenient method for preparing rigid-core ionic liquid crystals

• Julien Fouchet,
• Laurent Douce,
• Benoît Heinrich,
• Richard Welter and
• Alain Louati

Beilstein J. Org. Chem. 2009, 5, No. 51, doi:10.3762/bjoc.5.51

• general stability order to be I−< BF4− ≈ PF6−< CF3SO3−< (CF3SO2)2N− (Figure 4). For all the compounds, the mesomorphic behaviour and phase transition temperatures were investigated by polarized optical microscopy (POM), differential scanning calorimetry (DSC), and powder X-ray diffractometry (XRD). To

• avoid possible effects of hydration of the materials, all were dried in vacuo before X-ray and DSC analyses. The phase transition temperatures and the corresponding enthalpy changes derived for compounds 1a–e are compiled in Table 2, while typical results are displayed in Figure 5. The high stability of

• , z. Packing diagram of compound 1a in projection in the (b,c) lattice plane. Large spheres represent the iodine atoms. Spectra of absorption (red line) and emission (blue line) of 1a. TGA measurements of the compounds 1a–e (rate 10 °C·min−1, in air). Phase transition temperatures of compounds 1a–e

Shape- persistent macrocycle with intraannular alkyl groups: some structural limits of discotic liquid crystals with an inverted structure

• Sigurd Höger,
• Jill Weber,
• Andreas Leppert and
• Volker Enkelmann

Beilstein J. Org. Chem. 2008, 4, No. 1, doi:10.1186/1860-5397-4-1

• than spheres. For the larger macrocycles it is shown that longer adaptable substituents decrease the phase transition temperatures compared to previously described structures. Background During the past several years, the interest in the design and study of shape-persistent macrocycles with an

• structure, the aspect ratio of the macrocycles with their alkyl surrounding is too small to describe them as plates rather than spheres. For the larger macrocycles we could show that longer adaptable substituents decrease the phase transition temperatures. This parameter, absent in conventional discotics