A dendron based on natural amino acids: synthesis and behavior as an organogelator and lyotropic liquid crystal.
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Amino Acids↗
Biomedical subjects
Er-Qiang Chen
Publications and source records attributed to Er-Qiang Chen.
Frustrated molecular packing in highly ordered smectic phase of side-chain liquid crystalline polymer with rigid polyacetylene backbone.
Using poly(5-{[(4'-heptoxy-4-biphenylyl)carbonyl]oxy}-1-pentyne) as an example, we demonstrate the incorporative accommodation of the rigid polyacetylene backbones and the mesogenic pendants, which leads to a highly ordered smectic (Sm) phase with a frustrated structure. The polymer exhibits a recognizable sheetlike molecular shape due to its rigid backbone and relatively short spacer (three methylene units), and the building block of the liquid crystalline (LC) phase is the whole molecule. In the LC phase, five layers of the molecules stack as a smectic A (SmA) block, and adjacent SmA blocks glide halfway of the molecular width from one to another. In scanning tunneling microscopy (STM) experiments, the STM tip scrape is found to generate a regular nanopattern with periodic electron conductivity, of which the spacing is determined by the side-chain length.
Journal Article↗
Crust effect on multiscale pattern formations in drying micelle solution drops on solid substrates.
Spherical micelles of a polystyrene-b-poly(dimethylsiloxane) (PS-b-PDMS) diblock copolymer with the number-average molecular weight of 193 000 g/mol for PS and 39 000 g/mol for PDMS were obtained by using n-dodecane or n-octane as the selective solvent for the PDMS block. The drying process of micelle solution drops with relatively high polymer concentration on solid substrates and the resultant drying patterns were studied using optical microscopy and atomic force microscopy. The drying drops exhibited an inner solution "cap" connecting with an outer gelled "foot" through a transition zone. A crust was first formed on the surface of the transition zone and remained on the top of the foot region. An inhomogeneous stress perpendicular to the radial direction within the crust, which was due to the solvent evaporation accompanied by the receding of the solution cap, induced regular 45 degrees -tilted stripes (pleats) in the transition zone and main radial cracks in the foot region. The stripes and cracks have periods of a few and tens of microns, respectively. Concave micelle "bricks" were also observed between cracks. In addition to micelle close packing, these patterns demonstrate that drying micelle solution drops may provide a potential means to manipulate fine and multiscale structures for technological applications.
Journal Article↗
Manipulating supramolecular self-assembly via tailoring pendant group size of linear vinyl polymers.
In a series of poly[di(alkyl) vinylterephthalates] (PDAVTs) synthesized via radical polymerization, fine-tuning the size and shape of the side groups manipulated the supramolecular self-assembly and led to control over the formations between amorphous and 2D ordered hexagonal phases. To introduce the 2D long-range ordered structure, the size of the ester side groups at the 2- and 5-positions of the phenyl rings laterally attached to the backbones had to be in the range of propyl/isopropyl to hexyl. The relatively extended backbones observed in these polymers were attributed to steric effects from the side groups. When the n-alkyl groups were larger than hexyl, the ability to form the liquid crystalline phase gradually decreased. A completely disordered phase could be observed by substituting dodecyl groups as side groups.
Journal Article↗