2 research outputs found
Self-Organizable Vesicular Columns Assembled from Polymers Dendronized with Semifluorinated Janus Dendrimers Act As Reverse Thermal Actuators
The synthesis and structural analysis of polymers dendronized
with
self-assembling Janus dendrimers containing one fluorinated and one
hydrogenated dendrons are reported. Janus dendrimers were attached
to the polymer backbone both from the hydrogenated and from the fluorinated
parts of the Janus dendrimer. Structural analysis of these dendronized
polymers and of their precursors by a combination of differential
scanning calorimetry, X-ray diffraction experiments on powder and
oriented fibers, and electron density maps have demonstrated that
in both cases the dendronized polymer consists of a vesicular columnar
structure containing fluorinated alkyl groups on its periphery. This
vesicular columnar structure is generated by a mechanism that involves
the intramolecular assembly of the Janus dendrimers into tapered dendrons
followed by the intramolecular self-assembly of the resulting dendronized
polymer in a vesicular column. By contrast with conventional polymers
dendronized with self-assembling tapered dendrons this new class of
dendronized polymers acts as thermal actuators that decrease the length
of the supramolecular column when the temperature is increased and
therefore, are called reverse thermal actuators. A mechanism for this
reversed process was proposed
Complex Arrangement of Orthogonal Nanoscale Columns <i>via</i> a Supramolecular Orientational Memory Effect
Memory
effects, including shape, chirality, and liquid-crystallinity,
have enabled macroscopic materials with novel functions. However,
the generation of complex supramolecular nanosystems <i>via</i> memory effects has not yet been investigated. Here, we report a
cyclotriveratrylene-crown (CTV) compound that self-assembles into
supramolecular columns and spheres forming, respectively, hexagonal
and cubic mesophases. Upon transition from one phase to the other,
an epitaxial relationship holds, <i>via</i> an unprecedented
supramolecular orientational memory effect. Specifically, the molecular
orientation and columnar character of supramolecular packing is preserved
in the cubic phase, providing an otherwise inaccessible structure
comprising orthogonally oriented domains of supramolecular columns.
The continuous columnar character of tetrahedrally distorted supramolecular
spheres self-organized from the CTV derivative in the faces of the <i>Pm</i>3Ì…<i>n</i> lattice is the basis of this
supramolecular orientational memory, which holds throughout cycling
in temperature between the two phases. This concept is expected to
be general for other combinations of periodic and quasiperiodic arrays
generated from supramolecular spheres upon transition to supramolecular
columns