8 research outputs found
pH-Responsive Supramolecular Control of Polymer Thermoresponsive Behavior by Pillararene-Based Host–Guest Interactions
We
demonstrate precise control of the lower critical solution temperature
(LCST) behavior of a thermoresponsive polymer in water by pillararene-based
host–guest interactions. The LCST value of the polymer increases
upon the stepwise addition of either of the two pillararene hosts.
On account of the pH-responsiveness of the pillararene-based host–guest
interactions, the recovery of the LCST is achieved by treatment with
acid, reflecting the pH-responsive supramolecular control of the LCST
A Dual-Responsive Supra-Amphiphilic Polypseudorotaxane Constructed from a Water-Soluble Pillar[7]arene and an Azobenzene-Containing Random Copolymer
Macromolecular supra-amphiphiles
refer to a kind of macromolecular
amphiphiles whose hydrophlic and hydrophobic parts are connected by
noncovalent forces. They have applications in various fields, such
as drug delivery, sensor systems, and biomedical materials. Here we
report a novel molecular recognition motif between a new thermoresponsive
water-soluble pillar[7]arene (<b>WP7</b>) and an azobenzene
derivative. Furthermore, we utilized this recognition motif to construct
the first pillararene-based supra-amphiphilic polypseudorotaxane which
can self-assemble to form vesicles in water. Due to the dual-responsiveness
of the molecular recognition motif (the thermoresponsiveness of <b>WP7</b> and photoresponsiveness of azobenzene), the reversible
transformations between solid nanospheres based on the self-assembly
of the polymer backbone and vesicles based on the self-assembly of
the supra-amphiphilic polypseudorotaxane were achieved by adjusting
the solution temperature or UV–visible light irradiation. These
dual-responsive aggregation behaviors were further used in the controlled
release of water-soluble dye calcein molecules
A Supramolecular Cross-Linked Conjugated Polymer Network for Multiple Fluorescent Sensing
A supramolecular cross-linked network was fabricated
and demonstrated
to act as a multiple fluorescent sensor. It was constructed from a
fluorescent conjugated polymer and a bisammonium salt cross-linker
driven by dibenzo[24]crown-8/secondary ammonium salt host–guest
interactions. Compared with the conjugated polymer, the network has
weak fluorescence due to the aggregation of polymer chains. Thanks
to the multiple stimuli-responsiveness of host–guest interactions,
the fluorescence intensity of the system can be enhanced by four types
of signals, including potassium cation, chloride anion, pH increase,
and heating. Hence, the network can serve as a cation sensor, an anion
sensor, a pH sensor, and a temperature sensor. It can be used in both
solution and thin film. Interestingly, exposure of a film made from
this supramolecular cross-linked network to ammonia leads to an increase
of fluorescence, making it a good candidate for gas detection
Redox-Responsive Amphiphilic Macromolecular [2]Pseudorotaxane Constructed from a Water-Soluble Pillar[5]arene and a Paraquat-Containing Homopolymer
Here we report a redox-responsive
host–guest complex between
a new water-soluble pillar[5]arene (<b>WP5</b>) and a paraquat
derivative. Compared with the neutral form of the paraquat derivative
that binds <b>WP5</b> weakly, its dication form binds <b>WP5</b> much more strongly. Furthermore, we utilize this new water-soluble
redox-responsive molecular recognition motif to construct the first
pillararene-based amphiphilic macromolecular [2]pseudorotaxane, which
self-assembles into redox-responsive polymeric vesicles in water.
Such pillararene-based supramolecular vesicles were further used to
construct a drug delivery system to encapsulate and controlled release
DOX·HCl, an anticancer drug. The uptake of these DOX·HCl-loaded
supramolecular vesicles by cancer cells was studied with confocal
laser scanning microscopy. Meanwhile, DOX·HCl-loaded supramolecular
vesicles showed anticancer activity in vitro comparable to free DOX·HCl
under the examined conditions
Supramolecular Copolymer Constructed by Hierarchical Self-Assembly of Orthogonal Host–Guest, H‑Bonding, and Coordination Interactions
Supramolecular copolymers
with complex architectures and emergent
functions constitute a class of challenging but enticing synthetic
targets in polymer science. Individual building blocks can be tailored
to endow a resulting supramolecular copolymer with increased structural
and functional complexity. Herein, we describe the construction of
a linear supramolecular copolymer comprising mechanically interlocked
segments with hydrogen-bonding metallorhomboidal units. Specifically,
a hierarchical supramolecular polymerization of a crown ether-based
[2]rotaxane and a discrete organoplatinum(II) metallacycle driven
by 2-ureido-4-pyrimidinone (UPy) quadruple hydrogen bonding provides
the impetus for its formation. This system demonstrates enhanced structural
complexity accessed by the unification of orthogonal noncovalent interactions:
metal coordination, host–guest chemistry, and multiple hydrogen
bonding interfaces
Physical Removal of Anions from Aqueous Media by Means of a Macrocycle-Containing Polymeric Network
Reported here is
a hydrogel-forming polymer network that contains
a water-soluble tetracationic macrocycle. Upon immersion of this polymer
network in aqueous solutions containing various inorganic and organic
salts, changes in the physical properties are observed that are consistent
with absorption of the constituent anions into the polymer network.
This absorption is ascribed to host–guest interactions involving
the tetracationic macrocyclic receptor. Removal of the anions may
then be achieved by lifting the resulting hydrogels out of the aqueous
phase. Treating the anion-containing hydrogels with dilute HCl leads
to the protonation-induced release of the bound anions. This allows
the hydrogels to be recycled for reuse. The present polymer network
thus provides a potentially attractive approach to removing undesired
anions from aqueous environments
Supramolecular Micelles Constructed by Crown Ether-Based Molecular Recognition
A novel supramolecular amphiphilic polymer constructed
by crown ether-based molecular recognition has been fabricated and
demonstrated to self-assemble into core–shell supramolecular
micelles in water. The reversible transition between assembled and
disassembled structures can be achieved by changing the pH. This transition
was used to realize the controlled release of small molecules. The
supramolecular micelle was characterized by various techniques including
conductivity, transmission electron microscopy (TEM), dynamic laser
light scattering (DLS), and fluorescence titration. TEM images showed
dark gray spherical aggregates, and the mean size of the micelles
was 50 nm in diameter and of uniformly dispersed size, in good agreement
with the DLS results. The release of hydrophobic molecules from the
micelles was realized by adding acid (aqueous HCl), weakening the
host–guest interactions and leading to disassembly of the supramolecular
micelles
Hierarchical Self-Assembly: Well-Defined Supramolecular Nanostructures and Metallohydrogels via Amphiphilic Discrete Organoplatinum(II) Metallacycles
Metallacyclic cores
provide a scaffold upon which pendant functionalities
can be organized to direct the formation of dimensionally controllable
nanostructures. Because of the modularity of coordination-driven self-assembly,
the properties of a given supramolecular core can be readily tuned,
which has a significant effect on the resulting nanostructured material.
Herein we report the efficient preparation of two amphiphilic rhomboids
that can subsequently order into 0D micelles, 1D nanofibers, or 2D
nanoribbons. This structural diversity is enforced by three parameters:
the nature of the hydrophilic moieties decorating the parent rhomboids,
the concentration of precursors during self-assembly, and the reaction
duration. These nanoscopic constructs further interact to generate
metallohydrogels at high concentrations, driven by intermolecular
hydrophobic and π–π interactions, demonstrating
the utility of coordination-driven self-assembly as a first-order
structural element for the hierarchical design of functional soft
materials