Self-Assembly of Calix[4]arene-Based Amphiphiles Bearing Polyethylene Glycols: Another Example of "Platonic Micelles"

Dual-Responsive Hydrogels with Three-Stage Optical Modulation for Smart Windows

Since room temperature management consumes a large amount of building energy, thermochromic smart windows have been extensively used for temperature regulation and energy management. However, the development of the smart window is still limited by its simple thermochromic performance, unreasonable thermochromic temperature, and the lack of additional stimulation conditions. In this work, a dual-responsive hydrogel was developed by introducing sodium dodecyl sulfate (SDS) and sodium chloride into the cross-linking network of poly(N-isopropylacrylamide) (PNIPAM) and polyacrylamide (PAM) for energy-saving and privacy protection. By controlling the temperature from low (<15 °C) to medium (15-28 °C) to high (>28 °C), the dual-responsive hydrogel achieved a reversible three-stage transition of opaque-transparent-translucent. The hydrogel exhibited a satisfactory solar modulation ability (T_lum = 80.3%, ΔT_sol,15-18°C = 72.9%, ΔT_sol,18-35°C = 42.7%) and effective IR and UV shielding at high (or low) temperatures. Moreover, compared with traditional windows, smart windows made of dual-responsive hydrogels could offer better thermal insulation and heat preservation. The electrochromic properties of the dual-responsive hydrogel presented a facile strategy to meet the needs of different situations. The dual-responsive hydrogel features energy-saving, privacy protection, three-stage optical modulation, and multistimulus responsiveness, making it an ideal smart window candidate.

Characterizing block-copolymer micelles used in nanomedicines via solution static scattering techniques

Block copolymers are well recognized as excellent nanotools for delivering hydrophobic drugs. The formulation of such delivery nanoparticles requires robust characterization and clarification of the critical quality attributes correlating with the safety and efficacy of the drug before applying to regulatory authorities for approval. Static solution scattering from block copolymers is one such technique. This paper first outlines the theoretical background and current models for analyzing this scattering and then presents an overview of our recent studies on block copolymers.

Scattering Form Factor of Block Copolymer Micelles with Corona Chains Discretely Distributed on the Core Surface

Small-angle scattering is a powerful tool to investigate micellar structure, and a model form factor proposed by Pedersen and Gerstenberg [Pedersen, J. S.; Gerstenberg, M. Macromolecules 1996, 29, 1363-1365] has been used quite frequently to analyze experimentally obtained scattering data of block copolymer micelles. Their model consists of a spherical core and the Gaussian corona chains attached to the core surface; the corona chains are considered to be approximately continuously (evenly) distributed on the core surface. In this paper, we present a micellar form factor model in which the corona chains are discretely distributed on the core surface. Our proposed discrete model was found to deviate from the Pedersen-Gerstenberg model as well as another model [Svaneborg, C.; Pedersen, J. S. Phys. Rev. E 2001, 64, R01802.], which incorporates the approximate interference effect between the corona chains, in conditions in which the scattering from the corona chains is stronger than that from a core with lower number density of the corona chains.

Click inspired synthesis of p-tert-butyl calix[4]arene tethered benzotriazolyl dendrimers and their evaluation as anti-bacterial and anti-biofilm agents

CuAAC inspired calix-[4]arene tethered benzotriazolyl dendrimers were developed and investigated for their therapeutic potential, where 7 displayed potent anti-bacterial and anti-biofilm activities against drug-resistant & slime producing organisms.

Monodisperse micelles composed of poly(ethylene glycol) attached surfactants: platonic nature in a macromolecular aggregate

Among the many studies on micelles, dating back more than 100 years, we first found a series of monodisperse micelles: spherical micelles made from calix[4]arene surfactants exhibited monodispersity in aggregation number (Nagg) with values of 4, 6, 8, 12, and 20. We named these Platonic micelles because these values coincided with the face numbers of the Platonic solids. The preferred Nagg values were explained in relation to the mathematical Tammes problem: how to obtain the best coverage of a sphere surface with multiple identical circles. In this paper, we synthesized poly(ethylene glycol)-attached surfactants and carried out small-angle X-ray scattering (SAXS) and analytical ultracentrifugation (AUC) to determine the Nagg. We found that these polymeric surfactants also formed monodispersed micelles and Nagg discontinuously increased from 20 to 24, and then 32 with increasing the alkyl carbon numbers from 9 to 11 continuously. The determined Nagg was greater than 20 and the Platonic solid numbers. We assumed that the preferred Nagg values could be explained in relation to the Tammes problem as well.

Assembly behaviors of calixarene-based amphiphile and supra-amphiphile and the applications in drug delivery and protein recognition

Calixarene is the third generation of supra-molecular compounds after crown ether and cyclodextrin. Amphiphilic calixarene can be obtained by modulation with both hydrophilic group and hydrophobic alkyl chain. Compared with conventional surfactant, amphiphilic calixarene has much lower critical micelle concentration and is much easier to self-assemble into different morphological aggregates. Calixarene-basedsupra-amphiphile can be designed via noncovalent bonds due to the capability of calixarene to recognize surfactant; the binding of a surfactant with calixarene can decrease the critical micelle concentration of surfactant by several times. The calixarene-surfactant complex can self-aggregate to form spherical micelles, vesicles, and spherical nanoparticles, and the aggregation behavior can be controlled by the structures and the molar ratio of surfactant to calixarene and environmental factors. Calixarene-based amphiphile and supra-amphiphile show low cytotoxicity. They can load drugs and assemble into nanocapsules with drugs. The structure of the calixarene-drug complex can respond to external stimuli, rendering the sustained release of the drug and suggesting its potential application as a drug delivery system. Recently, calixarene has also been found to selectively bind proteins, suggesting its prospect in disease diagnosis and intervention treatment in clinics. This review elaborates on the research progress in the self-assembly behaviors of calixarene-based amphiphile and supra-amphiphile and the applications of the calixarenes in drug delivery and protein recognition. The prospectives for the studies are also provided in this review.

Tuning of the aggregation number of Platonic micelles with a binary mixture of calix[4]arene surfactants

The mixture ratios were used as a factor for aggregation number (N_agg) determination in binary mixtures of calix[4]arene surfactants.

Rediscovering the Monodispersity of Sulfonatocalix[4]arene-Based Micelles

When the micellar aggregation number ( N_agg) is small enough (<30), the N_agg matches the value of vertexes of a regular polyhedron: Platonic solids, and demonstrates perfect monodispersity. These micelles are named Platonic micelles and are particularly found in the system of calix[4]arene-based micelles due to the rigid structure of the backbone molecule. Although sulfonatocalix[4]arene-based micelles are among the most studied host molecules in supramolecular chemistry, their micellar properties as Platonic micelles have thus far been overlooked. In this study, we prepared various sulfonatocalix[4]arene-based amphiphiles bearing alkyl chains with different lengths and investigated their aggregation behavior. When the amphiphiles formed spherical micelles, they demonstrated monodispersity in terms of N_agg, whose value changed from 4 to 17, and then to 24, upon increasing the carbon number in each alkyl chain from C5 to C6, and then to C7, respectively. Although the numbers 17 and 24 do not match the vertices of regular polyhedra, these values can be reasonably explained by the Thomson problem, which considers the Coulomb potential for calculating the best packing on a sphere with multiple identical spherical caps. This study describes rediscovery of the monodispersity of sulfonatocalix[4]arene-based micelles, which is consistent with the idea of Platonic micelles.

Nanoconjugates of a calixresorcinarene derivative with methoxy poly(ethylene glycol) fragments for drug encapsulation

In order to obtain a non-toxic amphiphilic calixresorcinarene capable to form nanoconjugates for drug encapsulation, tetraundecylcalixresorcinarene functionalized by methoxy poly(ethylene glycol) chains has been synthesized. The macrocycle obtained is characterized by low hemotoxicity. In aqueous solution it forms nanoassociates that are able to encapsulate organic substrates of different hydrophobicity, including drugs (doxorubicin, naproxen, ibuprofen, quercetin). The micelles of the macrocycle slowed down the release of the hydrophilic substrates in vitro. In physiological sodium chloride solution and phosphate-buffered saline, the micelles of the macrocycle acquire thermoresponsive properties and exhibit a temperature-controlled release of doxorubicin in vitro. The combination of the low toxicity and the encapsulation properties of the obtained calixresorcinarene-mPEG conjugate shows promising potential for the use as a supramolecular drug-delivery system.