Disassembly Control of Saccharide-Based Amphiphiles Driven by Electrostatic Repulsion

Enhanced stability of crosslinked and charged unimolecular micelles from multigeometry triblock copolymers with short hydrophilic segments: dissipative particle dynamics simulation

High micellar stability and well-performed drug loading and release are two conflicting factors for unimolecular micelles as an ideal drug delivery system. Achieving the formation of unimolecular micelles with short hydrophilic blocks is a challenging and promising approach to solve this bottleneck and limitation of current unimolecular micelle systems. In this work, dissipative particle dynamics (DPD) simulation is used to study the synergetic effect of crosslinking and electrostatic repulsion on stability of unimolecular micelles and to analyze the micro-mechanism and factors influencing this synergetic stabilization strategy. The strategy can generate unimolecular micelles with extremely high stability for various supramolecular polymers with short hydrophilic chains. Protonation of DEAEMA blocks leads to a large improvement in micellar hydrophilicity. The protonated middle layer further shrinks through crosslinking to produce the largest charge density, enlarging the electrostatic repulsion between colloidal particles. Additionally, the crosslinking and protonation treatment maximizes the extension degree of hydrophilic EO segments due to the increasing steric hindrance and poor compatibility between DEAHEMA and EO blocks. In this study, the relation between shrinkage degree of hydrophobic cores and stability of unimolecular micelles is first reported. The above-mentioned transition of micellar structures and properties results in the maximum degree of core shrinkage (R_g of MMA blocks) corresponding to the high stability of unimolecular micelles. Further study shows that the increasing cyclization degree, the mode of end cyclization, and the crosslinking and electrostatic repulsion of the middle layer all exert favorable effects on the stability of unimolecular micelles due to controlled shrinkage of hydrophobic cores.

4-Hydroxymethyl-substituted oxazolidinone synthesis by tetraarylphosphonium salt-catalyzed reactions of glycidols with isocyanates

A tetraarylphosphonium catalyst enables efficient coupling reactions between glycidols and isocyanates to afford 4-hydroxymethyl-substituted oxazolidinones.

Synthesis of pyramidal tetraarylborate pentads

Tetrahedral tetraarylborate pentads were synthesized by a typical click reaction, copper-catalyzed azide–alkyne cyclization, which exhibited interesting ionic dissociation in low polar organic solvents.

Lipophilic polyelectrolyte gel derived from phosphonium borate can absorb a wide range of organic solvents

Herein, we demonstrate a polyelectrolyte gel which can absorb a wide range of organic solvents from dimethylsulfoxide (DMSO, permittivity: ε = 47.0) to tetrahydrofuran (ε = 5.6). The gel consists of polystyrene chains with small amounts (∼5 mol%) of lipophilic electrolytes derived from triphenylphosphonium tetraaryl borate. The swelling ability of the polyelectrolyte gel was higher than that of the alkyl ammonium tetraaryl borate previously reported by us, and this is attributed to the higher compatibility with organic solvents, as well as the higher dissociating ability, of the triphenyl phosphonium salt. The role of the ionic moieties was additionally confirmed by post modification of the polyelectrolyte gel via a conventional Wittig reaction, resulting in a nonionic gel. Our findings introduced here will lead to a clear-cut molecular design for polyelectrolyte gels which absorb all solvents.

Thermoresponsivity of polymer solution derived from a self-attractive urea unit and a self-repulsive lipophilic ion unit

Proper design of a self-attractive unit and a self-repulsive ion unit on a polymer chain successfully generated thermoresponsivity in non-aqueous solvents.