Structural Tunability of Multicompartment Micelles as a Function of Lipophilic–Fluorophilic Block Length Ratio

Multiscale Modeling Approach for the Aldol Addition Reaction in Multicompartment Micelle-Based Nanoreactor

Water has emerged as a versatile solvent for organic chemistry in recent years due to its abundance, low cost, and environmental friendliness. However, one of the most important reactions, the aldol reaction, in the presence of excess water exhibits low yields and poor enantioselectivities. In this regard, we have employed a multiscale modeling approach to investigate the aldol addition reaction catalyzed by l-proline in the hydrophobic compartment of multicompartment micelle (MCM) nanoreactor consisting of amphiphilic bottlebrush copolymer, which minimizes the water content at the reactive site. Through performing dissipative particle dynamics (DPD) simulation, it is found that the "clover-like" morphology of the MCM is formed from multiblock copolymer with a sequence of ethylene oxide-based hydrophilic blocks, styrene lipophilic blocks, l-proline catalyst blocks, and a pentafluorostyrene fluorophilic block in aqueous media. We find that the vicinity of the catalyst in the clover-like MCM has a low dielectric environment, which could facilitate the aldol addition reaction. Our DFT calculations demonstrate that the asymmetric aldol addition of l-proline-catalyzed acetone and 4-nitrobenzaldehyde is energetically more favorable under the low dielectric environment in MCM compared with other commonly used solvents such as DMSO, water, and vacuum condition.

Nonorthogonal Cascade Catalysis in Multicompartment Micelles

Multicompartment micelles (MCMs) containing acid and base sites in discrete domains are prepared from poly(norbornene)-based amphiphilic bottlebrush copolymers in aqueous media. The acid and base sites are localized in different compartments of the micelle, enabling the nonorthogonal reaction sequence: deacetalization - Knoevenagel condensation - Michael addition of acetals to 2-amino chromene derivatives. Computational simulations using dissipative particle dynamics (DPD) elucidated the bottlebrush composition required to effectively site-isolate the nonorthogonal catalysts. This contribution presents MCMs as a new class of nanostructures for one-pot multistep nonorthogonal cascade catalysis, laying the groundwork for the isolation of three or more incompatible catalysts to synthesize value-added compounds in a single reaction vessel, in water.

Computational and experimental studies on the micellar morphology and emission mechanisms of AIE and H-bonding fluorescent composites

In this work, we use density functional theory (DFT) calculated competitive hydrogen bonds and dissipative particle dynamics (DPD) simulated micellar structural information to uncover the CO2-expanded liquid (CXL)-aided self-assembled structure and emission mechanisms of the self-assembled fluorescent composites (SAFCs). Herein, the SAFCs are formed through the self assembly between diblock copolymer polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) blend and the dye molecule 4-(9-(2-(4-hydroxyphenyl)ethynyl)-7,10-diphenylfluoranthen-8-yl)phenol (4) in CO2-expanded toluene at 313.2 K and varied pressures. Firstly, from DPD simulation, we have demonstrated that the addition of CO2 to toluene favors both the expansion of the solvophobic P4VP phase and contraction of solvophilic PS chains, which facilitates the continuous morphological transitions of SAFCs from spherical micelles (3.0 MPa) through wormlike plus spherical micelles (4.0-4.8 MPa) to large vesicles (6.0-6.5 MPa) with pressure rise. Secondly, the DFT calculated bonding energies and IR spectra of the competitive hydrogen bonds help us to clarify the major type of hydrogen bonds determining the fluorescence (FL) performance of the SAFCs. Furthermore, we have revealed the SAFC emission mechanism via the pressure-tunable changes in the aggregation degrees and amount of hydrogen bonds involving 4 and P4VP chains. This work provides a good understanding for the morphology-property control of the self-assembled polymer composites in both microscopic and mesoscopic scales.

One-pot synthesis of linear triblock terpolymers and their aqueous self-assembly

Compartmentalized micelles are prepared through the self-assembly of linear triblock terpolymers containing hydrophilic (H), lipophilic (L), and fluorophilic (F) domains.

Effect of Block Length and Side Chain Length Ratios on Determining a Multicompartment Micelle Structure

Previous work has identified the importance of the lipophilic-fluorophilic block length ratio Rl in predicting the morphology of linear lipophilic-hydrophilic-fluorophilic (hereafter referred to as BAC) micelle systems. Here, a generalized form R of this structural parameter is developed that makes no assumption of BAC triblock co-polymer linearity, while still providing accurate predictions of the micelle morphology. The morphologies of BAC micelles formed by triblock co-polymers with R≪1 or R≫1 have similar features, with the only notable difference being an inversion of the lipophilic and fluorophilic regions. A destabilization of the single-core micelle structure occurs as R approaches unity from either direction. Finally, the extent to which the micelle morphology depends on the polymer architecture instead of the composition alone is examined, with a decreased patchiness observed in BAC systems with very long block lengths. Through the modification of both the R -value and the polymer architecture, the micelle morphology can be effectively tuned for use in immobilized catalysis and nanoreactor applications.