Flow chemistry controls self-assembly and cargo in Belousov-Zhabotinsky driven polymerization-induced self-assembly

High-Shear Enhancement of Biginelli Reactions in Macromolecular Viscous Media

Chemical reactions and transformations in non-traditional vessels have gained significant interest in recent years. Flow chemistry, with its advantages in mixing, mass transfer, scalability, and automation, is a driving force behind this paradigm shift. In particular, the Vortex Fluidic Device (VFD) has emerged as a versatile tool across various applications, from organic synthesis to materials science. In this study, the role of the VFD in performing the Biginelli reaction, a multicomponent reaction widely used in pharmaceutical and polymer science, for a post-polymerization modification is explored. By conducting the Biginelli reaction in the VFD, rapid product formation with low catalyst loading and without the need for high temperatures is achieved. However, the critical need to understand and know solution viscosity, especially within the context of modifying macromolecules is highlighted.

Seeded RAFT Polymerization-Induced Self-assembly: Recent Advances and Future Opportunities

Over the past decade, polymerization-induced self-assembly (PISA) has fully proved its versatility for scale-up production of block copolymer nanoparticles with tunable sizes and morphologies; yet, there are still some limitations. Recently, seeded PISA approaches combing PISA with heterogeneous seeded polymerizations have been greatly explored and are expected to overcome the limitations of traditional PISA. In this review, recent advances in seeded PISA that have expanded new horizons for PISA are highlighted including i) general considerations for seeded PISA (e.g., kinetics, the preparation of seeds, the selection of monomers), ii) morphological evolution induced by seeded PISA (e.g., from corona-shell-core nanoparticles to vesicles, vesicles-to-toroid, disassembly of vesicles into nanospheres), and iii) various well-defined nanoparticles with hierarchical and sophisticated morphologies (e.g., multicompartment micelles, porous vesicles, framboidal vesicles, AXn -type colloidal molecules). Finally, new insights into seeded PISA and future perspectives are proposed.

RAFT-mediated polymerization-induced self-assembly (RAFT-PISA): current status and future directions

Polymerization-induced self-assembly (PISA) combines polymerization and self-assembly in a single step with distinct efficiency that has set it apart from the conventional solution self-assembly processes. PISA holds great promise for large-scale production, not only because of its efficient process for producing nano/micro-particles with high solid content, but also thanks to the facile control over the particle size and morphology. Since its invention, many research groups around the world have developed new and creative approaches to broaden the scope of PISA initiations, morphologies and applications, etc. The growing interest in PISA is certainly reflected in the increasing number of publications over the past few years, and in this review, we aim to summarize these recent advances in the emerging aspects of RAFT-mediated PISA. These include (1) non-thermal initiation processes, such as photo-, enzyme-, redox- and ultrasound-initiation; the achievements of (2) high-order structures, (3) hybrid materials and (4) stimuli-responsive nano-objects by design and adopting new monomers and new processes; (5) the efforts in the realization of upscale production by utilization of high throughput technologies, and finally the (6) applications of current PISA nano-objects in different fields and (7) its future directions.

Modulation of the Belousov-Zhabotinsky Reaction with Lipid Bilayers: Effects of Lipid Head Groups and Membrane Properties

The Belousov-Zhabotinsky (BZ) reaction is an oscillating reaction due to periodic oscillations that happen in the concentration of some intermediates. Such systems can be applied together with hydrophobic membranes to create an autonomous behavior in artificial systems. However, because of a complex set of reactions happening in such systems, the interferences caused by hydrophobic membranes are not easily understood. In this study, we tested lipid membranes composed of trimethylammonium-propane (TAP) and phosphate (PA) lipids in an attempt to break down how the polar region of phosphatidylcholine (PC) lipid membranes affect the BZ reaction. According to our findings, the trimethylammonium group and membrane fluidity are crucial to change the frequency of oscillations in the reaction. In addition, the results also indicate a possible complexation of cerium ions with membranes with a phosphate head group.

Native Chemical Computation. A Generic Application of Oscillating Chemistry Illustrated With the Belousov-Zhabotinsky Reaction. A Review

Computing with molecules is at the center of complex natural phenomena, where the information contained in ordered sequences of molecules is used to implement functionalities of synthesized materials or to interpret the environment, as in Biology. This uses large macromolecules and the hindsight of billions of years of natural evolution. But, can one implement computation with small molecules? If so, at what levels in the hierarchy of computing complexity? We review here recent work in this area establishing that all physically realizable computing automata, from Finite Automata (FA) (such as logic gates) to the Linearly Bound Automaton (LBA, a Turing Machine with a finite tape) can be represented/assembled/built in the laboratory using oscillatory chemical reactions. We examine and discuss in depth the fundamental issues involved in this form of computation exclusively done by molecules. We illustrate their implementation with the example of a programmable finite tape Turing machine which using the Belousov-Zhabotinsky oscillatory chemistry is capable of recognizing words in a Context Sensitive Language and rejecting words outside the language. We offer a new interpretation of the recognition of a sequence of chemicals representing words in the machine's language as an illustration of the “Maximum Entropy Production Principle” and concluding that word recognition by the Belousov-Zhabotinsky Turing machine is equivalent to extremal entropy production by the automaton. We end by offering some suggestions to apply the above to problems in computing, polymerization chemistry, and other fields of science.

Concurrent self-regulated autonomous synthesis and functionalization of pH-responsive giant vesicles by a chemical pH oscillator

The semibatch BrO3--SO32- pH oscillator serves as the radical source for the in situ polymerization of the pH-responsive 2-(diisopropylamino)-ethyl methacrylate monomer on poly(ethylene-glycol)-macroCTA chain and generates an amphiphilic block copolymer. These building blocks concurrently self-assemble to micelles and then transforms to vesicles as the chain length of the hydrophobic block growths. Large amplitude oscillations in the concentration of H+ by the semibatch BrO3--SO32- are provoked when the conditions in the system are favorable. The oscillations control the protonation state of the tertiary amine group in the core segment of the block copolymer. Rhythmic assembly-disassembly of the polymer structures is observed. All processes, from the time- regulated autonomous formation of the building blocks, their self-assembly and the rhythmic disassembly-reassembly are governed by the same simple chemical system, in the same reaction vessel, without complicated multi step procedures and are fueled and kept out of equilibrium by the uniform inflow of SO32-.

Photochemically induced cyclic morphological dynamics via degradation of autonomously produced, self-assembled polymer vesicles

Autonomous and out-of-equilibrium vesicles synthesised from small molecules in a homogeneous aqueous medium are an emerging class of dynamically self-assembled systems with considerable potential for engineering natural life mimics. Here we report on the physico-chemical mechanism behind a dynamic morphological evolution process through which self-assembled polymeric structures autonomously booted from a homogeneous mixture, evolve from micelles to giant vesicles accompanied by periodic growth and implosion cycles when exposed to oxygen under light irradiation. The system however formed nano-objects or gelation under poor oxygen conditions or when heated. We determined the cause to be photoinduced chemical degradation within hydrated polymer cores inducing osmotic water influx and the subsequent morphological dynamics. The process also led to an increase in the population of polymeric objects through system self-replication. This study offers a new path toward the design of chemically self-assembled systems and their potential application in autonomous material artificial simulation of living systems.

Periodic Polymerization and the Generation of Polymer Giant Vesicles Autonomously Driven by pH Oscillatory Chemistry

Using the radicals generated during pH oscillations, a semibatch pH oscillator is used as the chemical fuel and engine to drive polymerization induced self-assembly (PISA) for the one-pot autonomous synthesis of functional giant vesicles. Vesicles with diameters ranging from sub-micron to ∼5 µm are generated. Radical formation is found to be switched ON/OFF and be autonomously controlled by the pH oscillator itself, inducing a periodic polymerization process. The mechanism underlying these complex processes is studied and compared to conventional (non-oscillatory) initiation by the same redox pair. The pH oscillations along with the continuous increase in salt concentration in the semibatch reactor make the self-assembled objects undergo morphological evolution. This process provides a self-regulated means for the synthesis of soft giant polymersomes and opens the door for new applications of pH oscillators in a variety of contexts, from the exploration of new geochemical scenarios for the origin of life and the autonomous emergence of the necessary free-energy and proton gradients, to the creation of active functional microreactors and programmable release of cargo molecules for pH-responsive materials.

Non-thermally initiated RAFT polymerization-induced self-assembly

This review summarizes the recent non-thermal initiation methods in RAFT mediated polymerization-induced self-assembly (PISA), including photo-, redox/oscillatory reaction-, enzyme- and ultrasound wave-initiation.

PISA: construction of self-organized and self-assembled functional vesicular structures

PISA reaction networks alone, integrated with other networks, or designing properties into the amphiphiles confer functionalities to the supramolecular assemblies.

Chemical Oscillation and Morphological Oscillation in Catalyst-Embedded Lyotropic Liquid Crystalline Gels

Liquid crystalline gels offer promising means in generating smart materials due to programmable mechanics and reversible shape changes in response to external stimuli. We demonstrate a simple and convenient method of constructing catalyst-embedded lyotropic liquid crystalline (LLC) gels and achieve chemomechanical oscillator by converting chemical waves in Belousov–Zhabotinsky (BZ) reaction. We observe the directed chemical oscillations on LLC sticks accompanied by small-scale oscillatory swellings–shrinkages that are synchronized with the chemical waves of an LLC stick. To amplify the mechanical oscillations, we further fabricate small LLC fibers and achieve macroscopically oscillatory bending–unbending transition of the LLC fiber driven by a BZ reaction.

Trending methods employed for polymerization induced self-assembly

Mother Nature produces a perfectly defined architecture that inspires researchers to make polymeric macromolecules for an array of functions. The present article describes recent development in the PISA to synthesize polymeric nano-objects.

Enabling technologies in polymer synthesis: accessing a new design space for advanced polymer materials

This review discusses how developments in laboratory technologies can push the boundaries of what is achievable using existing polymer synthesis techniques.