Modern Trends in Polymerization-Induced Self-Assembly

Polymerization-induced self-assembly (PISA) is a powerful and versatile technique for producing colloidal dispersions of block copolymer particles with desired morphologies. Currently, PISA can be carried out in various media, over a wide range of temperatures, and using different mechanisms. This method enables the production of biodegradable objects and particles with various functionalities and stimuli sensitivity. Consequently, PISA offers a broad spectrum of potential commercial applications. The aim of this review is to provide an overview of the current state of rational synthesis of block copolymer particles with diverse morphologies using various PISA techniques and mechanisms. The discussion begins with an examination of the main thermodynamic, kinetic, and structural aspects of block copolymer micellization, followed by an exploration of the key principles of PISA in the formation of gradient and block copolymers. The review also delves into the main mechanisms of PISA implementation and the principles governing particle morphology. Finally, the potential future developments in PISA are considered.

Modeling of Miniemulsion Polymerization of Styrene with Macro-RAFT Agents to Theoretically Compare Slow Fragmentation, Ideal Exchange and Cross-Termination Cases

A 5-dimensional Smith-Ewart based model is developed to understand differences for reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization with theoretical agents mimicking cases of slow fragmentation, cross-termination, and ideal exchange while accounting for chain length and monomer conversion dependencies due to diffusional limitations. The focus is on styrene as a monomer, a water soluble initiator, and a macro-RAFT agent to avoid exit/entry of the RAFT leaving group radical. It is shown that with a too low RAFT fragmentation rate coefficient it is generally not afforded to consider zero-one kinetics (for the related intermediate radical type) and that with significant RAFT cross-termination the dead polymer product is dominantly originating from the RAFT intermediate radical. To allow the identification of the nature of the RAFT retardation it is recommended to experimentally investigate in the future the impact of the average particle size (dp) on both the monomer conversion profile and the average polymer properties for a sufficiently broad dp range, ideally including the bulk limit. With decreasing particle size both a slow RAFT fragmentation and a fast RAFT cross-termination result in a stronger segregation and thus rate acceleration. The particle size dependency is different, allowing further differentiation based on the variation of the dispersity and end-group functionality. Significant RAFT cross-termination is specifically associated with a strong dispersity increase at higher average particle sizes. Only with an ideal exchange it is afforded in the modeling to avoid the explicit calculation of the RAFT intermediate concentration evolution.

Recent advances in colloidal nanocomposite designviaheterogeneous polymerization techniques

Recent advances in colloidal nanocomposite design by heterogeneous polymerization are reviewed, with a specific focus on encapsulation and particle-based stabilization for specific materials applications.

Photochemistry for Well-Defined Polymers in Aqueous Media: From Fundamentals to Polymer Nanoparticles to Bioconjugates

This review article highlights recent developments in the field of photochemistry and photochemical reversible deactivation radical polymerization applied to aqueous polymerizations. Photochemistry is a topic of significant interest in the fields of organic, polymer, and materials chemistry because it allows challenging reactions to be performed under mild conditions. Aqueous polymerization is of significant interest because water is an environmentally benign solvent, and the use of water enables complex polymer self-assembly and bioconjugation processes to occur. This review focuses on powerful new developments in photochemical aqueous polymerization reactions and their applications to the synthesis of well-defined polymer nano-objects and bioconjugates. It is anticipated that these aqueous photopolymerizations will enable the next generation of self-assembled structures and biohybrid materials to be developed under mild and environmentally friendly conditions.

Micellar polymerization: Computer simulations by dissipative particle dynamics

Nowadays, micellar polymerization is widely used in different fields of industry and research, including modern living polymerization technique. However, this process has many variables and there is no comprehensive model to describe all features. This research presents simulation methodology which describes key properties of such reactions to take a guide through a variety of their modifications. Dissipative particle dynamics is used in addition to Monte Carlo scheme to simulate initiation, propagation, and termination events. Influence of initiation probability and different termination processes on final conversion and molecular-weight distribution are presented. We demonstrate that prolonged initiation leads to increasing in polymer average molecular weight, and surface termination events play major role in conversion limitation, in comparison with recombination. © 2018 Wiley Periodicals, Inc.

Optimization of the high-throughput synthesis of multiblock copolymer nanoparticles in aqueous media via polymerization-induced self-assembly

High-throughput synthesis of multiblock copolymer nanoparticles via PISA.

Nitroxide-mediated polymerization-induced self-assembly of amphiphilic block copolymers with a pH/temperature dual sensitive stabilizer block

Comb-like P(PEOMA₃₀₀-co-MAA-co-S)-SG1 macroalkoxyamine terpolymer initiators with dual pH/temperature responsive behavior were synthesized by nitroxide-mediated polymerization and used to control the emulsion polymerization of BMA with a small proportion of styrene.

Effect of Small Reaction Locus in Free-Radical Polymerization: Conventional and Reversible-Deactivation Radical Polymerization

When the size of a polymerization locus is smaller than a few hundred nanometers, such as in miniemulsion polymerization, each locus may contain no more than one key-component molecule, and the concentration may become much larger than the corresponding bulk polymerization, leading to a significantly different rate of polymerization. By focusing attention on the component having the lowest concentration within the species involved in the polymerization rate expression, a simple formula can predict the particle diameter below which the polymerization rate changes significantly from the bulk polymerization. The key component in the conventional free-radical polymerization is the active radical and the polymerization rate becomes larger than the corresponding bulk polymerization when the particle size is smaller than the predicted diameter. The key component in reversible-addition-fragmentation chain-transfer (RAFT) polymerization is the intermediate species, and it can be used to predict the particle diameter below which the polymerization rate starts to increase. On the other hand, the key component is the trapping agent in stable-radical-mediated polymerization (SRMP) and atom-transfer radical polymerization (ATRP), and the polymerization rate decreases as the particle size becomes smaller than the predicted diameter.

Block copolymer synthesis by controlled/living radical polymerisation in heterogeneous systems

We review the range of CLRP-controlled syntheses of block copolymer particles in dispersed systems, which are being exploited to create new opportunities for the design of nanostructured soft materials.

Synthesis of multi-hollow clay-armored latexes by surfactant-free emulsion polymerization of styrene mediated by poly(ethylene oxide)-based macroRAFT/Laponite complexes

We report the RAFT-mediated synthesis of Laponite-armored latexes by surfactant-free emulsion polymerization.

Fundamentals of RAFT Polymerization

This chapter sets out to describe the fundamental aspects of radical polymerization with reversible addition-fragmentation chain transfer (RAFT polymerization). Following a description of the mechanism we describe aspects of the kinetics of RAFT polymerization, how to select a RAFT agent to achieve optimal control over polymer molecular weight, composition and architecture, and how to avoid side reactions which might lead to retardation or inhibition.