Group-Transfer Polymerization-Induced Self-Assembly (GTPISA) in Non-polar Media: An Organocatalyzed Route to Block Copolymer Nanoparticles at Room Temperature

Polymerization-induced self-assembly (PISA) enables the synthesis at large scale of a wide variety of functional nanoparticles. However, a large number of works are related to controlled radical polymerization (CRP) methods and are generally undertaken at elevated temperatures (>50 °C). Here is the first report on methacrylate-based nanoparticles fabricated by group transfer polymerization-induced self-assembly (GTPISA) in non-polar media (n-heptane). This GTPISA process is achieved at room temperature (RT) using 1-methoxy-1-(trimethylsiloxy)-2-methylprop-1-ene (MTS) and tetrabutylammonium bis-benzoate (TBABB) as initiator and organic catalyst, respectively. Under these conditions, well-defined metal-free and colorless diblock copolymers are produced with efficient crossover from the non-polar stabilizing poly(lauryl methacrylate) (PLMA) block to the non-soluble poly(benzyl methacrylate) (PBzMA) segment. The resulting PLMA-b-PBzMA block copolymers simultaneously self-assemble into nanostructures of various sizes and morphologies. GTPISA in non-polar solvent proceeds rapidly at RT and avoids the use of sulfur or halogenated compounds or metallic catalysts associated with the implementation of CRP methods, thus expanding the potential of PISA formulations for applications in non-polar environments.

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.

Dispersion Polymerization versus Emulsifier-Free Emulsion Polymerization for Nano-Object Fabrication: A Comprehensive Comparison

Although the preparation of nano-objects by emulsifier-free controlled/living radical emulsion polymerization has drawn much attention, the morphologies of these formed objects are difficult to predict and to reproduce because of the much more complex nucleation mechanisms of emulsion polymerization compared to only one self-assembling nucleation mechanism of controlled radical dispersion polymerization. The present study compares dispersion polymerization with emulsifier-free emulsion polymerization in terms of nucleation mechanism, polymerization kinetics, and disappearance behavior of the macrochain transfer agent, gel permeation chromatograms curves of the obtained block copolymer as well as the structural and morphological differences between the produced nano-objects on the basis of published data. Moreover, the effects of the inherently heterogeneous nature of emulsion polymerization on the mechanism of reversible addition-fragmentation transfer polymerization and the nano-object morphology are examined, and efficient agitation and adequate solubility of the core-forming monomer in water are identified as the most crucial factors for the fabrication of nonspherical nano-objects.

Achieving Fast Self-Healing and Reprocessing of Supertough Water-Dispersed "Living" Supramolecular Polymers Containing Dynamic Ditelluride Bonds under Visible Light

It is very challenging to achieve polymers that are mechanically robust and fast self-healable at ambient conditions, which are highly desirable for smart materials of the next-generation. Herein, combining dynamic ditelluride bonds and 2-ureido-4[1H]-pyrimidinone (UPy) moieties in the main chains, a novel type of visible-light-induced self-healing water-dispersed supramolecular polymers (DTe-WSPs) with outstanding healing properties were developed. The prepared DTe-WSPs emulsions showed excellent emulsion stability, and highly transparent DTe-WSPs films obtained from these emulsions exhibited much improved mechanical properties and fast recoverability after the incorporation of UPy groups, owing to the physical cross-links formed by quadruple hydrogen-bonded UPy moieties. Supertoughness (105.2 MJ m^-3) and fast self-healability under visible light (healing efficiency of 85.6% within 10 min) could be achieved simultaneously with the adjustment of the ditelluride content and the UPy content, and the toughness of our polymers is higher than those of the reported ambient temperature self-healable polymers. The visible-light-induced ditelluride metathesis is a predominant factor in the healing process of DTe-WSPs, and the ditelluride metathesis triggered by photothermy and hydrogen bonding could also afford the ultimate healing result. Meanwhile, DTe-WSPs can be reprocessed using visible light, providing a facile way to process polymers at mild conditions. To our surprise, the "living" DTe-WSPs exhibited the ability to initiate the polymerization of vinyl monomers under visible light, which is first reported for water-dispersed self-healing polymers. We considered the elaborated design philosophy, based on the readily available, clean, safe, and easily manipulated visible light, which can not only provide inspiration for preparing fast ambient temperature self-healing and reprocessing polymer materials with robust mechanical properties but also develop a new macroinitiator to initiate the ambient temperature polymerization of vinyl monomers.

Polymerization techniques in polymerization-induced self-assembly (PISA)

The development of controlled/“living” polymerization greatly stimulated the prosperity of the fabrication and application of block copolymer nano-objects.

Living Ab Initio Emulsion Polymerization of Methyl Methacrylate in Water Using a Water-Soluble Organotellurium Chain Transfer Agent under Thermal and Photochemical Conditions

Ab initio emulsion polymerization of methyl methacrylate (MMA) using a water-soluble organotellurium chain transfer agent in the presence of the surfactant Brij 98 in water is reported. Polymerization proceeded under both thermal and visible light-irradiation conditions, giving poly(methyl methacrylate) (PMMA) with controlled molecular weight and low dispersity (Đ<1.5). Despite the formation of an opaque latex, the photoactivation of the organotellurium dormant species took place efficiently, as demonstrated by the quantitative monomer conversion and temporal control. Control of polymer particle size (PDI<0.030) was also achieved using a semi-batch monomer addition process. The PMMA polymer in the particles retained high end-group fidelity and was successfully used for the synthesis of block copolymers.

A synthetic route to ultra-high molecular weight polystyrene (>106) with narrow molecular weight distribution by emulsifier-free, emulsion organotellurium-mediated living radical polymerization (emulsion TERP)

We propose a route to synthesizing ultra-high molecular weight (>10⁶) polystyrene (PS) having a narrow molecular weight distribution by controlled/living radical polymerization.

Polymeric filomicelles and nanoworms: two decades of synthesis and application

This review highlights the substantial progress in the syntheses and applications of filomicelles, an emerging nanomaterial with distinct and useful properties.

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.

Amphiphilic Polymerizable Porphyrins Conjugated to a Polyglycerol Dendron Moiety as Functional Surfactants for Multifunctional Polymer Particles

An amphiphilic polyglycerol dendron (PGD) conjugated porphyrin (PGP) bearing a polymerizable group was successfully synthesized. The PGP was used as an effective surfactant in emulsion and microsuspension polymerization systems to prepare styrene and methacrylate polymer particles, and the use of PGP provided the simple polymer particles with fluorescence derived from the metalloporphyrin and high colloidal stability due to the PGD. Furthermore, based on confocal laser scanning microscopy, we observed that the particles spontaneously formed a core-shell morphology with the PGP localized in the shell region during the polymerization and demonstrated drug loading in the shell region using rhodamine B as a model drug. The results indicate that the use of the functional surfactant PGP led to the preparation of multifunctional polymer particles from simple monomer species, and the resulting particles possessed high colloidal stability, fluorescence, and drug loading capability.

Iron-catalyzed atom transfer radical polymerization

This article reviews the preparation of polymers using iron-catalyzed atom transfer radical polymerization.

Emulsifier-free, organotellurium-mediated living radical emulsion polymerization (emulsion TERP) of styrene: poly(dimethylaminoethyl methacrylate) macro-TERP agent

Emulsifier-free, organotellurium-mediated living radical emulsion polymerization of styrene was successfully carried out using poly(dimethylaminoethyl methacrylate)–n-butyl tellanyl as control agent and 4,4′-azobis(2-amidinopropane) hydrochloride as initiator.

Seeded dispersion RAFT polymerization and synthesis of well-defined ABA triblock copolymer flower-like nanoparticles

Flower-like triblock copolymer nanoparticles containing a central looped solvophilic block and two outer solvophobic blocks are prepared by seeded dispersion RAFT polymerization.