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Journal ArticleDOI

Visible Light-Mediated Polymerization-Induced Self-Assembly in the Absence of External Catalyst or Initiator

12 Apr 2016-ACS Macro Letters (American Chemical Society)-Vol. 5, Iss: 5, pp 558-564
TL;DR: In this article, the use of visible light to mediate a RAFT dispersion polymerization in the absence of external catalyst or initiator to yield nanoparticles of different morphologies according to a polymerization-induced self-assembly (PISA) mechanism was reported.
Abstract: We report the use of visible light to mediate a RAFT dispersion polymerization in the absence of external catalyst or initiator to yield nanoparticles of different morphologies according to a polymerization-induced self-assembly (PISA) mechanism. A POEGMA macro-chain transfer agent (macro-CTA) derived from a 4-cyano-4-((dodecylsulfanylthiocarbonyl)sulfanyl)pentanoic acid (CDTPA) RAFT agent can be activated under blue (460 nm, 0.7 mW/cm2) or green (530 nm, 0.7 mW/cm2) light and act simultaneously as a radical initiator, chain transfer agent, and particle stabilizer under ethanolic dispersion conditions. In particular, the formation of worm-like micelles was readily monitored by the increase of reaction viscosity during the polymerization; this method was shown to be particularly robust to different reaction parameters such as macro-CTAs of varying molecular weight. Interestingly, at high monomer conversion, different morphologies were formed depending on the wavelength of light employed, which may be due t...
Citations
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Journal ArticleDOI
TL;DR: A comprehensive overview of the fundamentals and applications of various photomediated CRP techniques, including atom transfer radical polymerization, reversible addition-fragmentation chain transfer (RAFT), nitroxide mediated polymerization (NMP), and other procedures are discussed in this article.

460 citations

Journal ArticleDOI
TL;DR: Alternative PISA protocols are paid particular attention to, which allow the preparation of nanoparticles with improved control over copolymer morphology and functionality, and have been optimized via high-throughput polymerization and recently evaluated within flow reactors for facile scale-up syntheses.
Abstract: In this Perspective, we summarize recent progress in polymerization-induced self-assembly (PISA) for the rational synthesis of block copolymer nanoparticles with various morphologies. Much of the PISA literature has been based on thermally initiated reversible addition–fragmentation chain transfer (RAFT) polymerization. Herein, we pay particular attention to alternative PISA protocols, which allow the preparation of nanoparticles with improved control over copolymer morphology and functionality. For example, initiation based on visible light, redox chemistry, or enzymes enables the incorporation of sensitive monomers and fragile biomolecules into block copolymer nanoparticles. Furthermore, PISA syntheses and postfunctionalization of the resulting nanoparticles (e.g., cross-linking) can be conducted sequentially without intermediate purification by using various external stimuli. Finally, PISA formulations have been optimized via high-throughput polymerization and recently evaluated within flow reactors for facile scale-up syntheses.

339 citations


Cites methods from "Visible Light-Mediated Polymerizati..."

  • ...Page 4 judicious selection of the macro-RAFT agent, these polymerizations can also be initiated using visible light without requiring an external initiator or catalyst, thus simplifying this RAFT dispersion polymerization formulation.(106) Sumerlin, Zhang and co-workers employed a photoinitiator to initiate the polymerization of 2-hydroxypropyl methacrylate (HPMA) in water at 25 °C....

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Journal ArticleDOI
TL;DR: This review will cover the fundamentals of the PISA mechanism and review some features and limitations of RAFT-mediated PISA in terms of the choice of the components involved, the nature of the nano-objects that is achievable, the morphologies that are accessible and how they can be controlled, and some potential applications.
Abstract: After a brief history that positions polymerization-induced self-assembly (PISA) in the field of polymer chemistry, this Review will cover the fundamentals of the PISA mechanism. Furthermore, this Review will also give an overview of some of the features and limitations of RAFT-mediated PISA in terms of the choice of the components involved, the nature of the nanoobjects that can be obtained and how the syntheses can be controlled, as well as some potential applications.

307 citations

Journal ArticleDOI
TL;DR: The purpose of this mini‐review is to examine some of these recent advances that have been made in Photo‐PISA processes, particularly in light of the specific advantages that may exist in comparison with conventional thermally initiated systems.
Abstract: The polymerization-induced self-assembly (PISA) process is a useful synthetic tool for the efficient synthesis of polymeric nanoparticles of different morphologies. Recently, studies on visible light initiated PISA processes have offered a number of key research opportunities that are not readily accessible using traditional thermally initiated systems. For example, visible light mediated PISA (Photo-PISA) enables a high degree of control over the dispersion polymerization process by manipulation of the wavelength and intensity of incident light. In some cases, the final nanoparticle morphology of a single formulation can be modulated by simple manipulation of these externally controlled parameters. In addition, temporal (and in principle spatial) control over the Photo-PISA process can be achieved in most cases. Exploitation of the mild room temperature polymerizations conditions can enable the encapsulation of thermally sensitive therapeutics to occur without compromising the polymerization rate and their activities. Finally, the Photo-PISA process can enable further mechanistic insights into the morphological evolution of nanoparticle formation such as the effects of temperature on the self-assembly process. The purpose of this mini-review is therefore to examine some of these recent advances that have been made in Photo-PISA processes, particularly in light of the specific advantages that may exist in comparison with conventional thermally initiated systems.

269 citations

Journal ArticleDOI
TL;DR: In this paper, the authors highlight the progress realized in recent years on light-responsive polymers and provide some guidelines towards the rational design of photo-responsive block copolymers and present the different photoresponsive moieties that have been used so far.

247 citations

References
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Journal ArticleDOI
TL;DR: The authors provides a third update to the review of reversible deactivation radical polymerization (RDRP) achieved with thiocarbonylthio compounds (ZC(S)SR) by a mechanism of reversible addition-fragmentation chain transfer (RAFT) that was published in June 2005.
Abstract: This paper provides a third update to the review of reversible deactivation radical polymerization (RDRP) achieved with thiocarbonylthio compounds (ZC(=S)SR) by a mechanism of reversible addition-fragmentation chain transfer (RAFT) that was published in June 2005 (Aust. J. Chem. 2005, 58, 379). The first update was published in November 2006 (Aust. J. Chem. 2006, 59, 669) and the second in December 2009 (Aust. J. Chem. 2009, 62, 1402). This review cites over 700 publications that appeared during the period mid 2009 to early 2012 covering various aspects of RAFT polymerization which include reagent synthesis and properties, kinetics and mechanism of polymerization, novel polymer syntheses, and a diverse range of applications. This period has witnessed further significant developments, particularly in the areas of novel RAFT agents, techniques for end-group transformation, the production of micro/nanoparticles and modified surfaces, and biopolymer conjugates both for therapeutic and diagnostic applications.

1,612 citations

Journal ArticleDOI
TL;DR: This approach has quickly become a powerful and versatile technique for the synthesis of a wide range of bespoke organic diblock copolymer nano-objects of controllable size, morphology, and surface functionality.
Abstract: In this Perspective, we discuss the recent development of polymerization-induced self-assembly mediated by reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerization. This approach has quickly become a powerful and versatile technique for the synthesis of a wide range of bespoke organic diblock copolymer nano-objects of controllable size, morphology, and surface functionality. Given its potential scalability, such environmentally-friendly formulations are expected to offer many potential applications, such as novel Pickering emulsifiers, efficient microencapsulation vehicles, and sterilizable thermo-responsive hydrogels for the cost-effective long-term storage of mammalian cells.

850 citations

Journal ArticleDOI
TL;DR: A comprehensive survey of photo-CRP reactions can be found in this article, where a large number of methods are summarized and further classified into subcategories based on the specific reagents, catalysts, etc., involved.
Abstract: The use of light to mediate controlled radical polymerization has emerged as a powerful strategy for rational polymer synthesis and advanced materials fabrication. This review provides a comprehensive survey of photocontrolled, living radical polymerizations (photo-CRPs). From the perspective of mechanism, all known photo-CRPs are divided into either (1) intramolecular photochemical processes or (2) photoredox processes. Within these mechanistic regimes, a large number of methods are summarized and further classified into subcategories based on the specific reagents, catalysts, etc., involved. To provide a clear understanding of each subcategory, reaction mechanisms are discussed. In addition, applications of photo-CRP reported so far, which include surface fabrication, particle preparation, photoresponsive gel design, and continuous flow technology, are summarized. We hope this review will not only provide informative knowledge to researchers in this field but also stimulate new ideas and applications to further advance photocontrolled reactions.

738 citations

Journal ArticleDOI
TL;DR: A metal-free ATRP process, mediated by light and catalyzed by an organic-based photoredox catalyst, is reported that resulted in block copolymer formation was facile and could be combined with other controlled radical processes leading to structural and synthetic versatility.
Abstract: Overcoming the challenge of metal contamination in traditional ATRP systems, a metal-free ATRP process, mediated by light and catalyzed by an organic-based photoredox catalyst, is reported. Polymerization of vinyl monomers are efficiently activated and deactivated with light leading to excellent control over the molecular weight, polydispersity, and chain ends of the resulting polymers. Significantly, block copolymer formation was facile and could be combined with other controlled radical processes leading to structural and synthetic versatility. We believe that these new organic-based photoredox catalysts will enable new applications for controlled radical polymerizations and also be of further value in both small molecule and polymer chemistry.

720 citations

Journal ArticleDOI
TL;DR: A photoinduced living polymerization technique is reported, which is able to polymerize a large range of monomers, including conjugated and unconjugated monomer, using ultralow concentrations of an iridium-based photoredox catalyst and a low energy visible LED as the light source.
Abstract: Controlled/living radical polymerization techniques have transformed polymer chemistry in the last few decades, affording the production of polymers with precise control over both molecular weights and architectures. It is now possible to synthesize almost an infinite variety of macromolecules using nonspecialized equipment, finding applications in high-tech industry. However, they have several shortcomings. Until recently, living radical polymerizations could not be controlled by an external stimulus, such as visible light, pH, mechanical, chemical, etc. Moreover, they are usually sensitive to trace amounts of oxygen in the system. In this Article, we report a photoinduced living polymerization technique, which is able to polymerize a large range of monomers, including conjugated and unconjugated monomers, using ultralow concentrations of an iridium-based photoredox catalyst (typically 1 ppm to monomers) and a low energy visible LED as the light source (1–4.8 W, λmax = 435 nm). The synthesis of homopolym...

695 citations