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.

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Living Radical Polymerization by the RAFT Process - A Second Update

Department of Chemistry, Department of Radiology, Washington University in Saint Louis, Saint Louis, Missouri 63130, Department of Chemistry, Texas A&M University, College Station, Texas 77842, Cancer Center Karolinska, Department of Oncology-Pathology CCK, R8:03 Karolinska Hospital and Institute, SE-171 76 Stockholm, Sweden, and Department of Chemistry and Biochemistry, Department of Materials, and Materials Research Laboratory, University of California, Santa Barbara, California 93106

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Applications of Orthogonal “Click” Chemistries in the Synthesis of Functional Soft Materials

Radical addition-fragmentation chemistry in polymer synthesis

Monomers composed of a (meth)acrylate moiety connected to a short poly(ethylene)glycol (PEG) chain are versatile building-blocks for the preparation of “smart” biorelevant materials. Many of these monomers are commercial and can be easily polymerized by either anionic, free-radical, or controlled radical polymerization. The latter approach allows synthesis of well-defined PEG-based macromolecular architectures such as amphiphilic block copolymers, dense polymer brushes, or biohybrids. Furthermore, the resulting polymers exhibit fascinating solution properties in aqueous medium. Depending on the molecular structure of their monomer units, non linear PEG analogues can be either insoluble in water, readily soluble up to 100 °C, or thermoresponsive. Thus, these polymers can be used for building a wide variety of modern materials such as biosensors, artificial tissues, smart gels for chromatography, and drug carriers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3459–3470, 2008

Polymerization of oligo(ethylene glycol) (meth)acrylates: Toward new generations of smart biocompatible materials

Interest in thermoresponsive polymers has steadily grown over many decades, and a great deal of work has been dedicated to developing temperature sensitive macromolecules that can be crafted into new smart materials. However, the overwhelming majority of previously reported temperature-responsive polymers are based on poly(N-isopropylacrylamide) (PNIPAM), despite the fact that a wide range of other thermoresponsive polymers have demonstrated similar promise for the preparation of adaptive materials. Herein, we aim to highlight recent results that involve thermoresponsive systems that have not yet been as fully considered. Many of these (co)polymers represent clear opportunities for advancements in emerging biomedical and materials fields due to their increased biocompatibility and tuneable response. By highlighting recent examples of newly developed thermoresponsive polymer systems, we hope to promote the development of new generations of smart materials.

New directions in thermoresponsive polymers.

We examine the influence of the macromolecule chain length on the cloud point temperature (Tcp) and the temperature of the coil-to-globule transition (TM) in aqueous solutions of hydrophobically modified (HM) telechelic poly(N-isopropylacrylamides) (PNIPAM) ranging in concentration from 0.01 to 35 g L-1 (0.1−310 mmol of NIPAM L-1). The telechelic HM-PNIPAM samples with n-octadecyl termini were obtained by RAFT polymerization of NIPAM in dioxane in the presence of S-1-n-octadecyl-S‘-(α,α‘-dimethyl-α‘ ‘-N-n-octadecylacetamide)trithiocarbonate as a chain transfer agent. Their molar mass (Mn) ranged from 12 000 to 49 000 g mol-1 with a polydispersity index lower than 1.20. The cloud point temperatures, measured by monitoring the temperature-induced changes in scattering intensity, decreased significantly with increasing polymer concentration, this effect being more pronounced with decreasing polymer molar mass. In contrast, the temperature of the PNIPAM chain coil-to-globule collapse (30 ± 1 °C) was only slig...

Impact of end-group association and main-chain hydration on the thermosensitive properties of hydrophobically modified telechelic poly(N-isopropylacrylamides) in water

Poly(N-isopropylacrylamide)s (PNIPAMs) with cholesteryl or pyrenyl moieties at each chain end (CH-PNIPAMs or Py-PNIPAMs) were prepared via end-group modification of α,ω-dimercapto poly(N-isopropylacrylamides), ranging in molecular weight from ∼ 7000 to 45,000 g mol−1 with a polydispersity index of 1.10 or lower. The telechelic thiol functionalized PNIPAMs were obtained by aminolysis of α,ω-di(isobutylthiocarbonylthio)-poly(N-isopropylacrylamide)s (iBu-PNIPAMs) obtained by reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide in the presence of the difunctional chain transfer agent, diethylene glycol di(2-(1-isobutyl)sulfanylthiocarbonylsulfanyl-2-methyl propionate) (DEGDIM). The self-assembly of the polymers in water was assessed by fluorescence spectroscopy, using the intrinsic emission of Py-PNIPAM or the emission of pyrene added as a probe in aqueous solutions of CH-PNIPAM. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 314–326, 2008

An efficient synthesis of telechelic poly (N‐isopropylacrylamides) and its application to the preparation of α,ω‐dicholesteryl and α,ω‐dipyrenyl polymers

Thermoresponsive self-assembled nanogels were conveniently prepared by cholesterol end-capped poly(N-isopropylacrylamide) (PNIPAM) in water. Both cholesterol end-capped PNIPAMs (telelchelic cholesterol PNIPAM, tCH-PNIPAM) formed flower-like nanogels by the self-assembling of four to five polymer chains with multiple domains of cholesterol in water at 20 °C. Meanwhile, one end-group cholesterol-capped PNIPAM (semitelechelic cholesterol PNIPAM, stCH-PNIPAM) was also formed as a nanogel by the self-assembling of 15-20 polymer chains with 3 to 4 cholesterol domains. The hydrophobic cholesterol domains of tCH-PNIPAM nanogels were maintained above the lower critical solution temperature (LCST) of PNIPAM (>32 °C). Differently, the hydrophobic domains of stCH-PNIPAM were disrupted by cholesterol-free PNIPAM chain ends and formed large mesoglobules above the LCST. These transition controls of hydrophilic end-capped smart polymers may open new methodologies to design thermoresponsive nanosystems.

Florence Segui

Papers

Impact of end-group association and main-chain hydration on the thermosensitive properties of hydrophobically modified telechelic poly(N-isopropylacrylamides) in water

An efficient synthesis of telechelic poly (N‐isopropylacrylamides) and its application to the preparation of α,ω‐dicholesteryl and α,ω‐dipyrenyl polymers

Heat-Induced Flower Nanogels of Both Cholesterol End-Capped Poly(N-isopropylacrylamide)s in Water.