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The article describes a new novel class of Reversible chain Transfer catalyzed polymerizations (RTCPs) with germanium, tin and phosphorus catalyst. These catalysts are widely used because of their low toxicity and low costs.

Organostibines serve as excellent mediators for living radical polymerization (LRP). Furthermore, the generation of ethyl radical from triethylstibine was demonstrated by an electron spin resonance spectroscopic study.

A report that MX-chain complex [NiBr-(chxn)2]Br2 is different from the charge-density-wave (CDW) complexes is presented. In this complex, an unpaired electron in the Ni(super 3+)3d(sub z)2 orbital is strongly localized on the Ni atom owing to the strong electron correlation.

Living radical polymerization (LRP) is recognized as a powerful method to synthesize nanostructural macromolecules with defined structures possessing various functional groups, which are not compatible with ionic or metal-catalyzed polymerization conditions. Organotellurium-mediated living radical polymerization (TERP) is a new class of LRP, which shows versatility, molecular weight controllability, functional group compatibility and ease of polymer-end transformation.

The reaction mechanism of living radical polymerization using organic catalysts, a reversible complexation mediated polymerization (RCMP), was studied using both theoretical calculations and experiments. The studied catalysts are tetramethylguanidine (TMG), triethylamine (TEA), and thiophene. Methyl 2-iodoisobutyrate (MMA-I) was used as the low-molar-mass model of the dormant species (alkyl iodide) of poly(methyl methacrylate) iodide (PMMA-I). For the reaction of MMA-I with TEA to generate MMA• and •I-TEA radicals (activation process), the Gibbs activation free energy for the inner-sphere electron transfer mechanism was calculated to be 39.7 kcal mol-1, while the observed one was 25.1 kcal mol-1. This difference of the energies suggests that the present RCMP proceeds via the outer-sphere electron transfer mechanism, i.e., single-electron transfer (SET) reaction from TEA to MMA-I to generate MMA• and •I-TEA radicals. The mechanism of the deactivation process of MMA• to generate MMA-I was also theoretically studied. For the studied three catalysts, the theoretical results reasonably elucidated the experimentally observed polymerization behaviors. [ABSTRACT FROM AUTHOR]

A new method of producing carbon-centered radicals was discovered through the reaction of an alkyl iodide (R-I) with organic salts to reversibly generate the corresponding alkyl radical (R•). Via this new reaction, the organic salts were used as new and highly efficient organic catalysts in living radical polymerization. The catalysts included common and inexpensive compounds such as tetrabutylammonium iodide and methyltributylphosphonium iodide. Notably, the catalysts were highly reactive. They enabled the synthesis of high-molecular-weight polymers (up to Mn = 140?000) and the control of acrylate polymerization, which had been difficult with other organic catalysts. The organic salt catalysts were highly versatile, reacting with methacrylate, acrylate, styrene, acrylonitrile, and functional methacrylate monomers. Well-defined block copolymers were also prepared by using this method. A kinetic study quantitatively confirmed the high reactivity of these catalysts. Attractive features of this system include its low cost, its ease of operation, and its ability to access a wide range of polymer designs. [ABSTRACT FROM AUTHOR]

Photoinduced reversible complexation mediated polymerization(photo-RCMP) was developed as a new photoinduced living radical polymerization(LRP). It consisted of an alkyl iodide as a dormant species and anamine as a catalyst, using visible light at 350–600 nm. Theamine catalysts include such common compounds as tributylamine. Mechanistically,the polymerization is induced by the photolysis of the dormant speciesand dormant species/catalyst complex, which frequently occurs as themain activation process. The polymer molecular weight and its distribution(Mw/Mn= 1.1–1.4)were well controlled in the polymerizations of methyl methacrylateand some functional methacrylates up to fairly high conversions inmany cases. Perfectly no polymerization took place without photoirradiation,meaning that the system is an ideal photo “on”–“off”switchable system. The polymerization rate was also finely tunableby the external irradiation power. Attractive features of photo-RCMPinclude the uses of inexpensive compounds and visible light, goodpolydispersity control, good tolerance to functional groups, and fineresponse to external photoirradiation. [ABSTRACT FROM AUTHOR]

In the field of solid-state chemistry and physics, there is much interest in one-dimensional (1-D) electron systems because pronounced phenomena characteristic of 1-D systems have been observed such as the Haldane gap in integer spin antiferromagnetic compounds, solitons and polarons observed in ru-conjugated polymers, slow relaxation of magnetization in several ferromagnetic and ferrimagnetic compounds known as single-chain-magnets. Halogen-bridged 1-D metal complexes (MX-chains) also have been attractive targets because of the highly isolated 1-D chain structure and the variety of the electronic states which can be tuned by substituting those components. MX-chain complexes with a mixed-valence structure have been widely studied as 1-D materials with strong electron-lattice interactions.

A versatile strategy for the fabrication of block copolymers by the combination of two discrete living polymerization techniques─reversible complexation mediated living radical polymerization (RCMP) and photoinduced radical oxidation addition deactivation (PROAD) processes─is reported. First, RCMP is conducted to yield poly(methyl methacrylate) with iodide end groups (PMMA-I). In the following step, PMMA-I is used as macroinitiator for living PROAD cationic polymerization of isobutyl vinyl ether. Successful formation of the block copolymers is confirmed by 1 H NMR, FT-IR, GPC, and DSC investigations.

Poly(furfuryl methacrylate) (PFMA) brushes were cross-linked using bismaleimide cross-linkers via the Diels-Alder (DA) reaction at 70 °C, generating cross-linked PFMA brushes (PFMA brush gels). The cross-linked PFMA brushes were decross-linked at 110 °C via the retro-Diels-Alder (rDA) reaction, offering the temperature-responsive reversible PFMA brush gels. The wettability of the brush was tunable by cross-linking and decross-linking. The use of a disulfide containing bismaleimide as a cross-linker gave the S-S bond at the cross-linking point. The S-S bond was cleaved upon thermal or photo stimulus and regenerated through oxidative stimulus, offering another reversible decross-linking/cross-linking pathway of the PFMA brush gel. The use of photo stimulus together with photomasks further offered patterned brushes with the cross-linked and decross-linked domains. The combination of the DA/rDA reactions and the reversible S-S bond cleavage provided multistimuli-responsive brush gels for switching the surface properties in unique manners. The reversible cross-linking, multiresponsiveness, access to patterned structures, and metal-free synthetic procedure are attractive features in the present approach for creating smart functional surfaces.

Herein, nontoxic and metabolizable choline iodide analogues, including choline iodide, acetylcholine iodide, and butyrylcholine iodide, were successfully utilized as novel catalysts for "green" living radical polymerization (LRP). Through the combination of several green solvents (ethyl lactate, ethanol, and water), this green LRP process yielded low-polydispersity hydrophobic, hydrophilic, zwitterionic, and water-soluble biocompatible polymethacrylates and polyacrylates with high monomer conversions. Well-defined hydrophobic-hydrophilic and hydrophilic-hydrophilic block copolymers were also synthesized. The accessibility to a range of polymer designs is an attractive feature of this polymerization. The use of nontoxic choline iodide catalysts as well as green polymerization conditions can contribute to sustainable polymer chemistry.

Herein, a new reaction of an alkyl iodide (R-I) with an azide anion (N 3 - ) to reversibly generate the corresponding alkyl radical (R • ) is reported. Via this new reaction, N 3 - was used as an efficient catalyst in living radical polymerization, yielding a well-defined polymer-iodide. A particularly interesting finding was the solvent selectivity of this reaction; namely, R-I and N 3 - generated R • in nonpolar solvents, while the substitution product R-N 3 was generated in polar solvents. Exploiting this unique solvent selectivity, a one-pot synthesis of polymer-N 3 was attained. N 3 - was first used as a catalyst for living radical polymerization in a nonpolar solvent to produce a polymer-iodide and was subsequently used as a substitution agent in a polar solvent by simply adding the polar solvent, thereby transforming the polymer-iodide to polymer-N 3 in one pot. This one-pot synthesis was further applied to obtain N 3 -chain-end-functionalized polymer brushes on the surface, uniquely controlling the N 3 coverage (number density). Using the chain-end N 3 , the obtained linear and brush polymers were connected to functional molecules via an azide-alkyne click reaction. The attractive features of this system include facile operation, access to unique polymer designs, and no requirement for using excess NaN 3 . In addition to N 3 - , thiocyanate ( - SCN) and cyanate ( - OCN) anions were also studied.

Photocontrolled organocatalyzed living radical polymerization was conducted over a wide range of irradiation wavelengths (350-750 nm). The polymerization was induced and controlled at the desired wavelengths by exploiting suitable organic catalysts. This system was finely responsive to the irradiation wavelength; the polymerization was instantly switched on and off, and the polymerization rate was sensitively modulated by altering the irradiation wavelength. The polymer molecular weight and its distribution (M(w)/M(n) = 1.1-1.4) were well controlled for methacrylate monomers up to fairly high conversions in many cases. The monomer scope encompassed various functional methacrylates, and their block copolymers were obtained. The feasibility of such a wide range of wavelengths and the fine response to the wavelength are unprecedented features. As a unique application of the wavelength-responsive nature of this system, we demonstrated "one-pot" selective regulation of living radical polymerization and another type of polymerization (ring opening polymerization), where the regulation was achieved by simply altering the irradiation wavelength. Facile operation and applicability to a wide range of polymer designs are advantages of this polymerization.

Linear and miktoarm star-shaped diblock copolymers consisting of single-stranded DNA and poly(N-isopropylacrylamide) (PNIPAAm) with various compositions were synthesized via atom transfer radical polymerization and click chemistry. The temperature-responsive phase transition behavior, micellization, was systematically examined using UV-vis spectrometry, high-sensitivity differential scanning calorimetry, dynamic light scattering, and small-angle X-ray scattering. The lower critical solution temperature (LCST) increased, and its enthalpy decreased with decreasing PNIPAAm content. The copolymers self-assembled into well-defined nanoparticles having a core composed of PNIPAAm and a coronal layer of DNA above LCST. The particle size and micellar aggregation number of copolymer chains depended on the macromolecular composition and chain architecture. On the other hand, regardless of their factors, the surface area occupied by one DNA strand was found to be almost unchanged. The hybridization of DNA on the nanoparticles with fully complementary one induced the aggregation of the particles in a non-cross-linking configuration. The nanoparticle composed of miktoarm star copolymer showed a quicker DNA-hybridization response in this non-cross-linking aggregation compared with the case of a linear analogue.