Syndiotactic-specific polymerization of NIPAAm

The radical polymerization of N-isopropylacrylamide (NIPAAm) was carried out in toluene at low temperatures in the presence of silyl alcohols, such as triethylsilanol (TESiOH). Poly(NIPAAm) with a racemo dyad content of 75 % was obtained at –80 °C with a 4:1 TESiOH to monomer ratio loading. NMR analysis has suggested that the mechanism for syndiotactic induction, in the presence of silyl alcohols, may be similar to that observed with alkyl alcohols. In this case, a 1:2 complex formation, via hydrogen bonding interactions, leads to the induction of syndiotactic specificity

Hussein Ali Abdulsater, Shi‘i Doctrine, Mu‘tazili Theology : al-Sharīf al-Murtaḍā and Imami Discourse

書評と紹

東アジア産非海産貝類の進化的放散

要約のみTohoku University千葉聡課

Syndiotactic- and Heterotactic-Specific Radical Polymerizations of N-n-Propyl-α-fluoroacrylamide and Phase-Transition Behaviors of Aqueous Solutions of Poly(N-n-propyl-α-fluoroacrylamide)

Radical polymerization of N-n-propyl-α-fluoroacrylamide (NNPFAAm) was investigated in several solvents at low temperatures in the presence or absence of Lewis bases, Lewis acids, alkyl alcohols, silyl alcohols, or fluorinated alcohols. Different effects of solvents and additives on stereospecificity were observed in the radical polymerizations of NNPFAAm and its hydrocarbon analogs such as N-isopropylacrylamide (NIPAAm) and N-n-propylacrylamide (NNPAAm); for instance, syndiotactic (and heterotactic) specificities were induced in radical polymerization of NNPFAAm in polar solvents (and in toluene in the presence of alkyl and silyl alcohols), whereas isotactic (and syndiotactic) specificities were induced in radical polymerizations of the hydrocarbon analogs under the corresponding conditions. In contrast, heterotactic specificity induced by fluorinated alcohols was further enhanced in radical polymerization of NNPFAAm. The effects of stereoregularity on the phase-transition behaviors of aqueous solutions of poly(NNPFAAm) were also investigated. Different tendencies in stereoregularity were observed in aqueous solutions of poly(NNPFAAm)s from those in solutions of the hydrocarbon analogs such as poly(NIPAAm) and poly(NNPAAm). The polymerization behavior of NNPFAAm and the phase-transition behavior of aqueous poly(NNPFAAm) are discussed based on possible fluorine–fluorine repulsion between the monomer and propagating chain-end, and neighboring monomeric units

Hydrogen-bond-assisted syndiotactic-specific radical polymerization of N-isopropylacrylamide : The solvent effect on the stereospecificity

Radical polymerizations of N-isopropylacrylamide (NIPAAm) in several solvents at low temperatures in the absence or presence of hexamethylphosphoramide (HMPA) or 3-methyl-3-pentanol (3Me3PenOH) were examined. The isotacticities of the poly(NIPAAm)s obtained in the absence of HMPA and 3Me3PenOH at lower temperatures slightly increased as the polarities of the solvents used increased. The addition of HMPA significantly induced the syndiotactic-specificity even in polar solvents such as tetrahydrofuran and acetone, although the use of the solvents having proton-donating ability, such as chloroform, prevented the induction of the syndiotactic-specificity, even if their polarities are low. In the presence of 3Me3PenOH, a good correlation between the polarities of the solvents used and the syndiotacticities of the obtained poly(NIPAAm)s was observed, and poly(NIPAAm) with r = 73% was obtained using the toluene/methylcyclohexane mixed solvent

Polyiodide Production Triggered by Acidic Phase of Aqueous Solution Confined in Carbon Nanospace

Polyiodide species were synthesized by the acceleration of an acidic environment in the nanospace of single-walled carbon nanotubes (SWCNT) with light irradiation. Raman and EXAFS results strongly support the production of polyiodide species after the adsorption of CsI on SWCNT from aqueous solution. Interestingly, the reaction was initiated by the nano-confined acidic phase formed in a basic environment. The acidic phase plays an essential role as an oxidant for the production of the diiodine that is a source of polyiodide

Heterotactic poly(N-isopropylacrylamide) prepared via radical polymerization in the presence of fluorinated alcohols

Radical polymerization of N-isopropylacrylamide in toluene at –40°C in the presence of fourfold amounts of fluorinated alcohols was investigated. The 13C NMR analysis of the obtained polymers suggested that the addition of fluorinated alcohols induced heterotactic-specificity in radical polymerization of NIPAAm, although syndiotactic poly(NIPAAm)s were obtained by adding alkyl alcohols as we have previously reported. To the best of our knowledge, this is the first synthesis of heterotactic poly(NIPAAm)