Bio-based vinylphenol family: Synthesis via decarboxylation of naturally occurring cinnamic acids and living radical polymerization for functionalized polystyrenes

A series of bio-based vinylphenols or hydroxystyrenes is prepared by simple decarboxylation of various naturally occurring cinnamic acids such as o-, m-, and p-coumaric; caffeic; ferulic; and sinapinic acids, which possess hydroxy groups and other substituents at different positions on the aromatic ring. After protection of the phenolic moieties with trialkylsilyl groups, reversible addition–fragmentation chain-transfer polymerization is accomplished with cumyl dithiobenzoate to afford various bio-based hydroxyl-protected polystyrenes with controlled molecular weights and narrow molecular weight distributions. Subsequent deprotection of the silyl groups under mild conditions results in a series of well-defined functionalized polystyrenes possessing different numbers (mono-, di-, tri-) of hydroxy groups at different positions (o, m, p). The obtained functionalized polystyrenes show unique thermal properties depending on the substituents, and those with phenol and catechol groups serve as reducing agents for silver ions. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 91–100     

Crystal Structures and Phase‐Transition Dynamics of Cobaltocenium Salts with Bis(perfluoroalkylsulfonyl)amide Anions: Remarkable Odd–Even Effect of the Fluorocarbon Chains in the Anion

Crystal structures and thermal properties of cobaltocenium salts with bis(perfluoroalkylsulfonyl)amide (C_nF_2n+1SO₂)₂N anions [n=0 ( 1 ), 1 ( 1 a ), 2 ( 1 b ), 3 ( 1 c ), and 4 ( 1 d )] and the 1,1,2,2,3,3‐hexafluoropropane‐1,3‐disulfonylamide anion ( 2 ) were investigated. In these solids, the cations are surrounded by four anions around their C₅ axis, and stacking of these local structures forms two kinds of assembled structures. In the salts with even n ( 1 , 1 b , and 1 d ), the cation and anion are arranged alternately to form mixed‐stack columns in the crystal. In contrast, in the salts with odd n ( 1 a and 1 c ), the cations and anions independently form segregated‐stack columns. An odd–even effect was also observed in the sum of the phase‐change entropies from crystal to melt. All of the salts exhibited phase transitions in the solid state. The phase transitions to the lowest‐temperature phase in 1 , 1 a , and 2 are accompanied by order–disorder of the anions and symmetry lowering of the space group, which results in the formation of an ion pair. Solid‐state ¹³C NMR measurements on 1 a and 1 b revealed enhanced molecular motions of the cation in the higher‐temperature phases.     

Halogen-Induced Controllable Cyclizations as Diverse Heterocycle Synthetic Strategy

In organic synthesis, due to their high electrophilicity and leaving group properties, halogens play pivotal roles in the activation and structural derivations of organic compounds. Recently, cyclizations induced by halogen groups that allow the production of diverse targets and the structural reorganization of organic molecules have attracted significant attention from synthetic chemists. Electrophilic halogen atoms activate unsaturated and saturated hydrocarbon moieties by generating halonium intermediates, followed by the attack of carbon-containing, nitrogen-containing, oxygen-containing, and sulfur-containing nucleophiles to give highly functionalized carbocycles and heterocycles. New transformations of halogenated organic molecules that can control the formation and stereoselectivity of the products, according to the difference in the size and number of halogen atoms, have recently been discovered. These unique cyclizations may possibly be used as efficient synthetic strategies with future advances. In this review, innovative reactions controlled by halogen groups are discussed as a new concept in the field of organic synthesis.     

Interconvertible Living Radical and Cationic Polymerization through Reversible Activation of Dormant Species with Dual Activity

The polymerization of vinyl monomers generally requires the selection of an appropriate single intermediate, whereas in copolymerization, the selection of the comonomer is limited by the intermediate. Herein, we propose interconvertible dual active species that can connect comonomers through different mechanisms to produce specific comonomer sequences in a single polymer chain. More specifically, two different stimuli, that is, a radical initiator and a Lewis acid, are used to activate the common dormant C? SC(S)Z group into radical and cationic species, thereby inducing interconvertible radical and cationic copolymerization of acrylate and vinyl ether to produce a copolymer chain that consists of radically and cationically polymerized segments. The dual reversible activation provides control over molecular weights and multiblock copolymers with tunable segment lengths.     

Design,synthesis, and characterization of a partially chlorinated acrylic copolymer for low‐loss and thermally stable graded index plastic optical fibers

As a novel material of low loss and high thermal stability, a graded index plastic optical fiber (GI POF) comprised of a copolymer of methyl α‐chloro acrylate (MCA) and 2,2,2‐trichloroethyl methacrylate (TCEMA) was prepared and the thermal, mechanical, and optical characteristics were investigated. Although each homopolymer had low loss and desirable high thermal stability, they had crucial disadvantages for the fiber fabrication process. To draw a MCA polymer (PMCA) fiber, it has to be heated above 270 °C. However, the polymer started to decompose at a lower temperature and produced numerous bubbles. In contrast, TCEMA polymer (PTCEMA) is too brittle to roll up during heat drawing. In this study, we succeeded to improve the strong viscoelasticity and the low decomposition temperature of PMCA and the brittleness of PTCEMA by copolymerizing MCA and TCEMA. In addition, the glass transition temperatures (T_g) of the copolymers were in the range of 133–147 °C and the transmittances of the copolymers were much higher than that of PMMA which has been commonly used as a base material of POF. A suitable GI POF was obtained using the MCA and TCEMA copolymer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3352–3361, 2009     

Fast shrinking kinetics of poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) hydrogels containing a nonionic surfactant

Shrinking kinetics of poly(N-isopropylacrylamide) gels prepared in the presence of a nonionic surfactant C9PE10 was investigated. The shrinking rate of the gels containing more than 6 wt.% of C9PE10 showed about a thousand-fold increase. From the analysis of the shrinking process and the small-angle X-ray scattering profiles, the fast shrinking kinetics was attributed to the incorporation of spatial heterogeneity of the network structure, which is caused by the addition of the surfactant.     

A bicyclic conjugated diene monomer,tetrahydroindene, for cationic polymerization and a novel alicyclic hydrocarbon polymer with heat resistance

This study was directed toward the cationic polymerization of tetrahydroindene (i.e., bicyclo[4.3.0]‐2,9‐nonadiene), a bicyclic conjugated diene monomer, with a series of Lewis acids, especially focusing on the synthesis of high‐molecular‐weight polymers and subsequent hydrogenation for novel cycloolefin polymers with high service temperatures. EtAlCl₂ or SnCl₄ induced an efficient and quantitative cationic polymerization of tetrahydroindene to afford polymers with relatively high molecular weights (number‐average molecular weight > 20,000) and 1,4‐enchainment bicyclic main‐chain structures. The subsequent hydrogenation of the obtained poly(tetrahydroindene) with p‐toluenesulfonyl hydrazide resulted in a saturated alicyclic hydrocarbon polymer with a relatively high glass transition (glass‐transition temperature = 220 °C) and improved pyrolysis temperature (10% weight loss at 480 °C). The new diene monomer was randomly copolymerized with cyclopentadiene at various feed ratios in the presence of EtAlCl₂ to give novel cycloolefin copolymers, which were subsequently hydrogenated into alicyclic copolymers with variable glass‐transition temperatures (70–220 °C). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6214–6225, 2006