Maximal Thurston-Bennequin numbers of alternating links

We show that the upper bound of the maximal Thurston-Bennequin number for an oriented alternating link given by the Kauffman polynomial is sharp. As an application, we confirm a question of Ferrand. We also give a formula of the maximal Thurston-Bennequin number for all two-bridge links. Finally, we introduce knot concordance invariants derived from the Thurston-Bennequin number and the Maslov number of a Legendrian knot.     

An invariance principle for non-symmetric Markov processes and reflecting diffusions in random domains

Summary We study an invariance principle for additive functionals of nonsymmetric Markov processes with singular mean forward velocities. We generalize results of Kipnis and Varadhan [KV] and De Masi et al. [De] in two directions: Markov processes are non-symmetric, and mean forward velocities are distributions. We study continuous time Markov processes. We use our result to homogenize non-symmetric reflecting diffusions in random domains.     

New synthesis of spirocycles by utilizing in situ forming hypervalent iodine species

A very effective spirocyclization procedure for installing nucleophiles (Nu = N(3), NO(2), SCN, SO(2)Tol, and halogens) via iodonium(III) salts has been developed using the combination of iodoarene and mCPBA. The high-yielding syntheses of the cyclohexadienone-type spirocyclic compounds 2 having varied functionalities in the skeletons have been achieved from the aryl alkynes 1 with the optimized bis(iodoarene) 3h.     

Metal-free C-H cross-coupling toward oxygenated naphthalene-benzene linked biaryls

The intermolecular C-H cross-coupling between aromatic ethers has been achieved for the first time using perfluorinated hypervalent iodine(III) compounds as extreme single-electron-transfer (SET) oxidants. The demonstrations of this specific coupling could provide a direct route to valuable oxygenated mixed naphthalene-benzene biaryls 3 only, without formation of other biaryl-derived byproducts.     

Amylose's recognition of chirality in polylactides on formation of inclusion complexes in vine-twining polymerization

Amylose selectively includes poly(L-lactide) (PLLA) among the poly(lactide)s (PLAs) to produce an inclusion complex when the phosphorylase-catalyzed polymerization of α-D-glucose 1-phosphate is performed in the presence of PLLA, poly(D-lactide) (PDLA), or poly(DL-lactide) (PDLLA) (vine-twining polymerization). This result indicates that amylose recognizes the chirality in PLAs on the formation of an inclusion complex in vine-twining polymerization. Modeling calculations support the amylose's chiral recognition in favor of PLLA and the atomistic details of the inclusion complex which involved the preferred orientation of the constituent molecular chains with respect to their fiber axis is proposed.     

Synthesis of syndiotactic‐rich star‐shaped poly(methyl methacrylate) by core‐first group transfer polymerization using N‐(trimethylsilyl)bis(trifluoromethanesulfonyl)imide

The N‐(trimethylsilyl)bis(trifluoromethanesulfonyl)imide‐catalyzed (Me₃SiNTf₂‐catalyzed) group transfer polymerization (GTP) of methyl methacrylate (MMA) has been studied for synthesizing stereospecific star‐shaped poly(methyl methacrylate)s (PMMAs). The catalytic property of Me₃SiNTf₂ for the GTP of MMA using 1‐methoxy‐1‐trimethylsilyloxy‐2‐methyl‐propene as the initiator was confirmed by a kinetic investigation and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry measurement. The initiating efficiency (f) of Me₃SiNTf₂ was 0.94–1.00, which was estimated by the value of M_n(calcd)/M_n(SEC). The Me₃SiNTf₂‐catalyzed GTP of MMA was carried out using initiators possessing three, four, and six MTS groups (MTS₃, MTS₄, and MTS₆, respectively) under the condition of [MMA]₀/[MTS₃, MTS₄, or MTS₆]₀ = 120 at ?55 °C. All the obtained PMMAs exhibited unimodal and narrow molecular weight distributions as M_w/M_ns = 1.03–1.04 and the M_w(MALS)s of the 3‐, 4‐, and 6‐armed star‐shaped PMMAs (PMMA₃, PMMA₄, and PMMA₆, respectively) were 12.9, 12.9, and 13.4 kgmol^?1, respectively, which fairly agreed with the calculated M_w(calcd) values. The syndiotacticities, rrs, of PMMA₃, PMMA₄, and PMMA₆ were in the range of 87–89%. The stereoblock synthesis of PMMA₃, PMMA₄, and PMMA₆ was performed by the first and second polymerizations at ?55 and 45 °C; the rrs of the first and second PMMA blocks were 87.0, 87.0, and 86.0% and 65.0, 65.0, and 64.0%, respectively. The glass transition temperatures (T_gs) were 118.1, 115.8, and 111.5 °C for the respective syndiotactic‐rich PMMA₃, PMMA₄, and PMMA₆ and 111.5, 109.7, and 107.6 °C for the respective stereoblock ones. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and characterization of cyclic P3HT as a donor polymer for organic solar cells

In this study, cyclic poly(3‐hexylthiophene‐2,5‐diyl) (c‐P3HT) with a controlled M_n was synthesized by the intramolecular cyclization of α‐bromo‐ω‐ethynyl‐functionalized P3HT via the Sonogashira coupling reaction. The effect of the cyclic structure, which does not have terminal groups of polymers, on the photoelectric conversion characteristics was investigated in comparison to linear P3HT (l‐P3HT). c‐P3HT was successfully synthesized with M_n ≈ 17,000, dispersity ≈ 1.2, and regioregularity ≈ 99%. The hole mobility was determined to be 5.1 × 10^?4 cm² V^?1 s^?1 by time‐of‐flight (TOF) experiment. This was comparable to that of l‐P3HT of 5.6 × 10^?4 cm² V^?1 s^?1. Organic solar cell systems were fabricated with each polymer by blending them with [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM). The l‐P3HT:PC₇₁BM system showed a dispersive TOF photocurrent profile for electron transport, whereas a nondispersive profile was observed for c‐P3HT:PC₇₁BM. In addition, an amount of collected electrons in c‐P3HT:PC₇₁BM was greater than that in l‐P3HT:PC₇₁BM for TOF experiments. The photoelectric conversion characteristics were improved by using c‐P3HT rather than l‐P3HT (power conversion efficiency [PCE] = 4.05% vs 3.23%), reflecting the nondispersive transport and the improvement of electron collection. PCEs will be much improved by applying this cyclic concept to highly‐efficient OSC polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 266–271     

Recyclable helical poly(phenylacetylene)‐supported catalyst for asymmetric aldol reaction in aqueous media

A novel one‐handed helical poly(phenylacetylene) bearing L‐hydroxyproline pendants (poly(PA‐P)) was synthesized as an eco‐friendly polymer‐supported catalyst for asymmetric reactions. The helical poly(PA‐P) catalyzed the asymmetric aldol reactions of cyclohexanone with p‐nitrobenzaldehyde, and showed good recyclability and higher enantiomeric excess (ee) in aqueous medias than that in organic medias. The one‐handed helicity of poly(PA‐P) was clearly affected by the water content in the aqueous media. The helical poly(PA‐P) showed the higher enantioselectivity (ee = 99%) than its monomer PA‐P (ee = 54%) in THF/H₂O (H₂O vol % = 25.0 vol %). After the one‐handed helical structure of poly(PA‐P) was destroyed by grinding treatment, the ee of the reaction clearly decreased from 99 to 49%. These indicate that the one‐handed helical structure of poly(PA‐P) played an important role in the high enantioselectivity of the asymmetric aldol reactions in the aqueous media. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1024–1031