Polymeric fibers and microporous films by photo‐crosslinking of triphenylene‐derived liquid crystals

Two series of photoreactive discotic liquid crystals consisting of a triphenylene core and six cinnamate units with one ( TPC1 _n ) or two ( TPC2 _n ) n‐alkoxy groups (C _nH_2n+1O; n = 10–14), respectively, as peripheral groups are synthesized. Both of them are polymerized into fibers up to 2 mm long by UV irradiation in liquid paraffin in the columnar LC temperature ranges. The fiber structures seem to be preconstructed in liquid paraffin. In addition, TPC2 _n are shown to form microporous films up to 15 μm in diameter by simply casting the solutions of some solvents followed by drying for several minutes in air at room temperature. Photoirradiation of the films in the LC temperature range converts them to polymeric ones while preserving the microporous and hexagonally ordered structure. From comparison with TPC1 _n and the hydrogenated derivative of TPC2 ₁₂ , the porous film‐forming property is suggested to result from the combination of the double bond of the cinnamoyl group and the two long alkoxy chains on the phenyl ring. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 605–612     

Direct synthesis of radioactive carbon labeled fullerences using nuclear reactions

The¹¹C and¹⁴C labeled fullerenes were produced by charged-particle and neutron irradiation, of C₆₀, C₇₀ and their mixture. It was found that a carbon atom of fullerence can be easily exchanged with a radioactive carbon atom produced by a nuclear reaction. The HPLC method was effective for identification and purification of various labeled fullerene families as chemically stable compounds. The radiochemically interesting aspect of the results is not only the production of¹¹C and¹⁴C labeled fullerenes but also the formation of radioactive higher fullerenes which can be simultaneously produced with high yield and in carrier-free form.     

Interaction between charged soft microcapsules and red blood cells: effects of PEGylation of microcapsule membranes upon their surface properties

Four types of hydrophilic gel microcapsules containing water have been prepared by an interfacial polymerization method. Each type of microcapsules has a membrane of different composition. Using three kinds of monomers, N,N-dimethylacrylamide (DMAAm), 4-(aminomethyl)styrene (AmSt), and N,N-dimethylaminopropylacrylamide (DMAPAA), one type of aqueous copolymer having primary and tertiary amino groups was obtained. By the polymerization of three kinds of monomers, DMAAm, AmSt, and 2-[(methacryloyloxy)ethyl] trimethylammoniumchloride (METAC), another type of aqueous copolymer having primary and quaternary ammonium groups was also obtained. Two more types of copolymers were synthesized by copolymerization of -acryloxy-ω-methoxy-poly(ethylene glycol) (a-PEG) with the above two kinds of monomer mixture. These copolymers were polymerized with terephthaloyldichloride at the water/oil interface to prepare four types of microcapsules containing water, i.e., poly(DMAAm-co-DMAPAA-co-AmSt-alt-terephthalic acid) microcapsules, poly(DMAAm-co-DMAPAA-co-AmSt-co-PEG-alt-terephthalic acid) microcapsules, poly (DMAAm-co-METAC-co-AmSt-alt-terephthalic acid) microcapsules, and poly (DMAAm-co-METAC-co-AmSt-co-PEG-alt-terephthalic acid) microcapsules, which will be abbreviated to MC 1, MC 2, MC 3, and MC 4, respectively. It has been predicted that the microcapsule membranes are hydrophilic and soft and have two-sublayer structures from electrophoretic mobility measurements and from the analysis of the data with Ohshima’s electrokinetic theory for soft particles. The outer sublayers of MC 1 and MC 2 are negatively charged and those of MC 3 and 4 are slightly positively charged. Also, the surfaces of MC 1 and MC 2 are harder than those of MC 3 and 4. By PEGylation, the surface charge density in the membranes decreases and the surface becomes softer. It has been found that the membrane of red blood cells (RBC) is also soft and is composed of two-sublayers, the outer sublayer of which is negatively charged and the inner one is positively charged. The interaction of four types of microcapsules with RBC has been studied. It was found that microcapsules with soft surfaces (MC 3 and MC 4) do not interact with RBC, even though the microcapsule surfaces are positively charged and the surface of RBC is negatively charged. On the other hand, microcapsules with negatively charged but harder surfaces (MC 1) interact with RBC to introduce hemolysis. The membrane surface of MC 2, which is obtained by PEGylation of MC 1, becomes softer than that of MC 1 so that the interaction with RBC was weakly suppressed. From these, it was concluded that the dominant factor to control the interaction between synthetic polymer surfaces and biological cell surfaces is not the surface charges carried by the polymer surfaces but the softness of the polymer surfaces.     

Study of protein fluctuation with an effective inter-Cα atomic potential derived from average distances between amino acids in proteins

The conformational dynamics around the native structure of bovine pancreatic trypsin inhibitor (BPTI) in both the oxidized and reduced forms was analyzed by a Monte Carlo method using an approximate residue–residue potential derived from the statistics of average distances between C^α atoms of residues as proposed by the present author (T. Kikuchi, J Comput Chem 1996, 17, 226–237). The results from using this effective potential are similar to those from molecular dynamics simulations, taking all atoms into account, and are consistent with temperature factors from an X-ray analysis and disulfide formation from a kinetic experiment. This agreement suggests that the essential nature of the potential energy surface formed by the potential around the native structure closely mimics the actual energy landscape within the resolution of C^α atomic fluctuation. Furthermore, it is expected that the potential we found can describe the basic properties of folding kinetics. Examination of the fluctuation property of the native structure of BPTI threaded by a sequence from cytochrome b562 reveals differences specific to the sequence and this result also shows that the dynamical properties obtained in our calculations are not only ascribed to the geometrical constraints of the initial conformation but also the force field specifically produced by a sequence. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 713–719, 1999     

Nucleophilic Addition of Telluroxides to a Cationic Ditelluroxane: Oligotelluroxanes

Tellurane oligomers with oxo bridges, namely, the oligotelluroxanes 3 , were prepared from the cationic ditelluroxane 1 and the telluroxide 2 . The reactivity of 3 depends on the cationic character of the terminal telluronium group, and decreases with increasing chain length. Hence the degree of oligomerization can be selectively controlled by means of the ratio of the starting materials 1 and 2 .     

Ab initio GB study of chemical intermediates in solution; Ethylenesulfonium ion in hydrolysis of 2-chloroethyl methyl sulfide

Ab initio MO theory including solvent effects has been applied to the structure and reactivity of methyl ethylenesulfonium ion, 1 , in aqueous solution as a model of the three-membered cyclic sulfonium intermediate expected in the toxic action of sulfur mustard. The 6-31 + G* geometry optimization of the cyclic sulfonium ion 1 suggested that the ring size of 1 is expanded slightly by solvation. The contour lines map of the interaction energy between 1 and Cl⁻ has a very shallow and wide well at 5–6 Å distance from 1 . This is the solvent-separated ion pair, and the contact ion pair was not found between 1 and Cl⁻. The calculated energy diagrams for the S_N2-type reactions of 1 with Cl⁻, H₂O, and OH⁻ that give ring-opened compounds indicated the following: (1) The energy of the 1 + Cl⁻ system is similar to that of chloroethyl methyl sulfide (CEMS, 2 ), and the interconversion between 1 + Cl⁻ and 2 occurs easily in aqueous solution. The 3-21 + G(*) and 6-31 + G* activation energies for the 2 → 1 + Cl⁻ reaction, 20–22 kcal/mol, agree well with the experimental enthalpy of activation for the hydrolysis of 2 . (2) The reaction of 1 with OH⁻ gives a very stable hydroxyl compound, 4 , and no transition state was found. (3) The reaction of 1 with H₂O gives an unstable addition product that is expected to be converted to 4 with the assistance of another H₂O molecule. This mechanism is consistent with that proposed by Bartlett and Swain in their pioneering work on the hydrolysis of sulfur mustard. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:503–510, 1998