Abstract:The two blocks of a polystyrene-block-poly(2-cinnamoylethyl methacrylate), PS-b-PCEMA, sample, with 1.25 Â 10 3 styrene and 158 CEMA units, segregate in bulk films. PCEMA forms cylinders that disperse in the continuous matrix of PS when annealed at 110 AE 28C. UV photolysis cross-linked the PCEMA cylinders. Separating the cross-linked PCEMA cylinders by dissolving PS in toluene or THF yielded isolated nanofibers with PCEMA core and PS shell. Light scattering studies in toluene or chloroform revealed that the nanofibers were wormlike with a persistence length of $ 400 nm, a molar mass exceeding 10 10 g mol
À1, and a radius of $ 43 nm. The nanofibers formed lyotropic liquid crystalline phases in bromoform and the order ± disorder transition temperature of the liquid crystals increased with nanofiber concentration.
The wave functions and enthalpies of formation of the ground states of iodomethanes CH 4 3x I x and iodomethyl radicals CH 3 3x I x . (x = 133) were calculated ab initio with regard to electron correlation. The geometries of the molecules of these compounds were determined, as well as the normal mode frequencies and other parameters, which were used for calculating the thermodynamic functions in the 031500 K range.These functions were used for calculating the constants of the CH 4 3x I x 76 47 CH 4 3x I x 31 + I and CH 4 3x I x + I 76 47 CH 4 3x I x 31 + I 2 equilibria, which, in turn, were used for calculating the corresponding rate constants in the high concentration limit.Studies of gas-phase pyrolysis of alkyl halides have been successfully used in developing fundamentals of chemical kinetics for almost a century [1,2]. The key reactions for the alkyl halides being pyrolyzed are those between (halo)alkyl radical and atomic hydrogen: R . + H . 76 RH, halogen: R . + Hlg . 76 RHlg, or hydrogen halide molecules: R . + HHlg 76 RH + Hlg . , Hlg = Cl, Br, I.Hence, these pyrolytic experiments furnish kinetic and thermochemical information about free radicals [336]. For the last-named reactions (CH 3 . + HI, CH 3 . + HBr, C 2 H 5 . + HBr, CH 2 Br . + HI...), peculiar phenomenon of a negative activation energy was recently discovered [739], whose nature still remains to be elucidated [10313]. Accurate thermodynamic and kinetic parameters of chloro-, bromo-, and iodoalkanes and their corresponding radicals are also essential for solving less fundamental but practically vital problems, such as, e.g., simulation of the Earth ozone layer depletion or modeling of incineration of halogencontaining waste.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.