查看更多>>摘要：The phase separation processes of various ther-moplastics-modified thermosetting systems which show upper critical solution temperature (UCST) or lower crit-ical solution temperature (LCST) were studied with emphasis on the temperature dependency of the phase separation times. It was found that the phase separation time-temperature relationship follows the Arrhenius equation. The cure-induced phase separation activation energy Ea(ps) generated from the equation is independent of the method used to measure phase separation time. In our experimental ranges it is found that Ea (ps) is inde-pendent of the thermoplastic (TP) content,TP molecular weight and curing rate but it varies with the cure reaction kinetics and the chemical environments of the systems.
查看更多>>摘要：The H-shaped block copolymers (PTMSPMA)2-PEG(PMPSTMSPMA)2 with two compositions, (EG)91-b-(TMSPMA)92 and (EG)455-b-(TMSPMA)176 have been successfully synthesized by atom transfer radical polymer-ization (ATRP) of tri(methoxylsilyl)propyl methacrylate (TMSPMA) at room temperature in methanol. The ini-tiation system applied was composed of 2,2-bis(methylene α-bromoisobutyrate)propionyl terminated poly(ethylene glycol) (Br2PEGBr2) with Mn= 4000 or 20000, CuBr and 2,2'-bipyridine. The macroinitiator, Br2PEGBr2, was pre-pared by the reaction of two hydroxyl groups terminated PEG with 2,2-bis(methylene α-bromoisobutyrate)propionyl chloride. The NMR spectroscopy and GPC measurements were used to characterize the structure and molecular weight and molecular weight distribution of the resultant copolymers. The H-shaped block copolymers Sam 1 and Sam 2 were self-assembled in DMF/water mixtures and then the trimethoxysilyl groups in PTMSPMA were cross-linked by condensation reaction in the presence of triethylamine. Stable large-compound vesicles with 10 nm diameter of cavities were formed for Sam 1 which contains a short PEG chain. However, the self-assembling of the Sam 2 in the selective solvents resulted in big vesicles aggre-gates. These two different morphologies of aggregates are attributed to their relative chain length of water soluble PEG. The vesicles formed from Saml with short PEG chains have big surface energy which will lead them to self-assemble further, forming large-compound vesicles.
查看更多>>摘要：The synthesis of α-amino-β-keto-esters (β-oxo dipeptides) was studied. Corresponding α-amino-β-keto-esters were prepared from BOC-(L)-Valine and BOC-(L)-isoleucine by coupling with (D,L)-threonine hydro-chloride and oxidation with Dess-Martin periodinane (DMP) with a total yield of 48% and 38%, respectively.
查看更多>>摘要：The partial molar volumes of components in supercritical ammonia synthesis system are calculated in detail by the calculation formula of partial molar volume derived from the R-K equation of state under different conditions. The objectives are to comprehend phase beha-vior of components and to provide the theoretic explana-tion and guidance for probing novel processes of ammonia synthesis under supercritical conditions. The conditions of calculation are H2/N2= 3, at a concentra-tion of NH3 in synthesis gas ranging from 2% to 15%, Concentration of medium in supercritical ammonia syn-thesis system ranging from 20% to 50%, temperature ran-ging from 243 K to 699 K and pressure ranging from 0.1 MPa to 187 MPa. The results show that the ammonia synthesis system can reach supercritical state by adding a suitable supercritical medium and then controlling the reaction conditions. It is helpful for the supercritical ammonia synthesis that medium reaches supercritical state under the conditions of the corresponding total pres-sure and components near the normal temperature or near the critical temperature of medium or in the range of tem-perature of industrialized ammonia synthesis.
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