简介:Thisworkdealswiththekineticsofco-condensationpolymerizationofAB2andABmonomers,givingexpressionsofthetwo-dimensionalmolecularweightdistributionfunctionandthenumber/weightaveragemolecularweightsoftheresultingcopolymers.Thetwo-dimensionalmolecularweightdistributiondependsontwoindices,nandl,whicharetherespectivenumbersofAB2andABunitsinacopolymerspecies.Theevolutionofthetwo-dimensionalweightandzdistributionsduringtheco-condensationpolymerizationhasbeenevaluatedsystematically.Finally,thetwo-dimensionaldistributionwastransformedintoaone-dimensionalmolecularweightdistributionwithonlyonevariable(themolecularweightoftheproductsinsteadofthedegreeofpolymerization).Thecalculatedresultsshowthatthehighlybranchedcopolymerhasaverybroadmolecularweightdistributionwhentheco-condensationpolymerizationapproachescompletion.
简介:Theeffectofthehot-chargingtreatmentontheperformanceofAB2andAB5hydrogenstoragealloyelectrodeswasinvestigated.Theresultshowedthatthetreatmentcanmarkedlyimprovethevoltageplateauratio(VPR),thehighratedischargeability(HRDA),thediffusioncoefficientofhydrogenDHandthedischargecapacityoftheAB2hydrogenstoragealloyelectrode.TheSEManalysisshowedthatthehot-chargingtreatmentbringsaboutaNi-richsurfaceduetothedissolutionofZroxides.ItisalsoveryhelpfulfortheimprovementofthekineticpropertiesofAB2hydrogenstoragealloyelectrodebecausethemicrocrackingo.fthesurfaceresultsinfreshsurface.ThiscanbethebasicmodificationtreatmentforNiMHbatteryusedinelectricvehicles(EVs)inthefuture.ButforAB5typealloys,thetreatmenthasthedisadvantageofimpairingthecomprehensiveelectrochemicalproperties,becausethesurfaceofthealloymaybecorrodedduringthetreatment.Themechanismofthesurfacemodificationoftheelectrodeisalsoproposed.
简介:ThereactionofsingletoxygenwithethylenehasbeenstudiedattheabinitiolevelwithbothHF/3-21GandHF/6-31Gbasissets,fullyoptimizingthegeometriesofthecriticalpoints.Thetransitionstateleadingtotheintermediateperoxiranefromtheinitialreactantsisfound,Iocatedat81.71kJ/molabovethedissociationlimit.Thevibrationalanalysisisdonewithtwobasissets.Fromtheresultsitcanbeseenthatthefrequencieshavenotbeenmadeanimprovementobviouslywithaugmented6-31Gcomparedto3-21Gbasis;itfollowsthatmainreasonfortoohighHF/3-21Gfrequencycouldmainlybethevibrationalanharmonicity.TheeigenvectorcorrespondingtothesingleimaginaryvibrationalfrequencyisdominatedbythelargerO-Odistance.Thefindingofthetransitionstateconfirmsthattheperoxiraneminimumcanbereachablepassingthroughaperoxirane-likesaddlepoint.Inaddition,themechanismsofthereactionformingoxiranearediscussedaswell.
简介:Sphere-likecompoundC8H17Si(OPhC12H25)3N(1)formsmesophases.Inordertoinvestigatetherelationshipbetweenmolecularstructureandliquidcrystalproperties,structuralstudiesarecarriedoutonthemodelmoleculesofcompound1anditssubstitutedderivativesusingahinitiocalculations.TheresultsshowthatthecyanoorchlorosubstitutedtribenzosilatranecompoundsR1Si(OPhR2)3N(R1R2=CNorCl)havemuchbiggerdipolemomentsoranisotropyofpolarizabilityandmorelikespherethanthecorrespondingalkylsubstitutedcompounds.Cyanoorchlorosubstitutedtribenzosilatraneswouldbebettercandidatesforsphere-likemeso-gens.