学科分类
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4 个结果
  • 简介:Poly(aryleneetherdiketone)swerepreparedbythearomaticnucleophilicdisplacementreactionof4,4’-difluorobenzilwithdifferentbisphenolsinthepresenceofan-hydrouspotassiumcarbonateindiphenylsulfoneatelevatedtemperature.Thepolymersobtainedhadinherentviscosityof0.51~0.63dL/g,andexhibitedglasstransitiontemper-aturerangingfrom136~217℃mainlydependingonthebisphenolsusedinthepolymersynthesis.Thermogravimetryofthesepolymersshowedexcellentthermalstability,indi-catingthat10%weightlossesofthepolymerswereobservedintherangeabove428℃and438℃inairandnitrogen,respectively.ThemechanicalpropertiesofthesepolymerswerealsodescribedandthepermeabilityoffivepolymersforH2,O2andN2wasdeterminedat30℃.

  • 标签: Poly(arylene ETHER diketone) Thermal BEHAVIOR High-temperature
  • 简介:Baker'syeastmediatedreductionofopticallyactivediketoneisdescribed.Thetwoketogroupsareefficientlydifferentiatedandtheeevalueoftherecoveredmaterialisconsiderablyraised.Itaffordshighlyopticallyactivekeyintermediatesefficientlyforthesynthesisofnaturalpolyhydroxylatedagarofuranproducts.

  • 标签: 酵母 沉香呋喃 倍半萜 简化
  • 简介:Anewtypeofβ-diketonebasedsidechainliquidcrystallinepolysiloxanes(DKLCP)withdifferentlengthofflexiblespacersandendgroupshavebeensynthesizedbyhydrosilationreaction.Thisisliquidcrystalpolymers(LCP)usingcoordinatingβ-diketoneligandasmesogens.ThephasebehaviourofDKLCPpolymerswasstudiedbydifferentialscanningcalorimetryandpolarizingmicroscopy.X-raydiffractioninvestigationsdemonstratedthatthepolysiloxaneswithsufficientlylongflexiblespacersweresmecticliquidcrystalpolymers,whilethosewithmuchshorterspacerswerenematicones.

  • 标签: Β-DIKETONE BASED SIDE CHAIN liquid crystal
  • 简介:Anewtypeofpalladiumchelateofβ-diketone-basedsidechainliquidcrystalpolysiloxane(Pd-DKLCP)hasbeensynthesizedbychelationreactionofpalladiumdichloridewithpolymericligand,β-diketonepolysiloxane(DKLCP),usingTHFassolventatR.T..ThePd-chelationresultsingreatlyincreasingthephasetransitiontemperatureTKandtheenthalpychange△HKfromcrystaltoliquidcrystalstateandmakingthetemperaturerangeofLCstate△T(△T=TCl-TK)widened.AllthesechelatesPd-DKLCP’sdonotshowTCluntildecompositionat205℃.ItisnoteworthythatthePd-chelationcanexertmorepositiveeffectonthemesomorphicbehaviourofthepolymerligandthanthecounterpartCu-DKLCPdoes.Itisprobableduetothebiggersizeofdisc-likemesogenformedfromβ-diketoneandPd+2ionwith4dorbital.

  • 标签: Β-DIKETONE PALLADIUM CHELATE Metal-coordinating liquid crystal