简介：Aseriesof'hairy-rod'polyimides,BBPA(n),withmultiplealkylsidechainswaspreparedfrom3,3′,4,4′biphenyltetracarboxylicdianhydride(BPDA)and4,4′-biphenyldiaminesubstitutedinthe2,2′-positionswithbenzoate,whichwassubstitutedinthe3,4,5-positionswithethersidechainsofvaryinglengths.Thenumberofthemethyleneunits,n,inthesealkylsidechainswereinevennumbersrangingfrom8to18.Combiningtechniquesofone-dimensional(1D)and2Dwideanglex-raydiffraction,1DsmallangleX-rayscattering,differentialscanningcalorimetryexperiments,itwasfoundthatthisseriesof'hairy-rod'polyimidespossessamicro-phaseseparationbetweenthebackbonesandsidechains.Thisledtotheformationoforderedstructuresintwodifferentlengthscales,ofwhichbotharehexagonalpacking:oneisattributedtothealkylsidechainsonthesub-nanometerscale,andanotherisforthewholepolymerchainsonthenanometerscale.Thedevelopmentofthehexagonalstructureonthesub-nanometerscalewascriticallydependentuponthelengthsofthealkylsidechains.Threerelaxationprocesseswerecapturedbydynamicmechanicalanalysis,i.e.,segmentalmotionofthebackbones,α,themeltingofthesidechaincrystals,β1,whichexitsonlyforthematerialswithlongersidechains(n=18,16);andthesubglassrelaxationofsidechains,β2.Thepeakrelaxationtemperatureoftheαprocessdecreasedwithincreasingthelengthofsidechains,whiletheoneoftheβ2processincreased.Theactivationenergyoftheαrelaxationwasrelativelyindependentonthelengthofsidechain,whereas,β2processshowedtheincreasingofactivationenergywithincreasingthelengthofsidechains.