A series of“hairy-rod”polyimides,BBPA（n）,with multiple alkyl side chains was prepared from 3,3’,4,4’-biphenyltetracarboxylic dianhydride（BPDA）and 4,4’-biphenyldiamine substituted in the 2,2’-positions with benzoate,whichwas substituted in the 3,4,5-positions with ether side chains of varying lengths.The number of the methylene units,n,inthese alkyl side chains were in even numbers ranging from 8 to 18.Combining techniques of one-dimensional（1D）and 2Dwide angle x-ray diffraction,1D small angle X-ray scattering,differential scanning calorimetry experiments,it was found thatthis series of“hairy-rod”polyimides possess a micro-phase separation between the backbones and side chains.This led to theformation of ordered structures in two different length scales,of which both are hexagonal packing:one is attributed to thealkyl side chains on the sub-nanometer scale,and another is for the whole polymer chains on the nanometer scale.Thedevelopment of the hexagonal structure on the sub-nanometer scale was critically dependent upon the lengths of the alkylside chains.Three relaxation processes were captured by dynamic mechanical analysis,i.e.,segmental motion of thebackbones,α,the melting of the side chain crystals,β;,which exits only for the materials with longer side chains（n=18,16）;and the subglass relaxation of side chains,β;.The peak relaxation temperature of the αprocess decreased withincreasing the length of side chains,while the one of the β;process increased.The activation energy of the αrelaxation wasrelatively independent on the length of side chain,whereas,β;process showed the increasing of activation energy withincreasing the length of side chains.
