Abstract: Secondary doping by m-cresol in polyaniline composite, which was prepared by insitu emulsion po1ymerization technique and cast from solution, was studied by UV-Vis-NIR,ESR, WAXDand so on.The po1yaniline content of the composite used in the present studyis 11.0% (wt).After secondary doping and then dedoping the composite showed a new ab-sorbance at 580～800 nm, which directly demonstrated the increase of conjugation lengththrough expanding polyaniline backbone.The difference of absorbance intensity at 600～800nm implies that polyaniline backbone can expand more completely in CSPEmatrix than inSBS.The results from ESRin situ measurement show two kinds of interaction between thecarriers of conductive backbone: after secondary doping, ESRintensity of PAn/CSPEmarkedly decreased and aΔH_pp kept constant, which indicates that secondary doping inducedipolaron: secondary doping enhanced a ΔH_pp of PAn/SBSfrom 3.O× 10^-4 Tto 5.6 × 10^-4 Tbut the intensity of ESRdid not markedly change, which means that secondary dopingcaused spin-spin interaction of polarons between conductive backbone.The results above canbe explained by phase structure of composite caused by compatibility between polyaniline andmatrix.It was found from WAXDof the composite after secondary doping that PAn/SBShad longer-range order crystal peak at 2.4.(2θ) whereas PAn/CSPEhad not.SEMwas alsotaken for composites.The results supported the difference between two kinds of compositein phase structure-

Key words: Secondary doping, Polyaniline, Composite, Matrix effect