The structure and adsorption characteristics of a lignin-type superplasticizer (GCL1-JB).GCL1-JB was prepared by graft sulfonation of alkali lignin from bamboo pulp black liquor and purified by ultrafilter and ion exchange resin.Four GCL1-JB fractions with narrow molecular weight distribution were obtained from gel column chromatography separation and selected to study the structural and adsorption characteristics.Results showed that GCL1-JB had structure features of both high molecular weight and a high degree of sulfonation.The four GCL1-JB fractions had no obvious difference in chemical structure

but with increasing molecular weight

the content of sulfonate groups decreased and the content of aromatic groups increased.Four GCL1-JB fractions were used as polyanions to build up multilayer films on planar substrate by using poly-(diallydimethylammonium chloride) (PDAC) as the polycation.The surfaces of GCL1-JB/PDAC layer-by-layer self-assembled films were generally flat

and their surface roughness was about 1~2 nm.The GCL1-JB with higher molecular weight had a larger adsorbed amount.This phenomenon could be explained in this way.The GCL1-JB with higher molecular weight had a less content of sulfonate groups

inducing less electrostatic repulsion.Therefore

the GCL1-JB with higher molecular weight had larger molecular curling

which caused a larger adsorbed amount.