A new cationic polyelectrolyte has been synthesized by the modification of polyacrylamide (PAm) with formaldehyde (F) and dicyanodiamide (D). Methylol polyacrylamide (PAm·M) was first formed by the reaction of PAm with F in basic medium

then the cationic polyacrylamide (PAm·MG) was formed by the further reaction of PAm·M with D. Products of various content of methylol group or cationic group could be obtained by controlling the molar ratio of F. The structure and composition of both PAm·M and PAm·MG were identified by IR spec-trum and elementary analysis. The content of methylol group in PAm·M was examined by iodometry. The charge density of PAm·MG was determined by conductometric titration and turbidimetric titration

and Mw by small angle laser light scattering method.