The linear increment of the absorbance may suggest
that the polymers are uniformly adsorbed on silk surface via
the electrostatic interaction between the ternary ammonium
group [AN+A] of PDDA and the acrylic acid group [ACOO] of PAA. SEM was also conducted to check surface morphologies of silk
fibers modified with 2, 4, 6 and 8 bilayers of PAA/PDDA films