N-octadecylated polyethyleneimine (PEI18C) comb-like polymers with different substitution degrees (DS) ranging from 47%~17.6% have been successfully fabricated through alkylation technique.The structure

crystallization behavior and thermal stability of PEI18C comb-like polymers with different DS had been systemically characterized by Fourier transform infrared spectroscopy (FTIR)

differential scanning calorimetry (DSC)

wide-angle X-ray diffraction (WAXD) and thermogravimetric analysis (TGA)

and also the effect of DS on the side-chain crystallization and the critical crystallization phenomenon of C18 side groups grafted along PEI backbone were also deeply investigated.The results show that the degree of crystallinity and the number of crystallizable carbon atoms in the C18 side chains of PEI18C comb-like polymers decreased from 54% to 20.3%

and from 11.4 to 4.3

respectively

with the DS decreasing from 47% to 17.6%.In the meantime

the packing mode of confined C18 side groups along PEI molecules display the same manner regardless of the variation of DS

and C18 side groups also take the hexagonally packed structure.The results further demonstrated that the degree of substitution of side alkyl groups or the dispersion density of side groups along polymeric backbones also acts as an important role in the aspect of controlling the side-chain crystallization and the critical crystallization behavior of comb-like polymer

besides the lengthscale of side alkyl chains and the rigidity of polymeric main chains.And

the crystallization behavior and thermal stability of comb-like polymers with different DS are further discussed from the viewpoint of side-chain crystallization.