A series of poly(n-alkyl-acrylate)s (PAAn) and poly(octadecyl acrylate-co-n-alkyl acrylate)s (P(AA18-co-AAn)) (n

the side chain carbon number) were synthesized with AIBN as initiator at 60℃ for 24 h in nitrogen atmosphere.The molecular weight of the polymers and the polymer dispersity index were measured with gel permeation chromatography (GPC).The thermal behaviors of PAAn and P(AA18-co-AAn) were studied by differential scanning calorimetry (DSC).The results manifest that，for homopolymers

there is a gradual increase of fusion heats and melting points with the side-chain carbon number ranging from 10 to 20

because more units of methylene enter into the crystal lattice for PAAn with longer side chains length.At the same time

the melting endothermal peak of PAAn was not detected in DSC running as the n was less than 10

which meant that 10 was the critical side chain carbon number for the discrimination of crystallizable and non-crystallizable PAAn.For copolymers of AA18 with crystalline homologous AAn (n=10

12

14

16) series

the crystallinity (Xc) of copolymers was between the values of the corresponding homopolymers

and it increased with increasing the content of AA18

and the corresponding melting ranges had a maximum value at certain AA18 content.The value of extent of equilibrium crystallinity (Xc/Xcmax) of P(AA18-co-AA14) and P(AA18-co-AA16) changes little with increasing content of AA18

because the side chain carbon number of monomers has little difference and the affection of the other side chain is small.While the Xc/Xcmax of P(AA18-co-AA10) and P(AA18-co-AA12) increases at first and then decreases.The more difference of side chain carbon numbers (18/12

18/10) led to the interactional disturbing effect

and many defects would occur during crystallization.At the same time

the shorter side chain length of AA10 and AA12 decreased the crystallizing ability obviously resulting in much less Xc.For the copolymers of AA18 with non-crystalline homologous AAn (n=4

6

8) series

both Xc and Xcmax increased with increasing content of AA18

since AA18 was the only crystallizable component.With increasing the side chain carbon number of non-crystalline homologous AAn series (n=4

6

8) of the same AA18 mole fraction

the values of Xc/Xcmax decreased

while the maximum values of melting range almost kept constant.