Poly(ethylene oxide) (PEO) with different molecular weight (PEO10k

PEO4k

PEO2k) was modified by octadecyl end groups.The end group tethering density on the folding surface was tuned by changing the molecular weight of PEO.The crystallization and melting behavior of modified PEO were studied by differential scanning calorimetry (DSC)

polarized optical microscopy (POM) and atomic force microscopy (AFM).DSC results show that the PEOs tend to form nonintegral-folding (NIF) crystals after end-group modification.For PEO with molecular weight of 104

octadecyl end groups significantly hinder the nucleation of PEO and cause a slight increase of free energy of folding surface.However

it has very little effect on the equilibrium melting temperature.For PEO4k and PEO2k after end-group modification

the equilibrium melting temperatures greatly depressed.The octadecyl end group hampers the transformation of PEO4k IF(1) crystal to IF(0) crystal.In situ AFM observation shows the stability of PEO2k NIF crystals increases greatly and the chain length arranged in the IF(0) crystal is also shortened after introducing the octadecyl end groups.The thickening of lamellae will increase the tethering density of octadecyl end groups on the lamella surface

while the tendency of the octadecyl chains to adopt maximum conformation entropy requests the tethering density to be decreased.The competition between these two processes leads to the above changes of crystallization and melting behaviors.