AFM-tip-induced crystallization of poly(ethylene oxide) melt droplets

Abstract

The AFM-tip-induced crystallization of poly(ethylene oxide) (PEO) melt droplets was studied. The melt droplets with a height of 50 100 nm and a lateral size of 2 3 ?m were obtained by melting the PEO ultra-thin films on a mica surface. For the PEO samples with average molecular weights (M_n) ranging from 1.0?10³ g/mol to 1.0?10⁴ g/mol, the lateral perturbation from the AFM tip in the hard-tapping or nanoscratch modes could not induce the growth of the flaton lamellae. In contrast, under AFM nanoindentation mode, the tip-induced crystallization occurred when a sufficiently high vertical tip force was applied to the melt droplets of PEO with M_n"e1.0?10⁴ g/mol. Moreover, the experimental results indicated that the AFM-tip-induced crystallization of PEO in the nanoindentation process had molecular weight dependence.