The effects of interfacial interactions on lamellar morphologies in thin and ultrathin films and nanocomposites of LLDPE

The transition from edge-on to flat-on morphology under confinement in spin-cast pristine and carbon nanofiber (CNF) or nanoclay (NC) filled linear low-density polyethylene thin films is investigated with emphasis on the surface interaction component. The morphology transition is observed by scanning probe microscopy and is linked to melting point depression and shear modulus decrease at the corresponding transition. A thermodynamic model, based on Gibbs’ free energy of crystallization according to Hoffman’s crystallization theory, is proposed to account for these phenomena. Particularly, the model can predict the confined film thickness at the morphology transition and, in part, the extent of melting point downshifting.