Substrate Effect on the Melting Temperature of Thin Polyethylene Films

Abstract

Strong dependence of the crystal orientation, morphology, and melting temperature (Tm) on the substrate is observed in the semicrystalline polyethylene thin films. The Tm decreases with the film thickness decrease when the film is thinner than a certain critical thickness, and the magnitude of the depression increases with increasing surface interaction. We attribute the large Tm depression to the decrease in the overall free energy on melting, which is caused by the substrate attraction force to the chains that competes against the interchain force which drives the chains to crystallization.

Lamellar orientation of polyamide 6 thin film crystallization on solid substrates

“…For the film with the thickness approaching the radius of gyration of polymer M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 4 chains, flat-on lamellae are usually observed. This film thickness dependence of lamellar orientation is widely encountered in many polymer systems [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. For example, Schönherret et al have found that for poly(ethylene oxide) thin films on the oxidized silicon substrate lamellae are oriented edge-on when the films are thicker than 1 µm, while in the films thinner than 300 nm lamellae are preferentially flat-on [9].…”

Electrospun polymer nanofibers: Mechanical and thermodynamic perspectives

“…Mechanistic models have attributed such behavior, for both two-dimensional and one-dimensional nanosystems, to surface effects. 19,[60][61][62][63] Although surface phenomena clearly play a role in the final properties of materials of reduced sizes, detailed analyses shows that surface effect alone cannot adequately explain the experimental observations. In the following sections, we first review the mechanical properties of several electrospun fibers and describe the related testing methods.…”

“…Experimental studies have demonstrated the effect of size on the mechanical and thermodynamic properties of nano-objects, as seen with the elastic moduli of hollow fibers 9 and electrospun nanofibers, [10][11][12][13][14] which sharply increase below a certain fiber diameter, as well as shifts in object melting temperatures. 15,16 Similarly, thickness and surface interactions of ultrathin polymer films (the film thickness is in the order of 2R g of a polymer chain, or less) highly influence their glass transition and melting temperatures, [17][18][19] polymer dynamics in the glassy state, 20 crystallization kinetics and degree of crystallinity, [21][22][23] phase behavior, 24 and morphology. 25,26 For all the above examples, the portion of ''surface material'' is comparable with the bulk, due to extremely small object size, therefore, the ansatz claiming ''nano-object ¼ bulk þ surface'' seems relevant for such systems from a physical point of view.…”

Electric field enhanced sample preparation for synthetic polymer MALDI-TOF mass spectrometry via Induction Based Fluidics (IBF)

“…The substrate effect has been known to change morphology and T m of polymers based upon the affinity of the polymer to substrate [41]. This effect was considered when taking crosspolarization images on both glass and steel.…”