Kinetics and morphology of crystallization in supported polymeric films (thickness from 10 nm up to 0.250 mm) of poly(ethylene terephthalate) (PET) have been investigated by dielectric spectroscopy, infrared spectroscopy (FTIR, ATR, RAIR,XRD) and Atomic Force Microscopy (AFM). Different morphological properties of crystallites have been found for crystallization obtained at different temperatures and for films with different thickness and with different substrates . By means of AFM techniques, the crystallization kinetics located at the free surface (air/polymer) were monitored, by estimating the time evolution of the crystalline over the amorphous surface. The presence of crystalline regions on the surface of polymeric films can be revealed, besides by the AFM topography that can keep track of the formation of crystallites, also by different scanning probe techniques, among which the most promising are those able to track the viscoelastic properties: indeed a very different modulus and mechanical loss tangent are associated, above the temperature of glass transition, to the crystalline fraction compared to the amorphous one . For thick samples, the kinetics at the free surface was found much faster than within the bulk, the last one measured by RAIR, XRD and dielectric technique. Reducing the thickness, as the free surface approached the substrate, the crystallization kinetics probed by AFM technique became slower and slower, already for film of some hundreds on nm thick. This effect was more relevant for strongly interacting substrates, up to prevent crystallization in very thin films. Finally, the crystallization kinetics measured through AFM was compared and found similar to that from ATR investigation, which is also a techniques more related to the superficial layer of the film
Effect of Free Surface and Substrate Interaction on the Crystallization of PET Ultrathin Films
Labardi M;Prevosto D;
2009
Abstract
Kinetics and morphology of crystallization in supported polymeric films (thickness from 10 nm up to 0.250 mm) of poly(ethylene terephthalate) (PET) have been investigated by dielectric spectroscopy, infrared spectroscopy (FTIR, ATR, RAIR,XRD) and Atomic Force Microscopy (AFM). Different morphological properties of crystallites have been found for crystallization obtained at different temperatures and for films with different thickness and with different substrates . By means of AFM techniques, the crystallization kinetics located at the free surface (air/polymer) were monitored, by estimating the time evolution of the crystalline over the amorphous surface. The presence of crystalline regions on the surface of polymeric films can be revealed, besides by the AFM topography that can keep track of the formation of crystallites, also by different scanning probe techniques, among which the most promising are those able to track the viscoelastic properties: indeed a very different modulus and mechanical loss tangent are associated, above the temperature of glass transition, to the crystalline fraction compared to the amorphous one . For thick samples, the kinetics at the free surface was found much faster than within the bulk, the last one measured by RAIR, XRD and dielectric technique. Reducing the thickness, as the free surface approached the substrate, the crystallization kinetics probed by AFM technique became slower and slower, already for film of some hundreds on nm thick. This effect was more relevant for strongly interacting substrates, up to prevent crystallization in very thin films. Finally, the crystallization kinetics measured through AFM was compared and found similar to that from ATR investigation, which is also a techniques more related to the superficial layer of the filmI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
