Differential pressure experiment to probe hole growth in freely standing polymer films
نویسندگان
چکیده
We have developed a sensitive experiment which allows the measurement of the growth of holes in thin freely standing polystyrene ~PS! films at elevated temperatures. In the experiment, a constant small pressure difference is applied and maintained across the freely standing film, and the formation and growth of holes is detected as a flow of air through the film. From measurements of freely standing PS films for which the glass transition temperature Tg is equal to the bulk value Tg bulk , as well as for films that are sufficiently thin that Tg is 30 °C less than Tg bulk , we find that substantial chain mobility occurs only at temperatures that are comparable to Tg bulk . The results can be interpreted as a shear thinning effect, which is consistent with previous optical microscopy measurements of hole growth in freely standing PS films. © 2003 American Institute of Physics. @DOI: 10.1063/1.1568541#
منابع مشابه
Hole growth in freely standing polystyrene films probed using a differential pressure experiment.
We have probed the whole chain mobility of polymer molecules confined to freely standing films by measuring the flow of gas through holes growing in the films at elevated temperatures using a differential pressure experiment. Freely standing polystyrene films were measured for the temperature range 92 degrees C<T<105 degrees C for films with two different molecular weights Mw=717 x 10(3) and 22...
متن کاملHole Nucleation and Growth in Free-Standing Polystyrene Ultrathin Films
Nucleation and growth of holes in free-standing ultrathin (<100 nm) polymer films are examined via opticalmicroscopy in order to gain a better understanding of these phenomena.Hole nucleation is quantified with a free energy barrier based on a simple capillary model. Additionally, holes are found to grow exponentially in accordance with previous studies in the literature. Ultrathin films of pol...
متن کاملEvidence of convective constraint release during hole growth in freely standing polystyrene films at low temperatures.
Hole growth measurements were performed using optical microscopy on freely standing polystyrene films at temperatures that were slightly larger than the bulk value of the glass transition temperature T(bulk)g. For the measured range of temperatures, we have observed a transition from linear growth of the hole radius R during the early stages to exponential growth of R at later times. We have ch...
متن کاملGlass Transition Reductions in Thin Freely-standing Polymer Films: a Scaling Analysis of Chain Confinement Effects
In this paper we present a new analysis of data on the reduced glass transitions observed in thin freely-standing films. The empirical analysis presented is highly suggestive of the existence of a mechanism of mobility in thin freely-standing films that is inhibited in the bulk and distinct from the usual cooperative motion near the glass transition temperature Tg. A tentative mechanism for Tg ...
متن کاملAnomalous Dynamics of Polymer Films
This chapter reviews the recent experiments involving the dynamics of polymer films with thickness comparable to the gyration radius of the polymer, which overwhelmingly show that their glass transition temperature, Tg, depends on the film thickness and can sometimes differ significant from that of the bulk. The greatest mystery is the onset film thickness of this phenomenon being ~50 nm, much ...
متن کامل