QUATITATIVE MEASUREMENTS OF SOFTENING TEMPERATURE OF NANOSCALE POLYMER THIN FILMS

Jing Zhou, Brian Berry, Alamgir Karim, Chad Snyder & Christopher Soles

Polymers Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899-8541, USA

Abstract

Nano-thermomechanometry (nano-TM) is emerging as a promising technique for probing thermophysical properties of multiphase materials and nanocomposites at nanoscales, which can not be realized using any conventional thermal analyses or microscale Wollaston scanning tip method. However, the observed nano-TM transition temperatures always considerably deviate from the thermodynamic thermal transition temperatures, i.e. glass transition and melting temperatures. This has been a puzzling mystery and poses a severe hurdle towards the development of quantitative nano-thermal analysis. Herein, we report the systematic study of nano-thermomechanometry on glassy polymer thin films. It is found that the observed transition temperature, T_transt, adopts a logarithmic relation with the square root of ramping rate, R, as , based upon which the quasi-equilibrium thermal transition temperature, T₀, can be obtained from non-equilibrium measurements. We discovered that the observed shift of nano-TM transition temperature is a reflection of the intrinsic interplay between thermal and mechanical properties induced by size effect and nanoconfinement. This is further supported by the finite element method (FEM) simulation of heat transfer and mechanical stress distribution. This study has important implication in the fundamental understanding of mechanically coupled thermophysical phenomena, and enables the opportunity to de-couple all interlinked parameters for standardized, quantitative nano-thermal analysis.  

Name: Jing Zhou

Mentors name: Alamgir Karim, Chad Snyder, Christopher Soles

Division: Polymers Division

Laboratory: MSEL

Address: Room A323, BLDG. 224

Mail stop: 8541

Tel: (301)975-4599

FAX: (301)975-3928

Email: jingzhou@nist.gov

Sigma Xi member? No.

Category: Materials