Measurement of thermal parameters and mechanical properties of polymers by atomic force microscopy

Abstract

A novel technique has been developed to determine thermal transitions locally, e.g. the glass transition of polymers, with atomic force microscopy (AFM). The microscope was operated in stationary non-contact mode, using it like a dynamic mechanical analyser on a molecular scale, thereby measuring the resonance frequency of the AFM cantilever, which oscillates above the sample surface, as a function of temperature. The thermal transitions of the underlying polymer are clearly visible as a change in the resonance frequency. Using the AFM in this mode allows the determination of the thermal properties of a material at a specific spot on the sample on a molecular scale. Measurements were performed on different polymers, polymer blends, structured polymers, layered systems and thin films.

A Review on Methods and Theories to Describe the Glass Transition Phenomenon: Applications in Food and Pharmaceutical Products

“…Figure 21 shows the glass transition temperature of two different polymers. Measurements using this technique agreed well with values determined using other techniques [128].…”

“…As the temperature can be controlled, this permits to determine the thermal properties of the sample such as the glass transition, melting, or crystallization temperatures [126][127][128]. Based on this method, the glass transition appears as a plateau in the linearly decreasing frequency curves [127,128]. Figure 21 shows the glass transition temperature of two different polymers.…”

“…AFM data for two different latex polymers showing the plateau locating the glass transition temperature (from[128])…”

Determination of the Glass Transition Temperature of Freestanding and Supported Azo-Polymer Thin Films by Thermal Assisted Atomic Force Microscopy

“…At the glass transition temperature, changes in enthalpy H Δ and entropy S Δ of the CFAO thin films are changed and it can lead to reversible jumps of the AFM phase during heating (red curve) and cooling (blue curve). 20 For stable and reliable AFM measurements with in-situ heating/cooling, we heat or cool the polymer step-by-step by a value of 20 °C at a linear thermal rate of 5 o C/min. This stepwise regime permits the sample to be in a near-equilibrium state.…”

Thermal analysis and topographical characterization of films of styrene‐butadiene blends

“…25 Various modes of scanning probe microscopy (SPM) have been used to study thermal properties of polymer films, including hot-stage and scanning thermal microscopy, [26][27][28][29][30][31][32][33][34][35][36][37][38][39] friction (lateral) force microscopy, [40][41][42] shear-modulated scanning force microscopy, 43,44 force-distance measurements, 45 scanning local acceleration microscopy, 46 and detection of the resonance frequency of an SPM probe oscillating just above a heated sample. [47][48][49][50] detecting thermal transitions in styrene-butadiene copolymer latex films 51,52 and polyester and styrene/ acrylate composite powders. 53 The resonance frequency (x) of a heated probe oscillating above the sample surface was determined at different probe temperatures (T p ).…”