Morphology Mapping of Phase-Separated Polymer Films Using Nanothermal Analysis

Abstract

Polymers films are attractive, in part, because their physical properties can be tuned by blending polymer with complementary characteristics. However, blending is typically challenging because most polymers will undergo phase separation, resulting in unpredictable behavior. Here, we introduce band excitation nanothermal analysis (BE-NanoTA) as a nondestructive AFM-based technique for mapping the near surface, thermal properties of polymeric coatings. BE-NanoTA was used to investigate phase separation and domain growth in poly(styrene-ran-acrylonitrile):poly(methyl methacrylate) SAN: PMMA films. The size and shape of PMMA-rich domains are consistent with prior measurements on the same system using a destructive method, namely UV-ozone etching of PMMA followed by topography mapping using standard AFM. Moreover, new insights into the mechanism of phase separation were uncovered including the observation of SAN-and PMMA-rich channels near the surface at early times as well as small SAN-rich domains trapped within large PMMA domains during intermediate times. Because it is nondestructive, BE-NanoTA can be used to explore in situ phase evolution in soft matter systems (e.g., polymer nanocomposites) which do not lend themselves to the UV-ozone etching method.

A spectroscopic and thermal investigation into the relationship between composition, secondary structure and physical characteristics of electrospun zein nanofibers

“…The detected transition temperature is recorded and assigned a colour based on the selected palette; hence, an image is assembled based on transition temperatures. 35,36 In the present case, we have applied the technique to interrogate the non-woven mats of fibres produced via the electrospinning process. The probe size, which typically would examine a region of some 400x400nm, has been applied to a sample of the fiber mat in a two dimensional raster pattern in order to explore the ability of the technique to examine changes in thermal transition temperatures on altering the composition, as well as to develop the potential of the technique as a means of examining nanofiber mats as a potential quality control tool.…”

Force field induced heterogeneous molecular orientation within polyacrylonitrile monofilaments

“…When the tip is in contact with the sample, the heat of tip will result in a local expansion followed by soening when the temperature reaches the decomposition point. 23,24 These changes will be monitored through the vertical movement of the tip measured by laser deection. Fig.…”

Atomic Force Microscope Controlled Topographical Imaging and Proximal Probe Thermal Desorption/Ionization Mass Spectrometry Imaging

“…Material was thermally desorbed from the surface using AN2−300 nanothermal analysis (nano-TA) AFM probes (Anasys Instruments). Temperature calibration of the nano-TA AFM probes was carried out using the measured melting point transitions of the polymeric samples polycarbolactone (PCL), high-density polyethylene (HDPE), and polyethylene terephthalate (PET)) 26,27 and fitting the values to a quadratic regression, a technique first introduced by Lee et al 28 Data Collection and Image Creation. For measurements in spot-sampling mode, the AFM was controlled using custom software that allowed varying of both time spent and AFM tip temperature on the surface.…”