Search

The nanomechanical properties of polymers are sensitively affected by subtle differences in molecular structures. When the modulus of high-density polyethylene (HDPE) was measured with an atomic fo...

Atomic force microscopy (AFM) offers nanoscale mapping of materials’ properties. Especially, our modified AFM termed “nanorheological AFM” enables us to measure the accurate frequency-dependent storage and loss moduli and loss tangent over a sixth-order frequency range without any temperature control at nanoscale resolution. These dynamic properties obtained by nanorheological AFM can be compared with those using bulk dynamic mechanical analysis (DMA) measurements. In this paper, we applied this technique to silica-filled styrene–butadiene rubber (SBR) to investigate the nature of the interfacial rubber region existing between a rubber matrix and silica particles at different temperatures. The dynamics properties of the interfacial rubber region were different from those of matrix rubber regions. The master curve obtained by this technique perfectly coincided with that by bulk DMA. Furthermore, it was found that the behavior of bulk loss tangent could be predicted by the contributions from both matrix and...

The mobility gradient of polymer chains near a solid interface plays an important role in explaining a complex behavior of relaxation dynamics and thermodynamic properties observed for various poly...

Cholesteric liquid crystal elastomer (CLCE) films, whose helical axis is parallel to a direction in the film plane, exhibit a periodic surface undulation with a period corresponding to a half-pitch (about 100 μm) of the helical director configuration. Temperature variation drives not only a finite macroscopic uniaxial deformation along the helical axis but also a marked variation in the surface undulation. AFM results demonstrate that the surface undulation varies thermoreversibly like a stationary wave with an amplitude of about 600 nm. The top and bottom positions at 40 °C become the bottom and top ones, respectively, at 130 °C, while the undulation disappears near 100 °C. Microspectroscopy reveals the periodic spatial variation in optical birefringence, which reflects the quasi-helical superstructure of local directors in the CLCE films. The combined analysis of the results of AFM and microspectroscopy indicates that the thermally induced variation in the surface undulation becomes largest at positions...

The viscoelastic response of inhomogeneous rubbery blends upon interacting with an atomic force microscopy (AFM) cantilever is characterized in both the contact and intermittent contact states. In particular, loss tangent spectra and images are measured in tapping mode AFM at relatively high frequencies (>105 Hz) and in an AFM-based method in the contact state recently developed for the characterization of the viscoelasticity of soft materials in a frequency range of 100–104 Hz. Comparing the measured data to that from a bulk technique reveals that a combination of these two methods can qualitatively characterize the nanoscale viscoelastic behavior of inhomogeneous rubbers over an unprecedented frequency range. However, the loss tangent measured in the tapping mode is overestimated compared to those measured in the contact state and the bulk technique, which is attributed to the existence of the adhesion energy hysteresis during the approach and withdrawal of the tip from the sample in the tapping mode. S...

A novel atomic force microscopy (AFM) method is used for nanometer-scale mapping of the frequency dependence of the storage modulus, loss modulus, and loss tangent (tan δ) in rubber specimens. Our ...

This work deals with the tensile drawing behavior of poly(lactic acid) (PLA) in the amorphous state at room temperature. Nanomechanical mapping method is applied to obtain the submicrometer morphology together with mechanical properties using atomic force microscopy (AFM). By carefully collecting the data of PLA specimens deformed with different elongation, we managed to monitor the microscopic structural/mechanical evolution simultaneously, and thus, the microscopic deformation mechanism was studied phenomenologically. The PLA matrix shows a highly heterogeneous response to the external stress. The stress is concentrated in some preferential places, thereby leading to high local Young’s modulus and giving rise to crazes perpendicular to the tensile direction. However, in the position away from the crazes, the matrix undergoes no stress and shows similar Young’s modulus as neat PLA specimens. The inhomogeneous stress distribution results in the catastrophic fracture of the matrix at an early state, which ...

The surface morphology and nanomechanical properties of poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS) having different compositions were investigated using nanomechanical mapping measurements based on atomic force microscopy. We obtained the deformation image, true surface morphology, high-resolution Young’s modulus map, and map of deviated work simultaneously in a force mapping. Such maps were successfully used to identify and characterize the composition and better understand the relationship between microstructure and properties of SEBS samples. It is found that the obtained Young’s modulus and deformation values, both for polystyrene (PS) or poly(ethylene-co-butylene) (PEB) blocks, strongly depend on the microstructure that is dominated by the composition. As the PS composition increase, the modulus of PS blocks increases from 19.2 ± 2.5 MPa for SEBS (10/80/10) to 823.0 ± 168.1 MPa for SEBS (33.5/33/33.5), while PEB’s increases from 8.7 ± 2.1 MPa for SEBS (10/80/10) to 97.6 ± 17.8 MPa for SEBS...

A technique based on atomic force microscopy (AFM) for dynamic measurement of mechanical properties of a single polymer chain was proposed. AFM cantilever was mechanically oscillated at approximately 10 kHz during stretching process. By this technique, we could quantitatively estimate elongation-dependent changes of stiffness and viscosity of a single chain itself with using a phenomenological model. The solvent effect on the viscosity in low extension regions was investigated. It was ensured that the viscosity under 10 kHz perturbation was attributed to monomer-solvent friction. Viscosity quantization corresponding to consecutive detachments of polymer chains was also observed.