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 method includes a modified AFM instrument, which has an additional piezoelectric actuator placed between the specimen and AFM scanner. The specimen and AFM cantilever are oscillated by this actuator with a frequency between 1 Hz and 20 kHz. On the basis of contact mechanics between the probe and the sample, the viscoelastic properties were determined from the amplitude and phase shift of the cantilever oscillation. The values of the storage and loss moduli using our method are similar to those using bulk dynamic mechanical analysis (DMA) measurements. Moreover, the peak frequency of tan δ corresponds to that of bulk DMA measurements.

We review nano-palpation atomic force microscopy, which offers quantitative mechanical property mapping especially for soft materials. The method measures force-deformation curves on the surfaces of soft materials. The emphasis is placed on how both Hertzian and Derjaguin-Muller-Toporov contact mechanics fail to reproduce the experimental curves and, alternatively, how the Johnson-Kendall-Roberts model does. We also describe the force-volume technique for obtaining a two-dimensional map of mechanical properties, such as the elastic modulus and adhesive energy, based on the above-mentioned analysis. Finally, we conclude with several counterpart measurements, which describe the viscoelastic nature of soft materials, and give examples, including vulcanized isoprene rubber and the current status of ISO standardization.

Much more attention has been directed to biodegradable polymers due to their potential applications in the fields related to environmental protection in the last two decades. According to the difference in preparation methods, biodegradable polymers can be classified into two types. One is the biosynthetic polymer, such as bacterial polyhydroxyalkanoates (PHAs). Among them poly(hydroxybutyrate) (PHB) is probably the most extensively studied biodegradable thermoplastic polymer. Ha et al. recently reviewed the miscibility, properties and biodegradability of blends containing either PHB or poly(3-hydroxybutyrate-cohydroxyvalerate).1 The other is the chemosynthetic polymer, such as the aliphatic polyesters. Poly(butylene succinate) (PBSU) and poly(ethylene succinate) (PES) are just two of them. The chemical structures of PBSU and PES are (-OCH The crystal structure, crystallization and melting behaviour of PBSU have been reported in literature. 2-4Polymer blending is often performed in order to improve the physical properties and extend the application fields of PBSU. PBSU was found to be miscible with poly(vinylidene fluoride), poly(vinylidene chloride-co-vinyl chloride), poly(ethylene oxide) (PEO) and poly(vinyl phenol).5-9 On the other hand, PBSU was found to show no miscibility with PHB, poly(3-hydroxybutyrate-co-hydroxyvalerate) and poly("-caprolactone). [10][11][12] We also studied the subsequent melting behavior of PBSU crystallized nonisothermally from the melt. 13The crystal structure, crystallization behaviour and melting behaviour of PES have been reported in literature.14-16 The crystallization and morphology of PES in binary miscible blends of two crystalline polymers have also been reported recently, such as in PES/PHB and PES/PEO blends. 17,18 We also studied the subsequent melting behavior of PES crystallized nonisothermally from the melt and the crystallization kinetics as well as subsequent melting behaviour of PES from the amorphous glassy state. 13,19 Crystallinity is known to play an important role in the physical properties and biodegradability of biodegradable polymers. Meanwhile, the crystalline structure and morphology of semicrystalline polymers are also influenced greatly by the thermal history. Therefore, much more attention should be paid to the crystallization kinetics study since it affects not only the crystalline structure and morphology of semicrystalline polymers but also the final physical properties and biodegradability for the biodegradable polymers. However, to the best of our knowledge, the overall crystallization kinetics studies, especially the nonisothermal crystallization kinetics studies from the melt, of PBSU and PES have not been reported so far in literature. But it is essential to study the nonisothermal crystallization kinetics from the viewpoint of practical application because most polymer processing operations are carried out under nonisothermal conditions.In this note we reported our results on the nonisothermal crystallization kinetics of PBSU and PES from the ...