Poly(vinylidine fluoride) (PVDF) is a semicrystalline polymer which is known to exist in several polymorphic phases, namely, α, β, and γ. Each one of these polymorphic phases is characterized by unique features such as spherulite formation in the case of the α and γ phases and the presence of large piezoelectric and ferroelectric activity in the β phase. Despite being widely used as thin coatings in sensors, lack of reports on nanomechanical properties suggests that investigation of mechanical properties of PVDF, let alone those of its polymorphic phases, seems to have evaded the sight of the research community. Herein, we report the nanomechanical properties of the α, β, and γ phases of PVDF. The modulus and hardness values were evaluated from nanoindentation experiments; it was found that the electroactive β phase is the softest among the three polymorphic phases. This result was further confirmed by scratch experiments. We have attempted to establish a correlation between the microstructure and nanomechanical properties of these phases. This work sheds light on the mechanisms responsible for the observed mechanical behavior and the role of tie molecules and amorphous content in providing flexibility to the polymer.
Single layer and multilayer polymer thin film coating on polymer substrate are gaining significant importance in different industries. The quantitative and qualitative estimation of interface response for thin film coating under different service conditions is significantly important from the perspective of modeling and designing novel materials. However, to characterize an interface between the soft polymer layer and soft polymer substrate is challenging because of the confinement effect, surface roughness, the viscoelastic nature of the polymers involved, and most importantly, the comparable mechanical properties of soft polymeric film and polymer substrate. Nanoindentation technique was applied in this work to find out the mechanical response of thin film PMMA (100-200 nm) and Epoxy interfaces of different interfacial strengths. Interfaces of different strengths were obtained by exposing the filmsubstrate system to different service conditions. It has been observed from this study that pile-up plays a major role in finding out the mechanical response of the interfaces of different strengths. The hardness was observed to increase as the interfacial strength reduces.
Atomically precise clusters of noble metals are considered to be an important class of advanced materials. Crystals of these clusters composed of inorganic cores and organic ligands are fascinating owing to their tunable and unique properties. Understanding their mechanical properties can give more insight into the design of nanocluster‐based devices. Here, we probe the mechanical response of single crystals of Ag29(BDT)12(TPP)4 cluster (BDT=1,3 benzenedithiol, TPP=triphenylphosphine) under both quasi‐static and dynamic loading conditions. Surprisingly, the measured reduced Young's modulus (Er) and hardness (H) were 4.48 and 0.285 GPa, respectively, similar to those of polymers and much smaller than the values for bulk silver. These observations indicate a significant role of capping ligands on the physical properties of such materials. The observed storage modulus, loss modulus and loss factor were also found to be similar to those of polymers. The magnitude of loss factor suggested the ability of nanocrystals to absorb energy under dynamic loading. These studies of mechanical properties of cluster materials could be useful in developing their applications.
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