The effect of rigid polymeric particles addition on the local dynamic heterogeneity and the ultrasound attenuation of butyl acrylate-methyl methacrylate copolymers

Heterogeneity Assisted Damping Enhancement of Low and High Frequency Mechanical Waves in a Soft Polymer Nanocomposite

“…The heterogeneous and multiphase SPNs were comprehensively characterized in our group’s previous works. ,,,, The synthesized matrix (MMA/BA 30/70 wt % copolymer) intrinsically possessed both dynamic and morphological heterogeneities, as dispersion of high- T g MMA-rich copolymers in soft BA-rich copolymers. Its molecular dynamic heterogeneity was nearly 75 °C, extracted from its components DSC-based T g difference (Table ).…”

“…Generally, extracted T g from 1 Hz loss modulus of DMTA is always a few degrees higher than DSC based T g at 10–20 °C min –1 heating ramps. , Here, the assigned tan δ-peak T g instead of G ″ and applied lower heating rate (5 °C min –1 ) intensified the expected disparity. To evaluate the viscoelastic behavior of the matrix at ultrasound spectroscopy, its glass transition was shifted to the applied frequency (10 MHz) based on the extrapolated activation energy of similar copolymers (MBC50 and MBC40) to MBC30. Thus, the lower and higher transitions of DMTA at frequency of 1 Hz shifted to 25 and 100 °C, corresponding to −20 and 55 °C in DSC by considering the aforementioned differences (as much as 45 °C).…”

“…In other words, quite miscible or immiscible polymers yield the lowest energy dissipation, whereas intermediate levels of molecular mixing or microheterogeneity may maximize damping . Accordingly, copolymerization, polymer blending, interpenetrating polymer networks (IPNs), gradient polymers or continuous gradient IPNs, dispersed rigid nanoparticles in polymeric matrices, dangling chains containing polymer networks, and small organic molecules with intermolecular hydrogen bond forming capability are diverse strategies for broadening the damping temperature ranges of polymeric systems. Among them, IPNs have been extensively investigated with a long history, in which intimate mixing produces microheterogeneous domains with a range of local compositions and a broad tan δ profile .…”