We demonstrate that the poly(butyl acrylate) (PBA) elastomers containing considerable amounts of dangling chains with uniform lengths exhibit pronounced viscoelastic relaxation (tan δ > 1) at characteristic frequencies. The elastomers are obtained by the copolymerization of monoacryloyl- and diacryloyl-terminated precursor PBA with narrow size distributions. The molecular weights of the precursors are smaller than the critical molecular weight for the onset of entanglement coupling. The relaxation time of the elastomers (τD) is proportional to the square of the molecular weight of the dangling chains equivalent to the monofunctional PBA (M D), and τD is about 2.5 times larger than the relaxation time of the corresponding free guest chains in the elastomers (τG). These observations are close to the expectations from the Rouse-chain dynamics without entanglement effect (τD ∼ M D 2 and τD = 4τG). These results provide an important basis for the understanding of the dynamics of the unentangled chains whose one end is tethered to the permanent networks. The results also offer a route of molecular control of characteristic frequency and strength of mechanical damping of elastomers.

In this paper, the properties of the barium titanate (BT)/polyvinylidene fluoride (PVDF) composites were controlled by the self-assembly of the BT secondary particle groups. The self-assembled BT/PVDF composites of 520 vol.% BT were prepared with the difference in the viscosity of polyethylene glycol (PEG) of dispersants involved in the self-assembly process. The multifractal properties and dielectric properties of the self-assembled BT/PVDF composites were investigated with controlling by the formation of the self-assembled BT secondary particle groups. The dielectric constant (¾¤) increased with an increase in the average secondary particle area (S) of the BT particles. The S increased with an increase in the viscosity of PEG; whereas, the ¾¤ decreased with the increase in viscosity. The multifractal analysis indicated that the distribution of self-assembled BT secondary particle groups was affected by PEG viscosity. The sample with PEG1000 had aggregates with a BT/PVDF/BT heterointerface, the sample with PEG20000 had agglomerates with a BT/BT interface, and the sample with PEG2000 had both, aggregates and agglomerates. The BT/PVDF/BT heterointerface in the BT aggregates played an important role in improving the dielectric properties of the BT/PVDF composites. Overall, the viscosity of the dispersant affected the self-assembly process as well as the ¾¤. It was suggested that the multifractal properties and dielectric properties were controlled by the self-assembly of the BT secondary particle groups.

The effect of self-assembled barium titanate (BT) aggregates in polyvinylidene fluoride (PVDF) matrix on the α-β phase transition was investigated. The self-assembled BT/PVDF composites were prepared with and without dispersant in the self-assembled process. The addition of dispersants increased the average secondary particle area (S) of the BT particles and promoted the BT/PVDF/BT hetero-interface. FT-IR showed that the αβ phase transition of the composites enhanced with increasing S. The Cole-Cole plot was estimated the existence of orientation polarization and interface polarization. According to these results, we proposed a BT/PVDF/BT hetero-interface model based on the double Schottky barrier model.

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