Dielectric Study of Dynamic Heterogeneity in Miscible Blends of Polyethers and Poly(vinylethylene)

Abstract

Dynamic heterogeneity in miscible blends was investigated by the use of dielectric relaxation spectroscopy for blends composed of poly(vinylethylene) (PVE) and various polyethers, i.e., poly(butylene oxide) (PBO), poly(isopropyl glycidyl ether) (PiPGE), poly(n-butyl glycidyl ether) (PnBGE), and poly(tert-butyl glycidyl ether) (PtBGE). All polyethers are type AB polymers and exhibit both the dielectric normal-and segmentalmode relaxations, but PVE exhibits only the segmental relaxation. The data indicate that the loss curves for the segmental relaxation of PVE/PBO blends are bimodal in the range of PBO content less than 0.25. Since the dielectric relaxation strength of PBO is much higher than that of PVE, unimodal loss curves are seen at high PBO content. The effective glass transition temperatures for the fast and slow modes estimated with the Lodge-McLeish model agree fairly well with the temperatures at which segmental relaxation times become ca. 100 s. The ratio of the relaxation times for the normal and segmental modes log(τ n /τ s ) increases with increasing content of PVE. The correlation length of concentration fluctuation has been deduced to be 1.0 nm from the behavior of broadening of the relaxation spectra for the segmental and normal modes of PBO. In blends of polyethers such as PnBGE/PtBGE, the loss curves for the segmental modes are unimodal but are asymmetrical when the fraction of one component is 0.25 or 0.75. The asymmetrical loss curve can be attributed to the bimodal relaxation spectrum even though the loss curve is unimodal. The separation between the fast and slow modes in blends of the polyethers has been estimated by utilizing log(τ n /τ s ) as a tool to estimate the location of the segmental loss peaks of the components.

Dielectric study of dynamical heterogeneity in blends of polyethers

“…This indicates the distinct segmental dynamics of the components. For the frequency dependence curves of all blends examined here the same behavior has been observed as reported previously [17]. Fig.…”

“…As pointed out previously [17], the separation between the normal-and segmental modes for pure PnBGE is wider than that for the blend. This suggests that the loss peak of the segmental mode of PnPGE locate around C since the separation between the normal-and segmental modes increases by blending [17]. Then the loss peak for PtBGE should locate around D as schematically sketched by the dotted line.…”

“…The a s is the segmental mode of the blends and is due to slightly decoupled cooperative motions of the components. As discussed in our previous paper [17], the shape of the a s mode changes with composition. When the content of low-T g component is 75%, the loss curve is broad in high T side.…”

“…Recently we reported a dielectric study of dynamical heterogeneity in miscible polymer blends of PVE and polyesters, namely, poly(butylenes oxide) (PBO), poly(isopropylglycidyl ether) (PiPGE), poly(n-butylglycidyl ether) (PnBGE), and poly(t-butylglycidyl ether) (PtBGE) [17]. We also reported the dielectric behavior of these polyethers in the pure state [18,19].…”

Polyglycerol-based polymer network films for potential biomedical applications

“…42 Pure GGE when polymerized has a T g of 26 C with copolymers having lower T g , which varies between this maximum and the corresponding minimum T g of the respective monoglycidyl ether homopolymers (values in Table 4). 43 This variance in T g correlates to the ratio of monoglycidyl ether to crosslinker GGE and is also specific to the nature of the monoglycidyl ether sidechain. For example, it is evident in Fig.…”