Sub-T g Transitions

Nature of Ferroelectric Behavior in Main-Chain Dipolar Glass Nylons: Cooperative Segmental Motion Induced by High Poling Electric Field

“…Second, it is unlikely that the α transition temperature can be significantly decreased by high poling electric field. Instead, ferroelectric switching should be facilitated by sub- T g relaxations . In general, for main-chain polar polymers [i.e., polar groups are directly attached to the main chain, e.g., PVDF, polycarbonate (PC), polysulfone (PSF), polyesters, and nylons], the β relaxation is usually related to the onset or precursors of long-range segmental motions (i.e., the α relaxation) and thus can be considered as short-range segmental motions.…”

“…High dielectric constant (ε r ) and low loss dielectric polymers are attractive for advanced electrical and power applications, such as electric energy storage (i.e., film capacitors), − electromechanical actuation (i.e., dielectric elastomers , and electrostrictive polymers), and electrocaloric cooling. − From recent studies, , enhanced dielectric constant for polymers can be realized by utilizing orientational (or dipolar) polarization from dipolar groups, such as nitrile (3.9 D), sulfone (4.5 D), amide (3.7 D), urea (4.5 D), and thiourea (4.89 D) groups. According to different dipole–dipole and domain–domain interactions, dipolar polymers can be categorized into four types: normal ferroelectric, relaxor ferroelectric, paraelectric, and dipolar glass polymers. , Among these, a promising candidate is the dipolar glass polymer, where weakly interacting dipolar groups are confined in the glassy polymer matrix. , It is the free volume that permits dipole mobility below the glass transition temperature ( T g , i.e., sub- T g transitions) . Since the long-range segmental motion of polymer chains is largely frozen below T g , ionic and electronic conduction losses can be significantly reduced. , …”

Physical Stabilization of Pharmaceutical Glasses Based on Hydrogen Bond Reorganization under Sub-Tg Temperature

“…Since motions of side chains/substituents can occur even in sub- T g region, this probably results from relaxation of such side chains. Moreover, as temperature increases, the motion commences from smaller (with lower activation energies) to larger groups (with higher activation energies); , thus, the irregular temperature dependence probably reflects formation of different kinetically trapped structures through such local relaxation. These structures may not be the energetically most favored state, as was observed for small organic molecules, whose relaxation apparently stopped before reaching the energetically expected state .…”

“…Thus, annealing is a promising strategy to stabilize pharmaceutical glasses, and a temperature just below T g (sub- T g ) is reasonable choice for effective relaxation without crystallization because only small molecular units such as side chains relax at the sub- T g region, and the long-range segmental motion necessary for the crystallization is frozen. ,, Herein we report influence of sub- T g annealing on the physical stabilities and structures of pharmaceutical glasses. First, in order to discuss general trends, we demonstrate the impact of sub- T g annealing on the stabilities of pharmaceutical agents (acetaminophen, AAP; chlorpropamide, CPA; indomethacin, IDM; tolbutamide, TLB; and ritonavir, RTV), and then analyze details by focusing on RTV, which exhibited a significant stabilization after the annealing.…”

The hepatitis B e antigen suppresses IL-1β-mediated NF-κB activation in hepatocytes

“…To confirm the expression of transfected constructs, HBeAg levels in cell lysate (intracellular p25 and p22) and cell supernatant (p25, p22 and secreted p17) were determined using the Abbott Architect quantitative serology platform (Abbott Diagnostics) with cross-reference to the Paul Ehrlich HBeAg reference standard [23]. To standardize intra-assay…”