Influence of the Organoclay Content on the Structure, Morphology, and Surface Related Properties of Novel Poly(dimethylsiloxane)-Based Polyurethane/Organoclay Nanocomposites

Novel poly­(dimethylsiloxane)-based polyurethane nanocomposites (TPU-NCs) were synthesized using in situ polymerization with the nanoclay Cloisite 30B. Differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical thermal analysis showed that TPU-NCs with an organoclay content of ≤5 wt % exhibited increased thermal stability, storage modulus, and hard-segment melt temperatures but decreased degrees of crystallinity. TPU-NCs displayed increased surface hydrophilicity and enhanced surface free energy with increasing organoclay content. Small- and wide-angle X-ray scattering confirmed intercalated formations of organoclays in the nanocomposites. Individual clay particles on the surfaces of TPUs with lower organoclay loadings (1 or 3 wt %) or organoclay agglomerates in TPUs with higher amounts of organoclay (≥5 wt %) were detectable using scanning electron microscopy. The relatively smooth and homogeneous character of pure TPU and the distinctly heterogeneous and rough surfaces of TPU-NCs were detected via atomic force microscopy. Among the nanomaterials prepared, TPU-NCs with 1 wt % organoclay provided the best balance between the organoclay concentration and the functional properties desired in biomedical applications

Study of the Properties of Urethane–Siloxane Copolymers Based on Poly(propylene oxide)‑<i>b</i>‑poly(dimethylsiloxane)‑<i>b</i>‑poly(propylene oxide) Soft Segments

Segmented polyurethanes (PURs) were prepared from α,ω-dihydroxy­poly­(propylene oxide)-<i>b</i>-poly­(dimethylsiloxane)-<i>b</i>-poly­(propylene oxide) (PPO–PDMS) as the soft segment and 4,4′-diphenylmethane diisocyanate and 1,4-butanediol as the hard segment, via two-step polyaddition process in solvent mixture. The content of hard segments is in the range from 10 to 60 wt %. The structure and composition of PURs are determined by ¹H NMR, ¹³C NMR, and ATR-FTIR spectroscopy. Incorporation of PPO–PDMS leads to improvements in thermal stability. Small- and wide-angle X-ray scattering experiments indicate that synthesized PURs with higher content of hard segments have more developed and distinct phase separated morphologies. Dynamic mechanical thermal analysis shows that copolymers have multiple transitions, characteristic for phase-separated systems. The water contact angle increases while water absorption decreases with increasing content of PPO–PDMS segments. The PURs prepared in this work show good thermal, mechanical features with phase separated morphology and high water resistance that enable their widespread application

Structure, Thermal, and Morphological Properties of Novel Macroporous Amino-Functionalized Glycidyl Methacrylate Based Copolymers

Novel macroporous functionalized copolymers with different cross-linker concentrations and porosity parameters were synthesized by reaction of the pendant epoxy groups of poly­(glycidyl methacrylate-<i>co</i>-ethylene glycol dimethacrylate) (poly­(GMA-<i>co</i>-EGDMA)) with hexamethylene diamine, 1,3-bis­(3-aminopropyl)­tetramethyldisiloxane, and α,ω-diaminopropyl poly­(dimethylsiloxane). The copolymers were prepared in forms of spherical beads and characterized by Fourier transform infrared (FTIR), ¹³C and ²⁹Si solid-state NMR, mercury porosimetry, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Copolymers prepared with the higher cross-linker concentrations have better thermal stability, higher glass transition temperatures, higher specific surface areas, and smaller pore diameters that correspond to half of the pore volumes. Our results show that functionalization significantly changed porosity parameters, mechanism of thermal degradation, and increased thermal stability in comparison with the initial copolymers. These macroporous copolymers could potentially have many applications, i.e. for sorption of heavy and precious metals or as material for gas chromatography columns

Curcumin Protects Hepatic Stellate Cells against Leptin-Induced Activation in Vitro by Accumulating Intracellular Lipids

Obesity and type II diabetes mellitus are often associated with hyperleptinemia and commonly accompanied by nonalcoholic steatohepatitis, which could cause hepatic fibrosis. During hepatic fibrogenesis, the major effectors hepatic stellate cells (HSCs) become active, coupling with depletion of cellular lipid droplets and downexpression of genes relevant to lipid accumulation. Accumulating evidence supports the proposal that recovering the accumulation of lipids would inhibit HSC activation. We recently reported that leptin stimulated HSC activation, which was eliminated by curcumin, a phytochemical from turmeric. The current study was designed to explore the underlying mechanisms, focusing on their effects on the level of intracellular lipids. We hypothesized that one of the mechanisms by which leptin stimulated HSC activation was to stimulate the depletion of intracellular lipids, which could be abrogated by curcumin by inducing expression of genes relevant to lipid accumulation. In this report, we observed that leptin dose dependently reduced levels of intracellular fatty acids and triglycerides in passaged HSCs, which were eliminated by curcumin. The phytochemical abrogated the impact of leptin on inhibiting the activity of AMP-activated protein kinase (AMPK) in HSCs in vitro. The activation of AMPK resulted in inducing expression of genes relevant to lipid accumulation and increasing intracellular lipids in HSCs in vitro. In summary, curcumin eliminated stimulatory effects of leptin on HSC activation and increased AMPK activity, leading to inducing expression of genes relevant to lipid accumulation and elevating the level of intracellular lipids. These results provide novel insights into mechanisms of curcumin in inhibiting leptin-induced HSC activation