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Low dielectric constant (k) polymers with excellent comprehensive properties are useful materials in the microelectronics industry as matrix resins or encapsulation layers. With the inherent low polarization, high reactivity, good processability, and low cost, poly(dicyclopentadiene) (PDCPD) has received considerable attention as low‐k materials. However, its practical application is limited by the relatively high thermal expansion and k value. Herein, three norbornene‐functionalized polyhedral oligomeric silsesquioxanes (POSSs) with T8, T10, and T12 polyhedral cores are synthesized and employed for enhancing the dielectric and comprehensive properties of PDCPD via reactive blending. The results show that these POSSs have good compatibility with PDCPD matrix and nano‐dispersed POSSs particles could be obtained. As a result, the materials' properties can be largely enhanced by varying the POSS content and POSS size. Especially, PT12N12‐40 (40 wt% of T12N12) shows the lowest k value (2.1) and coefficient of thermal expansion (63.4 ppm°C−1), highest glass transition temperature (202.5 °C), yield strength (78.0 MPa), and elastic modulus (2.36 GPa), along with excellent hydrophobicity. This study highlights a useful strategy to fabricate high‐performance low‐k polymer nanocomposites by using larger POSS and reactive blending, which provides useful materials for the future microelectronic industry and high frequency communication. [ABSTRACT FROM AUTHOR]

This article focus on derive the process-structure-property relationship of Poly(L-lactide) (PLLA) fibers prepared by two-step melt spinning process. The spinning temperature, spinning rate, drawing temperature as well as draw ratio were studied to analyze the influence of process variables on the structure and properties of PLLA fibers. It suggests that the crystallinity, lamellar orientation structure and mechanical properties of fibers are dependent on the spinning conditions, including melt-spinning and hot-drawing process. An approximate linear correlation resulted between the orientation degree and tensile strength of PLLA fibers, which means that the oriented structure plays a dominant role to enhance PLLA fibers. PLLA fibers with high performance of 499 MPa and 5.30 GPa in tensile strength and Young's modulus separately have been realized by the selected spinning parameters. The results provide a theoretical direction for enhancing PLLA fibers by adjusting the structure characteristic via modifying the spinning parameters. [ABSTRACT FROM AUTHOR]

Background. Th17 cell differentiation is involved in the development and progression of many diseases, such as rheumatoid arthritis and systemic lupus erythematosus. Present study mainly focused on the role of LINC-XIST in Th17 cell differentiation. Methods. The naïve CD4+ T cells were isolated from human whole blood. Cells were cultured under Th17 cell-polarizing condition for 6 days. The expression of LINC-XIST and miR-153-3p was measured by qPCR. The relationship between LINC-XIST, miR-153-3p, and ETS1 was predicted by TargetScan website and authenticated by luciferase reporter assay. ELISA assays were conducted to evaluate the IL-17 concentration. Western blot was utilized to measure the protein expression of ETS1. Th17 cell frequency was examined by flow cytometry. Results. The expression of XIST markedly decreased and miR-153-3p expression markedly increased with Th17 cell differentiation. The mRNA expression of IL-17, IL-17 concentration, and Th17 cell frequency were observably decreased in overexpressed LINC-XIST group. Luciferase reporter assay authenticated that miR-153-5p was directly regulated by LINC-XIST. miR-153-3p inhibitor observably decreased IL-17 concentration, mRNA expression of IL-17, and Th17 cell frequency while si-XIST reversed this impact. ETS1 was confirmed to be regulated by miR-153-5p via luciferase reporter assay. In addition, ETS1 markedly decreased IL-17 mRNA expression, IL-17 concentration, and Th17 cell frequency while miR-153-5p mimic reversed this impact. Conclusion. LNCRNA XIST inhibited miR-377-3p to hinder Th17 cell differentiation through upregulating ETS1. [ABSTRACT FROM AUTHOR]

Constructing stereocomplex (SC) crystallites at the interface of poly(L‐lactide) (PLLA)/elastomer blends represent a promising strategy to develop heat‐resistant and super‐tough PLLA materials because such SC crystallites can behave as not only nucleator to accelerate crystallization of PLLA matrix but also interfacial binder to strengthen interface. The properties of blends could be largely dominated by the SC interfacial layer, however, it is still unclear how the interfacial structure affects nucleating efficiency and interfacial strength. Herein, taking PLLA/poly(ethylene‐co‐methyl acrylate‐graft‐poly(D‐lactide)) (EMA‐g‐PDLA) blends as an example, EMA‐g‐PDLA bearing different chain lengths and grafting densities is prepared to tailor the size and packing density of interface‐localized SC crystallites. The results indicate that the interfacial structure and properties of the blends have been successfully manipulated. Compared with low‐graft‐density long PDLA chains, high‐graft‐density short ones can readily collaborate with PLLA chains to form numerous SC crystallites with smaller size and higher packing density at the interface and thus dramatically enhance the impact toughness and matrix crystallization rate. Moreover, the toughness is dominated by the content of SC crystallites, but the matrix crystallization is determined by their size and packing density. The work provides a new understanding of SC structure controlling the properties of PLLA/elastomer blends. [ABSTRACT FROM AUTHOR]