Comparison of Three Interfacial Conductive Networks Formed in Carbon Black-Filled PA6/PBT Blends.

Interfacial localization of carbon fillers in cocontinuous-structured polymer blends is well-known as a high-efficiency strategy for conductive network formation. However, a comparison with interfacial localization of carbon fillers in sea-island-structured polymer blends is lacking. Here, three types of highly efficient conductive networks formed on the basis of interfacial localization of carbon black (CB) in polyamide 6 (PA6)/poly(butylene terephthalate) (PBT) blends with different blend compositions (80/20, 50/50 and 20/80 vol/vol) were investigated and compared in terms of electrical resistivity, morphology as well as rheological and mechanical properties. The order of the electrical percolation threshold of CB in the three blends is 50/50 < 20/80 < 80/20, which can be attributed to different network structures. The rheological percolation thresholds are close to the electrical ones, confirming the formation of CB networks. The formation mechanisms for the three types of CB network structures are analyzed. All the three types of PA6/PBT-6 vol% CB composites showed improved tensile strength compared with PA6/PBT blends, being in favor for practical applications.

Artemisia pollen allergy in China: Component-resolved diagnosis reveals allergic asthma patients have significant multiple allergen sensitization.

BACKGROUND: Artemisia pollen allergy is a major cause of asthma in Northern China. Possible associations between IgE responses to Artemisia allergen components and clinical phenotypes have not yet been evaluated. This study was to establish sensitization patterns of four Artemisia allergens and possible associations with demographic characteristics and clinical phenotypes in three areas of China. METHODS: Two hundred and forty patients allergic to Artemisia pollen were examined, 178 from Shanxi and 30 from Shandong Provinces in Northern China, and 32 from Yunnan Province in Southwestern China. Allergic asthma, rhinitis, conjunctivitis, and eczema symptoms were diagnosed. All patients' sera were tested by ImmunoCAP with mugwort pollen extract and the natural components nArt v 1, nArt ar 2, nArt v 3, and nArt an 7. RESULTS: The frequency of sensitization and the IgE levels of the four components in Artemisia allergic patients from Southwestern China were significantly lower than in those from the North. Art v 1 and Art an 7 were the most frequently recognized allergens (84% and 87%, respectively), followed by Art v 3 (66%) and Art ar 2 (48%). Patients from Northern China were more likely to have allergic asthma (50%) than patients from Southwestern China (3%), and being sensitized to more than two allergens increased the risk of allergic asthma, in which co-sensitization to three major allergens Art v 1, Art v 3, and Art an 7 is prominent. CONCLUSIONS: Component-resolved diagnosis of Chinese Artemisia pollen-allergic patients helps assess the potential risk of mugwort-associated allergic asthma.

Nevirapine-polycaprolactone crystalline inclusion complex as a potential long-acting injectable solid form.

Nevirapine (NVP) is recommended by WHO as the antiretroviral treatment to prevent HIV passing from mother to child. However, the once-daily oral administration results in poor patient compliance, and a long-acting injectable form of NVP is desirable. Using single-crystal X-ray diffraction and other characterization methods, we demonstrated NVP can form crystalline inclusion complex (IC) with the biodegradable hydrophobic poly(ε-caprolactone) (PCL), and investigated the potential of the NVP-PCL IC microparticles as a long-acting injectable solid form. Compared with pure NVP crystals and NVP/polylactide microparticles, the NVP-PCL IC crystals showed significantly decreased solubility and slower dissolution rate, making it more suitable to be developed to achieve sustained-release profiles. In addition, the NVP-PCL IC microparticles with an average diameter below 10 µm can be conveniently prepared by spray drying and are found to be easily injectable through a 25G needle. These results demonstrated the possibility of using drug-polymer IC microparticles as long-acting injectable forms, providing a new approach to design sustained-release drug products.

An in situ-forming zwitterionic hydrogel as vitreous substitute.

Zwitterionic polymers have shown ultra-low biofouling properties at surfaces and excellent biocompatibility as implant. In this study, an in situ-forming zwitterionic hydrogel was designed and evaluated, both in vitro and in vivo, as a long-term vitreous substitute. The zwitterionic polymer poly(MPDSA-co-AC) was designed as a copolymer of the sulfobetaine methacrylamide and acryloyl cystamine monomers, providing the zwitterionic components and the thiol functional groups, respectively. The in situ gelation was via the thiol-ene Michael addition reaction with α-PEG-MA as the crosslinker. The gelation time, rheological properties, swelling profiles, and the transparency of zwitterionic hydrogels were studied in detail. Two systems with different crosslinker concentrations were tested in a rabbit model, and the one with the thiol-ene ratio of 2 : 1 showed excellent biocompatibility in vivo, formed space-filling hydrogels and remained transparent in the vitreous cavity for the 2 month implantation period. Therefore, in situ-forming zwitterionic hydrogels represent a promising material system as a vitreous substitute and possibly for other soft tissue replacements.

Evaluation of an in situ chemically crosslinked hydrogel as a long-term vitreous substitute material.

Currently there is no material that can be used as a long-term vitreous substitute, and this remains an unmet clinical need in ophthalmology. In this study, we developed an injectable, in situ chemically crosslinked hydrogel system and evaluated it in a rabbit model. The system consisted of two components, both based on multi-functional poly(ethylene glycol) (PEG) but with complementarily reactive end groups of thiol and active vinyl groups, respectively. The two components are mixed and injected as a solution mixture, react in vivo via the Michael addition route and form a chemically crosslinked hydrogel in situ. The linkages between the end groups and the backbone PEG chains are specially designed to ensure that the final network structure is hydrolysis-resistant. In the rabbit study and with an optimized operation protocol, we demonstrated that the hydrogel indeed formed in situ after injection, and remained transparent and stable during the study period of 9 months without significant adverse reactions. In addition, the hydrogel formed in situ showed rheological properties very similar to the natural vitreous. Therefore, our study demonstrated that this in situ chemically crosslinked PEG gel system is suitable as a potential long-term vitreous substitute.

Toward the synthesis of sequence-controlled vinyl copolymers.

An ATRA based strategy to synthesize vinyl copolymers with monomer-level sequence control is proposed. In each cycle, one allyl alcohol is added to the ATRP chain end, and then the hydroxymethyl residue is oxidized to carboxylic acid and a side group is introduced via esterification, making the new chain end active for the next cycle.

Poly(butylene succinate) and its copolymers: research, development and industrialization.

Poly(butylene succinate) (PBS) and its copolymers are a family of biodegradable polymers with excellent biodegradability, thermoplastic processability and balanced mechanical properties. In this article, production of the monomers succinic acid and butanediol, synthesis, processing and properties of PBS and its copolymers are reviewed. The physical properties and biodegradation rate of PBS materials can be varied in a wide range through copolymerization with different types and various contents of monomers. PBS has a wide temperature window for thermoplastic processing, which makes the resin suitable for extrusion, injection molding, thermoforming and film blowing. Finally, we summarized industrialization and applications of PBS.

[Study on the orientation of poly(propylene terephthalate) fiber].

Poly (trimethyleneterephthalate) is a new polymer material. Using polaroid and horizontal ATR accessories combining FTIR spectrometer, the orientation of PPT fiber undergoing different drawing rate was studied. The dichroic ratio and orientation function were determined. The results show that both the dichroic ratio and the orientation function increased with drawing rate, but for dichroic ratio, there was a plateau when drawing rate was above 2,500 m.min-1.