Hydroxyl-functional hexagonal boron nitride nanosheets (OH-BNNSs) were prepared successfully by ultrasonic treatment, and then homogeneous dispersions of OH-BNNSs in 1,4-butanediol (BDO) were obtained. Various techniques were applied to characterize the OH-BNNSs and their hydroxyl functional groupd. Furthermore, biodegradable poly(butylene succinate) (PBS)/OH-BNNS nanocomposites were prepared by in situ polymerization of succinate acid (SA) and BDO containing well-dispersed OH-BNNS. The nucleating effect of low OH-BNNS loadings on PBS in the PBS/OH-BNNS nanocomposites was investigated. It is found that OH-BNNSs significantly improve the melt-crystallization temperature and degree of crystallinity of PBS during the nonisothermal crystallization process without changing the crystal structure of PBS. Moreover, the Avrami exponent n calculated for isothermal crystallization increased from 2 to 3 after the addition of 0.05 wt % OH-BNNSs. The nucleation density of PBS spherulites in the nanocomposites increased dramatically. These results demonstrate that OH-BNNSs function as an outstanding nucleating agent of PBS.

•Redox-initiated gelation is successfully conducted inside the rabbit eyes.•The redox-initiated gelation kinetic is characterized in detail in vitro.•The in-situ-formed PEG-based hydrogel is evaluated as vitreous substitute.Currently there is no material clinically available as a long-term vitreous substitute. In this study, an in-situ gelation system based on α-poly(ethylene glycol) methacrylate (α-PEG-MA) and a redox-initiated radical polymerization/crosslinking reaction was evaluated for this purpose. Ammonium persulfate (APS) and N,N,N′,N′-tetramethyl ethylene diamine (TMEDA) were used as initiators. The gelation time, rheological properties, reaction kinetics and swelling profiles were studied in detail and the system with 10 wt% of α-PEG-MA and 8 mM APS/TMEDA was chosen as the optimal material for in vivo studies. Using the rabbit as the animal model, we showed that the system did form a space-filling and transparent gel in the vitreous cavity, and the inflammation response could be controlled to an acceptable level.A redox-initiated in-situ-formed PEG hydrogel as vitreous substitute.

The details of poly(butylene fumarate) (PBF) as highly effective nucleating agent for poly(butylene succinate) (PBS) were systematically studied via X-ray diffraction, differential scanning calorimeter, polarized optical microscopy, and atom force microscopy. All results show that PBF can significantly improve the melt-crystallization temperature and the degree of crystallinity of PBS during the nonisothermal crystallization process. Both crystallization time span and spherulitic size of PBS decrease drastically with the addition of a small amount of PBF, which shows that PBF not only enhances the primary nucleation of PBS by epitaxial mechanism, but also greatly accelerates the secondary nucleation during spherulite growth. The secondary nucleation parameters of PBS, Kg and G0, are notably improved just with a small amount of PBF. Furthermore, the appearance of wrinkles on PBF-nucleated PBS ultrathin film visually suggests that PBF indeed affects the subsequent growth behavior, besides the primary nucleation.

Novel morphology of banded spherulite was observed in poly[(R)-3-hydroxyvalerate) (PHV) during its isothermal crystallization at temperatures between 50 and 80 °C. A novel optical technique, Polscope was applied to obtain both the birefringence retardation and azimuth angle of the slow optical axis at each pixel in the micrograph of the polycrystalline specimen. It is revealed that two different morphological regions, normal and eye-like regions, are derived from different growth axes of the lamellae along the radial direction. In the normal region, lamellae grow and twist along b axis, leading to the alternative strong and weak positive birefringence. In the eye-like region, they grow and twist along a axis, resulting in the alternative positive and negative birefringence. It is of particular interest to note that PHV lamellae in the two regions exhibit the opposite twist senses. To the best of our knowledge, it is the first report that an optically pure chiral polymer contains two lamellar twist senses in one spherulite. We attribute the driving force of lamellar twist in PHV spherulite to the unbalanced anisotropic surface stresses. A mechanical model is proposed to interpret the opposite twisting senses along the two orthogonal growth axes. The results demonstrate that the growth axis is one of the factors determining the twist handedness of the lamellae of chiral polymers.