Biobased Terpene Derivatives: Stiff and Biocompatible Compounds to Tune Biodegradability and Properties of Poly(butylene succinate)

Different copolymers incorporating terpene oxide units (e.g., limonene oxide) have been evaluated considering thermal properties, degradability, and biocompatibility. Thus, polycarbonates and polyesters derived from aromatic, monocyclic and bicyclic anhydrides have been considered. Furthermore, ring substitution with myrcene terpene has been evaluated. All polymers were amorphous when evaluated directly from synthesis. However, spherulites could be observed after the slow evaporation of diluted chloroform solutions of polylimonene carbonate, with all isopropene units possessing an R configuration. This feature was surprising considering the reported information that suggested only the racemic polymer was able to crystallize. All polymers were thermally stable and showed a dependence of the maximum degradation rate temperature (from 242 °C to 342 °C) with the type of terpene oxide. The graduation of glass transition temperatures (from 44 °C to 172 °C) was also observed, being higher than those corresponding to the unsubstituted polymers. The chain stiffness of the studied polymers hindered both hydrolytic and enzymatic degradation while a higher rate was detected when an oxidative medium was assayed (e.g., weight losses around 12% after 21 days of exposure). All samples were biocompatible according to the adhesion and proliferation tests performed with fibroblast cells. Hydrophobic and mechanically consistent films (i.e., contact angles between 90° and 110°) were obtained after the evaporation of chloroform from the solutions, having different ratios of the studied biobased polyterpenes and poly(butylene succinate) (PBS). The blend films were comparable in tensile modulus and tensile strength with the pure PBS (e.g., values of 330 MPa and 7 MPa were determined for samples incorporating 30 wt.% of poly(PA-LO), the copolyester derived from limonene oxide and phthalic anhydride. Blends were degradable, biocompatible and appropriate to produce oriented-pore and random-pore scaffolds via a thermally-induced phase separation (TIPS) method and using 1,4-dioxane as solvent. The best results were attained with the blend composed of 70 wt.% PBS and 30 wt.% poly(PA-LO). In summary, the studied biobased terpene derivatives showed promising properties to be used in a blended form for biomedical applications such as scaffolds for tissue engineering

Supramolecular Ligands in Gold(I) Catalysis

A supramolecular ligand-template strategy is applied to gold(I) catalysis. The supramolecular ligands, formed from a phosphoramidite backbone and two templates, display different regioselectivity in the hydroalkoxylation of allenes compared to non-supramolecular analogues. Based on these findings, the catalytic activity of gold(I) complexes could be tunable at

DTorial: An interactive tutorial framework for blind users in a Web 2.0 world

Effective tutorial systems can help promote products by reducing barriers of learning new applications. With dynamic web applications becoming as complex as desktop programs, there is a growing need for online tutorial/help systems. For visually impaired users the key limitations of traditional help systems are 1) poor access to help content with assistive technology, and 2) frequent reliance on videos/images to identify parts of web applications and demonstrate functionality. In this paper, we present a new interaction model, targeted towards screen-reader users, that describes how to embed an interactive tutorial within a web application. The interaction model is demonstrated within a system called DTorial, a fully functional dynamic audiobased tutorial with embedded content. While remaining within the web application, users can rapidly access any tutorial content, injected inline near relevant application controls, allowing them to quickly apply what they just heard to the application itself, without ever losing their position or having to shift windows. The model and implementation are grounded in sighted user help-systems literature and an analysis of screen-reader and Web-Application interactions. Lessons learned from the incremental design and evaluations indicate that providing visually impaired users with dynamic, embedded, interactive audio-based tutorial systems can reduce the barriers to new Web- Applications