Poly(dimethylsiloxane-urethane) membranes: effect of linear siloxane chain and caged silsesquioxane on gas transport properties

Functionalization of octaspherosilicate (HSiMe2O)8Si8O12 with buta-1,3-diynes by hydrosilylation

Hydrosilylation with octaspherosilicate (HSiMe2O)8Si8O12 (1) has provided hundreds of molecular and macromolecular systems so far, making this method the most popular in the synthesis of siloxane-based, nanometric, cubic, and reactive building blocks. However, there are no reports on its selective reaction with 1,3-diynes, which allows for the formation of new products with unique properties. Therefore, herein we present an efficient protocol for monohydrosilylation of symmetrically and non-symmetrically 1,4-disubstituted buta-1,3-diynes with 1. The compounds obtained bear double and triple bonds and other functionalities (e.g., Br, F, OH, SiR3), making them highly desirable, giant building blocks in organic synthesis and material chemistry. These compounds were fully characterized by 1H, 13C, 29Si, 1D NOE, 1H-13C HSQC NMR, FT-IR, and MALDI TOF MS, EA, UV-Vis, and TGA analysis. The TGA proved their high thermal stability up to 427 ℃ (Td10%) for compound 3j.

A printing-spray-transfer process for attaching biocompatible and antibacterial coatings to the surfaces of patient-specific silicone stents

An antibacterial coating with stable antibacterial properties and favorable biocompatibility is recognized as an effective method to prevent bacterial adhesion and biofilm formation on biomedical implant surfaces. In this study, a convenient and low-cost printing-spray-transfer process was proposed that enables reliably attaching antibacterial and biocompatible coatings to patient-specific silicone implant surfaces. A desktop three-dimensional printer was used to print the mold of silicone implant molds according to the characteristics of the diseased areas. Multiwalled carbon nanotubes (MWCNTs) uniformly decorated with silver nanoparticles (AgNPs/CNTs) were synthesized as the antibacterial materials for the spray process. The well-distributed AgNPs/CNT coating was anchored to the silicone surface through an in-mold transfer printing process. Stable adhesion of the coatings was assessed via tape testing and UV-vis spectra. Hardly any AgNPs/CNTs peeled off the substrate, and the adhesion was rated at 4B. Antibacterial activity, Ag release, cell viability and morphology were further assessed, revealing high antibacterial activity and great biocompatibility. The process proposed herein has potential applications for fabricating stable antibacterial coatings on silicone implant surfaces, especially for patient-specific silicone implants such as silicone tracheal stents.

Study of Gases Permeation in Necklace-Shaped Dimethylsiloxane Polymers Bearing POSS Cages

The transport of small gases (H₂, CO₂, N₂, O₂) through a series of novel membranes based on necklace-shaped inorganic polymers (DMS@POSS), in which a polyhedral oligomeric silsesquioxane (POSS) cage unit and soft chains of oligo-dimethyl siloxane (DMS) were alternately connected, was investigated. The influence of the DMS chain length and crosslinking density of the DMS@POSS on membrane properties were studied. The membranes revealed characteristic structure-property relation towards both glass transition and gases transport. Specifically, clear dependence of properties from the length of DMS units (or overall siloxane content) was revealed. Gas transport properties, when compared to state-of-art polydimethylsiloxane and commercial silicone rubber, demonstrated significantly higher selectivity of DMS@POSS for carbon dioxide (in CO₂/N₂), hydrogen (in H₂/N₂) and oxygen (in O₂/N₂) but lowered permeability, proportional to the amount of POSS in the material. With a precise control over mechanical and thermal properties compared to conventional silicone rubbers, described materials could be considered as materials of choice in niche gas separation or other applications.

Selective Hydrosilylation of Alkynes with Octaspherosilicate (HSiMe2 O)8 Si8 O12

Comprehensive studies on platinum-catalyzed hydrosilylation of a wide range of terminal and internal alkynes with spherosilicate (HSiMe2 O)8 Si8 O12 (1 a) were performed. The influence of the reaction parameters and the types of reagents and catalysts on the efficiency of the process, which enabled the creation of a versatile and selective method to synthesize olefin octafunctionalized octaspherosilicates, was studied in detail. Within this work, twenty novel 1,2-(E)-disubstituted and 1,1,2-(E)-trisubstituted alkenyl-octaspherosilicates (3 a-m, 6 n-t) were selectively obtained with high yields, and fully characterized (1 H, 13 C, 29 Si NMR, FTIR, MALDI TOF or TOF MS ES+ analysis). Moreover, the molecular structure of the compound (Me3 Si(H)C=C(H)SiMe2 O)8 Si8 O12 (3 a) was determined by X-ray crystallography for the first time. The developed procedures are the first that allow selective hydrosilylation of terminal silyl, germyl, aryl, and alkyl alkynes with 1 a, as well as the direct introduction of sixteen functional groups into the 1 a structure by the hydrosilylation of internal alkynes. This method constituted a powerful tool for the synthesis of hyperbranched compounds with a Si-O based cubic core. The resulting products, owing to their unique structure and physicochemical properties, are considered novel, multifunctional, hybrid, and nanometric building blocks, intended for the synthesis of star-shaped molecules or macromolecules, as well as nanofillers and polymer modifiers. In the presented syntheses, commercially available reagents and catalysts were used, so these methods can be easily repeated, rapidly scaled up, and widely applied.

Polyhedral oligomeric silsesquioxane/polyamide bio-nanocomposite membranes: structure-gas transport properties

Prepared cost-effective and environmentally-friendly POSS/PA by facile synthesis via solvent casting method. Conspectus study and morphology correlation with gas-transport properties. Effective H-bonds of POSS and PA facilitate separation properties.