We demonstrated here a novel and facile synthesis of two-dimensional (2D) covalent organic thin film with pore size around 1.5 nm using a planar, amphiphilic and substituted heptacyclic truxene based triamine and a simple dialdehyde as building blocks by dynamic imine bond formation at the air/water interface using Langmuir-Blodgett (LB) method. Optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM), all unanimously showed the formation of large, molecularly thin and free-standing membrane that can be easily transferred on different substrate surfaces. The 2D membrane supported on a porous polysulfone showed a rejection rate of 64 and 71% for NaCl and MgSO, respectively, and a clear molecular sieving at molecular size around 1.3 nm, which demonstrated a great potential in the application of pretreatment of seawater desalination and separation of organic molecules.
In this study, we probe various aspects of a post-polymerization double-modification strategy involving sequential thiol–epoxy and esterification reactions for the preparation of dual-functional homopolymers.
A new synthesis of hyperbranched polymers through proton transfer polymerization of thiol and epoxide groups is presented. For this, an AB 2 monomer bearing two epoxides and a thiol groups is synthesized. Base-catalyzed proton transfer polymerization of this monomer led to the formation of a polythioether-based hyperbranched polymer with a 65−69% degree of branching and carrying about 2% of disulfide-based structural defects. This polymer contained two reactive sites, a hydroxyl group and an epoxide unit, distributed throughout the branched scaffold. The epoxide groups could be employed in anchoring an alkyl, aryl, or ethylene oxide chain through a thiol−epoxy reaction, while the hydroxyl groups produced during the polymerization and the first functionalization reactions could be engaged in attaching positively charged primary ammonium groups to the branched backbone. These sequential postpolymerization modifications transformed the general dual-reactive scaffold into dual-functionalized hyperbranched materials with potential utility in the arena of gene delivery applications.
A synthetic route is developed for the preparation of an AB-type of monomer carrying an epoxy and a thiol group. Base-catalyzed thiol-epoxy polymerization of this monomer gave rise to poly(b-hydroxythio-ether)s. A systematic variation in the reaction conditions suggested that tetrabutyl ammonium fluoride, lithium hydroxide, and 1,8-diazabicycloundecene (DBU) were good polymerization catalysts. Triethylamine, in contrast, required higher temperatures and excess amounts to yield polymers. THF and water could be used as polymerization mediums. However, the best results were obtained in bulk conditions. This required the use of a mechanical stirrer due to the high viscosity of the polymerization mixture. The polymers obtained from the AB monomer route exhibited significantly higher molecular weights (M w 5 47,700, M n 5 23,200 g/mol) than the materials prepared from an AA/BB type of the monomer system (M w 5 10,000, M n 5 5400 g/mol). The prepared reactive polymers could be transformed into a fluorescent or a cationic structure through postpolymerization modification of the reactive hydroxyl sites present along the polymer backbone.
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