Synthesis and characterization of arylmethyl sulfone dendrimers and hyperbranched poly(phenylene sulfide)/poly(sulfone)

In recent years, nonlinear polymers such as dendritic and hyperbranched macromolecules have attracted considerable attention owing to the potential new properties of their highly branched, highly functionalized, three-dimensional globular structures. Chemists have begun to explore controlled ways of making synthetic polymers with highly branched structures, known as dendrimers and hyperbranched polymers. Dendrimers have a well-defined and perfectly branching structure, and are built up by either a stepwise divergent or convergent approach. Hyperbranched polymers are prepared by a one-step polymerization process that yields a highly branched, irregular structure.;A synthetic approach to an arylmethyl sulfone dendrimer was explored based on a convergent synthesis. An A2B monomer with activated A sites and protected B site is required, and 5-sulfo-isophthalic acid sodium salt was used as a starting material. First, two carboxylic acids at the A sites were protected by esterification in methanol/concentrated sulfuric acid, then the sulfonic acid at the B site was protected by making a sulfonate ester via the sulfonyl chloride. Second, two A sites were activated by reducing the esters to benzyl alcohols, then transforming to benzyl chlorides to generate the phenyl 3,5---bis-chloromethyl-benzenesulfonate monomer. Following a common method for synthesis of sulfones, this monomer was reacted with benzenesulfinic acid sodium salt to make a generation I (G1) arylmethyl sulfone dendrimer. The deprotection of the phenylbenzenesulfonate was not successful. Literature methods such as decomposition with hydrazine and reduction all failed.;Hyperbranched poly(phenylene sulfide) was prepared from 3,5-dichlorobenzenethiol by one-pot approach using K2CO3 as base, NMP as solvent, and 150°C for 8 hours. Hyperbranched poly(phenylene sulfone) was generated by oxidization with H2O2 from hyperbranched poly(phenylene sulfide). A core-terminated hyperbranched poly(phenylene sulfide) was prepared by adding 1,3,5-trichlorobenzene as a core under the same conditions. An end-capped hyperbranched poly(phenylene sulfide) was made by adding 2-naphthalenethiol as an end-cap. The polymers were primarily characterized by size exclusion chromatography with light scattering detection (which provided the molecular weights and distributions) and thermal methods such as differential scanning calorimetry/thermogravimetric analysis. Polymerization for 8 hours at 150°C in NMP gave hyperbranched poly(phenylene sulfide) with an Mw of 29 kD and a polydispersity of 1.1; core-terminated hyperbranched poly(phenylene sulfide) with an Mw of 14 kD and a polydispersity of 1.1 and end-capped hyperbranched poly(phenylene-sulfide) an Mw of 18 kD and a polydispersity of 1.2. Hyperbranched poly-(phenylene sulfide), core-terminated hyperbranched poly(phenylene sulfide), end-capped hyperbranched poly(phenylene sulfide) and hyperbranched poly(phenylene sulfone) were amorphous with Tg of 74, 66, 75 and 203°C respectively and no apparent crystallinity by differential scanning calorimetry (DSC). Thermogravimetric analysis(TGA) showed that the materials were very thermally stable, with decomposition temperatures between 375 and 545°C in both air and N2 atmospheres.