Macromolecules, Vol.50, No.24, 9656-9665, 2017
Comb Polymer Network of Polydimethylsiloxane with a Novolac Stem: Synthesis via Click Coupling and Surface Morphology Architecturing by Solvents
Cuprous iodide-catalyzed azide alkyne cycloaddition (CuAAC) offered an easy route for the synthesis of organic-inorganic comb polymer networks with a short stem composed of novolac and arms made of lightly cross-linked polydimethylsiloxane (PDMS). This was achieved by the click reaction between novolac propargyl ether (NPE) and azide telehelic PDMS (PDMS-AZ) in a single step at near-ambient conditions. The precursors were absolutely characterized. The reaction, monitored by differential scanning calorimetry and rheometry, implied the cross-linking occurring at relatively low temperatures. The gelation occurred at a lower conversion than predicted by the Flory-Rehner equation. The reaction was facilitated by polar solvents. Dynamic mechanical analysis (DMA) implied biphasic behavior for the cross-linked polymer, the transitions of the soft and hard segments appearing at -110 and 26 degrees C, respectively. The calculated cross-link densities tallied well with the expected network structure. Solvents influenced the reorganization of the soft and hard segments as reflected in the water contact angle of these resins cast from different solvents. The morphological analyses by scanning electron microscopy and atomic force microscopy substantiated these findings.