Novel Organic/Inorganic Hybrid Star Polymer Surface-Crosslinked with Polyhedral Oligomeric Silsesquioxane

Novel organic/inorganic hybrid star polymer was prepared dually crosslinked within inner-core via divinylbenzene (DVB) and outer-surface via octafunctional polyhedral oligomeric silsesquioxane (POSS). Core cross-linked star polymers bearing dialkynyl-terminated polystyrene arms, (dialkynyl-PS)(n)-CCL, were synthesized at first by the atom transfer radical polymerization (ATRP) of DVB using alpha,alpha-dialkynyl-terminated PS macroinitiator, followed by the subsequent fractionation. Under high dilution conditions, (dialkynyl-PS)(n)-CCL was subjected to surface cross-linking with octa(3-azidopropyl) polyhedral oligomeric silsesquioxane, POSS-(N-3)(8), via click reaction, affording POSS-functionalized hybrid polymer doubly cross-linked within core and surface regions, SCL-(PS)(n)-CCL. FT-IR, H-1 NMR, GPC, and elemental analysis results revealed that on average, the obtained hybrid polymer possesses a cross-linked PDVB inner core, similar to 14 linear PS arms (the M-w per arm of 5.1 kDa), and similar to 4-5 POSS moieties at outer surface. Differential scanning calorimetry (DSC) thermograms and thermogravimetric analysis (TGA) revealed that after surface cross-linking the thermal stability of SCL-(PS)(n)-CCL is considerably improved. This work provides a proof-of-concept example for the preparation of dually cross-linked hybrid star polymer, which represents a novel category of organic/inorganic composite materials with unique chain architectures.