Abstract
Hyperbranched siloxane-based polymers with ultra-high molecular weight were synthesized by the Piers–Rubinsztajn reaction between octakis(dimethylsiloxy) octasilsesquioxane with different dialkoxysilanes, using tris(pentafluorophenyl) borane as the catalyst. The origin of the high molecular weight is explained by the high reactivity of the catalyst and strain energy of isolated small molecule in which all eight silane groups close into rings on the sides of a single cubic cage. The structural tuneability was further demonstrated by use of methyl(3-chloropropyl)diethoxysilane, which generates a polymer with similar ultra-high molecular weight. Introduction of phosphonate groups through the chloropropyl sites later leads to functionalized polymers which can encapsulate various transition metal nanoparticles.
Highlights
Polyhedral oligomeric silsesquioxanes (POSSs), as first synthesized by D.W
We previously reported the synthesis of hyperbranched polysiloxanes through de-alkyl coupling reaction between hydrosilane and tetraethylorthosilicate catalyzed by B(C6 F5 )3 [36]
As shown in Scheme 1, polymer 1 was synthesized by the reaction of Q8 DMS with diphenyldimethoxysilane in cyclohexane, using tris(pentafluorophenyl) borane as the catalyst
Summary
Polyhedral oligomeric silsesquioxanes (POSSs), as first synthesized by D.W. Scott in 1946 [1], have attracted considerable attention. The alkene functional groups are first introduced into POSS cage molecules through organic synthesis, and polymerization techniques such as RAFT [14,15,16,17], ATRP [18,19], ROMP [20,21,22] allow subsequent generation of POSS-cage-containing polymers either by themselves or with other alkene monomers. Other ways, such as coupling reactions, have been utilized for a similar purpose.
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