Cyclic Polysiloxanes with Linked Cyclotetrasiloxane Subunits

Yu, Jianyi; Liu, Yuzhou

doi:10.1002/ange.201703347

Cited by 8 publications

(1 citation statement)

References 40 publications

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“…328 Another interesting and unique structure generated with the Piers−Rubinsztajn reaction is the structure of silicones with a multicyclic pattern. Chojnowski and co-workers 329 330 The formation of the macrocyclic structure of the linked cyclotetrasiloxane was confirmed by the absence of end groups from both NMR and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) analysis. For the high-molecular-weight fraction of the polymer sample, which is not suitable for MALDI-TOF analysis, the authors obtained atomic force microscopy (AFM) images to confirm the ring architecture.…”

Section: Lewis Acid-catalyzed Polymerization Involving (Hydro)silanesmentioning

confidence: 95%

Polymerization of Polar Monomers Mediated by Main-Group Lewis Acid–Base Pairs

2018

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The development of new or more sustainable, active, efficient, controlled, and selective polymerization reactions or processes continues to be crucial for the synthesis of important polymers or materials with specific structures or functions. In this context, the newly emerged polymerization technique enabled by main-group Lewis pairs (LPs), termed as Lewis pair polymerization (LPP), exploits the synergy and cooperativity between the Lewis acid (LA) and Lewis base (LB) sites of LPs, which can be employed as frustrated Lewis pairs (FLPs), interacting LPs (ILPs), or classical Lewis adducts (CLAs), to effect cooperative monomer activation as well as chain initiation, propagation, termination, and transfer events. Through balancing the Lewis acidity, Lewis basicity, and steric effects of LPs, LPP has shown several unique advantages or intriguing opportunities compared to other polymerization techniques and demonstrated its broad polar monomer scope, high activity, control or livingness, and complete chemo-or regioselectivity, as well as its unique application in materials chemistry. These advances made in LPP are comprehensively reviewed, with the scope of monomers focusing on heteroatom-containing polar monomers, while the polymerizations mediated by main-group LAs and LBs separately that are most relevant to the LPP are also highlighted or updated. Examples of applying the principles of the LPP and LP chemistry as a new platform for advancing materials chemistry are highlighted, and currently unmet challenges in the field of the LPP, and thus the suggested corresponding future research directions, are also presented. CONTENTS 4.1.4. Vinyl Phosphonates 4.1.

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Section: Lewis Acid-catalyzed Polymerization Involving (Hydro)silanesmentioning

confidence: 95%

Polymerization of Polar Monomers Mediated by Main-Group Lewis Acid–Base Pairs

2018

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One‐Pot Sequence‐Controlled Synthesis of Oligosiloxanes

et al. 2018

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Silicones (organopolysiloxanes) have found applications in awide range of researchareas,and their unique and valuable properties have rendered these materials virtually irreplaceable.D espite the fact that silicones have been employed industrially for more than 70 years,s ynthetic routes to generate silicones remain limited, and the sequence-controlled synthesis of oligo-and polysiloxanes still represents am ajor challenge in silicone chemistry.D escribed here is ah ighly selective sequence-controlled synthesis of linear, branched,a nd cyclic oligosiloxanes by simple iteration of two reactions,s pecifically,aB(C 6 F 5 ) 3 -catalyzed dehydrocarbonative cross-coupling of alkoxysilanes with hydrosilanes and aB (C 6 F 5 ) 3 -catalyzed hydrosilylation of carbonyl compounds,i nas ingle flask. The sequence of the resulting oligosiloxanes can be controlled precisely by the order of addition of the hydrosilane monomers.Silicones,that is,oligomeric and polymeric compounds that contain repeating -Si-O-backbone (siloxane) units,e xhibit unique properties which include increased resistance to heat and oxidation, high gas permeability,a nd high electrical insulation, and are thus valuable materials with widespread industrial applications as oils,g reases,r ubbers,a nd resins. [1] However,t he persistent lack of ap ractical, reliable,a nd/or simple methods to precisely synthesize avariety of oligo-and polysiloxane sequences significantly limits their further development with respect to materials science and industrial applications.S uch materials are usually generated by the hydrolysis/dehydration of chlorosilanes or alkoxysilanes,o r by the base-or acid-catalyzed ring-opening polymerization of cyclic siloxane monomers. [2] While these methods are suitable for the industrial production of silicones from inexpensive silane monomers,c ontrol over the siloxane sequence is inherently impossible by these methods.I nc ontrast, several types of catalytic cross-coupling reactions for the formation of siloxane bonds have recently been reported by several research groups,e ven though control over the sequence in the resulting oligo-and polysiloxanes remains virtually unexplored. [3, 4] In rare,y et pioneering examples,M asamune and co-workers synthesized oligosiloxane dendrimers by step-bystep condensations of silanol and chlorosilane building blocks, [5] whereas the stepwise synthesis of sequence-specific oligosiloxanes was achieved using iterative condensations of silane monomers such as dichlorosilanes and silanediols. [6] However,these methods still rely on conventional condensations of silanols with chlorosilanes,and require astoichiometric amount of ab ase,s uch as pyridine or triethylamine,t o neutralize the concomitantly produced hydrogen chloride. Thus,t he generation of an equimolar amount of either pyridinium or ammonium salts after the formation of the siloxane bond is unavoidable,a nd aw orkup process to remove these byproducts is necessary after each siloxane bond-formation step,w hich renders the whole processes laborio...

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