Synthesis of Ladder Silsesquioxanes by in situ Polycondensation of Cyclic Tetravinylsiloxanetetraols

Abstract

Functionalized tetrahydroxy-cyclotetrasiloxanes are very attractive precursors of tetrasiloxane ring systems in linear silsesquioxanes (LPSQs). Vinyl groups are especially important since they can be employed for various chemical transformations (e.g. hydrosilylation, metathesis reactions, thiol-ene addition). However, isolation of such highly reactive species bearing small side substituents at silicon atoms with high yield is challenging. We overcame the problem by in situ condensation of 2,4,6,8-tetrahydroxy-2,4,6,8-tetravinyl-cyclotetrasiloxanes, derived from potassium organosiloxanolateOligomeric LPSQ materials having a siloxane backbone with ladder structure and functionalized with side vinyl groups were thus prepared. Hexamethyldisilazane was employed for chain termination. The liquid materials show remarkably good solubility in organic solvents. They were isolated and characterized using spectroscopic methods. Information on their structure and molecular masses was derived from MALDI-TOF and MALLS measurements. Size exclusion chromatography (RI detection, volume of elution measurements) was also used. The products were characterized by wide-angle X-Ray diffraction measurements (WAXS) and their thermal characteristics (TGA and DSC) were obtained.

Supramolecular self-assembly of linear oligosilsesquioxanes on mica – AFM surface imaging and hydrophilicity studies

“…Chemical modification of mica using reactive silanes was also reported [32][33][34][35] . The results are consistent with those already reported 40 by us 41 . We have found that muscovite mica can be easily modified using new linear oligosilsesquioxanes (LPSQ-COOH), functionalized with side 2-(carboxymethylthio)ethyl groups at their doublestrand backbone.…”

A Highly Effective Route to Si−O−Si Moieties through O‐Silylation of Silanols and Polyhedral Oligomeric Silsesquioxane Silanols with Disilazanes

“…Based on the known literature, [26,36] mechanisms of all transformationsa re illustrated in Figures 5a nd 6. The silylation by HMDS proceeds through the formation of af our-centered transition state and is followed by an ucleophilic attack of oxygen toward the silicon atom in the HDMS molecule.…”

“…Although inorganic materials, [19][20][21][22] alcohols, [23][24][25][26][27][28][29][30] phenols, [26][27][28][29] carbohydrates, [29] carboxylic acids, [31] oximes, [32] ande ven thiols [33] have been successfully silylated by various disilazanes, the use of these silylatinga gents in O-metalation of simple silanols and polyhedralo ligomeric silsesquioxane (POSS) silanols has never been comprehensivelys tudied.T herea re only few examples: Lebedeve tal. [36] They tested this reactionu nder many conditions and obtainedt he best resultsi nt oluene at 110 8Ca fter 24 h. Furthermore, Pike investigated the reactionb etween primary silylamines with somes ilanols in the presence of acidic and basic catalysts. [34] However,s ensitive halosilanes were utilized as additional substrates and activators.…”

“…[35] Kowalewskaa nd Nowacka employed HMDS forc hain terminationd uring the synthesis of ladder silsesquioxanes. [36] They tested this reactionu nder many conditions and obtainedt he best resultsi nt oluene at 110 8Ca fter 24 h. Furthermore, Pike investigated the reactionb etween primary silylamines with somes ilanols in the presence of acidic and basic catalysts. [37,38] Ac omprehensive survey of the use of commercially available disilazanes as well as simple silanols and POSS silanols has not been conducted.…”

Synthesis of Polycyclic and Cage Siloxanes by Hydrolysis and Intramolecular Condensation of Alkoxysilylated Cyclosiloxanes

“…Controlled intermolecular polycondensation of Ph 4 (HO) 4 Si 8 O 12 will enable the production of an ew ladder-like polysiloxane in as imilar manner to the synthesis of laddersiloxanes from cyclotetrasiloxanes (see Figure S21). [45,46] In addition, when Ph 4 (HO) 4 Si 8 O 12 is silylated with alkoxy(chloro)silanes and subjected to furtheri ntramolecular condensation, stepwise extension of the cage structure can be expected (see Figure S22). Please note that the feasibility of formation of such interesting structures may be low because of the strain of the bond angles.…”