Trimethylsilyl ethers of amphiphilic carbosilane dendrimers of the third–fifths generations. Specific features of hydrolysis at the water-air interface

Abstract

Carbosilane dendrimers from the third to fifth generation with hydroxy groups in the surface layer of the dendrimer were synthesized, as well as their analogs with latent hydroxy groups. The dendrimers differ by the density of the carbosilane core and hydrophilic shell. The amphiphilic nature of the synthesized compounds was manifested already for more hydro phobic trimethylsilyl derivatives of dendrimers. This allowed one to observe the hydrolysis of these objects during compression of their monolayers at the water surface in the Langmuir bath. The parameters of the molecular structure of the dendrimers exert a determining effect on the rate and completeness of the hydrolysis.Amphiphilic dendrimers are stable monomolecular mi celles, unlike multimolecular micelles, which are formed by linear amphiphilic systems. 1-3 This specific feature of molecular organization assumes a basically different be havior of amphiphilic dendrimers at the water-air inter face. Common micelle forming surfactants form classical lamellar monolayers with distinct orientation of each surfactant molecule in the monolayer, 4 whereas for dendrimers this rearrangement is joined with conforma tional strains. 5-12 From this point of view, investiga tion of the compression of monolayers of amphiphilic dendrimers with different molecular parameters can pro vide very important information on the relationship be tween the molecular structure of the dendrimers and con formational flexibility of their molecules upon a change in the external conditions. To obtain information of this kind, one need representative series of studied objects in which these or other structural factors are varied gradually in order to reveal certain tendencies and monitor their development.We have earlier 13 synthesized a series of amphiphilic dendrimers of the fifth generation with different densities of the molecular structure of the hydrophobic core of the dendrimer and hydrophilic shell. The purpose of the present work is to synthesize representative series of amphiphilic carbosilane dendrimers of the third-fifth generations with different ratios of the hydrophobic and hydrophilic parts of the molecular structure as the tri methylsiloxy derivatives and to study the hydrolysis pro cess in the monomolecular layers at the water-air in terface. Results and DiscussionSynthesis. Polyallyl carbosilane dendrimers with dif ferent densities of the molecular structure were used as A (hereinafter )

From the discovery of sodiumoxyorganoalkoxysilanes to the organosilicon dendrimers and back

“…36 For example, it was trimethylsilyl protection that allowed us to carry out a systematic investigation of carbosilane dendrimers with hydrophilic surface layer. 37 Fluorocontaining dendrimers belong to the hybrid siloxane carbosilane dendrimers. 38,39 All the library of LC dendrimers synthesized in collaboration with the group of Professor Shibaev from Moscow State University possesses flexible siloxane spacer 17,40,41 (Fig.…”