Cagelike Precursors of High-Molar-Mass Silsesquioxanes Formed by the Hydrolytic Condensation of Trialkoxysilanes

Abstract

High-molar-mass silsesquioxanes (SSQO) based on (3-glycidoxypropyl)trimethoxysilane (GPMS) and (3-methacryloxypropyl)trimethoxysilane (MPMS) were synthesized. The hydrolytic condensation of GPMS was performed using HCOOH (0.1 N) as catalyst, keeping the molar ratio H 2O/Si ) 3. A first step was performed in tetrahydrofuran (THF) at 50°C, followed by a second step in diglycidyl ether of bisphenol A (DGEBA), where temperature was increased in steps up to 140°C. The hydrolytic condensation of MPMS was performed in bulk with HCOOH 98%, at T ) 50 or 70°C, using molar ratios of HCOOH/Si ) 3 or 6. Homogeneous solutions were obtained for both silanes. The reaction was followed by size exclusion chromatography (SEC), and final products were characterized by matrix-assisted ultraviolet laser desorption/ionization time-of-flight mass spectrometry (UV-MALDI-TOF MS), FTIR, and 1 H and 29 Si NMR. Molar-mass distributions showed the presence of clusters corresponding to products formed in different generations. With the aid of UV-MALDI-TOF MS, the different species present in every cluster could be identified for one of the silsesquioxanes derived from MPMS. During the initial stage of the hydrolytic condensation, species with 7-12 Si atoms were produced. They mainly consisted of incompletely condensed polyhedra (species with 1-3 OH per molecule) and ladder-type structures (species with 4 OH per molecule). Species with more OH groups were condensed with a higher probability, giving place to a second generation of products. This process accounts for the presence of a cluster of species with 14-24 Si atoms and the enrichment of the first cluster in the more condensed structures (T 7(OH), T8(OH)2, and T9(OH)). Third and fourth generations of condensation products were also present. Structures of different species may be depicted as combinations of incompletely condensed polyhedra with ladder fragments.

Selective Vinyl Functionalization of Octakis(dimethylsiloxy)octasilsesquioxane with Allylbenzene and 1,5-Hexadiene and Copolymerization of the Products with Bis(dimethylsilyl)benzene

“…[37][38][39][40][41][42][43][44][45][46] Figure 3 shows the mass spectra in the 1500-2100 m=z range, using DHBA as matrix. 1a-c gave spectra corresponding to their ½M þ H þ ions.…”

UV-Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of synthetic polymers by using nor-harmane as matrix

“…Recently we have described the UV-MALDI analysis of four families of new polysilsesquioxanes whose oligomers structure could be assigned. [21][22][23][24][25] In these papers we only described in detail the spectra obtained in positive ion mode, and results of similar quality were obtained with various matrices i.e. GA, IAA, HABA and nor-harmane.…”

“…Low-soluble and nonsoluble polymers are generally not analyzable by UV-MALDI although the successful use of DMSO in the analysis of chiral polyhydroxy polyamides and the details for the sample preparation method has been described. 20 Nor-harmane has been shown to be a good UV-MALDI matrix for the analysis of a wide variety of non-commercial synthetic polymers [19][20][21][22][23][24][25] and bio-macromolecules, 6,9,12,13,16,17 In the present study commercially available synthetic polymers such as PEG, PMMA, PS and poly(dimethyl)siloxane (PDMS) have been selected for UV-MALDI analysis with nor-harmane. These experiments have been conducted in positive and negative ion modes and the efficiency of the desorption/ionization processes, with and without ionizing salt, have been compared.…”

“…2,3,4,7,8,10,11 Pyridoindole compounds such as commercial β-carbolines (9H-pyrido [3,4-b]indoles) have been reported as useful matrices for proteins, 12-15 sulfated carbohydrates 12,13,[15][16][17][18] and some non-commercial synthetic polymers (polyesters, polyamides and silesquioxanes). [19][20][21][22][23][24][25] Mercaptobenzothiazoles have also been reported as useful matrices for synthetic polymers. 5 It is interesting to point out that, although the dependence on wavelength of the laser source has been taken into account, [26][27][28][29] little attention has been paid to the chemical structure (functional groups or geometry) and photochemical properties of potential matrix compounds.…”

Hedgehog Buckyball: A High-Symmetry Complete Polyhedral Oligomeric Silsesquioxane (POSS)

“…The intensity of the MP-T60 present can be determined by GPC or size exclusion chromatography (SEC), and the mass of the elutant is again measured by a mass spectrometer [25,26]. Further research will be conducted on this MP-HBB to separate it from multiple MSSO structures using a gel permeation column.…”