Milutin N. Govedarica

The thermogravimetric analysis of some polysiloxanes

Thermogravimetric (TG) and differential thermogravimetric analyses (DTG) of some homo- and copolymers of dimethylsiloxane have been performed. The effect of the presence of hydrido-substituents and/or vinyl end-groups on the thermal and thermo-oxidative stability of the examined polysiloxanes was determined. In all cases it was found that these polysiloxanes are thermally less stable than the parent all-methyl polysiloxane.

Synthesis of α,ω-dicarboxypropyl oligodimethylsiloxanes by ion-exchange resin catalyzed equilibration polymerization

Abstract A series of α,ω-dicarboxypropyl oligodimethylsiloxanes of predetermined molecular weights was synthesized from octamethylcyclotetrasiloxane, D 4 , and 1,3-bis-(3-carboxypropyl)tetramethyldisiloxane (BCPTMDS) by a heterogeneously catalyzed equilibration polymerization reaction using a macroporous cation-exchange resin as an acidic catalyst. The structure of the obtained linear oligomers was verified by IR, 1 H- and 13 C-NMR spectroscopy, while their molecular weights were determined by 1 H-NMR spectroscopy, vapor pressure osmometry, functional group analysis and gel permeation chromatography. It was shown that the expected target molecular weights, ranging between 600 and 3500, were achieved with a satisfactory accuracy.

Functionalized oligopolysiloxanes by heterogeneously catalyzed equilibration polymerization reactions

SummaryA new general procedure for preparation of functionalized oligopolysiloxanes of predetermined molecular weight is described. It utilizes heterogeneously catalyzed siloxane equilibration polymerization reactions which do not require troublesome and sometimes difficult post-preparative work-up procedures usually encountered with the well known homogeneously catalyzed corresponding reactions. The method is described using as example the preparation of α, ω-telechelic vinyldimethylsiloxy-oligopolydimethylsiloxanes from octamethylcyclotetrasiloxane and 1,3-divinyltetramethyldisiloxane, but reference to the preparations of trimethylsiloxy-, dimethylsiloxy-and carboxypropyldimethylsiloxyoligopolydimethylsiloxanes, oligopolymethylhydridosiloxanes or their copolymers is also made.

Kinetics of the Formation of Poly(Methyldecylsiloxane) by Hydrosilylation of Poly(Methylhydrosiloxane) and 1-Decene

Poly(methylhydrosiloxane) [PMHS], prepared by siloxane equilibration reaction, was used for the hydrosilylation with 1-decene to obtain poly(methyldecylsiloxane) [PMDS]. Pt(0)-1,3- divinyltetramethyldisiloxane complex was used as a catalyst for hydrosilylation reaction. In order to investigate the kinetics of the formation of PMDS, a series of experiments was performed at different reaction temperatures (from 48 to 64 °C) with catalyst concentrations of 7.0 · 10-7 mol of Pt per mol of CH=CH2. All reactions were carried out in bulk, with equimolar amounts of the reacting Si-H and CH=CH2 groups. The course of the reactions was monitored by following the disappearance of the Si-H bands by quantitative infrared spectroscopy. The obtained results show that an induction period occurs at lower reaction temperatures and that the rate of Si-H conversion follows the first-order kinetics.