Chemistry

Corresponding Member of the Academy of Sciences of the USSR K. A. Andrianov

ON ROUTES FOR THE SYNTHESIS OF REGULAR ORGANOELEMENT POLYMERS OF SPATIAL STRUCTURE

High-molecular-weight compounds with branched, cross-linked, and spatial molecules are obtained by polymerization or polycondensation of various polyfunctional monomers. Polyfunctional monomeric compounds, irrespective of the reaction by which they are converted into polymers, lead to the formation of large molecules of irregular structure, with an arbitrary distribution of side branches and bridges between the main chains of the molecules. Attempts to regulate branching in the chains of the main molecules have so far not led to positive results. Meanwhile, the development of methods that make it possible to regulate the order of distribution of branches and of bridges linking the main chains is of great theoretical interest. By regulating the order of distribution and the distances between branches in the main chains of molecules, it is possible to influence the properties of polymers through the structure of the polymer molecules with only an insignificant change in its composition. We have carried out the synthesis of regular polymers of spatial structure on the basis of polyfunctional oligomers containing monofunctional groups at the ends of the branches. The synthesis of such oligomers and polymers was carried out by means of the following reactions:

$$ 4\mathrm{NaO}\left(\begin{array}{c} \mathrm{CH}_3\\ |\\ \mathrm{SiO}\\ |\\ \mathrm{CH}_3 \end{array}\right)_4\mathrm{ONa} +\mathrm{SiCl}_4 \to \mathrm{Si}\left[ \mathrm{O}\left(\begin{array}{c} \mathrm{CH}_3\\ |\\ \mathrm{Si}\\ |\\ \mathrm{CH}_3 \end{array}\right)_4\mathrm{ONa} \right]_4 +4\mathrm{NaCl}, $$

$$ \mathrm{Si}\left[ \mathrm{O}\left(\begin{array}{c} \mathrm{CH}_3\\ |\\ \mathrm{SiO}\\ |\\ \mathrm{CH}_3 \end{array}\right)_4\mathrm{Na} \right]_4 +4\mathrm{CH}_3\mathrm{COOH} \to \mathrm{Si}\left[ \mathrm{O}\left(\begin{array}{c} \mathrm{CH}_3\\ |\\ \mathrm{Si}\\ |\\ \mathrm{CH}_3 \end{array}\right)_4\mathrm{OH} \right]_4 +4\mathrm{CH}_3\mathrm{COONa}. $$

The yield of oligomer reaches 90–95%.

The silicon-organic polyfunctional oligomer, which is a mobile liquid at room temperature and contains reactive hydroxyl groups, readily condenses on heating at temperatures above 230°. Condensation of the oligomer proceeds by a stepwise mechanism, with elimination of water and formation of a polymer according to the scheme:

$$ 2\mathrm{Si}\left[ \left(\begin{array}{c} \mathrm{CH}_3\\ |\\ \mathrm{OSi}\\ |\\ \mathrm{CH}_3 \end{array}\right)_4 \mathrm{OH} \right]_4 \xrightarrow{\text{heating}} \left[ \mathrm{HO}\left(\begin{array}{c} \mathrm{CH}_3\\ |\\ \mathrm{SiO}\\ |\\ \mathrm{CH}_3 \end{array}\right)_4 \right]_3 \cdot \mathrm{SiO} \left[ \begin{array}{c} \mathrm{CH}_3\\ |\\ \mathrm{SiO}\\ |\\ \mathrm{CH}_3 \end{array} \right]_8 -\mathrm{Si} \left[ \begin{array}{c} \mathrm{CH}_3\\ |\\ \mathrm{OSi}\\ |\\ \mathrm{CH}_3 \end{array} \right]_4 \mathrm{OH} \Bigg]_3 . $$

In the initial stage of condensation the polymer retains its solubility in organic solvents, but on further heating it loses the ability to dissolve. Consequently, further condensation leads to higher-molecular-weight products formed

as a result of the interaction of terminal hydroxyl groups according to the scheme:

\[ n\left[ \mathrm{HO} \left( \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right)_4 \right]_8 \mathrm{Si{-}O{-}} \left[ \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right]_8 \mathrm{Si} \left[ \left( \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{OSi}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right)_4 \mathrm{OH} \right]_8 \longrightarrow \]

\[ \longrightarrow \begin{matrix} -\mathrm{O{-}Si{-}O{-}}\left(\begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array}\right)_8\mathrm{{-}Si{-}O{-}}\\ \quad\left(\mathrm{H_3CSiCH_3}\right)_8 \qquad\qquad \left(\mathrm{H_3CSiCH_3}\right)_8\\ \mathrm{O{-}Si{-}O{-}}\left(\begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array}\right)_8\mathrm{{-}Si{-}O{-}} \end{matrix} +\mathrm{H_2O}. \]

From the reaction scheme given it is evident that the distances between silicon atoms bonded to four oxygen atoms in the molecule are determined by twice the number of dimethylsiloxane groups in the oligomer taken into the reaction. The high functionality of the oligomer, upon deep polycondensation, leads to a spatial polymer in which the branches or bridges between the main chains are distributed regularly. The silicon atoms bonded to four oxygen atoms in the molecule are also distributed at equal distances from one another.

A polyorganosiloxane of regular structure was also obtained by condensation of a trifunctional oligomer according to the reaction:

\[ 3\mathrm{HO} \left[ \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right]_9 \mathrm{H} + \mathrm{C_6H_5SiCl_3} \xrightarrow{\mathrm{C_6H_5N}} \left[ \mathrm{HO} \left( \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right)_9 \right]_3 \mathrm{SiC_6H_5} + 3\mathrm{HCl}. \]

Upon heating, such an oligomer readily condenses with elimination of water according to the scheme:

\[ 2\left[ \mathrm{HO} \left( \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right)_9 \right]_3 \mathrm{SiC_6H_5} \longrightarrow \left[ \mathrm{HO} \left( \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right)_9 \right]_2 \mathrm{{-}Si{-}O} \left( \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{{-}SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right)_{18} \mathrm{{-}Si{-}} \left[ \left( \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{OSi}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right)_9 \mathrm{OH} \right]_2 + \mathrm{H_2O}. \]

In the initial stage of condensation, the reaction product remains soluble in benzene and toluene, but upon further heating it loses its ability to dissolve, converting into a structured polymer

\[ n\left[ \mathrm{HO} \left( \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right)_9 \right]_2 \left[ \begin{array}{c} \mathrm{C_6H_5}\\[-2mm] |\\[-2mm] \mathrm{SiO} \end{array} \right] \left[ \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{Si{-}O}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right]_{18} \left[ \begin{array}{c} \mathrm{C_6H_5}\\[-2mm] |\\[-2mm] \mathrm{Si} \end{array} \right] \left[ \left( \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{OSi{-}}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right)_9 \mathrm{OH} \right]_2 \longrightarrow \]

\[ \longrightarrow \begin{matrix} \mathrm{H_5C_6{-}Si{-}O} \left(\begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{{-}SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array}\right)_{18} \mathrm{{-}Si{-}C_6H_5} \\[1mm] \left(\mathrm{H_3CSiCH_3}\right)_{18} \qquad\qquad \left(\mathrm{H_3CSiCH_3}\right)_{18} \\[1mm] \mathrm{H_5C_6{-}Si{-}O} \left(\begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{{-}SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array}\right)_{18} \mathrm{{-}Si{-}C_6H_5} \end{matrix} +\mathrm{H_2O}. \]

A polymer of this composition is an elastic product at room temperature.

A study of the polycondensation reaction of \(\alpha,\omega\)-dihydroxydimethylsiloxane with titanium tetrachloride showed that, in the presence of ammonia, a titanoorganosiloxane oligomer containing monofunctional groups at the ends of the branches is formed. The reaction proceeds with formation of a polyfunctional titanodimethylsiloxane oligomer according to the scheme:

\[ \mathrm{HO} \left[ \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right]_{13} \mathrm{H} + \mathrm{TiCl_4} \xrightarrow{4\mathrm{NH_3}} 4\mathrm{NH_4Cl} + \left[ \mathrm{HO} \left( \begin{array}{c} \mathrm{CH_3}\\[-2mm] |\\[-2mm] \mathrm{SiO}\\[-2mm] |\\[-2mm] \mathrm{CH_3} \end{array} \right)_{13} \right]_4 \mathrm{Ti}. \]

The content of hydroxyl groups, titanium, and silicon, the elemental composition, and the molecular weight corresponded to the tetrafunctional titanodimethylsiloxane oligomer given in the equation. This compound is a liquid substance at room temperature,

readily soluble in benzene, toluene, and other solvents. An analogous reaction was carried out between α,ω-dihydroxydimethylsiloxane containing 13 dimethylsiloxane groups and titanium tetrachloride. As a result, a tetrafunctional oligomer was obtained whose composition, number of hydroxyl groups, and molecular weight corresponded to a compound of the following composition:

\[ \left[ \mathrm{HO} \left( \begin{array}{c} \mathrm{CH_3}\\ |\\ \mathrm{SiO}\\ |\\ \mathrm{CH_3} \end{array} \right)_{13} \right]_4 \mathrm{Ti}. \]

This tetrafunctional titanodimethylsiloxane oligomer was a viscous liquid at room temperature, readily soluble in organic solvents. The experiments described showed that in the reactions of α,ω-dihydroxydimethylsiloxanes or α,ω-sodium oxydimethylsiloxanes with tetrafunctional compounds, such as silicon tetrachloride or titanium tetrachloride, polyfunctional oligomers can be obtained. A twofold excess of the functional groups of one of the components and mild reaction conditions limit the development of the reaction in the direction of polymer formation. Such a course of reaction between di- and tri- or tetrafunctional compounds is important for developing methods of synthesis of polyfunctional organoelement oligomers containing monofunctional groups at the ends of the branches.

Tetrafunctional titanodimethylsiloxane oligomers, when heated at 150–200°, condense with liberation of water according to the reaction

\[ 2 \left[ \mathrm{HO} \left( \begin{array}{c} \mathrm{CH_3}\\ |\\ \mathrm{SiO}\\ |\\ \mathrm{CH_3} \end{array} \right)_{13} \right]_4 \mathrm{Ti} \rightarrow \left[ \mathrm{HO} \left( \begin{array}{c} \mathrm{CH_3}\\ |\\ \mathrm{SiO}\\ |\\ \mathrm{CH_3} \end{array} \right)_{13} \right]_3 \mathrm{TiO} \left( \begin{array}{c} \mathrm{CH_3}\\ |\\ \mathrm{SiO}\\ |\\ \mathrm{CH_3} \end{array} \right)_{26} \rightarrow \mathrm{Ti} \left[ \left( \begin{array}{c} \mathrm{CH_3}\\ |\\ \mathrm{OSi}\\ |\\ \mathrm{CH_3} \end{array} \right)_{13} \mathrm{OH} \right]_3 . \]

The polymer in the initial stage of condensation is soluble in benzene, toluene, and other organic solvents. Further heating leads to structuring of polytitanodimethylsiloxane through condensation reactions of the hydroxyl groups according to the scheme

\[ n \left[ \mathrm{HO} \left( \begin{array}{c} \mathrm{CH}\\ |\\ \mathrm{SiO}\\ |\\ \mathrm{CH_3} \end{array} \right)_{19} \right]_3 \mathrm{Ti} - \left( \begin{array}{c} \mathrm{CH_3}\\ |\\ \mathrm{OSi}\\ |\\ \mathrm{CH_3} \end{array} \right)_{26} - \mathrm{Ti} \left[ \left( \begin{array}{c} \mathrm{CH_3}\\ |\\ \mathrm{OSi}\\ |\\ \mathrm{CH_3} \end{array} \right)_{13} \right]_3 \mathrm{OH} \rightarrow \]

\[ \rightarrow -\mathrm{O}-\mathrm{Ti}-\mathrm{O}- \left( \begin{array}{c} \mathrm{CH_3}\\ |\\ \mathrm{OSi}\\ |\\ \mathrm{CH_3} \end{array} \right)_{26} -\mathrm{O}-\mathrm{Ti}-\mathrm{O}- \]

\[ \begin{array}{ccc} | & & |\\ \mathrm{O} & & \mathrm{O}\\ | & & |\\ (\mathrm{H_3CSiCH_3})_{26} & & (\mathrm{H_3CSiCH_3})_{26}\\ | & & |\\ \mathrm{O} & & \mathrm{O}\\ | & & |\\ -\mathrm{O}-\mathrm{Ti}- & \left( \begin{array}{c} \mathrm{CH_3}\\ |\\ \mathrm{OSi}\\ |\\ \mathrm{CH_3} \end{array} \right)_{26} & -\mathrm{O}-\mathrm{Ti}-\mathrm{O}- \end{array} \]

With the aid of this reaction, two polymers were obtained: polytitanodimethylsiloxane, in which the distance between titanium atoms was equal to 18 dimethylsiloxane groups, and polytitanodimethylsiloxane with 26 dimethylsiloxane groups between titanium atoms in the polymer molecular chain. The polymers obtained were elastic substances at room temperature.

The reactions of synthesis of organoelement polymers of regular structure described above show that the structure of large molecules of network and spatial structure can be regulated by changing the number of atoms and groups in the branches of polyfunctional oligomers. Polymers in the structured state are cyclic formations with a constant number of units in the cycle. As experiments show, physical properties—for example, the elasticity of structured regular polymers—change sharply with an increase in the number of units in the cycle. Polytitanodimethylsiloxane with distances between titanium atoms in the molecule equal to 26 dimethylsiloxane groups, in the structured state, is a highly elastic polymer at room temperature.

Polymers with a small number of dimethylsiloxane units between titanium atoms are brittle substances at room temperature.

At present, the reaction of conversion of polyfunctional oligomers into spatial polymers of regular structure is being studied, and their properties are being investigated as a function of the chemical composition and structure of the polymers.

Experimental Part

1. Synthesis of polysiloxydimethylsiloxane.

0.16 g-mole of α,ω-disodium oxydimethylsiloxane,

\[ \mathrm{NaO} \left[ \begin{array}{c} \mathrm{CH_3}\\ |\\ \mathrm{SiO}\\ |\\ \mathrm{CH_3} \end{array} \right]_4 \mathrm{Na} \]

is dissolved in benzene and, at 40–60° with stirring, 0.04 g-mole of silicon tetrachloride in benzene is introduced. After this the NaCl precipitate is separated, and 80% acetic acid is added to the mixture for neutralization. Sodium acetate is separated by centrifugation. The benzene is distilled off under vacuum. The resulting tetrafunctional titanodimethylsiloxane oligomer is purified with sorbents and analyzed; it is condensed by heating at 120–150°, during which water is evolved and the viscosity of the reaction product increases. At the beginning of heating, the polymer obtained is soluble in benzene and toluene, but then it passes into an insoluble and infusible state.

\[ \begin{array}{ll} \left. \begin{array}{c} \mathrm{CH_3}\\ |\\ [\mathrm{HO(SiO)}]_4\mathrm{Si}\\ |\\ \mathrm{CH_3} \end{array} \right. & \begin{array}{l} \text{Found \%: C 29.80; 29.65; OH 4.97; Si 37.4; 37.0; H 7.72; 7.91}\\ \text{Calculated \%: C 30.0; \quad OH 5.3; \quad Si 37.18; \quad H 7.8.} \end{array} \end{array} \]

Mol. wt. 1252–1258.

2. Synthesis of polyphenylsiloxydimethylsiloxane.

To 0.12 g-mole of α,ω-hydroxydimethylsiloxane,

\[ \mathrm{HO} \left[ \begin{array}{c} \mathrm{CH_3}\\ |\\ \mathrm{SiO}\\ |\\ \mathrm{CH_3} \end{array} \right]_9 \mathrm{H}, \]

dissolved in benzene, 0.03 g-mole of phenyltrichlorosilane in benzene is added. During the addition of phenyltrichlorosilane, dry ammonia is passed through. The precipitated ammonium chloride is separated, and benzene is distilled off from the filtrate under vacuum. The resulting oligomer is condensed into a polymer by heating at 130–150°. At the beginning of the condensation reaction the polymer dissolves in benzene and toluene, while upon further heating it passes into an insoluble and infusible state.

\[ \begin{array}{ll} & \text{Found \%: C 35.44; 35.51; Si 37.91; 37.98; H 3.18; 3.21; OH 2.31; 2.42}\\ \mathrm{C_{60}Si_{28}H_{170}O_{30}} & \text{Calculated \%: C 35.19; \quad Si 38.31; \quad H 3.03; \quad OH 2.49} \end{array} \]

Mol. wt. 2146.

3. Synthesis of polytitanodimethylsiloxane.

0.24 g-mole of α,ω-hydroxydimethylsiloxane is dissolved in benzene and, at 50–60°, a benzene solution of 0.06 mole of titanium tetrachloride is introduced, while gaseous ammonia is passed through. The ammonium chloride is filtered off and the benzene is distilled off. The resulting oligomer is filtered and condensed into a polymer by heating at 150–180°.

\[ \begin{array}{ll} & \text{Found \%: C 32.20; 32.84; Ti 1.18; 1.24; H 7.87; 8.15; OH 1.71}\\ \mathrm{C_{104}Si_{52}H_{316}O_{56}.} & \text{Calculated \%: C 31.4; \quad Ti 1.24; \quad H 7.96.} \end{array} \]

Mol. wt. 3920.

Institute of Organoelement Compounds
Academy of Sciences of the USSR

Received
27 V 1961