Q85P - Chemistry: Molecular Nature Of Matter And Change

Question

Show three units of a linear silicone polymer made from $\mathbf{(}\mathbf{C}{\mathbf{H}}_{\mathbf{3}}{\mathbf{)}}_{\mathbf{2}}\mathbf{Si}{\left(\mathbf{OH}\right)}_{\mathbf{2}}$with some  ${\left({\mathbf{CH}}_{\mathbf{3}}\right)}_{\mathbf{3}}\mathbf{SiOH}$added to the end chain.

Step-by-Step Solution

Answer

Silicon polymers are also called polysiloxanes. These are synthetic polymers where the backbone is silicon-oxygen. 

Introduction

Silicon polymers are also called polysiloxanes. These are synthetic polymers where the backbone is silicon-oxygen. Here organic groups are also attached to the silicon atom making a C-Si bond, in which the organic group is exposed to the outside. The simplest silicone is silane ${\mathbf{SiH}}_{\mathbf{4}}$. If oxygen is also present, they’ re called siloxanes.

General structure of the silicones

The silicones which are used vastly are those having methyl groups in the backbone. The general structure of these silicones can be represented as

Structure

The molecular formula given is of dimethylsilanol, where 2 methyl and 2 hydroxyl groups are present. The -OH groups of dimethylsilanols react with -OH group of another molecule of dimethylsilanols spontaneously to form polydimethyl siloxane. The structure of three units of a linear silicone polymer made from  $(\mathrm{C}{\mathrm{H}}_3{)}_2\mathrm{Si}{\left(\mathrm{OH}\right)}_2$ with some $(\mathrm{C}{\mathrm{H}}_3{)}_3\mathrm{SiOH}$ added to the end chain can be represented as