Write the chemical equation that represents the formation of
$$
\begin{array}{l}{\text { (a) polychloroprene from chloroprene (polychloroprene
is }} \\ {\text { used in highway-pavement seals, expansion joints, con- }}
\\\ {\text { veyor belts, and wire and cable jackets) }}\end{array}
$$ $$
\begin{array}{c}{\mathrm{CH}_{2}=\mathrm{CH}-\underset{\mathrm{C}}{\mathrm{C}=\mathrm{CH}_{2}}}
\\\ {\text { Chloroprene }}\end{array}
$$ $$
\begin{array}{l}{\text { (b) polyacrylonitrile from acrylonitrile
(polyacrylonitrile }} \\ {\text { is used in home furnishings, craft yarns,
clothing, and }} \\ {\text { many other items). }}\end{array}
$$ $$
\begin{array}{c}{\mathrm{CH}_{2}=\mathrm{CH}} \\ {\mathrm{I}} \\ {\text {
Acrylonitrile }}\end{array}
$$