The accumulation of synthetic microplastics in marine ecosystems is a major global environmental challenge. A key source of these pollutants is polyacrylonitrile (PAN), a synthetic addition polymer widely used to manufacture acrylic textile fibres. PAN is produced via the free-radical addition polymerisation of propenenitrile (acrylonitrile) monomers.
The displayed formula of a propenenitrile monomer is shown below:
Which of the following represents the correct repeating unit of the polymer polyacrylonitrile (PAN)?
[HCN∣∣−C−C−∣∣HH]n
\left[ \begin{array}{ccc} \text{H} & & \text{CN} \\ \vert & & \vert \\ -\text{C} & - & \text{C}- \\ \vert & & \vert \\ \text{H} & & \text{H} \end{array} \right]_n
H∣−C∣H−CN∣C−∣Hn
[HCN∣∣−C=C−∣∣HH]n
\left[ \begin{array}{ccc} \text{H} & & \text{CN} \\ \vert & & \vert \\ -\text{C} & = & \text{C}- \\ \vert & & \vert \\ \text{H} & & \text{H} \end{array} \right]_n
H∣−C∣H=CN∣C−∣Hn
[HH∣∣−C−C−∣∣HH]n
\left[ \begin{array}{ccc} \text{H} & & \text{H} \\ \vert & & \vert \\ -\text{C} & - & \text{C}- \\ \vert & & \vert \\ \text{H} & & \text{H} \end{array} \right]_n
H∣−C∣H−H∣C−∣Hn
[CNCN∣∣−C−C−∣∣HH]n
\left[ \begin{array}{ccc} \text{CN} & & \text{CN} \\ \vert & & \vert \\ -\text{C} & - & \text{C}- \\ \vert & & \vert \\ \text{H} & & \text{H} \end{array} \right]_n
CN∣−C∣H−CN∣C−∣Hn