Question

Synthetic polymers do not degrade in the environment for a long time. How can biodegradable synthetic polymers be made. Differentiate between biopolymers and biodegradable polymers and give examples of each type.

Answer 1

1. Poly β-hydroxybutyrate – co-β-hydroxy valerate (PHBV) It is obtained by the copolymerisation of 3-hydroxybutanoic acid and 3 - hydroxypentanoic acid. PHBV is used in speciality packaging, orthopaedic devices and in controlled release of drugs. PHBV undergoes bacterial degradation in the environment.

\[\begin{array}{cc}
\phantom{}\ce{OH}\phantom{.................................}\ce{OH}\phantom{...............................................................}\\
\phantom{.}|\phantom{....................................}|\phantom{.................................................................}\\
\ce{\underset{3-Hydroxybutanoic}{CH - CH - CH2 - COOH} + \underset{3-Hydroxypentanoic acid}{CH3 - CH2 - CH - CH2 - COOH} -> -(O - CH - CH2 - C - O - CH - CH2 - C)\underset{n}{-}}\\
\phantom{.......................................................................}|\phantom{............}||\phantom{.........}|\phantom{............}||\phantom{}\\
\phantom{.......................................................................}\ce{CH3}\phantom{.......}\ce{\underset{PHBV}{O}}\phantom{.......}\ce{CH2}\phantom{}\ce{CH3}\phantom{.....}\ce{O}\phantom{}
\end{array}\]

2. Nylon 2–nylon 6 It is an alternating polyamide copolymer of glycine \[\ce{(H2N – CH2 – COOH)}\] and aminocaproic acid \[\ce{[H2N(CH2)5COOH]}\] and is biodegradable.

Biopolymers are the natural polymers found in plants and animals like protein, fat, cellulose etc. Biodegradable polymers are polymers that contain functional groups similar to the functional groups present in biopolymers. They are not resistant to the environmental degradation processes.