5. Biodegradable Polymers

Biodegradable Polymers

A large number of polymers are quite resistant to the environmental degradation processes and are thus responsible for the accumulation of polymeric soild waste materials. These soild wastes cause acute environmental problems and remain undegraded for quite a long time. In view of the general awareness and concern for the problems created by the polymeric soild wastes, certain new biodegradable synthetic polymers have been designed and developed. These polymers contain functional groups similar to the functional groups present in biopolymers.

Aliphatic polyesters are one of the important classes of biodegradable poylmers. Some examples are given below :

(A) Poly b-hydroxybutyrate – co–b-hydroxy valerate (PHBV) :

It is obtained by the copolymerisatin of 3-hydroxybutanoic acid. PHBV is used in speciality packaging, orthopaedic devices and in controlled release of drugs. PHBV undergoes bacterial degradation in the environment.

(B) Nylon–2–nylon–6 :

It is an alternating polyamide copolymer of glycine (H₂N–CH₂–COOH) and amino caproic acid

[H₂N (CH₂)₅ COOH].

It is step-growth copolymer.

(C) Poly glycolic acid (PGA) and poly lactic acid (PLA) :- This copolymer is commercially called dextron.

Glycolic acid

A copolymer of PGA and PLA (90 : 10) was the first biodegradable polyester used for stitching of wounds after operation.

(D) Poly-S-caprolactone lactone (PCL) : - It is obtained by chain polymerization of the lactone of 5(or S) hydroxy hexanoic acid.

5(or S-) hydroxy hexanoic acid