Biodegradable Polymers :
By far the largest use of synthetic polymers is as plastic. A major portion of it is used as throwaway containers and packing materials. Since plastics do not disintegrate by themselves, they are not biodegradable over a period of time. Non- biodegradability is due the carbon-carbon bonds of addition polymers which are inert to enzyme catalysed reaction. These polymers create pollution problem.
Biodegradable polymers are the polymers that can be broken into small segments by enzyme catalysed reactions using enzymes produced by microorganisms. In biodegradable polymers, bonds that can be broken by the enzymes are inserted into the polymers. Therefore, when they are buried as waste, enzymes present in the ground can degrade the polymer.
One method involves inserting hydrolysable ester group into the polymer. For example, when acetal (I) is added during the polymerization of alkene, ester group is inserted into the polymeric chains. See fig.1.
Aliphatic polyesters are important class of biodegradable polymers. Some examples are described below :
(i) `text(Poly- Hydroxybutyrate)` `-CO- beta-` `text(Hydroxyvalerate (PHBV))`
It is a copolymer of `3`-hydroxybutanoic acid and `3`-hydroxypentanoic acid, in which the monomer units are connected by ester linkages. See fig.2.
The properties of PHBV vary according to the ratio of both the acids. `3`-Hydroxybutanoic acid provides stiffness and `3` hydroxypentanoic acid imparts flexibility to the co-polymer. It is used in specialty packaging, orthopaedic devices and even in controlled drug release. When a drug is put in a capsule of PHBV, It is released only after the polymer is degraded. PHBV also undergoes bacterial degradation in the environment.
(ii) `text[Poly (Glycolic Acid) And Poly (Lactic Acid)]`
They constitute commercially successful biodegradable polymers such as sutures. Dextran was the first bioadsorbable suture made for biodegradable polyesters for post- operative stitches.
Biodegradable polymers are the polymers that can be broken into small segments by enzyme catalysed reactions using enzymes produced by microorganisms. In biodegradable polymers, bonds that can be broken by the enzymes are inserted into the polymers. Therefore, when they are buried as waste, enzymes present in the ground can degrade the polymer.
One method involves inserting hydrolysable ester group into the polymer. For example, when acetal (I) is added during the polymerization of alkene, ester group is inserted into the polymeric chains. See fig.1.
Aliphatic polyesters are important class of biodegradable polymers. Some examples are described below :
(i) `text(Poly- Hydroxybutyrate)` `-CO- beta-` `text(Hydroxyvalerate (PHBV))`
It is a copolymer of `3`-hydroxybutanoic acid and `3`-hydroxypentanoic acid, in which the monomer units are connected by ester linkages. See fig.2.
The properties of PHBV vary according to the ratio of both the acids. `3`-Hydroxybutanoic acid provides stiffness and `3` hydroxypentanoic acid imparts flexibility to the co-polymer. It is used in specialty packaging, orthopaedic devices and even in controlled drug release. When a drug is put in a capsule of PHBV, It is released only after the polymer is degraded. PHBV also undergoes bacterial degradation in the environment.
(ii) `text[Poly (Glycolic Acid) And Poly (Lactic Acid)]`
They constitute commercially successful biodegradable polymers such as sutures. Dextran was the first bioadsorbable suture made for biodegradable polyesters for post- operative stitches.