Chemistry Molecular Mass of Polymers and Biodegradable Polymers
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### Topics Covered :

● Molecular Mass of Polymers
● Biodegardable Polymers
● Poly β-hydroxybutyrate-co-β-hydroxy valerate (PHBV)
● Nylon 2–nylon 6
● Polymers of Commercial Importance

### Molecular Mass of Polymers :

=> Polymer properties are closely related to their molecular mass, size and structure.

=> The growth of the polymer chain during their synthesis is dependent upon the availability of the monomers in the reaction mixture.

=> Therefore, the polymer sample contains chains of varying lengths and hence its molecular mass is always expressed as an average.

=> The molecular mass of polymers can be determined by chemical and physical methods.

### Biodegradable Polymers :

=> A large number of polymers are quite resistant to the environmental degradation processes and are thus responsible for the accumulation of polymeric solid waste materials.

=> These solid 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 solid 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 polymers.

=> Some important examples are given below :

### Poly β-hydroxybutyrate – co-β-hydroxy valerate (PHBV) :

=> It is obtained by the copolymerisation of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid.

color{green}("Uses ") :  PHBV is used in speciality packaging, orthopaedic devices and in controlled release of drugs.

=> PHBV undergoes bacterial degradation in the environment.

color{red}(undersettext(3-Hydroxybutanoic acid)(CH_3 - overset( overset(OH)(|))CH - CH_2-COOH) + undersettext(3-Hydroxypentanoic acid)(CH_3-CH_2- overset( overset(OH)(|))CH-CH_2-COOH) → undersettext(PHBV)((- O- underset(underset(CH_3)(|))CH-CH_2 - underset(underset(O)(||))C-O-underset(underset(CH_2CH_3)(|))CH-CH_2 - underset(underset(O)(||))C-)_n))

### Nylon 2–nylon 6 :

It is an alternating polyamide copolymer of glycine color{red}(H_2N–CH_2–COOH) and amino caproic acid color{red}([H_2N (CH_2)_5 COOH]) and is biodegradable.

### Polymers of Commercial Importance :

Besides, the polymers already discussed, some other commercially important polymers along with their structures and uses are given below in Table 15.1.