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Questions  >>  JEEMAIN and NEET  >>  Chemistry  >>  Polymers
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Q)

The polymer used in orthopedic devices andin controlled drug release is

$\begin {array} {1 1} (a)\;Orlon & \quad (b)\;PTFE \\ (c)\;SBR & \quad (d)\;PHBV \end {array}$

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A)
Poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) is apolyhydroxyalkanoate-type polymer. It is biodegradable, nontoxic, biocompatibleplastic produced naturally by bacteria and a good alternative for many non-biodegradable synthetic polymers. It is a thermoplastic linear aliphatic polyester
History
PHBV was first manufactured in 1983 by Imperial Chemical Industries (ICI). It is commercialized under the trade name Biopol. ICI (Zeneca) sold it to Monsanto in 1996. This was then obtained by Metabolix in 2001.[2][3] Biomer L is the trade name of PHBV from Biomer
Synthesis
PHBV is synthesized by bacteria as storage compounds under growth limiting conditions.It can be produced from glucose and propionate by the recombinantEscherichia coli strains. Many other bacteria like Paracoccus denitrificans and Ralstonia eutropha are also capable of producing it. It can also be synthesized from genetically engineered plants. PHBV is a copolymer of 3-hydroxybutanoic acid and 3-hydroxypentanoic acid. PHBV may also be synthesized from butyrolactoneand valerolactone in the presence of oligomeric aluminoxane as catalyst.
Structure
The monomers, 3-hydroxybutanoic acid and 3-hydroxypentanoic acid, are joined by ester bonds; the back bone of the polymer is made up of carbon and oxygen atoms. The property of the PHBV depends upon the ratio of these two monomers in it. 3-hydroxybutanoic acid provides stiffness while 3-hydroxypentanoic acid promotes flexibility. Thus PHBV can be made to resemble either polypropylene orpolyethylene by changing the ratio of monomers.Increase in the ratio of 3-hydroxybutanoic acid to 3-hydroxypentanoic acid results in an increase in melting point, water permeability, glass transition temperature (Tg) and tensile strength. However impact resistance is reduced.
Properties
PHBV is a thermoplastic polymer. It is brittle, has low elongation at break and low impact resistance
Uses
PHBV find its applications in controlled release of drugs, medical implants and repairs, specialty packaging, orthopedic devices and manufacturing bottles for consumer goods.It has very good scope in tissue engineering. The favoring properties are biocompatibility and in vivo degradation into its monomers, which are normal in the blood.
Ans : (d)
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