Chapter $6$ problem $7$

$7$ High molecular weight linear polyesters from $1,4-$butanediol $(HO-(C{H}_2{)}_4-OH)$ and terephthalic acid

$($HOOC$--\frac{C}{O}OH,$ with the acids in the para or opposite positions$)$ are successful engineering plastics

$($materials with high mechanical strength and good thermal stability$).$ They are, however, not used as

a blister $($sturdy$,$ see$-$through$)$ packaging material. A polymer for the blister$-$packaging market is mad

from the two monomers above plus isophthalic acid $($ meta $\{$:$--(\frac{C}{O}OH{)}_2).$ Explain the difference in

the applications.