2. A certain process (let\'s call it process A) for producing PVC results in a s
ID: 542874 • Letter: 2
Question
2. A certain process (let's call it process A) for producing PVC results in a stereoisomer of PVC which has a pronounced preference for the "trans" conformation in solution whereas another process (let's call it process B) results in a stereoisomer of PVC which has little preference for the various conformers (this is to say that the latter stereoisomer has "trans", and both "gauche" conformations that are all equally probable). Monodisperse fractions of molecular weight M are isolated from each type of PVC. Suppose that you measure the root-mean- square end-to-end distance, R, of the various PVC molecules. Will the ratio of RM for A process PVC be less than, the same of greater thanExplanation / Answer
For a freely jointed chain polymer wherein all-trans configuration is seen the square root of the mean-square end-to-end distance is smaller than that of a coiled polymer in a solution. This implies that the ratio of mean-square end-to-end distance to its molecular weight of a polymer is larger in the case of coiled polymer compared to that of a linear polymer. In a linear polymer the distance between end segments is shorter due to lack of consideration of bond angles, intra molecular and solvent interactions whereas in a coiled polymer, wherein the configuration is mixed (gauche and trans) these interactions are considered while calculating distance between end segments and square root of the mean-square end-to-end distance.
Accordingly the ratio of <r2>1/2/ M for A process PVC will be less than that for B process PVC when M is same for both kinds of polymers.
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