Chapter 14: Problem 12
Sketch cis and trans structures for (a) butadiene, and (b) chloroprene. Use twodimensional schematics per footnote 11 of this chapter.
Chapter 14: Problem 12
Sketch cis and trans structures for (a) butadiene, and (b) chloroprene. Use twodimensional schematics per footnote 11 of this chapter.
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Get started for freeFor a linear freely rotating polymer molecule, the total extended chain length \(L\) depends on the bond length between chain atoms \(d\), the total number of bonds in the molecule \(N\), and the angle between adjacent backbone chain atoms \(\theta\), as follows: $$ L=N d \sin \left(\frac{\theta}{2}\right) $$ Furthermore, the average end-to-end distance \(r\) for a randomly winding polymer molecule in Figure \(14.6\) is equal to $$ r=d \sqrt{N} $$ A linear polytetrafluoroethylene has a numberaverage molecular weight of \(500,000 \mathrm{~g} / \mathrm{mol}\); compute average values of \(L\) and \(r\) for this material.
The following table lists molecular weight data for a polypropylene material. Compute (a) the number-average molecular weight, (b) the weight-average molecular weight, and (c) the degree of polymerization. \begin{tabular}{rcc} \hline Molecular Weight Range \((\mathrm{g} /\) mol \()\) & \(\boldsymbol{x}_{\boldsymbol{i}}\) & \(\boldsymbol{w}_{\boldsymbol{i}}\) \\ \hline \(8,000-16,000\) & \(0.05\) & \(0.02\) \\ \(16,000-24,000\) & \(0.16\) & \(0.10\) \\ \(24,000-32,000\) & \(0.24\) & \(0.20\) \\ \(32,000-40,000\) & \(0.28\) & \(0.30\) \\ \(40,000-48,000\) & \(0.20\) & \(0.27\) \\ \(48,000-56,000\) & \(0.07\) & \(0.11\) \\ \hline \end{tabular}
The number-average molecular weight of a poly(styrene-butadiene) alternating copolymer is \(1,350,000 \mathrm{~g} / \mathrm{mol}\); determine the average number of styrene and butadiene repeat units per molecule.
Using the definitions for total chain molecule length \(L\) (Equation 14.11) and average chain end-to-end distance \(r\) (Equation 14.12), for a linear polyethylene determine the following: (a) the number-average molecular weight for \(L=2500 \mathrm{~nm}\) (b) the number-average molecular weight for \(r=20 \mathrm{~nm}\)
Calculate the number-average molecular weight of a random nitrile rubber [poly (acrylonitrile-butadiene) copolymer] in which the fraction of butadiene repeat units is \(0.30\) assume that this concentration corresponds to a degree of polymerization of 2000 .
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