Page-rank is simply a measure of how many backlinks there are to your site, and what "quality" of sites are backlinking to you. It has nothing whatsoever to do with bounce rate, other than the fact that if people aren't finding what they came to your site to find, they probably aren't backlinking to it.
In many ways, fixing bounce rate is more important than fretting about page-rank. Getting people to your site does you no good if they aren't staying, or turning into conversions!
In a lot of ways people are obsessing over search to the point they neglect everything else -- including repeat business. Ask your average brick and mortar how important repeat business is; anyone who knows anything about business knows getting people in the door is only a fraction of the fight. Selling them something and getting them to come back again is as if not more important.
One customer who visits once a week the next five years is worth a near infinite number of bounces... most bounces being the equivalent of people walking in the door and immediately turnstyling back out.