A problem: How do you make polymers out of monomers?
It's even harder than just getting molecules near each other and having them react. Polymerization is a dehydration reaction -- it removes water. It also requires energy input. So in aqueous regimes, you are much more likely to depolymerize than polymerize.
One way out could be to try to make the reactions go in desiccated environments, but it is hard to do chemistry (ie, form molecules) in non-solution environments.
Perhaps dehydration reactions can be driven by coupling these reactions, in solution, to hydration of another compound (what compound? who knows?).
This would more or less be a catalytic situation.
Or, maybe remove water released by dehydration by heating (visible or ultraviolet radiation from the Sun?) -- but this has not been shown to work.