Poly(3-hydroxybutyrate) from carbon monoxide

The potential applications of naturally occurring poly(3-hydroxybutyrate) (PHB) is demonstrated by a summary of its variable mechanical properties in comparison with different commercially available polymers. This comparison underlines the striking similarity to the most-produced materials in the world, the poly(olefin)s, which offers many possible applications depending on the correct polymer microstructure. However, there is a resulting competition with regard to product prices. When commercialization is addressed, low-cost raw materials as well as fast and simple polymer synthesis and purification are necessary. A brief look into today's biotechnological PHB synthesis is followed by a short discussion of potential raw materials. This clearly demonstrates that a non-fermentative synthesis is desirable. Therefore, this manuscript reviews the latest results of catalytic PHB synthesis. Besides alternating copolymerization of carbon monoxide and propylene oxide there is special focus on ring-opening polymerization of β-butyrolactone, which has gained increasing interest over the past decade. Since stereocontrol is relatively difficult to achieve during ring-opening polymerization, an outlook on stereoselective monomer synthesis concludes this article.