In the past 50years, petroleum chemical plastics have become the mostly used materials because of their various structures and good application performance. At present, they are widely applied in our daily life, including home appliance equipment, computer accessories, construction and sports facilities, medical equipment and various fibers, etc. In addition, the petroleum chemical plastics have gotten a lot of attention by biology and material fields due to the environmentally friendly character.
Among all of the petroleum chemical plastics, polymers polyhydroxyalkanoates (PHA) is an important one because of its special property and extensive application fields. PHA is a linear polymer compound composed by the R3HA unit which has an optical activity. Its material properties are mainly decided by the monomer composition. Because the PHA has many types of monomers and the chain lengths between different monomers are remarkable, then the material properties of different PHA are quite different, ranging from brittle duroplasts to soft elastomer. Besides, PHA is a synthetic production in the body of bacterial. And this makes sure of its stereospecificity, that is, all asymmetric carbon atoms in the main chain are R-configuration.
Although experienced nearly one hundred years after the PHA was found, people didn’t find its practical application value in a very long period of time. Until 1960s, worldwide oil crisis made people try to find the oil substitutes; PHA had caused the attention of academia and material subject because of their similar material properties with traditional plastics. In the recent 20 years, constantly facing the threats of the serious petroleum resources depletion and increasing environmental pollution, applications of PHA are considered to be the environmentally friendly degradable plastic due to its completely degradation and utilization of renewable resources.
Compared with the poly lactic acid (PLA), poly glycolic acid (PGA), and lactic-glycolic acid copolymer (PLGA), production of PHAs has many significant advantages. For instance, it has good biocompatibility, biodegradability and hot workability. More importantly, the research of PHA proves that the ability of biology compositing into new materials is almost infinite. Along with the continuously going deep into the research, more and more PHAs will be composited, thus promoting the development of corresponding biological materials. At the same time, we should see that although having made some progress on PHA research, the present cost of PHA production still higher than the plastic which the raw material is oil. A lot of work has to be focused on improving the raw material conversion rate and finding new PHAs. So, we still have a long way to go and many difficulties to overcome in the discovery of PHAs.