Monomers and Resulting Polymers from Biomass - Introduction to Chemicals from Biomass - page 193

begins with the slow uptake of water, which leads to the hydrolysis of ester link-
ages, breaking the polymer backbone into fragments. Additional water uptake
allows for further degradation of the ester bonds [190]. This degradation process
proceeds faster in amorphous polymers, which allows for a faster water uptake.
The hydrolytic decomposition renders these materials compostable. Their biological
compatibility and biodegradability make PLA and PGA attractive for biomedical
applications.

5.7.3 Applications of PLA

Both PLA and PGA and their copolymers offer strength and biodegradability,
required for biomedical applications. Sutures made from PGA/PLA copolymer
fibers were one of the first bioresorbable medical products and, for decades, these
copolymers have been used in various medical devices [199-202]. The mechani-
cal properties of PLA allow for fracture fixation devices, such as screws and
plates, that are absorbed by the body within a few weeks [203]. This approach has
the benefit that the affected area in the body is slowly reintroduced to stress as the
mechanical properties of the PLA degrade gradually over time [203]. Drug delivery
platforms were also developed, with drug release profiles tuned by copolymeriza-
tion of PLA with PGA or meso-lactide [204]. Recent work showed that it is possible
to build porous PLA scaffolds in order to culture different cell types for cell-based
gene therapy [187].
PLA offers better mechanical properties than PS for commercial packaging
applications [192]. A number of companies are producing PLA commercially
with PLA in most of the world's major consumer markets (Europe, Japan, and the
US) in medical devices and food packing [183-186, 190]. Unfortunately, for the
use of PLA to expand into new applications, several hurdles still need to be over-
come including brittleness, limited barrier properties, and low heat resistance.

5.8 Conclusion
This chapter provided an overview of the relevant research and industrial applica-
tions of monomers from biomass and their resulting polymers, highlighting their
versatility and the fact that monomers from renewable sources can compete with
fossil-based monomers. As scaling-up hurdles are overcome and chemistries are
optimized, the future offers many opportunities for these materials.

References

1. Iowa State University (2013) Photo Gallery: Biopolymers & Biocomposites Research Team.
Available at http://www.biocom.iastate.edu/newsroom/gallery.html (accessed 28 August 2014).
2. Khot, S.N., Lascala, J.J., Can, E. et al. (2001) Development and application of triglyceride-
based polymers and composites. Journal of Applied Polymer Science , 82 (3), 703-723.