Kristufek et al. report the synthesis of rapidly-cured isosorbide-based cross-linked polycarbonate elastomers.
Inexpensive starting materials from natural products (such as isosorbide, isomannide etc.) can allow for natural material to begin to compete with and (why not?) eventually replace petrochemicals as a source of monomers. Isosorbide-based materials in particular have attracted considerable attention due to both the rigidity of their fused ring systems and the easily-modifiable dual hydroxyl functionalities. However, the utility of isosorbide-based materials for elastomers is perhaps more limited. As such, in the current article, Wooley and co-workers aim to produce rapidly-photo-cross-linked isosorbide-based elastomers via thiol-ene chemistry that will have the additional potential to hydrolytically break down into their original building blocks.
This novel cross-linked network system was elegantly synthesized using a naturally-derived monomer, isosorbide dialloc (IDA) and cross linked with tri-methylpropane tris(3-mercaptopropionate) (TMPTMP) yielding IDA-co-TMPTMP, an optically transparent elastomer. All the IDA-co-TMPTMP networks were obtained by environmentally friendly methods including solvent-free conditions, low catalyst loading and UV irradiation. Importantly, a study of a constant UV cure time (1 minute) and variation of the thermal curing times led to the conclusion that this material is near its optimal thermal and mechanical properties without requiring post-cure heating.
The thermal decomposition temperature of the networks were consistent (320 °C) while the glass transition temperature remained below room temperature for all samples with a % elongation of 220-340%. The hydrolytic degradation of the material was also evaluated and found to afford 8.3±3.5% and 97.7±0.3% mass remaining after 60 days under accelerated basic and physiological neutral buffer conditions respectively. Finally, a cell viability assay and fluorescence imaging with adherent cells were also reported in order to show the potential of this material as a biomedical substrate. In conclusion, the rapid synthesis of this optically transparent flexible elastomer presented very interesting properties that could be very useful in biomedical applications or as environmentally-friendly materials.
Tips/comments directly from the authors:
- Because DMPA dissolves slowly in the reaction mixture, it is important to keep it in the dark while mixing and allow it to fully dissolve, resulting in the most uniform materials.
- Glass slides were used as the molds to maximize the light exposure to the reaction mixture of the two monomers, ensuring the rapid curing time.
- During the degradation study, it is important to change the solution at short (ca. 2 days), constant intervals to provide consistent results.
Rapidly-cured isosorbide-based cross-linked polycarbonate elastomers by T.S. Kristufek, S.L. Kristufek, L.A. Link, A.C. Weems, S. Khan, S.M. Lim, A.T. Lonnecker, J.E. Raymond, D.J. Maitland and K.L. Wooley, Polym. Chem., 2016, 7, 2045-2056, DOI: 10.1039/C5PY01659B
Dr. Athina Anastasaki is a Web Writer for Polymer Chemistry. She is currently an Elings fellow working alongside Professor Craig Hawker at the University of California, Santa Barbara (UCSB). Please visit http://www.haddleton.org/users/athina-anastasaki for more information.
