Thymine-Modified Silicones: A Bioinspired Approach to Cross-Linked, Recyclable Silicone Polymers

In DNA, thymine typically forms hydrogen bonds with adeninetohold two complementary strands together and to preserve the geneticcode. While thymine is typically absent in RNA, a thymine-thyminehydrogen bonding structure is reminiscent of the wobble region intRNA recognition, where noncanonical base pairing can occur. Thisnoncanonical base pairing can be applied to synthetic polymer systems,where thymine is free to hydrogen bond with itself. In this work,the natural hydrogen bonding capacity of thymine was used to producesilicone polymer systems designed to be cross-linked by hydrogen bonds.Backbone and end-group-modified silicones were synthesized with differingconcentrations of thymine, which facilitated the cross-linking ofthe polymeric strands. Removing the hydrogen on N3 which istypically involved in hydrogen bonding resulted in systemswith similar viscosities to the starting material and that were devoidof any apparent cross-links. Differential scanning calorimetry (DSC)studies of the thymine-modified polymers displayed thermal absorptionsand releases, indicative of bond breaking and reformation, around100 and 60 & DEG;C, respectively. The cycle of bond breaking and formationcould be repeated without any noticeable degradation of the chemicalstructure of the polymers. These polymeric materials could be readilyrecycled and remolded by heating them at 110 & DEG;C for 5 min, followedby cooling to room temperature, confirming their thermoplastic nature.

Automated summary

In this work, the natural hydrogen bonding capacity of thymine was used to produce silicone polymer systems that can be cross-linked by hydrogen bonds. These thymine-modified polymers displayed thermal absorptions and releases, indicative of bond breaking and reformation, and showed the ability to be recycled and remolded through heating and cooling.