(381i) Molecularly-Templated Reaction for Forming Poly(dimethyl siloxane)/Graphene Oxide Composite Elastomers
This study  explores the molecularly-templated reaction of pyrene-terminated telechelic poly(dimethyl siloxane) (PDMS) with GO. The polymer was terminated with pyrene ends connected to the main polymer chain through a secondary amide linkage. These pyrene ends form dynamic Ï-Ï interactions with GO surfaces, which reduce intermolecular spacing between amide groups near epoxides on the surface of GO, thereby templating the reaction. The key focus of this research was to generate a new method to crosslink polymers containing secondary amide groups with GO via an epoxy ring-opening reaction, and investigate the critical role of the pyrene end group participating as a catalyst during the crosslinking reaction. This chemical crosslinking reaction was confirmed and supported by infrared spectroscopy, oscillatory shear rheology, gel content, swelling ratio, and mechanical property measurements. We have also tuned the concentration of the secondary amide groups by modulating the molecular weight of the polymer main chain, and were able to prepare elastomers that are highly crosslinked (e.g., up to 96 wt % non-dissolving gel) but highly extensible (e.g., extensional strains of more than 200%) as well. For comparison, methoxy-terminated telechelic PDMS with the same secondary amide linkages and molecular weight was synthesized. As expected, this control material did not exhibit appreciable crosslinking with GO, illustrating the importance of pyrene end groups. Considering the crosslinked nature of the composites and generality of the proposed reaction, we believe this molecular-templating capability could introduce a wide range of cost-effective engineered composite elastomers beyond PDMS.
 Gas Permeation and Selectivity of Poly(dimethylsiloxane)/Graphene Oxide Composite Elastomer Membranes, H. Ha, J. Park, S. Ando, C.B. Kim, K. Nagai, B.D. Freeman and C.J. Ellison, Journal of Membrane Science, 518, 131-140 (Jun. 2016). http://dx.doi.org/10.1016/j.memsci.2016.06.028
 Molecularly-Templated Reaction for Forming Poly(dimethyl siloxane)-Graphene Oxide Composite Elastomers, H. Ha, K. Ha, and C.J. Ellison, under review.