Preparation of mechanically tough poly(dimethyl siloxane) through the incorporation of acetylated cyclodextrin-based topologically movable cross-links†
Poly(dimethyl siloxane) (PDMS) has been widely utilized in various fields of research. However, the weak mechanical properties of PDMS have limited the widespread application of this material in industry. Herein, we incorporated a movable cross-link as a topological cross-link into linear thiol-modified PDMS chains to prepare PDMS elastomers. Triacetylated γ-cyclodextrin (TAcγCD) was modified on PDMS chains through thiol–ene click chemistry. Both the Young's modulus and the toughness of the obtained PDMS elastomers with an appropriate modification ratio (Young's modulus, 31.1 MPa; toughness 30 MJ m−3) were approximately one hundred times higher than those of chemically cross-linked PDMS elastomers (Young's modulus, 0.3 MPa; toughness, 0.47 MJ m−3). The PDMS elastomers have advantages in terms of energy dissipation mechanisms as well as mechanical properties. The movable cross-links contributed to larger mechanical hysteresis areas and faster relaxation behavior. Structural studies involving differential scanning calorimetry and X-ray scattering measurements revealed that phase separation occurred by the addition of cyclodextrin, which changed the glass transition temperatures. Moreover, the nanometer-scale phase separation structure was attributed to good mechanical properties. We expect that these topological cross-links in PDMS elastomers will expand the material design strategies for noncarbon-based elastomers.