A versatile synthetic platform is reported that affords high molecular weight graft copolymers containing polydimethylsiloxane (PDMS) backbones and vinyl-based side chains with excellent control over molecular weight and grafting density. The synthetic approach leverages thiol–ene click chemistry to attach an atom-transfer radical polymerization (ATRP) initiator to a variety of commercially available poly(dimethylsiloxane-co-methylvinylsiloxane) (PDMS-co-PVMS), followed by controlled radical polymerization with a wide scope of vinyl monomers. Selective degradation of the siloxane backbone with tetrabutylammonium fluoride confirmed the controlled nature of side-chain growth via radical polymerization, yielding targeted side-chain lengths for copolymers containing up to 50% grafting density and overall molecular weights in excess of 1 MDa. In addition, by using a mixture of thiols, grafting density and functionality can be further controlled by tuning initiator loading along the backbone. For example, solid-state fluorescence of the graft copolymers was achieved by incorporating a thiol-containing fluorophore along the siloxane backbone during the thiol–ene click reaction. This simple synthetic platform provides facile control over the properties of a wide variety of grafted copolymers containing flexible PDMS backbones and vinyl polymer side chains.

Size-exclusion chromatography (SEC) was performed on a Waters Alliance HPLC system using two Tosoh TSKgel SuperHZM-N columns containing 3 µm crosslinked polystyrene beads and a Waters 2410 Differential Refractometer with chloroform with 0.25% triethylamine as the mobile phase at a 0.35 mL/min flow rate. Number and weight average molecular weights (M_n and M_w respectively) were calculated based on polystyrene standards to calculate dispersity (Ð), unless otherwise specified. Plotted data has been baseline-corrected and normalized. The dRI signal for SEC data in Figure 2 corresponding to the top two traces has been inverted to facilitate comparison with the bottom trace. 

¹H nuclear magnetic resonance (NMR) spectroscopy was performed on a Varian 600 MHz using a relaxation delay (d₁) of 4.8 seconds. ¹³C NMR spectroscopy was performed on a Bruker 500 MHz with a d₁ of 10 seconds. Signal ppm values were shifted to match the solvent signal to 7.257 ppm in ¹H and 77.17 ppm in ¹³C.

Differential Scanning Calorimetry (DSC) was performed on a TA instrument Q2000 DSC with three repeated cycles: heating from 25 °C to 150 °C, cooled to -150 °C, and heated to 150 °C. Only the final cycle is plotted. Glass transition values were calculated using a function in the Trios software.