Figure 2.

(a) Gel-permeation chromatography (GPC) chromatograms illustrating the high conversion of macromonomer starting materials into ultralong (DP = 1840, M_n = 2.02 MDa) bottlebrush polymer controls (soluble, non-networks). The absolute molecular weight of these bottlebrush polymers was determined via multiangle light scattering and converted to M_n via dispersity values found via GPC (M_n = M_w (Đ)⁻¹). This polymerization serves as a control for the length of the backbones polymerized in BBEs with equivalent M/I = 1000. The right side of the macromonomer GPC chromatogram is distorted because it occurs outside the lower bounds of our calibration standards. (b) Plot of the elastic modulus (E) determined via indentation for a series of bottlebrush elastomers with progressively larger n_x values. The large range of E available to these samples (E ∈ [0.5,88] kPa) illustrates the significance of the large kinetic chain lengths (R_K) available via living polymerization methods such as ROMP. (c) Synthetic schematic illustrating how the polymerization of mono- and bis-norbornene functionalized PDMS (M_w = 1 and 9 kDa, respectively) can produce PSAs with large viscous components due to their unique structural composition. Critical to this defect-driven design (D³) philosophy are the ratio of M/I and n_x and low polymerization concentrations (as low as 0.11 M in this study). The PSAs synthesized in this manner have large, dangling defects which behave globally as viscous-contributing defects. These engineered defects contribute strongly to the adhesive properties of synthesized samples. The backbones here are depicted as straight “rods” solely for ease of presentation of concepts—they are Rouse-like chains.