A Thermodynamic Roadmap for the Grafting-through Polymerization of PDMS₁₁MA

Grafting-through atom transfer radical polymerization (ATRP) was used to polymerize a sterically hindered poly(dimethylsiloxane) methacrylate (PDMS₁₁MA, M_n = 1000) macromonomer to high conversion as a function of temperature, solvent, initial monomer concentration, and pressure. Higher polymerization yields were obtained when polymerizations were conducted at (i) lower temperature (T), (ii) in a poor solvent for the side chain, (iii) higher initial monomer concentration ([M]₀), and (iv) higher pressure by mitigating the contribution of the equilibrium monomer concentration ([M]_eq). The enthalpy of polymerization (ΔH_p) and entropy of polymerization (ΔS_p) were more negative in poor solvents. Polymerizations at ambient pressure required higher [M]₀, use of a poor solvent, and lower temperatures to reach higher conversion with good control, whereas high pressure ATRP (HP-ATRP) displayed better control under dilute conditions. Grafting-through polymerization at high P and higher [M]₀ was less controlled, plausibly due to limited solubility and mobility of the copper catalyst in the highly viscous medium.