ICAR ATRP Polymerization-Induced Self-Assembly Using a Mixture of Macroinitiator/Stabilizer with Different Molecular...

The poly[oligo(ethylene oxide) methyl ether methacrylate]s, POEOMA₂₄ and POEOMA₇₈ with average degree of polymerization (DP) of 24 and 78, respectively, are separately achieved by initiators for continuous activator regeneration (ICAR) atom transfer radical polymerization (ATRP) of OEOMA₃₀₀ monomer. The mixtures of [POEOMA₂₄ ]₀ /[POEOMA₇₈ ]₀ = 1/1, 2/1, or 4/1 are employed as macroinitiator/stabilizer to practice the ICAR ATRP polymerization-induced self-assembly (PISA) of benzyl methacrylate (BnMA) at 65 °C. When the obtained dispersions are sequentially cooled to room temperature, diluted into ethanol, and observed by transmission electron microscopy (TEM) measurement, the cases of [POEOMA₂₄ ]₀ /[POEOMA₇₈ ]₀ = 1/1 or 2/1 and target DP_{PB n MA} = 100 or 200 lead to nanoparticles with irregular sizes, while the cases of [POEOMA₂₄ ]₀ /[POEOMA₇₈ ]₀ = 4/1 and target D_{PPB n MA} = 300 give the regular ones. When the obtained dispersions at a high temperature (65 °C) are directly diluted into room temperature ethanol and observed by TEM, nanoparticles with light contrast but clear contour can be observed. The results show that the higher content of POEOMA₇₈ tends to improve the solubility of diblock copolymer and thus leads to insufficient stabilization of the nanoparticles. The morphological difference from the room-temperature and 65 °C dispersions help elucidate the intrinsic character of the PISA system.