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

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 DPPBnMA = 100 or 200 lead to nanoparticles with irregular sizes, while the cases of [POEOMA24 ]0 /[POEOMA78 ]0 = 4/1 and target DPPBnMA = 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.