Nitroxide-Mediated Photo-Controlled/Living Radical Polymerization of Methacrylic Acid

Abstract

The photo-controlled/living radical polymerization of methacrylic acid (MAA) was performed at room temperature by irradiation with a high-pressure mercury lamp using azo initiators and 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl as the mediator in the presence of (4-tert-butylphenyl)diphenylsulfonium triflate ( t BuS) as the accelerator. Whereas the bulk polymerization yielded polymers with a bimodal molecular weight distribution in both the absence and presence of t BuS, the solution polymerization in methanol produced unimodal polymers with the molecular weight distribution of 2.0 -2.3 in the presence of t BuS. The molecular weight distribution of the resulting poly (MAA) decreased with an increase in t BuS. The dilution of the monomer concentration also reduced the molecular weight distribution. The use of the initiator with a low 10-h half-life temperature also effectively controlled the molecular weight. The livingness of the polymerization was confirmed by obtaining linear increases in the first-order conversion versus time, the molecular weight versus the conversion, and the molecular weight versus the reciprocal of the initiator concentration.

Elucidation of Acceleration Mechanisms by a Photosensitive Onium Salt for Nitroxide-Mediated Photocontrolled/Living Radical Polymerization

“…These onium salts served only as the accelerator for the polymerization and had no influence on the molecular weight control. However, the mechanisms of the acceleration by the onium salts were unclear, although possible mechanisms were proposed [51]- [53]. The present study determined that the acceleration by the onium salts for the photo-NMP was based on the electron transfer mechanism from MTEMPO to the onium salt in the excited state.…”

Morphological stability of worm-like vesicles consisting of amphiphilic diblock copolymer against external stress

“…[17] Some morphologies have already been created using poly(methacrylic acid)-block-poly(methyl methacrylaterandom-methacrylic acid), PMAA-b-P(MMA-r-MAA) by polymerization-induced self-assembly using the nitroxide-mediated photo controlled/living radical polymerization technique (photo NMP). [18] The morphologies include spherical vesicles, [17] the elliptical, [19] worm-like, [20,21] key-shaped, [22] villus-like, [23] and anastomosed tubular networks. [24] These morphologies were determined by the block length and molar ratio of the monomer unit in the diblock copolymer.…”