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

Eri Yoshida

doi:10.4236/ojpchem.2013.31004

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 (tBuS) as the accelerator. Whereas the bulk polymerization yielded polymers with a bimodal molecular weight distribution in both the absence and presence of tBuS, the solution polymerization in methanol produced unimodal polymers with the molecular weight distribution of 2.0 - 2.3 in the presence of tBuS. The molecular weight distribution of the resulting poly (MAA) decreased with an in- crease in tBuS. 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.

Highlights

(methacrylic acid) (PMAA), an important watersoluble polymer, has many industrial and medical applications, such as a dispersant for coatings [1], a hydrophilic modifier on a surface [2], and a component of drug carriers, like micelles, in drug delivery systems [3,4]
With the aim of precisely synthesizing hydrophilic architectures based on PMAA, the controlled radical polymerization of methacrylic acid (MAA) was exploited using various catalysts
Atom transfer radical polymerization (ATRP) was not applicable to MAA because this acidic monomer poisoned the catalysts by coordinating to the transition metal, protection of the monomer is needed for this polymerization [12,13]

Summary

Introduction

(methacrylic acid) (PMAA), an important watersoluble polymer, has many industrial and medical applications, such as a dispersant for coatings [1], a hydrophilic modifier on a surface [2], and a component of drug carriers, like micelles, in drug delivery systems [3,4]. With the aim of precisely synthesizing hydrophilic architectures based on PMAA, the controlled radical polymerization of methacrylic acid (MAA) was exploited using various catalysts. Reversible addition-fragmentation chain transfer (RAFT) polymerization produced PMAA with a narrow molecular weight distribution (Mw/Mn < 1.2) both in water [5] and in organic solvents [6,7,8,9,10]. Photoiniferter polymerization mediated by diethyldithiocarbamate yielded PMAA with the molecular weight distribution of ca. Atom transfer radical polymerization (ATRP) was not applicable to MAA because this acidic monomer poisoned the catalysts by coordinating to the transition metal, protection of the monomer is needed for this polymerization [12,13]. There are only a few examples of the copolymerization of MAA with the comonomers of styrene [14] and sodium 4-styrenesulfonate [15]

Methods

Results

Conclusion