Poly(methacrylic acid-ran-2-vinylpyridine) Statistical Copolymer and Derived Dual pH-Temperature Responsive Block Copolymers by Nitroxide-Mediated Polymerization

Abstract

Nitroxide-mediated polymerization using the succinimidyl ester functional unimolecular alkoxyamine initiator (NHS-BlocBuilder) was used to first copolymerize tert-butyl methacrylate/ 2-vinylpyridine (tBMA/2VP) with low dispersity (Đ = 1.30-1.41) and controlled growth (linear number average molecular M n versus conversion, M n = 3.8-10.4 kg·mol −1 ) across a wide composition of ranges (initial mol fraction 2VP, f 2VP,0 = 0.10-0.90). The resulting statistical copolymers were first de-protected to give statistical polyampholytic copolymers comprised of methacrylic acid/2VP (MAA/2VP) units. These copolymers exhibited tunable water-solubility due to the different pKas of the acidic MAA and basic 2VP units; being soluble at very low pH < 3 and high pH > 8. One of the tBMA/2VP copolymers was used as a macroinitiator for a 4-acryloylmorpholine/4-acryloylpiperidine (4AM/4AP) mixture, to provide a second block with thermo-responsive behavior with tunable cloud point temperature (CPT), depending on the ratio of 4AM:4AP. Dynamic light scattering of the block copolymer at various pHs (3, 7 and 10) as a function of temperature indicated a rapid increase in particle size >2000 nm at 22-27 • C, corresponding to the 4AM/4AP segment's thermos-responsiveness followed by a leveling in particle size to about 500 nm at higher temperatures.

History of nitroxide mediated polymerization in Canada

“…[ 146 ] Other controlling co‐monomers like 2‐vinylpyridine were successfully implemented to provide added pH‐responsiveness and tuning to the resulting copolymer LCST. [ 147 ]…”

Selective Solid-Phase Extraction of Meropenem from Human Blood Plasma Using a Molecularly Imprinted Polymer

“…Owing to the presence of OH -, H + , and NH in the structure of meropenem, as well as the pH value of meropenem (pKa1 = 2.9; pKa2 = 7.4) [18], the pH may influence its ionic form. That is why pH is important to be considered in studying the adsorption behavior of MA as the polymer has pKa of 5.4 [19]; thus, the high adsorption at pH 3 could be caused by the electrostatic interaction between meropenem in the anionic state and MA in the protonated state. The presence of a cavity also supported this high value.…”

Upper Critical Solution Temperature Behavior of pH-Responsive Amphoteric Statistical Copolymers in Aqueous Solutions

“…Moreover, copolymerization, e.g., statistical, random, gradient, block, graft, and star, can be used to manipulate the properties of the polymer. 40 Here, Varoqui et al 41 prepared a diblock copolymer composed of poly(sodium styrenesulfonate) (PNaSS) and poly(2-vinylpyridine) (P2VP) via anionic polymerization and focused on the polyelectrolyte behavior of this polyampholyte, that is, the electrochemical characteristics of the basic P2VP in the presence of the neighboring PNaSS chain. The degree of ionization of P2VP in the diblock copolymer was studied as a function of pH, with the phase separation of the polymer solution found to occur at a pH of <2.5.…”

“…A controlled polymer structure is often the prerequisite for achieving certain special properties that cannot be obtained from an uncontrolled polymer structure. Moreover, copolymerization, e.g., statistical, random, gradient, block, graft, and star, can be used to manipulate the properties of the polymer . Here, Varoqui et al prepared a diblock copolymer composed of poly­(sodium styrenesulfonate) (PNaSS) and poly­(2-vinylpyridine) (P2VP) via anionic polymerization and focused on the polyelectrolyte behavior of this polyampholyte, that is, the electrochemical characteristics of the basic P2VP in the presence of the neighboring PNaSS chain.…”