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 Mn versus conversion, Mn = 3.8–10.4 kg·mol−1) across a wide composition of ranges (initial mol fraction 2VP, f2VP,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.
Highlights
IntroductionThe manipulation of properties by copolymerization (e.g., graft, gradient, block, star architectures) has long been applied to impart desirable properties into polymers
The manipulation of properties by copolymerization has long been applied to impart desirable properties into polymers
The versatility of nitroxide-mediated polymerization (NMP) to produce dual stimuli-responsive block copolymers was highlighted where one block consisted of a statistical poly(ampholyte) comprised of methacrylic acid and
Summary
The manipulation of properties by copolymerization (e.g., graft, gradient, block, star architectures) has long been applied to impart desirable properties into polymers One such class that combines properties are poly(ampholytes) or poly(zwitterions), which contain both negative and positive charges on the chain, either on different monomers or within a single monomer unit [1]. Such copolymers were made via statistical free radical copolymerization of the unalike monomers [2,3,4]. There are drawbacks to using living polymerizations such as ionic polymerizations: meticulous air-free transfers; Processes 2017, 5, 7; doi:10.3390/pr5010007 www.mdpi.com/journal/processes
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