Synthesis and aqueous solution properties of sterically stabilized pH-responsive polyampholyte microgels

Tan, B. T. G.; Ravi, Palaniswamy; Tan, Lie Na; Tam, Kam Chiu

doi:10.1016/j.jcis.2007.01.019

Cited by 37 publications

(25 citation statements)

References 44 publications

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“…Such pH-sensitive behaviour is typical for polyampholyte microgels and was recently described for synthetic polyampholyte microgels of 40% poly(methacrylic acid) and 60% poly(2-(diethylamino)ethyl methacrylate) (PMAA/PDEA) having an isoelectrical pH of about 5.0. 36 A similar pH-behaviour was also reported for 150-280 nm human serum albumin microgels with an IEP of 5.0 that were produced by desolvation in ethanol and cross-linking using glutaraldehyde.…”

supporting

confidence: 67%

“…These values are slightly larger than those reported for pure b-lg microgels obtained at 1 wt% under similar heating conditions, 15,17 but the difference could be due to the fourfold higher protein concentration used here as well as due to the use of an industrial plate heat exchanger rather than a water bath for performing the heat treatment step as well as to the mineral composition of the whey protein isolate. 24 The appearance and size of the WPM were similar to those of the casein micelles held together by calcium phosphate bridges or internally cross-linked with the transglutaminase enzyme, 12,35 but also to that of synthetic microgels such as copolymers of poly-(methacrylic acid) and poly(2-(diethylamino)ethyl methacrylate) (PMAA/PDEA) 36 or lightly cross-linked sterically stabilized poly(2-vinylpiridine) latexes.…”

Section: Resultsmentioning

confidence: 78%

“…The swelling is marked for the acidic pH values where R max increases by more than 15% (pH 2.0), leading to a 40% increase in the WPM volume. Such behaviour is very characteristic for cross-linked amphiphilic polymer microgels, 8,36 but it was also described for gels of proteins such as egg albumin 48 or whey protein concentrate.…”

Section: à4mentioning

confidence: 80%

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Internal structure and colloidal behaviour of covalent whey protein microgels obtained by heat treatment

et al. 2010

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Covalently cross-linked whey protein microgels (WPM) were produced without the use of a chemical cross-linking agent. The hierarchical structure of WPM is formed by a complex interplay of heat denaturation, aggregation, electrostatic repulsion, and formation of disulfide bonds. Therefore, welldefined spherical particles with a diameter of several hundreds of nanometers and with relatively low polydispersity are formed in a narrow pH regime (5.8-6.2) only. WPM production was carried out on large scale by heating a protein solution in a plate-plate heat exchanger. Thereafter, the microgels were concentrated by microfiltration and spray dried into a powder. The spherical structure of the WPM was conserved in the powder. After re-dispersion, the microgel dispersions fully recovered their initial structure and size distribution. Due to the formation of disulfide bonds the particles were internally covalently cross-linked and were remarkably stable in a large pH range. Because of the pH dependent charge of the constituents the particles underwent significant size changes upon shifting the pH. Small angle X-ray scattering experiments were used to reveal their internal structure, and we report on the pH-induced structural changes occurring on different length scale. Our experiments showed that close analogies could be drawn to internally cross-linked and pH-responsive microgels based on weak polyelectrolytes. WPM also exhibited a pronounced swelling at pH values below the isoelectric point (IEP), and a collapse at the IEP. However, in contrast to classical microgels, WPM are not build up by simple polymer chains but possess a complex hierarchical structure consisting of strands formed by clusters of aggregated denatured proteins that act as primary building blocks. They were flexible enough to respond to changes of the environment, and were stable enough to tolerate pH values where the proteins were highly charged and the strands were stretched.

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confidence: 67%

Section: Resultsmentioning

confidence: 78%

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Internal structure and colloidal behaviour of covalent whey protein microgels obtained by heat treatment

et al. 2010

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“…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]. Originally, such copolymers were made via statistical free radical copolymerization of the unalike monomers [2][3][4]. Such pairs included methacrylic acid (MAA)/2-vinyl pyridine (2VP) [2], MAA/2-dimethylamino ethyl methacrylate (DMAEMA) [3,4] and acrylic acid (AA)/DMAEMA [5].…”

Section: Introductionmentioning

confidence: 99%

“…Originally, such copolymers were made via statistical free radical copolymerization of the unalike monomers [2][3][4]. Such pairs included methacrylic acid (MAA)/2-vinyl pyridine (2VP) [2], MAA/2-dimethylamino ethyl methacrylate (DMAEMA) [3,4] and acrylic acid (AA)/DMAEMA [5]. Later, the uncoupling of the charges was desired to make block copolymers, which led to dramatically different properties in solution.…”

Section: Introductionmentioning

confidence: 99%

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

2017

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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.

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Synthesis of Polyampholyte Janus‐like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization

Rudov

Oppermann

et al. 2019

Angewandte Chemie

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Controlling the distribution of ionizable groups of opposite charge in microgels is an extremely challenging task, which could open new pathways to design a new generation of stimuli‐responsive colloids. Herein, we report a straightforward approach for the synthesis of polyampholyte Janus‐like microgels, where ionizable groups of opposite charge are located on different sides of the colloidal network. This synthesis approach is based on the controlled self‐assembly of growing polyelectrolyte microgel precursors during the precipitation polymerization process. We confirmed the morphology of polyampholyte Janus‐like microgels and demonstrate that they are capable of responding quickly to changes in both pH and temperature in aqueous solutions.

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Synthesis and aqueous solution properties of sterically stabilized pH-responsive polyampholyte microgels

Cited by 37 publications

References 44 publications

Internal structure and colloidal behaviour of covalent whey protein microgels obtained by heat treatment

Internal structure and colloidal behaviour of covalent whey protein microgels obtained by heat treatment

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

Synthesis of Polyampholyte Janus‐like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization

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