Ionic and pH effects on the osmotic properties and structure of polyelectrolyte gels

Horkay, Ferenc; Basser, Peter J.

doi:10.1002/polb.21590

Cited by 26 publications

(26 citation statements)

References 34 publications

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“…Due to the only moderate acidity of the acrylic acid repeat units, full ionization of both SAPs is only observed at pH values > 10, whereas at the neutral pH of NaCl solutions, the degree of ionization is approx. 40% [ 48 , 49 , 50 ]. As a result, the fully deprotonated chains in the pore solution experience higher repulsive forces, which leads to stronger swelling.…”

Section: Resultsmentioning

confidence: 99%

Influence of Environmental Factors on the Swelling Capacities of Superabsorbent Polymers Used in Concrete

2020

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Superabsorbent polymers (SAP) are of major interest as materials to control the cement hydration process. The swelling behavior of the SAPs significantly influences the performance of the resulting concrete by slowly releasing polymer-bound water in order to maintain a consistent w/c value. A round-robin test conducted by the RILEM Technical Committee 260-RSC showed that the same batch of polymer can lead to large deviations in concrete performance and this was assumed to originate in different storage conditions of the SAP. In this contribution the change in the performance of two SAPs, a crosslinked poly(acrylate) and a crosslinked poly(acrylate-co-acrylamide), was assessed after ageing in standard climate, at 50 °C, and under UV irradiation. During storage in standard climate or 50 °C, ageing led to dehydration of the SAP, and this subsequently led to a higher water uptake during swelling. By contrast, UV irradiation reduced the water uptake, most likely as a result of photo-crosslinking. Dynamic water vapor sorption experiments indicated a strong dependence of the water uptake on both the ambient humidity and the temperature. As a result, cement mixtures containing SAP must be calculated on the dry mass of the SAP rather than the actual weight on site. A standard procedure of how to pack and handle SAP to be used in concrete is also provided.

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Section: Resultsmentioning

confidence: 99%

Influence of Environmental Factors on the Swelling Capacities of Superabsorbent Polymers Used in Concrete

2020

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“…However it must be discarded because that would decrease the length of chains between knots (increasing β) and it could also increase ν e , which would rebound in, apparently, increasing β too. Divalent counterions are related to the formation of linearly aligned regions which affect the rigidity,49 but it would also contribute to rise β with respect to univalent counterions. The reason for the low β value of PVI swollen in a diprotic acid solution is not clear at the moment.…”

Section: Resultsmentioning

confidence: 99%

Compression elastic modulus of neutral, ionic, and amphoteric hydrogels based on N‐vinylimidazole

Valencia¹,

Baselga²,

Piérola³

2009

J Polym Sci B Polym Phys

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Several hydrogels of N-vinylimidazole and sodium styrenesulfonate have been prepared by radical cross-linking copolymerization in aqueous solution, using N,N 0 -methylene-bisacrylamide as crosslinker. Depending on composition, these hydrogels were neutral, amphoteric, cationic or anionic. Compression-strain measure-ments were performed on samples as-synthesized and swollen in deionized water or in acid aqueous solutions, with and without salt. It was thus found that the cross-linking densities determined by compression measurements on assynthesized sam-ples are in good accordance with those calculated by means of the model of polymer networks with pendant vinyl groups. A non-Gaussian parameter (b) was introduced to explain that the elastic moduli (G) of samples swollen at equilibrium are larger than predicted by the Gaussian model. The b values of the neutral or ionized systems increase with swelling and fall into a single curve, which denotes a common behav-ior. Swelling has two opposite effects on G; on the one hand G decreases because the polymer volume fraction diminish and the system shifts from the affine limit to the phantom one; on the other, b increases and contributes to increasing G. The balance of those two opposite effects determines the variation of G with swelling. The possi-ble contribution of ionic crosslinks to m e for the polyampholyte and for the polycation wearing divalent counteranions was discussed.A peculiar system is poly(sodium styrenesulfonate), whose cross-linking density is much lower than expected.

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“…The gelling mechanisms and properties of some pHresponsive polymers are affected by the salt concentration, ionic strength and temperature. Horkay and Basser [59] showed that increasing the calcium concentration in a nearphysiological solution containing PAA induced reversible volume transition. Other studies have demonstrated sol-gel transition in response to pH, ionic strength and temperature stimuli [60][61][62].…”

Section: Mechanism Of Gel Formationmentioning

confidence: 99%

Ophthalmic gels: Past, present and future

Al-Kinani

Zidan

El-Said

et al. 2018

Advanced Drug Delivery Reviews

146

100

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Aqueous gels formulated using hydrophilic polymers (hydrogels) along with those based on stimuli responsive polymers (in situ gelling or gel forming systems) continue to attract increasing interest for various eye health-related applications. They allow the incorporation of a variety of ophthalmic pharmaceuticals to achieve therapeutic levels of drugs and bioactives at target ocular sites. The integration of sophisticated drug delivery technologies such as nanotechnology-based ones with intelligent and environment responsive systems can extend current treatment duration to provide more clinically relevant time courses (weeks and months instead of hours and days) which will inevitably reduce dose frequency, increase patient compliance and improve clinical outcomes. Novel applications and design of contact lenses and intracanalicular delivery devices along with the move towards integrating gels into various drug delivery devices like intraocular pumps, injections and implants has the potential to reduce comorbidities caused by glaucoma, corneal keratopathy, cataract, diabetic retinopathies and age-related macular degeneration. This review describes ophthalmic gelling systems with emphasis on mechanism of gel formation and application in ophthalmology. It provides a critical appraisal of the techniques and methods used in the characterization of ophthalmic preformed gels and in situ gelling systems along with a thorough insight into the safety and biocompatibility of these systems. Newly developed ophthalmic gels, hydrogels, preformed gels and in situ gelling systems including the latest in the area of stimuli responsive gels, molecularly imprinted gels, nanogels, 3D printed hydrogels; 3D printed devices comprising ophthalmic gels are covered. Finally, new applications of gels in the production of artificial corneas, corneal wound healing and hydrogel contact lenses are described.

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Ionic and pH effects on the osmotic properties and structure of polyelectrolyte gels

Cited by 26 publications

References 34 publications

Influence of Environmental Factors on the Swelling Capacities of Superabsorbent Polymers Used in Concrete

Influence of Environmental Factors on the Swelling Capacities of Superabsorbent Polymers Used in Concrete

Compression elastic modulus of neutral, ionic, and amphoteric hydrogels based on N‐vinylimidazole

Ophthalmic gels: Past, present and future

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