Gels | Special Issue : Colloid Chemistry

Editorial

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3 pages, 154 KiB

Open AccessEditorial

Colloid Chemistry

by Clemens K. Weiss

Gels 2018, 4(3), 64; https://doi.org/10.3390/gels4030064 - 23 Jul 2018

Cited by 3 | Viewed by 3297

Abstract

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(This article belongs to the Special Issue Colloid Chemistry)

Research

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8 pages, 10152 KiB

Open AccessCommunication

Controlling the Organization of Colloidal Sphero-Cylinders Using Confinement in a Minority Phase

by Niek Hijnen and Paul S. Clegg

Gels 2018, 4(1), 15; https://doi.org/10.3390/gels4010015 - 2 Feb 2018

Cited by 1 | Viewed by 3857

Abstract

We demonstrate experimentally that a phase-separating host solvent can be used to organize colloidal rods into different cluster and network states. The rods are silica sphero-cylinders which are preferentially wet by the water-rich phase of an oil–water binary liquid system. By beginning with [...] Read more.

We demonstrate experimentally that a phase-separating host solvent can be used to organize colloidal rods into different cluster and network states. The rods are silica sphero-cylinders which are preferentially wet by the water-rich phase of an oil–water binary liquid system. By beginning with the rods dispersed in the single-fluid phase and then varying the temperature to enter the demixed regime, a precisely chosen volume of water-rich phase can be created. We then show how this can be used to create independent clusters of rods, a percolating network, a network of clusters or a system that undergoes hindered phase separation. These different modes are selected by choosing the relative volumes of the rods and the water-rich phase and by the timing of the temperature change. Full article

(This article belongs to the Special Issue Colloid Chemistry)

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2873 KiB

Open AccessFeature PaperArticle

Hydrogel Microparticles as Sensors for Specific Adhesion: Case Studies on Antibody Detection and Soil Release Polymers

by Alexander Klaus Strzelczyk, Hanqing Wang, Andreas Lindhorst, Johannes Waschke, Tilo Pompe, Christian Kropf, Benoit Luneau and Stephan Schmidt

Gels 2017, 3(3), 31; https://doi.org/10.3390/gels3030031 - 8 Aug 2017

Cited by 10 | Viewed by 5684

Abstract

Adhesive processes in aqueous media play a crucial role in nature and are important for many technological processes. However, direct quantification of adhesion still requires expensive instrumentation while their sample throughput is rather small. Here we present a fast, and easily applicable method [...] Read more.

Adhesive processes in aqueous media play a crucial role in nature and are important for many technological processes. However, direct quantification of adhesion still requires expensive instrumentation while their sample throughput is rather small. Here we present a fast, and easily applicable method on quantifying adhesion energy in water based on interferometric measurement of polymer microgel contact areas with functionalized glass slides and evaluation via the Johnson–Kendall–Roberts (JKR) model. The advantage of the method is that the microgel matrix can be easily adapted to reconstruct various biological or technological adhesion processes. Here we study the suitability of the new adhesion method with two relevant examples: (1) antibody detection and (2) soil release polymers. The measurement of adhesion energy provides direct insights on the presence of antibodies showing that the method can be generally used for biomolecule detection. As a relevant example of adhesion in technology, the antiadhesive properties of soil release polymers used in today’s laundry products are investigated. Here the measurement of adhesion energy provides direct insights into the relation between polymer composition and soil release activity. Overall, the work shows that polymer hydrogel particles can be used as versatile adhesion sensors to investigate a broad range of adhesion processes in aqueous media. Full article

(This article belongs to the Special Issue Colloid Chemistry)

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10522 KiB

Open AccessFeature PaperArticle

Temperature-Triggered Colloidal Gelation through Well-Defined Grafted Polymeric Surfaces

by Jan Maarten Van Doorn, Joris Sprakel and Thomas E. Kodger

Gels 2017, 3(2), 21; https://doi.org/10.3390/gels3020021 - 3 Jun 2017

Cited by 5 | Viewed by 5312

Abstract

Sufficiently strong interparticle attractions can lead to aggregation of a colloidal suspension and, at high enough volume fractions, form a mechanically rigid percolating network known as a colloidal gel. We synthesize a model thermo-responsive colloidal system for systematically studying the effect of surface [...] Read more.

Sufficiently strong interparticle attractions can lead to aggregation of a colloidal suspension and, at high enough volume fractions, form a mechanically rigid percolating network known as a colloidal gel. We synthesize a model thermo-responsive colloidal system for systematically studying the effect of surface properties, grafting density and chain length, on the particle dynamics within colloidal gels. After inducing an attraction between particles by heating, aggregates undergo thermal fluctuation which we observe and analyze microscopically; the magnitude of the variance in bond angle is larger for lower grafting densities. Macroscopically, a clear increase of the linear mechanical behavior of the gels on both the grafting density and chain length arises, as measured by rheology, which is inversely proportional to the magnitude of local bond angle fluctuations. This colloidal system will allow for further elucidation of the microscopic origins to the complex macroscopic mechanical behavior of colloidal gels including bending modes within the network. Full article

(This article belongs to the Special Issue Colloid Chemistry)

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3173 KiB

Open AccessArticle

Photo-Crosslinkable Colloids: From Fluid Structure and Dynamics of Spheres to Suspensions of Ellipsoids

by Avner P. Cohen, Maria Alesker, Andrew B. Schofield, David Zitoun and Eli Sloutskin

Gels 2016, 2(4), 29; https://doi.org/10.3390/gels2040029 - 16 Nov 2016

Cited by 4 | Viewed by 5813

Abstract

Recently-developed photo-crosslinkable PMMA (polymethylmethacrylate) colloidal spheres are a highly promising system for fundamental studies in colloidal physics and may have a wide range of future technological applications. We synthesize these colloids and characterize their size distribution. Their swelling in a density- and index- [...] Read more.

Recently-developed photo-crosslinkable PMMA (polymethylmethacrylate) colloidal spheres are a highly promising system for fundamental studies in colloidal physics and may have a wide range of future technological applications. We synthesize these colloids and characterize their size distribution. Their swelling in a density- and index- matching organic solvent system is demonstrated and we employ dynamic light scattering (DLS), as also the recently-developed confocal differential dynamic microscopy (ConDDM), to characterize the structure and the dynamics of a fluid bulk suspension of such colloids at different particle densities, detecting significant particle charging effects. We stretch these photo-crosslinkable spheres into ellipsoids. The fact that the ellipsoids are cross-linked allows them to be fluorescently stained, permitting a dense suspension of ellipsoids, a simple model of fluid matter, to be imaged by direct confocal microscopy. Full article

(This article belongs to the Special Issue Colloid Chemistry)

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1947 KiB

Open AccessFeature PaperCommunication

Carbamate-Based Bolaamphiphile as Low-Molecular-Weight Hydrogelators

by Laurent Latxague, Alexandra Gaubert, David Maleville, Julie Baillet, Michael A. Ramin and Philippe Barthélémy

Gels 2016, 2(4), 25; https://doi.org/10.3390/gels2040025 - 28 Sep 2016

Cited by 19 | Viewed by 6013

Abstract

A new bolaamphiphile analog featuring carbamate moieties was synthesized in six steps starting from thymidine. The amphiphile structure exhibits nucleoside-sugar polar heads attached to a hydrophobic spacer via carbamate (urethane) functions. This molecular structure, which possesses additional H-bonding capabilities, induces the stabilization of [...] Read more.

A new bolaamphiphile analog featuring carbamate moieties was synthesized in six steps starting from thymidine. The amphiphile structure exhibits nucleoside-sugar polar heads attached to a hydrophobic spacer via carbamate (urethane) functions. This molecular structure, which possesses additional H-bonding capabilities, induces the stabilization of low-molecular-weight gels (LMWGs) in water. The rheological studies revealed that the new bolaamphiphile 7 stabilizes thixotropic hydrogels with a high elastic modulus (G′ > 50 kPa). Full article

(This article belongs to the Special Issue Colloid Chemistry)

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6657 KiB

Open AccessArticle

Immobilization of Colloidal Monolayers at Fluid–Fluid Interfaces

by Peter T. Bähler, Michele Zanini, Giulia Morgese, Edmondo M. Benetti and Lucio Isa

Gels 2016, 2(3), 19; https://doi.org/10.3390/gels2030019 - 8 Jul 2016

Cited by 4 | Viewed by 5995

Abstract

Monolayers of colloidal particles trapped at an interface between two immiscible fluids play a pivotal role in many applications and act as essential models in fundamental studies. One of the main advantages of these systems is that non-close packed monolayers with tunable inter-particle [...] Read more.

Monolayers of colloidal particles trapped at an interface between two immiscible fluids play a pivotal role in many applications and act as essential models in fundamental studies. One of the main advantages of these systems is that non-close packed monolayers with tunable inter-particle spacing can be formed, as required, for instance, in surface patterning and sensing applications. At the same time, the immobilization of particles locked into desired structures to be transferred to solid substrates remains challenging. Here, we describe three different strategies to immobilize monolayers of polystyrene microparticles at water–decane interfaces. The first route is based on the leaking of polystyrene oligomers from the particles themselves, which leads to the formation of a rigid interfacial film. The other two rely on in situ interfacial polymerization routes that embed the particles into a polymer membrane. By tracking the motion of the colloids at the interface, we can follow in real-time the formation of the polymer membranes and we interestingly find that the onset of the polymerization reaction is accompanied by an increase in particle mobility determined by Marangoni flows at the interface. These results pave the way for future developments in the realization of thin tailored composite polymer-particle membranes. Full article

(This article belongs to the Special Issue Colloid Chemistry)

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Review

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5811 KiB

Open AccessFeature PaperReview

Gels Obtained by Colloidal Self-Assembly of Amphiphilic Molecules

by Paula Malo de Molina and Michael Gradzielski

Gels 2017, 3(3), 30; https://doi.org/10.3390/gels3030030 - 3 Aug 2017

Cited by 24 | Viewed by 8418

Abstract

Gelation in water-based systems can be achieved in many different ways. This review focusses on ways that are based on self-assembly, i.e., a bottom-up approach. Self-assembly naturally requires amphiphilic molecules and accordingly the systems described here are based on surfactants and to some [...] Read more.

Gelation in water-based systems can be achieved in many different ways. This review focusses on ways that are based on self-assembly, i.e., a bottom-up approach. Self-assembly naturally requires amphiphilic molecules and accordingly the systems described here are based on surfactants and to some extent also on amphiphilic copolymers. In this review we are interested in cases of low and moderate concentrations of amphiphilic material employed to form hydrogels. Self-assembly allows for various approaches to achieve gelation. One of them is via increasing the effective volume fraction by encapsulating solvent, as in vesicles. Vesicles can be constructed in various morphologies and the different cases are discussed here. However, also the formation of very elongated worm-like micelles can lead to gelation, provided the structural relaxation times of these systems is long enough. Alternatively, one may employ amphiphilic copolymers of hydrophobically modified water soluble polymers that allow for network formation in solution by self-assembly due to having several hydrophobic modifications per polymer. Finally, one may combine such polymers with surfactant self-assemblies and thereby produce interconnected hybrid network systems with corresponding gel-like properties. As seen here there is a number of conceptually different approaches to achieve gelation by self-assembly and they may even become combined for further variation of the properties. These different approaches are described in this review to yield a comprehensive overview regarding the options for achieving gel formation by self-assembly. Full article

(This article belongs to the Special Issue Colloid Chemistry)

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5328 KiB

Open AccessFeature PaperReview

Hydrogels for Biomedical Applications: Cellulose, Chitosan, and Protein/Peptide Derivatives

by Luís J. Del Valle, Angélica Díaz and Jordi Puiggalí

Gels 2017, 3(3), 27; https://doi.org/10.3390/gels3030027 - 17 Jul 2017

Cited by 157 | Viewed by 20927

Abstract

Hydrogels based on polysaccharide and protein natural polymers are of great interest in biomedical applications and more specifically for tissue regeneration and drug delivery. Cellulose, chitosan (a chitin derivative), and collagen are probably the most important components since they are the most abundant [...] Read more.

Hydrogels based on polysaccharide and protein natural polymers are of great interest in biomedical applications and more specifically for tissue regeneration and drug delivery. Cellulose, chitosan (a chitin derivative), and collagen are probably the most important components since they are the most abundant natural polymers on earth (cellulose and chitin) and in the human body (collagen). Peptides also merit attention because their self-assembling properties mimic the proteins that are present in the extracellular matrix. The present review is mainly focused on explaining the recent advances on hydrogels derived from the indicated polymers or their combinations. Attention has also been paid to the development of hydrogels for innovative biomedical uses. Therefore, smart materials displaying stimuli responsiveness and having shape memory properties are considered. The use of micro- and nanogels for drug delivery applications is also discussed, as well as the high potential of protein-based hydrogels in the production of bioactive matrices with recognition ability (molecular imprinting). Finally, mention is also given to the development of 3D bioprinting technologies. Full article

(This article belongs to the Special Issue Colloid Chemistry)

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15602 KiB

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Droplets, Evaporation and a Superhydrophobic Surface: Simple Tools for Guiding Colloidal Particles into Complex Materials

by Marcel Sperling and Michael Gradzielski

Gels 2017, 3(2), 15; https://doi.org/10.3390/gels3020015 - 4 May 2017

Cited by 29 | Viewed by 10228

Abstract

The formation of complexly structured and shaped supraparticles can be achieved by evaporation-induced self-assembly (EISA) starting from colloidal dispersions deposited on a solid surface; often a superhydrophobic one. This versatile and interesting approach allows for generating rather complex particles with corresponding functionality in [...] Read more.

The formation of complexly structured and shaped supraparticles can be achieved by evaporation-induced self-assembly (EISA) starting from colloidal dispersions deposited on a solid surface; often a superhydrophobic one. This versatile and interesting approach allows for generating rather complex particles with corresponding functionality in a simple and scalable fashion. The versatility is based on the aspect that basically one can employ an endless number of combinations of components in the colloidal starting solution. In addition, the structure and properties of the prepared supraparticles may be modified by appropriately controlling the evaporation process, e.g., by external parameters. In this review, we focus on controlling the shape and internal structure of such supraparticles, as well as imparted functionalities, which for instance could be catalytic, optical or electronic properties. The catalytic properties can also result in self-propelling (supra-)particles. Quite a number of experimental investigations have been performed in this field, which are compared in this review and systematically explained. Full article

(This article belongs to the Special Issue Colloid Chemistry)

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2511 KiB

Open AccessFeature PaperReview

Physicochemical Properties and the Gelation Process of Supramolecular Hydrogels: A Review

by Abdalla H. Karoyo and Lee D. Wilson

Gels 2017, 3(1), 1; https://doi.org/10.3390/gels3010001 - 1 Jan 2017

Cited by 55 | Viewed by 15017

Abstract

Supramolecular polysaccharide-based hydrogels have attracted considerable research interest recently due to their high structural functionality, low toxicity, and potential applications in foods, cosmetics, catalysis, drug delivery, tissue engineering and the environment. Modulation of the stability of hydrogels is of paramount importance, especially in [...] Read more.

Supramolecular polysaccharide-based hydrogels have attracted considerable research interest recently due to their high structural functionality, low toxicity, and potential applications in foods, cosmetics, catalysis, drug delivery, tissue engineering and the environment. Modulation of the stability of hydrogels is of paramount importance, especially in the case of stimuli-responsive systems. This review will update the recent progress related to the rational design of supramolecular hydrogels with the objective of understanding the gelation process and improving their physical gelation properties for tailored applications. Emphasis will be given to supramolecular host–guest systems with reference to conventional gels in describing general aspects of gel formation. A brief account of the structural characterization of various supramolecular hydrogels is also provided in order to gain a better understanding of the design of such materials relevant to the nature of the intermolecular interactions, thermodynamic properties of the gelation process, and the critical concentration values of the precursors and the solvent components. This mini-review contributes to greater knowledge of the rational design of supramolecular hydrogels with tailored applications in diverse fields ranging from the environment to biomedicine. Full article

(This article belongs to the Special Issue Colloid Chemistry)

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793 KiB

Open AccessReview

Transport Phenomena in Gel

by Masayuki Tokita

Gels 2016, 2(2), 17; https://doi.org/10.3390/gels2020017 - 11 May 2016

Cited by 22 | Viewed by 5968

Abstract

Gel becomes an important class of soft materials since it can be seen in a wide variety of the chemical and the biological systems. The unique properties of gel arise from the structure, namely, the three-dimensional polymer network that is swollen by a [...] Read more.

Gel becomes an important class of soft materials since it can be seen in a wide variety of the chemical and the biological systems. The unique properties of gel arise from the structure, namely, the three-dimensional polymer network that is swollen by a huge amount of solvent. Despite the small volume fraction of the polymer network, which is usually only a few percent or less, gel shows the typical properties that belong to solids such as the elasticity. Gel is, therefore, regarded as a dilute solid because its elasticity is much smaller than that of typical solids. Because of the diluted structure, small molecules can pass along the open space of the polymer network. In addition to the viscous resistance of gel fluid, however, the substance experiences resistance due to the polymer network of gel during the transport process. It is, therefore, of importance to study the diffusion of the small molecules in gel as well as the flow of gel fluid itself through the polymer network of gel. It may be natural to assume that the effects of the resistance due to the polymer network of gel depends strongly on the network structure. Therefore, detailed study on the transport processes in and through gel may open a new insight into the relationship between the structure and the transport properties of gel. The two typical transport processes in and through gel, that is, the diffusion of small molecules due to the thermal fluctuations and the flow of gel fluid that is caused by the mechanical pressure gradient will be reviewed. Full article

(This article belongs to the Special Issue Colloid Chemistry)

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5917 KiB

Open AccessReview

Self-Healing Supramolecular Hydrogels Based on Reversible Physical Interactions

by Satu Strandman and X.X. Zhu

Gels 2016, 2(2), 16; https://doi.org/10.3390/gels2020016 - 8 Apr 2016

Cited by 74 | Viewed by 19422

Abstract

Dynamic and reversible polymer networks capable of self-healing, i.e., restoring their mechanical properties after deformation and failure, are gaining increasing research interest, as there is a continuous need towards extending the lifetime and improving the safety and performance of materials particularly in [...] Read more.

Dynamic and reversible polymer networks capable of self-healing, i.e., restoring their mechanical properties after deformation and failure, are gaining increasing research interest, as there is a continuous need towards extending the lifetime and improving the safety and performance of materials particularly in biomedical applications. Hydrogels are versatile materials that may allow self-healing through a variety of covalent and non-covalent bonding strategies. The structural recovery of physical gels has long been a topic of interest in soft materials physics and various supramolecular interactions can induce this kind of recovery. This review highlights the non-covalent strategies of building self-repairing hydrogels and the characterization of their mechanical properties. Potential applications and future prospects of these materials are also discussed. Full article

(This article belongs to the Special Issue Colloid Chemistry)

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