Water Swelling Characteristics Research Articles

4D Printing Dual Stimuli-Responsive Bilayer Structure Toward Multiple Shape-Shifting

4D printing has been attracting widespread attention because its shape and performance can change under stimuli. The existing 4D printing technology is mostly limited to responsive to single stimulus, which means that the printing structure can only change under a pre-specified stimulus. Here we propose a 4D printing strategy with dual stimuli-responsive shape-shifting that responds to both temperature and water, by using a direct ink writing 3D printing method to deposit a polyurethane elastomer material with water-swelling characteristics on a heat-shrinkage shape memory polymer material to form a bilayer structure. Based on the systematic study of the adapted printing parameters of the polyurethane elastomer, the effect of programmable variables on the deformation shape was investigated. The diversified printing structure exhibits rich structural changes under one or both of the two stimuli of temperature and water. This research provides a universal multiple stimuli-responsive 4D printing method, which can effectively improve the intelligent responsiveness of 4D printing structures by combining multiple smart materials.

Marine Spongia collagens: Protein characterization and evaluation of hydrogel films

ABSTRACTFibrous proteins such as collagens are important raw materials for the production of new bio‐based or biomimetic materials. A rich source of collagen is found in the extracellular skeletal matrix of marine or sea sponges, an anatomically simple animal species. This abundant source of collagens was explored for its potential to create a hydrogel suitable as a biomaterial for drug delivery and tissue engineering. Collagen proteins were extracted from the skeletons of hard and soft species of sponges from the Spongia genus. The protein profile, amino acid composition, and partial sequences of the extracted proteins were determined, and the protein extracts were fabricated with chitosan and organic cross‐linkers to create hydrogel films. The amino acid compositions and sequences of Spongia collagens are similar to collagens obtained from other species. Spongia collagens are hydrophilic and mechanically fragile. Blending these with chitosan and the organic crosslinkers, genipin and glyceraldehyde, formed blended films with improved mechanical performance and structural integrity and improved stress–strain and water swelling characteristics. These material properties show the potential of the films to be used as hydrogel biomaterials in medical applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47996.

Design and molecular dynamics of multifunctional sulfonated poly(dimethylaminoethyl methacrylate)/mica hybrid cryogels through freezing-induced gelation.

This article addresses various strategies that have been explored to design sulfonated poly(dimethylaminoethyl methacrylate)/mica hybrid-gels with optimized network parameters and mechanical/swelling properties. A series of hybrid cryogels and hydrogels containing amino and sulfonic acid groups were prepared from N,N-dimethylaminoethyl methacrylate (DMAEMA) and 2-acrylamido-2-methyl-1-propane sulfonic acid in the presence of inorganic additive mica via a cryogelation process and conventional in situ copolymerization. Cryogelation was used to fine-tune the mechanical properties of the PDMAEMA-based hybrid gels. The effects of pH, temperature and mica content on the network parameters, mechanical properties and swelling behavior were discussed. X-ray diffractometry and Fourier transform infrared spectroscopy confirmed that mica particles had participated in (cryo)polymerization, and the thermal stability and surface morphologies were improved by the addition of mica. The profile of water loss, decomposition of amine groups and breakdown of PDMAEMA chains of the resulting hybrid gels were determined by thermogravimetric analysis. A critical mica concentration was found for the hybrid hydrogels where the degree of swelling attains a maximum value. Below 0.50% (w/v) of mica, the ionic nature of mica dominates its crosslinker effect. The hybrid cryogels were tough and able to recover at room temperature after compression testing. The prepared hybrid-gels showed an enhanced swelling response and on-off switching swelling characteristics in water and in aqueous NaCl solutions. The parameters of equilibrium swelling, the initial swelling rate, the diffusional exponent, and the diffusion coefficient were evaluated and the swelling kinetics of the hybrid hydrogels and cryogels in water followed the pseudo second order model. All the prepared hybrid hydrogel and cryogel materials with tunable mechanical stability and elasticity can be excellent candidates for designing smart materials.

Water-swellable elastomers: synthesis, properties and applications

Abstract Water-swellable elastomers (WSE) constitute a class of rubbery materials that have been widely studied both in academia and industry during the last 25 years. Market pull is the major driver for the exploration of these materials. The need of WSE in several sealing applications has driven the attention of many academic researchers toward the possibility to provide a rubber with water-swelling characteristics. As commercial rubbers are hydrophobic materials, making them swell in water presents an interesting and difficult challenge. This paper reviews the scientific and patent literature on the fundamental aspects of WSE: the various synthetic approaches, the properties of the corresponding polymers (not only the swelling performance but also the mechanical behavior), and some of their applications. Particular attention is paid to the chemical structure/performance relationships of WSE. Finally, the authors speculate on a great future for WSE that can be rationally designed for improved and/or new applications.

Poly(N,N-dimethylacrylamide-co-acrylamide) Grafted Hydroxyethyl Cellulose Hydrogel: A Useful Congo Red Dye Remover

Composite hydrogel was prepared by cross-link copolymerization of a mixture of acrylamide, and N,N-dimethylacrylamide using N,N′-methylene-bis-acrylamide as a cross-linking agent onto hydroxyethyl cellulose backbone. Several hydrogels (H1–H5) were prepared by varying the amount of acrylamide and N,N-dimethylacrylamide. Swelling characteristics in water of all the hydrogels were evaluated to identify the hydrogel having highest water swelling property. The hydrogel showing highest water swelling performance (H3) was characterized by FTIR spectroscopy, XRD and SEM studies. Swelling and deswelling kinetic studies of the hydrogel (H3) were also carried out. The hydrogel (H3) was used for the removal of congo red (CR), a toxic azo dye from its aqueous solution. Adsorption dynamics, kinetics and isotherms were also evaluated. The adsorption follows a pseudo second order kinetics, and the sorption data were well fitted with Langmuir adsorption isotherm. The hydrogel (H3) showed a high monolayer adsorption capacity (Qm = 102.4 mg g−1) for the CR dye adsorption.

Synthesis of Upconverting Hydrogel Nanocomposites Using Thiol‐Ene Click Chemistry: Template for the Formation of Dendrimer‐Like Gold Nanoparticle Assemblies

The synthesis of upconverting hydrogel nanocomposites by base-catalyzed thiol-ene click reaction between 10-undecenoic acid capped Yb(3+)/Er(3+)-doped NaYF4 nanoparticles and pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) as tetrathiol monomer is reported. This synthetic strategy for nanocomposite gels is quite different from works where usually the preformed gels are mixed with the nanoparticles. Developing nanocomposites by surface modification of capping ligands would allow tuning and controlling of the separation of the nanoparticles inside the gel network. The hydrogel nanocomposites prepared by thiol-ene click reaction show strong enhancement in luminescence intensity compared to 10-undecenoic acid-capped Yb(3+)/Er(3+)-doped NaYF4 nanoparticles through the upconversion process (under 980 nm laser excitation). The hydrogel nanocomposites display strong swelling characteristics in water resulting in porous structures. Interestingly, the resulting nanocomposite gels act as templates for the synthesis of dendrimer-like Au nanostructures when HAuCl4 is reduced in the presence of the nanocomposite gels.

Equilibrium Swelling of Hydrophilic Polyacrylates in Humid Environments

The hydrophilicity of polymers, as indicated by their swelling characteristics in water, is an important parameter with regard to their use as coatings which are able to modify the wettability and adhesive properties of a material. We have investigated the swelling behavior of a series of hydrophilic random copolymer coatings in controlled humidity environments and in water. Swelling data were obtained from a quartz crystal microbalance (QCM) and from spectroscopic ellipsometry. The hydrophilic polymers are based on polyacrylates with low molecular weight side chains of poly(ethylene glycol) (PEG). These polymers also contain a random distribution of acrylic acid. Triblock copolymers with these random copolymers as the midblock and poly(methyl methacrylate) (PMMA) as the end blocks have also been investigated. At low and intermediate humidities, the swelling behavior of appropriately chosen block copolymers is similar to the swelling behavior of the corresponding polymers that do not have the PMMA end blo...

Synthesis of porous polymeric membranes by polymerization of micro-emulsions

In this study the polymerization of monomer-containing micro-emulsions to yield porous polymeric membranes is demonstrated. A micro-emulsion system composed of methyl methacrylate and acrylic acid as monomers, ethyleneglycol dimethacrylate as crosslinking agent, sodium dodecylsulfate as surfactant and water was studied. An identical surfactant-free system, formed using the same monomers, crosslinking agent and water but without surfactant, was also studied and the micro-emulsions formed at certain compositions were polymerized. Our earlier work with these systems had indicated the porous morphology of the polymer to be dependent on the microstructure of the precursor micro-emulsion. In the present study micro-emulsion compositions which showed inferential evidence of a bicontinuous structure were polymerized to form membranes by using photo-initiated polymerization with ultra-violet radiation. The membranes formed had a thickness of 10–12 μm. The swelling characteristics in water of the polymeric material constituting the membranes was evaluated as a function of pH. The tensile properties of the membranes were also evaluated. The permeability of the membranes was examined using aqueous solutions of acrylic acid. The results indicate the permeability of the membranes to be dependent on the composition of the precursor micro-emulsion due to the relationship between the polymer morphology and micro-emulsion structure. This study conclusively shows the feasibility of synthesizing porous polymeric membranes by utilizing the structure of micro-emulsions.