Swelling Process and Order-Disorder Transition of Hydrogel Containing Hydrophobic Ionizable Groups

Uchida, Makoto; Kurosawa, Manabu; Osada, Yoshihito

doi:10.1021/ma00117a031

Cited by 69 publications

(77 citation statements)

References 4 publications

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“…Long alkyl side chains are anchored on the primary chains by the copolymerization of alkyl acrylates and another hydrophilic monomer. In early studies, hydrogels with crystalline domains were synthesized by copolymerizing acrylic acid (AA) and stearyl acrylate (SA) or acryloylhexadecanoic acid (AHA) [60,61]. Th e poly(SA-co-AA) and poly(AHA-co-AA) hydrogels show strong birefringence because of th e aggregation and crystallization of side chains.…”

Section: Block-copolymer Structured Hydrogelsmentioning

confidence: 99%

Hydrogels with self-assembling ordered structures and their functions

Gong

2011

NPG Asia Mater

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Biomimetic and bioinspired materials are receiving increasing attention because of their robust functionality and potential applications as artifi cial tissue [1,2]. For natural materials, a high degree of sophistication is achieved through self-organization of the various components into ordered and hierarchical structures following a well-defi ned pattern [2][3][4]. Biological tissue possesses these ordered structures, endowing the living organisms with mechanical toughness and functionality, as exemplifi ed by tissues such as bone and cartilage. Th erefore, eff orts should be made to introduce ordered and hierarchical structure into soft, and also hard, synthetic materials. Among the strategies developed to date, self-assembly is a convenient and powerful method for producing ordered structures [5].Self-assembly, the spontaneous organization of discrete components into organized structures, is widespread in nature, such as in protein folding and hybridization of the DNA double helix [3][4][5][6]. Self-assembled structures usually incorporate additional functionalities. For example, phospholipids form a lipid bilayer arou nd the cell as a barrier to the diffusion of ions and proteins, and tropocollagens self-assemble into fi brils collagens that are closely packed in parallel arrays in the tendon, endowing it with excellent mechanical properties [3]. Inspired by nature, molecular self-assembly that is directed through weak, noncovalent interactions has received tremendous attention for the development of systems with ordered structures and resultant functions [1,2,6,7]. Th ese eff orts have resulted in various functional materials based on self-assembled structures including solutions, elastomers, gels and hard materials [1,2,[7][8][9].Gels as a functional system is an emerging fi eld in themselves, possessing a responsiveness to external stimuli such as stress, light, temperature, pH and ionic strength [10]. Gels with molecular assemblies can be produced in organic solvent (organogels) or aqueous solvent (hydrogels). In this review, we focus primarily on functional hydrogels with self-assembled structures. Functional organogels produced by molecular self-assembly have been covered in several excellent reviews [11][12][13][14].Hydrogels as a functional material have their own advantages over organogels. Th e aqueous medium makes hydrogels an ideal candidate for soft biotissue, mimicking its functions for applications such as scaff olds for cell culturing [15,16]. However, producing structured hydrogels is not easy because the ordered structure formation and water content (which introduces fl uctuation) work in opposite directions. Th e typical kinds of molecules capable of forming self-assembled structures in aqueous media are amphiphile, block-copolymer and liquid-crystalline (LC) molecules. Under certain conditions, the ordered structures formed by molecular self-assembly can be frozen in physically or chemically crosslinked hydrogels with additional functionalities, such as anisotropic optical and mechanica...

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Section: Block-copolymer Structured Hydrogelsmentioning

confidence: 99%

Hydrogels with self-assembling ordered structures and their functions

Gong

2011

NPG Asia Mater

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“…Osada's research group has previously studied the hydrogel properties with different monomers such as acrylic acid (AA) and n-stearyl acrylate (SA) [poly(SA-co-AA) gel], 16-acryloylhexadecanoic acid (AHA) and acrylic acid (AA) [poly(AHA-co-AA) gel], hexadecyl acrylate (HA) and acrylic acid (AA) [poly(HA-co-AA) gel] system. [16][17][18] They reported that poly(SA-co-AA) gel has a more crystalline structure and very high Young's modulus compared to other gels because of the long n-stearyl acrylate (SA) side group. DMAA gel, on the other hand, shows very low mechanical stress which indicates that the DMAA becomes more fragile in the equilibrium swollen state.…”

Section: Resultsmentioning

confidence: 99%

A Low Cost Sensor Based Agriculture Monitoring System Using Polymeric Hydrogel

Kabir

Ahmed

Furukawa

2017

J. Electrochem. Soc.

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Polymeric superabsorbent hydrogels are the kind of gels that are obtained by chemically synthesizing with hydrophilic polymers to form a 3D-network structure. These hydrogels have been extensively used in agriculture over the last two decades as an absorbent. The aim of this work is to use the polymeric hydrogel to increase the water holding properties of growing media such as soil and to develop a low cost system for monitoring. Two types of polymeric hydrogels were prepared and the swelling ratio was determined. A three times higher swelling ratio was observed at DMAA (90 wt%) than that of SMG (30 wt%) even though both samples have the same cross-linker (MBAA). In contrast to DMAA, SMG gel has a greater crystalline network structure as measured by mechanical and dynamic light scattering. Experimental results suggest that the DMAA based hydrogel is suitable for agriculture. A low cost, sensor based, monitoring system was developed that indicates the merit of the system. Superabsorbent hydrogels realized by chemical synthesis are a particular class of macromolecular gels obtained from hydrophilic polymers in the form of three dimensional network structures. The cross-linked based polyacrylamide does not dissolve. However, it can become a hydrogel when water is added.1 Gels look like a solid material but basically gels are soft and wet materials and are capable of large deformation with external stimuli.2 In the hydrogel, polymer chain networks absorb a large number of water molecules. The hydrophilicity of the chains control the amount of water in the hydrogel.3 There are wide applications in different fields where gels are potentially used such as drug delivery, 4,5 tissue engineering 6,7 and biomaterials. 5 Recently, the superabsorbent hydrogels have attracted attention from agriculture. Generally, polyacrylamide and acrylamide-acrylate copolymer based cross-linked hydrogels are marketed for agriculture.The water shortage in irrigation becomes a big issue in those areas where the underground water level is not enough. The salty water, on the other hand, in the coastal areas cannot be used for irrigation due to the aggregation of water salinity.8 Nevertheless, demand of water is expected to be 50% higher than today by 2030. 9 In this context, the water resource management could be a challenge in near future. 10It is difficult to guarantee that the appropriate amount of water is proficiently and sensibly delivered to the agricultural field. In the literature, several solutions have reported to address this issue.11 The optimization of water in agriculture can be achieved by developing innovative resources and digital systems for real-time monitoring. Therefore, superabsorbent hydrogel may be an alternative approach to the optimization of water consumption in the agriculture field, because hydrogel can absorb and retain extremely large amounts of water relative to their own mass.12 Additionally hydrogels will reduce the irrigation frequency, cost and reduce both erosion of soil and water run-off. 13From the agric...

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“…The whole electrospinning process takes place in milliseconds. [8] Electrospun nanofibers have received a great deal of attention, as their high surface-to-volume ratio and inherent porous structure make them very suitable for use in efficient filtering systems, [9] wound dressings, [10] scaffolds for tissue engineering, [11] protective clothing, [12] reinforcement, [13] and more. [14] Several research groups have reported the preparation of sheath-core bicomponent polymer nanofibers through an electrospinning process using a coaxial two-capillary spinneret.…”

Section: Self-crimping Bicomponent Nanofibers Electrospun From Polyacmentioning

confidence: 99%

Self‐Crimping Bicomponent Nanofibers Electrospun from Polyacrylonitrile and Elastomeric Polyurethane

2005

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tails of this procedure have been published previously [18]. An aqueous solution of PBDT has a LC nature above 2.8 wt.-% (C * LC ). DMA-PAA-Q (Kohjin Co. Ltd.) was used as the monomer without further purification. MBAA (Junsei Chemical Co. Ltd.) was recrystallized with ethanol and used as a crosslinker. Acrylamide (AAm) (Junsei Chemical Co. Ltd.) was recrystallized with chloroform and used as the neutral monomer. Potassium persulfate (KPS) (Wako Pure Chemical Industries Ltd.) was recrystallized with water and used as the initiator. Water was deionized and purified with 0.22 lm and 5 lm membrane filters before use. 2 wt.-% PBDT, 2 mol L -1 DMAPAA-Q (or AAm), 0.5, 1, or 2 mol-% (to DMAPAA-Q) MBAA, and 0.1 mol-% KPS were dissolved in water. These solutions were poured into reaction cells consisting of a pair of glass plates with a 2 mm spacing. Radical polymerization was performed at 60°C. After gelation, the products were immersed in a large amount of water and allowed to reach an equilibrium state for a week.Measurements: The swelling degree of the gels, Q, is defined here as the weight ratio of a swollen to a dried gel [23]. The dried gels were obtained by keeping them in a desiccator for 12 h and in a vacuum oven at 60°C for 6 h.Optical-microscopy observation was performed using a crossed polarizing microscope (Olympus, BH-2) at room temperature. Sample gels were placed on glass plates and the upper free surfaces were observed. Birefringence, Dn, was measured by a crossed polarizing microscope with a Berek compensator [20]. In the measurement, many microscopic domains randomly oriented in the bulk were observed. Thus, we chose one of large domains and selected the orientation direction by turning the sample under the crossed polarizing microscope. Under these conditions, Dn was measured from the retardation. Average Dn was determined by measuring Dn several times for each sample.

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Swelling Process and Order-Disorder Transition of Hydrogel Containing Hydrophobic Ionizable Groups

Cited by 69 publications

References 4 publications

Hydrogels with self-assembling ordered structures and their functions

Hydrogels with self-assembling ordered structures and their functions

A Low Cost Sensor Based Agriculture Monitoring System Using Polymeric Hydrogel

Self‐Crimping Bicomponent Nanofibers Electrospun from Polyacrylonitrile and Elastomeric Polyurethane

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