Hydrophobic Association Hydrogels Research Articles

Temperature-Responsive Properties of Poly(acrylic acid-co-acrylamide) Hydrophobic Association Hydrogels with High Mechanical Strength

A novel type of hydrophobic association hydrogels (HA-gels) was prepared through micellar copolymerization of acrylic acid (AA), acrylamide (AAm) as basic monomers and a small amount of octylphenol polyoxyethylene ether acrylate with seven ethoxyl units (OP7-AC) as hydrophobic association monomer. The HA-gels exhibited desirable mechanical property and stably reversible phase transition between opaque and transparency. The influences of adding urea and varying AA:AAm molar ratio on the phase transition behavior were discussed, which indicated that the phase transition was introduced by forming or dissociating of hydrogen bonding between amide and carboxyl groups. The introduction of hydrophobic units (OP7-AC) to poly(acrylic acid-co-acrylamide) (P(AA-AAm)) copolymer would result in the adulterating and cross-linking effects on the transition temperature. The former sharply reduced the transition temperature while the later gradually raised it. The transition temperature became linearly dropping with the i...

Swelling Behavior of Hydrophobic Association Hydrogels with High Mechanical Strength

Hydrophobic association hydrogels (HA-gels) with high mechanical strength, self-healing capability and transparency were successfully prepared by micellar copolymerization, and associated micelles acted as physical crosslinking points in the network structure of HA-gels. In this study, the swelling behavior of HA-gels in distilled water at room temperature was investigated. With increasing the content of hydrophobic monomer in the HA-gels, the swelling degree of HA-gels decreased. According to the results of swelling experiments, a swelling model of HA-gels was proposed, which could reasonably explain the swelling behavior of HA-gels. Moreover, the effect of other test conditions on the swelling behavior of HA-gels was also investigated, such as temperature, sodium dodecyl sulfate (SDS), pH and NaCl. These results indicate that the swelling behavior of HA-gels could be strongly influenced under the conditions mentioned above.

Self-healing Mechanism and Mechanical Behavior of Hydrophobic Association Hydrogels with High Mechanical Strength

Hydrophobic association hydrogels (HA-gels) were prepared through micellar copolymerizationof acrylamide (AM) and a small amount of octyl phenol polyethoxy ether acrylate (OP-4-AC) in an aqueous solution containing sodium dodecyl sulfate (SDS) at 50°C. The resulting HA-gels exhibited excellent mechanical properties and transparency. However, the most striking properties were that HA-gels possessed the capability of self-healing. The mechanical properties of HA-gels were investigated by uniaxial stretching. The results showed that the mechanical properties of HA-gels could be varied greatly by changing OP-4-AC content in the range of OP-4-AC used. On the basis of the rubber elastic theory and using uniaxial stretching data, the effective network chain density and the average distance between the cross-linking points were calculated for HA-gels. For tensile measurements of altering crosshead speed, the modulus of HA-gels increased sharply with increasing crosshead speed. The stress-relaxation behavior of HA-gels consisted of two stages. Similar to rubbery, HA-gels exhibited obvious thermoelastic behavior and also showed a good rubberlike elastic property.

Network structure and compositional effects on tensile mechanical properties of hydrophobic association hydrogels with high mechanical strength

Hydrophobic association hydrogels (HA-gels) were successfully prepared through micellar copolymerization of acrylamide (AM) and a small amount of octylphenol polyoxyethylene acrylate (OP-4-AC) in an aqueous solution containing sodium dodecyl sulfate (SDS). HA-gels exhibited excellent mechanical properties and transparency. Especially, HA-gels possessed the capability of re-forming, such as self-healing and molding. From Fourier transform infrared, swelling behavior and re-forming capability of HA-gels, the network structure was established. On the basis of the micellar copolymerization theory, the statistical molecular theory of rubber elastic, and using uniaxial stretching data, the length of the hydrophobic microblocks, the effective network chain density and the molecular weight of the chain length between cross-linking points were evaluated for all HA-gels; furthermore, they were also evaluated for the region of medium deformation by the Mooney-Rivlin theory. For HA-gels, we investigated in detail the effects of the content of compositions in the initial solution, OP-4-AC, SDS and AM, on their tensile mechanical properties on the basis of the proposed network structure. The results clearly indicate their tensile strength, fracture energy, elastic modulus, and elongation strongly depended on their composition content.

Construction and Properties of Hydrophobic Association Hydrogels with High Mechanical Strength and Reforming Capability

AbstractHydrophobic association hydrogels (HA‐gels) with almost ideal properties were successfully prepared by micellar copolymerization, and the associated micelles acted as physical cross‐linking points in the network of HA‐gels. HA‐gels exhibit exceptional mechanical properties and transparency. However, the most striking properties are that HA‐gels possess the capability of self‐healing and remolding, which is mainly due to the dissociation and re‐association process of the associated micelles. Dried‐gels, which were prepared by stretching HA‐gels to a certain elongation for a period of time in the air, can be used as shrinkable or thermal sensitivity materials. HA‐gels have a broad selectivity for components, so we have synthesized HA‐gels with variously available properties by changing a corresponding component: thermoresponsive HA‐gels, nanosphere‐composite HA‐gels, and fluorescent HA‐gels. Therefore, we are sure that HA‐gels will be widely used in various fields, such as biology, medication, sensors, optics, and oil exploitation.magnified image