1H NMR Self-Diffusion Study of Morphology and Structure of Polyvinyl Alcohol Cryogels

Shapiro, Yury E.

doi:10.1006/jcis.1998.6033

Cited by 20 publications

(21 citation statements)

References 39 publications

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“…[45] This freeze-thaw process produces a two-phase composite structure, which has recently been studied in more detail. [46,47] Composite gels with polyvinylalcohol and other water-soluble polymers have also been studied. [48] There have been many recent studies of composite gels produced by irradiation of mixed solutions of polymers, and increases in strength have been reported, compared to single-polymer gels.…”

Section: Multiphase Gelsmentioning

confidence: 99%

Hydrogels for Soft Machines

2009

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Hydrogels have applications in surgery and drug delivery, but are never considered alongside polymers and composites as materials for mechanical design. This is because synthetic hydrogels are in general very weak. In contrast, many biological gel composites, such as cartilage, are quite strong, and function as tough, shock‐absorbing structural solids. The recent development of strong hydrogels suggests that it may be possible to design new families of strong gels that would allow the design of soft biomimetic machines, which have not previously been possible.

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Section: Multiphase Gelsmentioning

confidence: 99%

Hydrogels for Soft Machines

2009

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“…More recently, such poly(vinyl alcohol) gels with water contents of around 80 % were found to fail in compression at a few MPa [42]. This freeze-thaw process produces a two-phase composite structure which has recently been studied in more detail [43,44]. Composite gels with poly(vinyl alcohol) and other water-soluble polymers have also been studied [45].…”

Section: Multi-phase Gelsmentioning

confidence: 99%

Polymer Gel Actuators: Fundamentals

Calvert

2009

Biomedical Applications of Electroactive Polymer Actuators

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One view of materials development is to search for what materials correspond to empty spaces on a hypothetical multi-dimensional map of the properties of available materials. Following a biomimetic philosophy, for instance, it can be seen that tough ceramics and moldable short fiber composites with high moduli are possible but absent from the list of available synthetic materials. Likewise artificial muscle is missing, where the properties are defined as a developed stress of over 300 kPa, a linear contraction of 25 % and a response time of below one second. Currently dielectric elastomers come closest but have disadvantages [1,2].The actin-myosin muscle system provides the performance target for electroactive polymer actuators [3,4]. The process is driven chemically by the energy change from hydrolysis of the polyphosphate bond as ATP (adenosine triphosphate) binds to myosin and is converted to ADP (adenosine diphosphate) and phosphate. A simple chemical analogy suggests that muscle-like gels should be feasible but it is now clear that the task is much harder than it seems.Early work on gel actuation by Katchalsky-Katzir demonstrated that engines could be built using the chemical energy in diluting a lithium bromide solution to drive contraction and expansion of a collagen belt [5]. In essence, the collagen expands to take up the salt solution or contract to exclude the water. This change is both a molecular conformation change and a volume change. Other chemically driven gels, for instance polyacrylic acid fibers [6] which respond to a pH change, also rely on a solubility change giving rise to a volume change.

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“…It was found for the PVA solution in water-DMSO mixture that the crystalline sizes became smaller as the crystallization temperature was lowered (18). By the use of q-space imaging, it was shown that by introduction of the co-solvent like DMSO to cryogels before freezing, the solvent-filled pores became smaller and the interpore channels became very much shorter (12). The diameter of the PVA filaments is the same for all the cryogels; however, the lengths of filaments with only water is twice those of cryogels with a mixed solvent (12).…”

Section: Introductionmentioning

confidence: 98%

“…Applying DMSO or oligooxyethylene glycols as co-solvents, it is possible to achieve similar effects on the freezing point. The transparency and density of the PVA cryogel depend on the mixing ratio of water/DMSO and the crystallization temperature (12,16,18). When gelated at room temperature, the PVA solution makes a spinodal decomposition before gelation and becomes translucent because a spinodal decomposition rate is higher than its gelation rate.…”

Section: Introductionmentioning

confidence: 99%

“…By the use of q-space imaging, it was shown that by introduction of the co-solvent like DMSO to cryogels before freezing, the solvent-filled pores became smaller and the interpore channels became very much shorter (12). The diameter of the PVA filaments is the same for all the cryogels; however, the lengths of filaments with only water is twice those of cryogels with a mixed solvent (12). It has been demonstrated that the presence of DMSO in a system leads to a decrease of compartments; both pores and interpore channels resulted in the high transparency of cryogel.…”

Section: Introductionmentioning

confidence: 99%

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