Elution of polymers from physically cross-linked poly(vinyl alcohol) gels

Otsuka, Emiko; Sasaki, Shigeo; Koizumi, Kenta; Hirashima, Yumiko; Suzuki, Atsushi

doi:10.1039/c0sm00757a

Cited by 21 publications

(26 citation statements)

References 11 publications

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“…These values are shown to be nearly unchanged between both elongation directions, suggesting that the resistance to uniaxial load may be isotropic. According to the literature, any increment in the breaking stress and E of a CD gel during water exchange with drying will result in an increase in crystallinity. Thus, to understand the present results, it must be assumed that the initial tensile strength is determined not by the fibrils, but by the amorphous network.…”

Section: Resultsmentioning

confidence: 99%

“…More recently, a simple method to prepare PVA gel by cast‐drying has also been developed (CD gel) . In order to better understand the network structure produced by these methods on multiple‐scales, physical PVA gels have been subjected to scattering and thermal measurement experiments using X‐ray diffraction (XRD), Fourier‐transform infrared, and differential scanning calorimetry (DSC) techniques. As a result of XRD measurement, CD gel is known to consist of a swollen amorphous network of PVA that is physically crosslinked by microcrystallites, and is therefore similar to FT gel.…”

Section: Introductionmentioning

confidence: 99%

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Tear force of physically crosslinked poly(vinyl alcohol) gels with different submicrometer‐scale network structures

Noh

Bando

Ota

et al. 2014

J of Applied Polymer Sci

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Poly(vinyl alcohol) (PVA) gels can be easily prepared by either the freeze‐thawing (FT gel) method or by the cast‐drying (CD gel) method. Although the resulting nanostructured networks of the FT and CD gels are similar, their physical properties are quite different; while CD gels are transparent and elastic, FT gels are opaque and less elastic. Moreover, the tear energy of the FT gels is much greater than that of the CD gels, which is a direct result of micrometer‐scale differences in their network structures. In order to control the distribution of microcrystallites on nano‐ and micrometer scales, FT gels were prepared from PVA solutions with different water contents. As a result, the gel gradually became more transparent as the initial water content was decreased; and accordingly, the tear energy decreased. Tear resistance was improved in the case of FT gels by repeating the number of FT cycles, whereas with CD gels, this was achieved by increasing the gelation temperature. These results indicate that the microscopic network structures are characterized by a micrometer‐scale bundled‐polymer (fibril), which determines the tear energy of FT gels. Simple methods to control the fibril network structure of FT gels using a unidirectional freezing method are presented herein, with the swelling and mechanical properties of modified FT gels discussed in terms of their multiple‐scale network structures. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41356.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tear force of physically crosslinked poly(vinyl alcohol) gels with different submicrometer‐scale network structures

Noh

Bando

Ota

et al. 2014

J of Applied Polymer Sci

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“…The weight ratio of W 0 to pure water was kept constant (W 0 :water ¼ 3:695). [12] After 48 h, the weight of the swollen sample, W t , was measured. The sample was then dried at 60 C, and the dried weight, W d , was measured.…”

Section: Measurements Of Swelling Ratio and Elution Ratiomentioning

confidence: 99%

“…Recently, the elution from PVA cast gels has been measured quantitatively. [12] It was found that the cast gel film swelled and released lower-molecular-weight PVA into the external medium (water), and that this process stopped after the gel reached its equilibrium state. However, the elution restarted when the gel was put into fresh solution (water) and approached zero after sufficient water exchange [13,14] This elution behavior is inevitable in PVA cast gels, and physical gels in general, and presents a significant barrier to practical applications.…”

Section: Introductionmentioning

confidence: 99%

A Novel Method to Control the Elution Behavior of PVA Cast Gels

Sasaki

Suzuki

2015

Macromolecular Symposia

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Summary: Poly(vinyl alcohol) (PVA) gels, prepared by a cast-drying method, show excellent swelling and mechanical properties. However, the elution of polymers from such gels is one of the major hindrances for practical applications. In this study, PVA cast gels were prepared from a PVA powder, with a high degree of polymerization and hydrolysis, under different temperatures and humidities. The swelling ratio, elution ratio, crystallinity, and microcrystallite size were evaluated, and these were compared with each other. The lowest elution rate (<1%) was obtained under conditions of high drying temperature and high humidity. This indicates that polymer elution can be suppressed by controlling the size, number, and distribution of the microcrystallites.

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“…For example, the release of free chains from the gel was suppressed by adding KCl while it was promoted by adding tetramethylammonium chloride to the external solution 9. More recently, the elution of polymers from physically crosslinked PVA cast gels with high n DP and high r DH values was evaluated quantitatively using a total organic carbon (TOC) analyzer 10. It was found that a PVA cast gel film swelled and released uncrosslinked PVA into the outer water in a limited amount of water, and that this process stopped after the gel reached its equilibrium state.…”

Section: Introductionmentioning

confidence: 99%

Elution of polymers from poly(vinyl alcohol) cast gels with different degrees of polymerization and hydrolysis

Sasaki

Otsuka

Hirashima

et al. 2012

J of Applied Polymer Sci

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Poly(vinyl alcohol) (PVA) gels physically crosslinked by microcrystallites were prepared by a cast-drying method using PVA powders with different degrees of polymerization (n DP ) between 300 and 2400 and hydrolysis (r DH ) between 79.5 and 98.5 mol %. Polymer elution of gels in a limited amount of water was investigated by measuring the total carbon in the outer water by a total organic carbon analyzer. As a result, polymer elution was detected for all gels, the total amount of which depended on both n DP and r DH . In the cases of lower n DP and higher r DH , the gel became opaque and cracks were observed on the surface during a simple swelling process. On the other hand, polymers dissolved without cracks in the cases of higher n DP and lower r DH . These results are discussed on the basis of the network microstructure of the dried states before and after the polymer elution.

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Elution of polymers from physically cross-linked poly(vinyl alcohol) gels

Cited by 21 publications

References 11 publications

Tear force of physically crosslinked poly(vinyl alcohol) gels with different submicrometer‐scale network structures

Tear force of physically crosslinked poly(vinyl alcohol) gels with different submicrometer‐scale network structures

A Novel Method to Control the Elution Behavior of PVA Cast Gels

Elution of polymers from poly(vinyl alcohol) cast gels with different degrees of polymerization and hydrolysis

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