Effect of syndiotacticity on the aqueous poly(vinyl alcohol) gel 2. Syneresis of gel

Ogasawara, Kenji; Nakajima, Tatsuo; Yamaura, Kazuo; Matsuzawa, Shuji

doi:10.1007/bf01410910

Cited by 8 publications

(5 citation statements)

References 11 publications

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“…Thus, in production of fibrils, the use of s‐PVA afforded a higher degree of polymer crystallinity13 and increased tensile strength;14 increased syndiotacticity of PVA afforded hydrogels with improved mechanical characteristics, e.g. dynamic storage,15, 16 compressive,17 and elastic moduli18 as well as markedly increased melting temperature 19, 20. In other words, with PVA, a sub‐molecular level of polymer engineering affords an astonishing enhancement in the degree of polymer association, i.e.…”

Section: (Sub)molecular Polymer Engineeringmentioning

confidence: 99%

“…A sample of PVA obtained from poly(vinyl trifluoroacetate) appeared to be highly ordered in an X‐ray diffraction experiment, although the infrared measurements indicated that the material was identical to the “authentic” PVA. Though vinyl trifluoroacetate can indeed be used to make syndiotactic PVA,18, 21 the monomer is expensive and difficult to handle, so more facile approaches have been developed. Steric considerations strongly suggest that a racemo configuration of the adjacent monomer units is more favorable over the meso counterpart, a phenomenon that can be exploited in the synthesis of stereoregular PVA, specifically by choosing bulky monomers.…”

Section: (Sub)molecular Polymer Engineeringmentioning

confidence: 99%

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Poly(Vinyl Alcohol) Physical Hydrogels: New Vista on a Long Serving Biomaterial

Alves

Jensen

Smith

et al. 2011

Macromolecular Bioscience

209

159

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Poly(vinyl alcohol), PVA, and physical hydrogels derived thereof have an excellent safety profile and a successful history of biomedical applications. However, these materials are hardly in the focus of biomedical research, largely due to poor opportunities in nano- and micro-scale design associated with PVA hydrogels in their current form. In this review we aim to demonstrate that with PVA, a (sub)molecular control over polymer chemistry translates into fine-tuned supramolecular association of chains and this, in turn, defines macroscopic properties of the material. This nano- to micro- to macro- translation of control is unique for PVA and can now be accomplished using modern tools of macromolecular design. We believe that this strategy affords functionalized PVA physical hydrogels which meet the demands of modern nanobiotechnology and have a potential to become an indispensable tool in the design of biomaterials.

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Section: (Sub)molecular Polymer Engineeringmentioning

confidence: 99%

Section: (Sub)molecular Polymer Engineeringmentioning

confidence: 99%

Poly(Vinyl Alcohol) Physical Hydrogels: New Vista on a Long Serving Biomaterial

Alves

Jensen

Smith

et al. 2011

Macromolecular Bioscience

209

159

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“…Aqueous solutions of S-PVA form hard elastic gels more easily than those of A-PVA, and the melting point of S-PVA gel is remarkably higher than those of A-PVA gels. 6,7 The number of segments participating in the junction of PVA gel increased with syndiotacticity, and they were remarkably higher than the values of A-PVAs. 8 Especially, the phase separation in S-PVA gel was favored as syndiotacticity increased.…”

Section: Introductionmentioning

confidence: 95%

Phase Behavior and Physical Gelation of High Molecular Weight Syndiotactic Poly(vinyl alcohol) Solution

Choi

Kim

et al. 2001

Macromolecules

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The physical gelation behavior of high molecular weight (HMW) syndiotactic poly(vinyl alcohol) (S-PVA) was investigated in consideration of stereoregularity of the polymer. To precisely identify the effect of stereoregularity, syndiotactic diad (S-diad) contents of PVAs with the similar molecular weights were controlled to 61.5, 58.2, and 55.7%, respectively. The gel point (GP) of HMW S-PVA solution was determined by observing the frequency-independent loss tangent and the crossover between the relaxation exponents from the oscillatory shear experiment. The gelation process of HMW S-PVA solution with S-diad content over 58.2% was divided into two types with respect to the concentration of solution. The first type is the gelation that took place directly from sol to gel with a clear GP which was well coincident with the macroscopic gelation temperature (T gel). This is for the higher concentration regime. The second one is the gelation that occurred gradually accompanying the evolution of gel-like properties in sol state without a definite GP, which is for the lower concentration regime. The gel-like heterogeneity formed during the second type gelation might be related with the liquid-liquid phase separation. In contrast, HMW S-PVA solution with S-diad content of 55.7% followed only the first type gelation. The relaxation exponent of HMW S-PVA solution at GP decreased with concentration and had a lower value than the percolation value, 0.7. The higher fractal dimension indicates the structural compactness in the cross-linking system of HMW S-PVA. As compared with the other gelation system, lower gel stiffness was obtained, suggesting that the gelation of HMW S-PVA solution occurred without a serious crystallization.

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“…Stereoregularity has also been found to have a strong influence on the properties of PVA physical hydrogels 7–11. Typically, atactic PVA (a‐PVA) samples have a syndiotactic diad content below 53–55%.…”

Section: Introductionmentioning

confidence: 99%

Physical Hydrogels of Poly(vinyl alcohol) with Different Syndiotacticity Prepared in the Presence of Lactosilated Chitosan Derivatives

Masci

Husu

Murtas

et al. 2003

Macromolecular Bioscience

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Poly(vinyl alcohol) (PVA) physical hydrogels were prepared by repeated freeze–thawing cycles using aqueous solutions of two PVA samples having different degrees of syndiotacticity, a‐PVA and s‐PVA with 55% and 61% of syndiotactic diads, respectively. The hydrogels were prepared in the presence of different amounts of lactosilated chitosan derivatives (LC) of different molecular weight. The PVA stereoregularity was found to have a dramatic effect on the amount of PVA incorporated into the hydrogels, leading to remarkable differences in the swelling degree and porosity of a‐PVA and s‐PVA hydrogels. A significant amount of LC was retained in the hydrogels after equilibrium swelling. The swelling of the a‐PVA hydrogels was found to increase significantly by increasing the amount of LC while it was only slightly increased in the case of s‐PVA hydrogels. The amount of LC released after equilibrium swelling was lower when chitosan derivatives with higher molecular weights were used. Increased initial concentrations of LC resulted in much higher porosity of the hydrogels. TGA and DSC studies showed that LC is stabilized by the incorporation in the PVA hydrogels. The melting temperature of the crystalline regions of PVA was not significantly influenced by LC. Conversely, the extension of the crystalline domains increased in the presence of LC. The retention of a chitosan derivative bearing β‐D‐galactose side chain residues makes these hydrogels potentially useful as scaffolds for hepatocytes culture.Scanning electron micrographs of PVA‐LC hydrogels: (a) a‐PVA; (b) a‐PVA/LC150 80:20; (c) a‐PVA/LC150 50:50.magnified imageScanning electron micrographs of PVA‐LC hydrogels: (a) a‐PVA; (b) a‐PVA/LC150 80:20; (c) a‐PVA/LC150 50:50.

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Effect of syndiotacticity on the aqueous poly(vinyl alcohol) gel 2. Syneresis of gel

Cited by 8 publications

References 11 publications

Poly(Vinyl Alcohol) Physical Hydrogels: New Vista on a Long Serving Biomaterial

Poly(Vinyl Alcohol) Physical Hydrogels: New Vista on a Long Serving Biomaterial

Phase Behavior and Physical Gelation of High Molecular Weight Syndiotactic Poly(vinyl alcohol) Solution

Physical Hydrogels of Poly(vinyl alcohol) with Different Syndiotacticity Prepared in the Presence of Lactosilated Chitosan Derivatives

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