Sol-gel transition of poly(vinyl alcohol)-borate complex

Shibayama, Mitsuhiro; Hiroyuki, Yoshizawa; Kurokawa, Haruhisa; Fujiwara, Hiroshi; Nomura, Shunji

doi:10.1016/0032-3861(88)90182-6

Cited by 98 publications

(72 citation statements)

References 22 publications

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“…Already in 1949, Deuel and Neukom [54] suggested that complexation is the origin of the crosslinks in PVA borate solutions, as shown in Fig.11. In the Shibayama model [57], also shown in Fig.11, also sodium ions are needed in the process. This is in agreement with Cheng and Rodriguez [58] who demonstrated that the addition of boric acid without sodium anions to aqueous PVA solutions has almost no effect on the gelation properties.…”

Section: Poly(vinyl Alcohol) + Boratementioning

confidence: 99%

On the nature of crosslinks in thermoreversible gels

2006

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SummaryA review is given concerning the nature of crosslinks in thermoreversible gels. In these gels the crosslinks can be formed e.g. by means of crystallisation of parts of polymer molecules, by liquid-liquid phase separation in solution and in bulk, by hydrogen bridging, by complexation of polymer chains, by helix formation, by chemical equilibrium reaction or by interactions between side-chains. One example will be given for each of these eight possibilities of crosslink formation.

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Section: Poly(vinyl Alcohol) + Boratementioning

confidence: 99%

On the nature of crosslinks in thermoreversible gels

2006

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“…The kind of linkage which forms has been largely debated and in particular two models have been proposed. The first one suggests that the linkage between diols and borate ions has a mixed physical and chemical nature [6], while the second one implies only dynamic chemical cross-links between PVA chains and borate ions [7][8][9] and considers two types of interaction: monodiol complexation and crosslinking. After reaction the polymer chain behaves as a polyelectrolyte with electrostatic repulsions, resulting in an expansion of the network [10].…”

Section: Introductionmentioning

confidence: 99%

Poly(vinylalcohol)-borate hydrogels with improved features for the cleaning of cultural heritage surfaces

et al. 2015

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Abstract:Poly(vinylacohol) (PVA) is a versatile polymer capable of forming hydrogels useful in a wide range of applications. Hydrogels based on cross-linking of PVA with borax, and able to incorporate organic solvents, have been used in the field of cultural heritage as tool for cleaning the surfaces. Poly(ethylenoxide) (PEO) has been introduced in the formulations of PVA-borax, with the aim of increasing the gel compatibility with organic solvents and of improving the mechanical properties of the materials. The formulations were investigated with rheological characterization, solvent loss measurements and study of the free water through the determination of the Free Water Index. The PEO molecules do not participate in the formation of the network but have been found to be responsible for a decrement of the storage moduli, explained by a spacing between crosslinks and the partial disentanglement of the PVA chains. At the same time PEO produces in the gel an increase of the apparent relaxation time, thus stabilizing the dispersions and enhancing their ability to maintain the shape. Cleaning tests for removal of an acrylic coating on limestone have been also successfully performed.

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“…According to the other model, the borax ions hold together the polymeric chains by means of mixed physical/chemical linkages. This model was firstly proposed for poly-(vinylalcohol) [15] and it was recently suggested also for SCLG [16,17]. The considerable effort devoted to the study of polymer-ion complexes is due to the wide range of application of these systems.…”

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confidence: 99%

Guar gum/borax hydrogel: Rheological, low field NMR and release characterizations

Coviello¹,

Matricardi²,

Alhaique³

et al. 2013

Express Polym. Lett.

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Abstract. Guar gum (GG) and Guar gum/borax (GGb) hydrogels are studied by means of rheology, Low Field Nuclear Magnetic Resonance (LF NMR) and model drug release tests. These three approaches are used to estimate the mesh size (!) of the polymeric network. A comparison with similar Scleroglucan systems is carried out. In the case of GGb, the rheological and Low Field NMR estimations of ! lead to comparable results, while the drug release approach seems to underestimate !. Such discrepancy is attributed to the viscous effect of some polymeric chains that, although bound to the network to one end, can freely fluctuate among meshes. The viscous drag exerted by these chains slows down drug diffusion through the polymeric network. A proof for this hypothesis is given by the case of Scleroglucan gel, where the viscous contribution is not so significant and a good agreement between the rheological and release test approaches was found. Vol.7, No.9 (2013) 733-746 Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2013.71 * Corresponding author, e-mail: mariog@dicamp.univ.trieste.it © BME-PT mation in aqueous solution and a single coiled disordered conformation in methylsulphoxide or at high pH values (NaOH$>0.2 M) [10,11]. Due to its peculiar properties, SCLG was extensively used for various commercial applications (secondary oil recovery, ceramic glazes, food, paints, cosmetics, etc.) [12] and it was also investigated for modified/ sustained release formulations and ophthalmic preparations [13]. Actually, it is well known that borax is an efficient crosslinker for polymers bearing hydroxyl groups but the type of formed linkages is still debated and so far two main models have been proposed. The most popular one implies the existence of pure chemical crosslinks between the polymeric chains and borax [14], and it was proposed for the GG/ borax interactions. According to the other model, the borax ions hold together the polymeric chains by means of mixed physical/chemical linkages. This model was firstly proposed for poly-(vinylalcohol) [15] and it was recently suggested also for SCLG [16,17]. The considerable effort devoted to the study of polymer-ion complexes is due to the wide range of application of these systems. In particular, the complex between GG and borate was previously studied by several authors [18,19] that investigated the effect of polymer and borate concentration, temperature, environmental pH conditions, and GG molecular weight on the peculiar rheological properties detected by the frequency dependence of relaxation spectra. Furthermore, a detailed study of the crosslinking reaction of borate ion with polyhydroxy polymers was carried out by means of 11 Keywords: polymer gels, rheology, low field NMR, transport processes, mesh-size eXPRESS Polymer Letters

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Sol-gel transition of poly(vinyl alcohol)-borate complex

Cited by 98 publications

References 22 publications

On the nature of crosslinks in thermoreversible gels

On the nature of crosslinks in thermoreversible gels

Poly(vinylalcohol)-borate hydrogels with improved features for the cleaning of cultural heritage surfaces

Guar gum/borax hydrogel: Rheological, low field NMR and release characterizations

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