Complexation chemistry of sodium borate with poly(vinyl alcohol) and small diols: a boron-11 NMR study

Sinton, S. W.

doi:10.1021/ma00176a018

Cited by 180 publications

(134 citation statements)

References 8 publications

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“…Boric acid complexes with 1,2-diols are well known to pos-sess higher acidities as opposed to 1,3-diols. [15,21,22] The stronger acidity is primarily caused by ring strain. Complexes formed from 1,3-diols form six rings and are slightly more acidic compared to boric acid [15,22] but complexes from 1,2-diols are five rings and have considerable ring strain.…”

Section: Resultsmentioning

confidence: 99%

“…[7,8] Combined with the known ratio of mannose to galactose in guaran, boric acid preferentially forms crosslinks with mannose in a ratio of 2:1 in agreement with experiment. [5] Many authors have assumed borate is the reactive species [1,2,5,[8][9][10][11][12][13][14][15] while others have assumed cations to be involved. [14] In a few cases boric acid was proposed as the reactant but merely because the reactions took place at very low pH values.…”

Section: Introductionmentioning

confidence: 99%

“…A determination of this latter value shows that it is indeed low and was reported to be 20.5 kJ/mol. [15] The trivalent B atom in boric acid has an empty p orbital that is very electrophilic in nature; it rapidly reacts with various nucleophiles to form complexes. [19] Therefore, a much more likely alternative mechanism is to assume boric acid as the reactant.…”

Section: Introductionmentioning

confidence: 99%

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Crosslinking Mechanism of Boric Acid with Diols Revisited

Rietjens¹,

Steenbergen²

2005

Eur J Inorg Chem

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Complex formation of boric acid with diol functional groups is well known and many papers have been published assuming borate is the reactive species. Based on the high reactivity of boric acid towards nucleophiles, this paper assumes boric acid is the reactant. We prove this hypothesis by presenting a study of the reaction of the polymer guaran with boric acid under various conditions. A thermodynamic analysis of the underlying reactions does not show any differences between either crosslinking species. Thermodynamics shows that the concentration of the 2:1 crosslinks, that give rise to the enhanced viscosity, is proportional to [B], the boric acid concentration, [X2], the concentration of available crosslink sites and inversely proportional to [H+]. These predictions were all confirmed by experiment. However, a difference between the mechanisms is demonstrated in a kinetic analysis: Longer gel times are predicted with the mechanism based on boric acid as the pH of the fluid increases, that is exactly what is observed in practice. Evidence is provided fromvisco‐elastic measurements. A new approach to describeinter‐ and intramolecular crosslink formation is introduced and evidence for the correctness of this description is provided. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Crosslinking Mechanism of Boric Acid with Diols Revisited

Rietjens¹,

Steenbergen²

2005

Eur J Inorg Chem

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“…Borax is the commonly used crosslinking reagent of PVA, and it can crosslink PVA in several seconds. 1,[31][32][33] The crosslinking reaction is as follows:…”

Section: Surface Crosslinking Of Pva Blown Filmmentioning

confidence: 99%

Enhancing mechanical properties of poly(vinyl alcohol) blown films by drawing and surface crosslinking

Wang

2005

J of Applied Polymer Sci

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Thermal blowing of poly(vinyl alcohol) (PVA) film was successfully realized based on molecular complexation. Ways to enhance the performance of the PVA blown films (drawing and surface crosslinking) were studied. The experimental results showed that water exists in PVA films in different states through hydrogen bonds with PVA and other modifiers and influences the drawability of PVA films, as well as the structure and properties of the stretched films. When the initial water content of the film was higher than 35.0%, the draw ratio of the PVA film was quite large because of the effects of the bound water with PVA, as well as the plasticization of free water. With the increase of the initial water content in PVA, the free water content and draw ratio of the films increased but the strength of the films decreased because of the higher residual water in the films. Surface crosslinking can improve the stretchability of PVA films because more water remains in the films and disrupts the hydrogen bonding of PVA. In addition, crosslinking enhances the mechanical properties of stretched PVA films.

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“…Of particular interest is the PVA capability of forming a variety of hydrogel systems, which may be physically or chemically cross-linked, further expanding the possible applications of this versatile polymer. It is well known that polymers with hydroxyl groups form complexes with various ions such as borate [1][2][3][4] and vanadate [5]. PVA-ions complexation induces the formation of gel-like materials, capable of incorporating large amounts of water.…”

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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Complexation chemistry of sodium borate with poly(vinyl alcohol) and small diols: a boron-11 NMR study

Cited by 180 publications

References 8 publications

Crosslinking Mechanism of Boric Acid with Diols Revisited

Crosslinking Mechanism of Boric Acid with Diols Revisited

Enhancing mechanical properties of poly(vinyl alcohol) blown films by drawing and surface crosslinking

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

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