Spontaneous gelation of polymer solutions

Papkov, S. P.; Dibrova, A. K.

doi:10.1016/0032-3950(83)90260-5

Cited by 5 publications

(4 citation statements)

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“…This effect has been known for a long time and is the cause underlying the formation of aggregated supermolecular structures [1][2][3]. The formation of such structures is affected by the tacticity of the polymer and by the content of residual acetate groups [4]. These structures are supposedly formed also in dilute solutions [5] and contain amorphous and paracrystalline parts [5][6][7], the mutual ratio of which depends on experimental conditions during the preparation of solutions, and predominantly on the dissolution temperature.…”

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confidence: 97%

Rheological investigation of aqueous solutions of poly(vinyl alcohol) during ageing

Prokopová

Štern

Quadrat

1985

Colloid & Polymer Sci

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Abstract:The changes in viscosity and normal stress difference during the ageing of concentrated aqueous solutions of poly(vinyl alcohol) prepared at 80 ~ and the effect of the procedure used in the preparation of solutions on the course of these changes are described. The results are interpreted by means of shear compliance ]e and relaxation time 3~Key words: Polyvinylalcohol, ageing, concentrated solutions, non-Newtonian viscosity, normal stress.Aqueous solutions ofpoly(vinyl alcohol) (PVA) undergo the process of ageing, reflected predominantly in a rise in their viscosity with time which in concentrated solutions is followed by gel formation. This effect has been known for a long time and is the cause underlying the formation of aggregated supermolecular structures [1][2][3]. The formation of such structures is affected by the tacticity of the polymer and by the content of residual acetate groups [4]. These structures are supposedly formed also in dilute solutions [5] and contain amorphous and paracrystalline parts [5][6][7], the mutual ratio of which depends on experimental conditions during the preparation of solutions, and predominantly on the dissolution temperature. On the other hand, however, the process of ageing is affected not only by the dissolution temperature, but also by the temperature at which the ageing takes place, by the temperature prehistory of solutions, by the polymer concentration in solution and by the kind of the solvent [8][9][10][11]. In the existing studies dealing with the / problem of ageing of PVA solutions partial results are mostly presented in a descriptive manner, which does not lead to a more general and deeper characterization of theological changes in the supermolecular structures which arise during ageing. The only attempt at a quantitative explanation of the rheological behaviour of concentrated PVA solutions has been made by Nakagaki and Nishii [12]. Their interpretation is based on Rouse's theory of elasticity which holds for linear K 955 aggregates and intermolecular aggregation. In addition to a rise of viscosity with time, the formation of supermolecular structures during the ageing of concentrated PVA solutions is also reflected in their non-Newtonian behaviour [13]. So far, this effect has not been studied in greater detail, which made us use it, along with the measurement of normal stress, in a detailed investigation of the process of ageing.The objective of our investigations of concentrated aqueous PVA solutions consists in a systematic study of rheological properties during their ageing as a function of temperature, the experimental conditions during dissolution of the polymer and of the polymer concentration. In the present study we have combined viscosity and normal stress measurements. The quantitative interpretation of the results of our measurements was based on the values of shear compliance calculated from the measured values of the first normal stress difference, and of the relaxation time To calculated from the experimental dependence of r//r/o on ...

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confidence: 97%

Rheological investigation of aqueous solutions of poly(vinyl alcohol) during ageing

Prokopová

Štern

Quadrat

1985

Colloid & Polymer Sci

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“…Table 1 shows the compositions of spinning systems, including the TEOS content as a percentage of DMSO content, and its corresponding content in the finished fiber. Mixtures with 33% PAN at room temperature quickly form a gel [35] due to nitrilenitrile interactions in a concentrated solution. Therefore, to prevent gel formation during rheological measurements and fiber spinning procedures, the temperature inside the dosing device was maintained at 70 • C. Figure 3 Mixtures with 33% PAN at room temperature quickly form a gel [35] due to nitrilenitrile interactions in a concentrated solution.…”

Section: Pan-dmso-teos Spinning Solution Rheologymentioning

confidence: 99%

“…Mixtures with 33% PAN at room temperature quickly form a gel [35] due to nitrilenitrile interactions in a concentrated solution. Therefore, to prevent gel formation during rheological measurements and fiber spinning procedures, the temperature inside the dosing device was maintained at 70 • C. Figure 3 Mixtures with 33% PAN at room temperature quickly form a gel [35] due to nitrilenitrile interactions in a concentrated solution. Therefore, to prevent gel formation during rheological measurements and fiber spinning procedures, the temperature inside the dosing device was maintained at 70 °C.…”

Section: Pan-dmso-teos Spinning Solution Rheologymentioning

confidence: 99%

Polyacrylonitrile Fibers with a Gradient Silica Distribution as Precursors of Carbon-Silicon-Carbide Fibers

et al. 2023

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This study presents preparing and characterization of polyacrylonitrile (PAN) fibers containing various content of tetraethoxysilane (TEOS) incorporated via mutual spinning solution or emulsion using wet and mechanotropic spinning methods. It was shown that the presence of TEOS in dopes does not affect their rheological properties. The coagulation kinetics of complex PAN solution was investigated by optical methods on the solution drop. It was shown that during the interdiffusion process phase separation occurs and TEOS droplets form and move in the middle of the dope’s drop. Mechanotropic spinning induces the TEOS droplets to move to the fiber periphery. The morphology and structure of the fibers obtained were investigated by scanning and transmission electron microscopy, as well as X-ray diffraction methods. It was shown that during fiber spinning stages the transformation of the TEOS drops into solid silica particles takes place as a result of hydrolytic polycondensation. This process can be characterized as the sol-gel synthesis. The formation of nano-sized (3–30 nm) silica particles proceeds without particles aggregation, but in a mode of the distribution gradient along the fiber cross-section leading to the accumulation of the silica particles either in the fiber center (wet spinning) or in the fiber periphery (mechanotropic spinning). The prepared composite fibers were carbonized and according to XRD analysis of carbon fibers, the clear peaks corresponding to SiC were observed. These findings indicate the useful role of TEOS as a precursor agent for both, silica in PAN fibers and silicon carbide in carbon fibers that has potential applications in some advanced materials with high thermal properties.

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“…The necessity of obtaining phase and thermodynamic information for multicomponent polymer systems is indisputable, since that is the information that ultimately determines the structure, conditions of synthesis, processing, and thermodynamic stability of composite materials during their operation and storage [ 1 , 2 , 3 , 4 , 5 ]. One of the ways to solve this issue is related to the experimental determination of pair interaction parameters (

), which, according to the concepts of Flory–Huggins, Scott, and Patterson [ 6 , 7 , 8 ], characterize the interaction between polymer segments.…”

Section: Introductionmentioning

confidence: 99%

Determination of Pair Interaction Parameters of Multicomponent Polymer Systems

Chalykh,

Gerasimov,

Petrova

et al. 2023

Polymers

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From the examples of three and four-component polymer–polymer systems characterized by amorphous separation, an original technique for determining the pair parameters of interaction between components based on the sorption isotherms of common solvent vapor, particularly water vapor, has been developed. The possibility of calculating thermodynamic characteristics of multicomponent polymer compositions with specific interactions of functional groups from experimentally obtained sorption isotherms is shown. An algorithm for calculating pair interaction parameters, estimating concentration dependences of chemical potential and Gibbs free energy of mixing, and predicting the phase state of polymer mixtures was presented for the first time for such systems. The technique was tested on the example of systems poly(N-vinylpyrrolidone) (PNVP)–polyethylene glycol (PEG), PNVP–PEG–Poly(acrylic acid) (PAA), poly(N-vinylcaprolactam) (PNVCL)–PEG, and polyvinyl alcohol (PVA)–PEG.

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Spontaneous gelation of polymer solutions

Cited by 5 publications

References 4 publications

Rheological investigation of aqueous solutions of poly(vinyl alcohol) during ageing

Rheological investigation of aqueous solutions of poly(vinyl alcohol) during ageing

Polyacrylonitrile Fibers with a Gradient Silica Distribution as Precursors of Carbon-Silicon-Carbide Fibers

Determination of Pair Interaction Parameters of Multicomponent Polymer Systems

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