System for measurement of changes of LSI in polymer solution after electron pulse

L̵ubis, R.; Olejniczak, Jason; Rosiak, Janusz M.; Kroh, J.

doi:10.1016/1359-0197(90)90252-d

Cited by 7 publications

(6 citation statements)

References 1 publication

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“…A pulse radiolysis study on PVA by light generated by Ar–He laser demonstrated that the relation between changes in LSI and absorbed dose is nearly linear (at low doses). It was also proved that only a part of hydroxyl radicals react with the polymer macroradical 21. The effect of polymer concentration (in deoxygenated aqueous solutions) on crosslinking during γ irradiation was investigated 22.…”

Section: Introductionmentioning

confidence: 99%

Photodegradation of poly(vinyl alcohol) under UV and pulsed‐laser irradiation in aqueous solution

Vijayalakshmi

Madras

2006

J of Applied Polymer Sci

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ABSTRACT:The photodegradation of poly(vinyl alcohol) (PVA) in aqueous solution was investigated under UV exposure and pulsed-laser irradiation. The degradation under UV exposure was studied at different pH values and with the addition of potassium chloride and potassium dichromate. The pulsed-laser degradation of PVA was investigated with a Nd : YAG laser, operating at a wavelength of 266 nm with about 6-ns pulses. The pulsed-laser degradation was studied at different polymer concentrations and light intensities. Samples were analyzed by gel permeation chromatography. The degradation rate coefficients were determined by the application of a continuous distribution model. The photodegradation rates under UV exposure were highest at extremes of pH and were greatly enhanced by the addition of potassium chloride and potassium dichromate. The pulsed-laser degradation of the polymer decreased with increasing polymer concentration, although a threshold light intensity was required to initiate the degradation process.

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Section: Introductionmentioning

confidence: 99%

Photodegradation of poly(vinyl alcohol) under UV and pulsed‐laser irradiation in aqueous solution

Vijayalakshmi

Madras

2006

J of Applied Polymer Sci

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“…[17][18][19][20][21] Since PVA has good biocompatibility, 22 much attention has been paid to the formation of its hydrogels, in the forms of both microgels [17][18][19][20][21] and bulk gels. [23][24][25][26][27][28][29][30][31][32] There is a limiting irradiation dose, i.e., gelation dose (D g ), at which the gel formation sets in. At doses > D g , the irradiation yields either a bulk gel or microgel particles depending on the polymer concentration (C p ).…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Microgel Formation via Cross-Linking of Polymers in Their Dilute Solutions: Mathematical Explanation with Computer Simulations

2001

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The formation of poly(vinyl alcohol) microgels by γ-ray irradiation was previously studied by static and dynamic light scattering methods to obtain respectively the radius of gyration (Rg) and the hydrodynamic radius (Rh). It was proposed that the mechanism of this microgel formation was an intermolecular cross-linking step followed by an intramolecular cross-linking process. Presented herein is a mathematical model for interpreting the values of Rg and Rh, in which the Kirkwood theory of the friction factor was employed. To mimic the known extensions of "brushes", a set of "bias parameters" were employed for the purpose of making a directional preference in generating the configurations of both parent and branch chains. The simulations with this simple model are in very good agreement with the proposed mechanism of microgel formation in the poly(vinyl alcohol) system. Justification of using the "bias parameters" is supported by computationally intensive Brownian dynamics simulations of a collection of 216 "beads" with a "Velcro" pair potential, i.e., a short-range "attractive" pair potential that acts as a formation of a chemical bond between the beads. The advantage of the "bias" walk model is that it allows one to explore different molecular configurations on a smaller computer and thus to select an appropriate set of parameters for more extended and time-consuming simulations on mainframe computers.

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“…The irradiation method is one of the easiest ways to prepare PVA hydrogels without any chemical as the cross-linker. A number of studies − have therefore dealt with the gelation process of PVA in aqueous solvents as a function of the irradiation dose under various conditions of polymer concentration and molecular weight ( M w ). The experiments were usually performed in the absence of dissolved oxygen because oxygen is believed to cause the degradation of PVA during irradiation.…”

Section: Introductionmentioning

confidence: 99%

Viscometric and Light Scattering Studies on Microgel Formation by γ-Ray Irradiation to Aqueous Oxygen-free Solutions of Poly(vinyl alcohol)

et al. 1997

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The gelation process of aqueous oxygen-free solutions containing poly(vinyl alcohol) (PVA) by γ-ray irradiation was studied as a function of polymer concentration. Dynamic and static light-scattering techniques as well as the usual viscometric method were employed. PVA solutions turned into a “bulk” gel upon irradiation at high concentrations around 20 g/L, which corresponds to about 10 times that termed the critical concentration. Increases in the intrinsic viscosity ([η]) and hydrodynamic radius (R h) were observed before the gelation. The bulk gel did not form from diluted PVA solutions (1.6−2.0 g/L) but the solution became turbid due to the formation of microgel particles. In this process, both [η] and R h rapidly increased when increasing the irradiation dose up to a certain level (ca. 0.3 Mrad) at which solution turbidity appeared. When the irradiation was continued over this dose, [η] decreased and R h leveled off. We thus examined the changes in the molecular weight (M w) and radius of gyration (R g) and found that R g decreased while M w increased almost linearly. Thus, a decrease in R g/R h from 1.5 to 0.98 was observed in doses >0.3 Mrad. On the basis of the results obtained, we discussed in detail the mechanism of microgel formation from PVA in its diluted solution by γ-ray irradiation.

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System for measurement of changes of LSI in polymer solution after electron pulse

Cited by 7 publications

References 1 publication

Photodegradation of poly(vinyl alcohol) under UV and pulsed‐laser irradiation in aqueous solution

Photodegradation of poly(vinyl alcohol) under UV and pulsed‐laser irradiation in aqueous solution

Mechanism of Microgel Formation via Cross-Linking of Polymers in Their Dilute Solutions: Mathematical Explanation with Computer Simulations

Viscometric and Light Scattering Studies on Microgel Formation by γ-Ray Irradiation to Aqueous Oxygen-free Solutions of Poly(vinyl alcohol)

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