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Dye release behavior from polyvinyl alcohol films in a hydro-alcoholic medium: Influence of physicochemical heterogeneity
University of Sassari.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
University of Sassari.
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2012 (English)In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 403, 45-53 p.Article in journal (Refereed) Published
Abstract [en]

In this paper we investigated the release kinetics of a model drug-like compound (Coomassie brilliant blue) from polyvinyl alcohol (PVOH) films into a hydro-alcoholic solution as a function of the physicochemical properties of the polymer matrix. After 33 days of monitoring, the total amount released ranged from 10% for the high hydrolysis degree/low molecular weight PVOH films to 60% for the low hydrolysis degree/low molecular weight films. Mathematical modeling allowed for an estimation of the two diffusion coefficients (D 1 and D 2) that characterized the release profile of the dye from the films. The degree of hydrolysis dramatically affected both the morphology and the physical structure of the polymer network. A high hydroxyl group content was also associated with the shifting of second order and first order transitions toward higher temperatures, with a concurrent increase in crystallinity. Moreover, the higher the degree of hydrolysis, the higher the affinity of the polymer to the negatively charged molecule dye. Selection of the polymer matrix based on physicochemical criteria may help in achieving different release patterns, thereby representing the first step for the production of polymer systems with modulated release properties.

Place, publisher, year, edition, pages
2012. Vol. 403, 45-53 p.
Keyword [en]
Controlled release, Diffusion, Modeling, Morphology, Polyvinyl alcohol
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-93674DOI: 10.1016/j.colsurfa.2012.03.054ISI: 000304840700008Scopus ID: 2-s2.0-84860916013OAI: oai:DiVA.org:kth-93674DiVA: diva2:517247
Note
QC 20120529. Updated from submitted to published.Available from: 2012-04-23 Created: 2012-04-23 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Simulations of Semi-Crystalline Polymers and Polymer Composites in order to predict Electrical, Thermal, Mechanical and Diffusion Properties
Open this publication in new window or tab >>Simulations of Semi-Crystalline Polymers and Polymer Composites in order to predict Electrical, Thermal, Mechanical and Diffusion Properties
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Several novel computer simulation models were developed for predicting electrical, mechanical, thermal and diffusion properties of materials with complex microstructures, such as composites, semi-crystalline polymers and foams.

A Monte Carlo model for simulating solvent diffusion through spherulitic semicrystalline polyethylene was developed. The spherulite model, based on findings by electron microscopy, could mimic polyethylenes with crystallinities up to 64 wt%. Due to the dendritic structure of the spherulites, the diffusion was surprisingly independent of the aspect ratio of the individual crystals. A correlation was found between the geometrical impedance factor (τ) and the average free path length of the penetrant molecules in the amorphous phase. A new relationship was found between volume crystallinity and τ. The equation was confirmed with experimental diffusivity data for Ar, CH4, N2 and n-hexane in polyethylene.

For electrostatics, a novel analytical mixing model was formulated to predict the effective dielectric permittivity of 2- and 3-component composites. Results obtained with the model showed a clearly better agreement with corresponding finite element data than previous models. The analytical 3-component equation was in accordance with experimental data for nanocomposites based on mica/polyimide and epoxy/ hollow glass sphere composites. Two finite element models for composite electrostatics were developed.

It is generally recognized that the fracture toughness and the slow crack growth of semicrystalline polymers depend on the concentrations of tie chains and trapped entanglements bridging adjacent crystal layers in the polymer. A Monte Carlo simulation method for calculating these properties was developed. The simulations revealed that the concentration of trapped entanglements is substantial and probably has a major impact on the stress transfer between crystals. The simulations were in accordance with experimental rubber modulus data.

A finite element model (FEM) including diffusion and heat transfer was developed for determining the concentration of gases/solutes in polymers. As part of the FEM model, two accurate pressure-volume-temperature (PVT) relations were developed. To predict solubility, the current "state of the art" model NELF was improved by including the PVT models and by including chemical interactions using the Hansen solubility parameters. To predict diffusivity, a novel free-volume diffusion model was derived based on group contribution methods. All the models were used without adjustable parameters and gave results in agreement with experimental data, including recent data obtained for polycarbonate and poly(ether-etherketone) pressurized with nitrogen at 67 MPa.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. 59 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2012:15
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-93519 (URN)978-91-7501-290-2 (ISBN)
Public defence
2012-04-20, F2,, Lindstedtsvägen 28, entréplan, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20120420Available from: 2012-04-20 Created: 2012-04-20 Last updated: 2012-04-23Bibliographically approved

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