Showing papers by "Nicholas A. Peppas published in 1992"
TL;DR: In this paper, reinforced poly (vinyl alcohol) hydrogels were prepared by freezing aqueous solutions of 15 wt% PVA at −20°C for eighteen hours and thawing them at room temperature for six hours.
163 citations
TL;DR: The variations of the matrix relaxation and drug diffusion rates were quantified, by measuring the surface area exposed during matrix swelling and drug release as a function of impermeable coating coverage and location.
100 citations
TL;DR: In this paper, a new kinetic gelation simulation is presented to describe homopolymerizations of tetrafunctional monomers, which involves the incorporation of monomer molecules which occupy multiple sites with their functional groups at the ends, initiator molecules which decay into two radicals per initiator, and incorporation of a crankshaft-type motion for all of the species on a face-centered cubic lattice.
76 citations
TL;DR: In this article, a self-consistent, continuum theory for the transport of small molecular-weight fluids in polymeric media is established, which can describe Fickian, Case II and other non-Fickian diffusion phenomena.
72 citations
TL;DR: In this article, a profile of reaction rate as a function of time was obtained for free radical crosslinking polymerizations of ethylene glycol methacrylates and dimethacryls using differential scanning calorimetry.
46 citations
TL;DR: In this paper, a novel experimental method has been devised to measure the swelling force developed during the exposure of thin polymeric discs to a swelling agent, which is applied for the determination of the swelling forces developed during water absorption of various systems including copolymers of 2-hydroxyethyl methacrylate or methyl methACrylate with methacrylic acid or acrylic acid.
38 citations
30 citations
7 citations
TL;DR: In this article, trimethylolpropane trimethacrylate, glyceryl trimethacetyl, pentaerythritol tetraacrylated and dipentaerythrisol monohydroxypenta acrylate were polymerized by ultra-violet irradiation in the presence of 2,2-dimethoxy-2-phenylacetophenone as a photoinitiator.
6 citations
TL;DR: In this paper, the authors investigated the macromolecular structure of coals thermally treated at 35°C, 100°C and 150°C by dynamic penetrant transport in thin coal sections.
Abstract: The macromolecular structure of coals thermally treated at 35°C, 100°C and 150°C was investigated by dynamic penetrant transport in thin coal sections. The effects of temperature, carbon content in coal, and penetrant type on the transport mechanism were investigated. Dynamic swelling studies showed that penetrant transport into coal is a function of the average molecular weight between crosslinks, Mc. The penetrant transport mechanism at low activity is Fickian diffusion. The transport mechanism deviates from Fickian diffusion to anomalous transport, when the carbon content in coal and penetrant activity increase. Variations of the diffusion coefficients and relaxation constants were determined using a diffusion/relaxation coupled model.
2 citations
TL;DR: Swelling equations for polymeric networks that consist of two swellable but distinct phases were derived in this paper, which can be used to describe the equilibrium swelling behavior of certain two-phase network systems.
Abstract: Swelling equations were derived for polymeric networks that consist of two swellable but distinct phases. These equations can be used to describe the equilibrium swelling behavior of certain two-phase network systems. Using physicochemical measurements of the equilibrium polymer volume fraction, it was possible to calculate the number-average molecular weight between crosslinks, Mc, using these equations. The influence of several structural parameters on Mc was investigated. © 1992 John Wiley & Sons, Inc.