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LE Scriven

Publications and source records attributed to LE Scriven.

4 recordsLinked to original sources
PubMed1999

Microstructure Evolution in Polymer Latex Coatings for Whole-Cell Biocatalyst Application.

The microstructure evolution of two poly(vinyl acetate-co-acrylic acid) latex coatings was elucidated by cryogenic scanning electron microscopy (cryo-SEM) and atomic force microscopy. The stages documented are particle suspension, consolidation, deformation, partial coalescence into a coherent film, and rehydration of the latter. Of particular interest is formation of a porous polymeric matrix of desired porosity and permeability of remnant interstices between deformed and partially coalesced particles; the application is to biocatalytic coatings in which viable bacteria are imprisoned in porous latex coatings. Effects of drying condition and time, rehydration behavior of latex, and the presence of glycerol on the microstructure of latex coatings were revealed by time-sectioning and cryofracture techniques of cryo-SEM. Results showed that porosity and permeability can be controlled by choice of drying and rehydration protocols. Evidence showed that glycerol retarded particle deformation, compaction, and coalescence and that substantial amounts of glycerol were expelled to the surface of the coating as drying proceeded. Implications for design of bacteria-laden and bacteria-free coating layers are discussed. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Microstructure of a Biocatalytic Latex Coating Containing Viable Escherichia coli Cells.

Cryogenic scanning electron microscopy (cryo-SEM) was employed to visualize the microstructure of latex coatings in which viable Escherichia coli cells were entrapped for use as biocatalysts. Cryo-SEM examination of surfaces and fracture cross sections of dry and hydrated coatings cast with or without glycerol revealed two different porosities in the films: a macroporosity in which the bacterial cells reside and a microporosity made up of the interstitial voids between partially coalesced latex polymer particles. Polymer particle consolidation and coalescence in the cell-laden coatings were at an earlier stage than in cell-free latex coatings detailed in a companion paper. Coatings cast with glycerol showed a lesser degree of latex particle consolidation and coalescence than those cast without glycerol. However, the effect of glycerol was not as pronounced as in cell-free coatings. We conclude that part of the added glycerol is sequestered inside the bacterial cells and the portion remaining outside the cells retards the latex film formation process and enhances microporosity. Two commercial acrylic acid/vinyl acetate copolymer latexes were examined. Coatings made with the polydisperse latex showed less microporosity and a greater degree of particle welding than those made with the nearly monodisperse latex. Copyright 1999 Academic Press.

Journal Article↗