Electron Microscopic Observations on Cellulose Graft Copolymers: Radiation Induced Rayon-Styrene Graft Copolymers1

Abstract

Three types of commercial rayon (Fortisan, high-tenacity tire yarn, and modifiertype, high wet modulus yarn) were grafted with styrene, using the direct radiation method with gamma-rays from Co-60. The grafted filaments were examined in the electron microscope to investigate their morphology and fine structure, the location and distribution of polystyrene in the fiber, and whether the polystyrene was truly grafted.In all three grafted fibers, the polystyrene was distributed throughout the cross section of the filament and also appeared on the surface. As a result, the filaments expanded isometrically during grafting, but retained their original shape. The polystyrene grafted to the surface of the filament followed the original surface striations of the rayon and appeared as protruding ridges and valleys, rather than as uniform surface layers. The polystyrene inside the filament could not be removed hy exhaustive extraction of the intact yarn with benzene, but some of it could be removed by extracting the ultra-thin cross sections (ca. 500 & A r i n g ; thick) used for electron microscopic observations. The main portion of these ultri-thin sections was insoluble in solvents for both polystyrene and cellulose and is considered to be a true cellulose-styrene graft.The changes induced in the fine structure of the cross sections by alternate extraction with solvents for polystyrene and cellulose were followed, using the electron microscope. From a macroscopic viewpoint, it was concluded that the styrene grafted rayons are homogeneous. At a molecular level, however, they consist of a gross heterogeneous mixture of polystyrene homopolymer, cellulose, and true cellulose-styrene graft copolymer.

Electron Microscopy

“…Caro (84) concisely outlined the methods, problems and procedures of autoradiography in EM. After an evaluation of the quantitative aspects in terms of resolution, sensitivity, and specimen radioactivity, Salpeter and Bachman (517) estimated that the resolution of an individual silver deposit as recorded on an electron micrograph may soon be in the range of 300 A. The use of S35 in EM was demonstrated by Fewer et al (156).…”

“…They are similar to the fibers of the mitotic spindle and in certain cells some of the tubules are connected with satellites of the centrioles. In a study of the fine structure of microtubules of nucleated red blood cells by negative staining, Gall (182) observed that the individual microtubules were 300 A. in diameter and of various lengths, up to tens of microns. The wall consisted of 12 to 14 longitudinal subunits arranged in a circular pattern, an observation consistent with those of Ledbetter and Porter (349) who reported 13 subunits in transverse sections.…”

“…A method was described by Goodman and Lehmpfuhl (211) for obtaining electron diffraction diagrams in a convergent beam from selected samples, 300 A. in diameter. The axis of the incident electron beam in their setup was variable within a 6°cone in the Siemens Elmiskop I.…”

Location of some typical vinyl polymers within radiation‐grafted cotton fibers: An electron microscopical survey

“…Electron microscopical observations of radiation-induced rayon-styrene graft8 copolymers were published by Kaeppner and Huang in 1965. 4 The present paper reports electron microscopical investigations into both the relationship of the structure of the vinyl-cotton graft polymer to the original morphology of the cotton fiber and the distribution of the grafted vinyl polymer in the cotton fiber structure. The grafted vinyl monomers investigated in this study were acrylonitrile styrene, methyl methacrylate, and vinyl acetate.…”

“…action of styrene, acrylonitrile, methyl methacrylate, and other vinyl monomers with cellulosic films, filter paper, cellulose esters, cotton, and regenerated cellulosic fibers have been published. [2][3][4] Work in this area by Arthur and his co-workers a t the Southern Utilization Research and Development Division has been concerned with preparing radiation-induced graft copolymers of cotton and various vinyl monomers while retaining the fibrous nature and high molecular weight of the cotton c e l l~l o s e .~-~~ The copolymer technique results in enhancement of the best properties of cotton and acquisition of the properties of the grafted vinyl polymer and therefore more useful, new cotton products for specific end uses. These workers have found that the radiation-induced grafting of vinyl monomers to cotton leads to increased elongation, toughness, abrasion resistance, thermoplasticity, and rot resistance, and decreased stiffness and permanent set.…”