Measurements have been made of the charge density produced on dielectric surfaces by contact with metals of known difference in work function in vacuo. The injected charge density is dependent on the metal work function and, therefore, described by electron transfer for all the materials examined. Values of work function are presented for PVC, 4.85 ev; polyimide, 4.36 ev; PTFE, 4.26 ev; polycarbonate, 4.26 ev; PET, 4.25 ev; polystyrene, 4.22 ev; and nylon 66, 4.08 ev. The positions of some of these materials in the familiar 'triboelectric series' are readily described by their work functions.

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An investigation is described of the role of unsaturated groups in the molecular structure on charge trapping in synthetic polymers. An attempt has also been made to quantify the effect on carrier migration of doping these materials with halogens. Using a surface charge decay technique carrier mobility has been determined in vacuo for a number of synthetic polymers and also for both high-and low-density polyethylenes doped with halogens. These data are presented together with an account of concurrent measurements of optical absorption in the same materials. The data indicate a tendency for "pure polymers" with known higher unsaturation content to exhibit a lower carrier mobility. Increased mobility was observed with either bromine or iodine impregnation of polyethylene. The optical data show that the iodine enters the polymer as neutral molecules most of which emerge under atmospheric conditions. The remainder, however, form charge exchange complexes at unsaturation sites in the polymer. The role of complexes in carrier transport is discussed.The charge storage property of insulating materials--as exemplified in the electret--is becoming of widespread technological importance from microphones (6; and references therein) to prostheses (1). The elucidation of the underlying charge injection and carrier Key words: polymers, carrier mobility, conduction. migration processes in synthetic polymers is vital to the future utility of these materials in almost any capacity.Modern experimental techniques are yielding increasingly more definitive models of the basic mechanisms. It has been shown (3, 7) that carrier mobility in low conductivity polymers is extremely small, the carriers being predominantly located in traps. Carrier migration is described by a hopping process. Recently published data (2) indicate that both polymer crystallinity and molecular symmetry significantly affect the electret stability, that is, charge trapping, and further, that phenyl and unsaturated groups in the molecular structure can form traps. Previous work (4) has also shown that carrier mobility in these materials may be greatly increased by impregnating the polymer with iodine. This effect has been interpreted by postulating charge exchange complex formation in the polymer, the complexes effectively reducing trapping effects by "handing-on" the carriers. A charge exchange complex in the present context means an interaction between two species, the strength of which lies between a full chemical bond and a small orbital overlap.The present paper describes an investigation of the role of unsaturated groups in carrier trapping and an attempt to quantify the effects of doping on the transport mechanism. Using a surface-charge decay technique, carrier mobility has been determined in vacuo for a number of synthetic polymers and also for both high-density (HDPE) and low-density (LDPE) polyethylenes impregnated with halogens. An account of concurrent measurements of optical absorption in the same materials is also presented.The experimental r...

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