Variation in the optical sensing properties of dithiocarbamate polymer microspheres as function of surface morphology

Three polymers with N-ethanolamino-, N-benzylamino-, and N-t-butylamino-dithiocarbamate groups were synthesized from polyvinylbenzylchloride. Each of the three polymers was incorporated in a hydrogel membrane (PVA) cross-linked with glutaraldehyde to form a sensing element. The latter was, then, evaluated for its optical sensing behavior by subjecting it to varying concentrations (1.0x10-5 up to 0.1 M) of metal ions (Zn2+, Cd2+, Pb2+, Hg2+,Ca2+, Mg2+, K+, Na+, Cr3+, Ni2+, Cu2+). Significant response was observed for the Hg2+ ions while the others showed negligible or no response. The turbidity absorbance increased consecutively from the dithiocarbamate polymer derived from N-t-butylamine towards that from ethanolamine as the concentration of the Hg2+ solution increased. The response time measured for the three polymer microspheres ranged between 2 and 30 minutes. The aminodithiocarbamate polymers were stable at normal temperatures (25ο - 40 ο C) and as pH was changed between 2 and 7. In addition, the polymers demonstrated excellent stability with time and a capacity of 3.967, 3.787, 3.355 mmol Hg2+ ions per gram of polymer for the N-ethanolamino-, N-benzylamino-, and N-t-butylamino-dithiocarbamate respectively. SEM and Eds analyses showed an increase in size of about 25% in the case of complexation with N-ethanolamino-, no size change with N-benzylamino-, and a 16.6% decrease in size with N-t-butylamino-dithiocarbamate.We are grateful to professor W.R.Seitz and his research group, of the University of New Hampshire (USA) for supplying us with the polymer polyvinylbenzylchloride.We are also grateful to professor M.Khamis of Al-Quds University for financial support for the SEM analyses