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A unique feature of molecular iodine by far, is its ability to bind to polymeric materials. A plethora of natural and synthetic polymers develop complexes when treated with molecular iodine, or with a mixture of mole cular iodine and potassium iodide. Many unexpected findings have been encountered upon complexation of iodine and the polymer skeleton, including the color formation, the polymer morphology changes, the compl exation sites or regions, the biological activity, and the electrical conductivity enhancement of the complexes, with poly iodides (I n¯) , mainly I 3¯ and I 5¯, as the actual binding species. Natural polymers that afford such complexes with iodine species are starch (amylose and amylopectin), chitosan, glycogen, silk, wool, albumin, cellulose, xylan, and natural rubber; iodinestarch being the oldest iodinenatural polymer complex. By contrast, numerous synthetic polymers are prone to make com plexes, including poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP), nylons, poly(Schiff base)s, poly aniline, unsaturated polyhydrocarbons (carbon nano tubes, fullerenes C 60 /C 70 , polyacetylene; iodinePVA being the oldest iodinesynthetic polymer complex.

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Functionalizations of poly(vinyl alcohol) (PVA) congruent with the desired applications are herein discussed. The chemical modifications of PVA with different molecular weights and hydrolysis degrees via conventional chemistries, namely esterification, carbamation, etherification, and via the modern ones such as click chemistry, led to finished materials with a wide range of applications and uses: membrane fuel cells, biologicals and biomedicals, adsorption of heavy metals and other contaminants, molecular sensing or chemosensor for detection of some useful molecules or toxic ones, separation of mixtures, catalysis in organic and inorganic syntheses. Different forms of the duly modified PVAs were employed in such applications, including: hydrogels, films, membranes, and nanoparticles. The incorporated modifying agents onto PVA matrixes brought some changes that were in tune with the projected applications. These modifying agents were not confined to molecular compounds but also to macromolecular ones which are graphene, hyaluronic acid, β-cylcodextrin, polystyrene, poly(4-vinylpyridine), and poly(L-lactic acid). Downloaded by [University of Cambridge] at 07:33 23 August 2015 2

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Five vinylcatechol precursors have been synthesized by either alcohol dehydration or Wittig coupling techniques. Dehydration of the appropriate sec‐phenethyl alcohol is the most efficient synthetic approach: the following monomers (yields) are reported: 5‐vinyl‐1,3‐benzodioxole, I (63%); 3,4‐dimethoxystyrene, II (45%); 2,3‐dimethoxystyrene, III (85%);6‐vinyl‐1,4‐benzodioxane.IV(65%); and4‐vinyl‐l,3‐benzodioxole, V(50%). The monomers can be converted by free‐radical techniques to polymers with molecular weights up to 95,000. Monomers I, II, IV, and V polymerized in the presence of stannic chloride; monomers I, III, and IV yielded polymers upon treatment with butyllithium. With the exception of poly IV, the blocking groups can be removed by treatment with boron trichloride followed by methanolysis to liberate poly(3‐vinyl‐ or 4‐vinylcatechol). Suprisingly, the stability of the catechol polymers depends upon the substituent distribution; poly(3‐vinylcatechol) is more stable than any polycatechol previously reported. It is soluble in methanol, autooxidizes very slowly, but can be oxidized by ceric ammonium nitrate to poly(3‐vinyl‐1,2‐benzoquinone).

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