Chemical modification of poly(vinyl chloride)-Still on the run

摘要

Poly(vinyl chloride) (PVC) has continued to be a research topic in polymer science since its discovery in the early 19th century. Its internal structural defects, which stem from its direct manufacture (via free radical polymerization), heighten its peculiarities, including its thermal instability. Apart from the addition of organic and inorganic thermal stabilizers, improved chemistry in the formation of PVC has been proposed to alleviate some of its intrinsic limiting properties. This chemistry, mainly via the chemical transformations of this polymeric material, has been broadened by widespread ongoing research. The so-called anomalous or labile chlorine atoms, that is, the tertiary and allylic chlorines, and the normal secondary ones coupled with a varying content of carbon-carbon double bonds, have been subjected to numerous chemical modifications. The latter were undertaken not only for routine chemical reactions, but also for the sake of enhancing the properties, understanding PVC-related phenomena, and the use of PVC in specific applications. The different reactions on PVC, basically dechlorination, involved nucleophilic and radical substitutions, elimination or dehydrochlorination, and grafting polymerizations via cationic and free radical pathways (old processes or new ones, ATRP and LCRP). Leading and attractive applications of the chemically modified PVCs were ion-selective electrode membranes, membrane sensors, and biomedical devices. In this paper, an account of many of the chemical modifications of PVC based on reports over the last decade is delineated, along with related applications. These modifications are presented according to the bond formed (C_(PVC)-X) between the PVC carbon C_(PVC) and the atom X (X = N, O, S, Hal) of the modifying molecule.