Iodine transfer polymerization (ITP) of vinylidene fluoride (VDF). Influence of the defect of VDF chaining on the control of ITP

Iodine transfer polymerization (ITP) of vinylidene fluoride (VDF) in the presence of two chain transfer agents (CTA, such as C6F13I and HC2F4CH2I) is presented. Various experimental conditions in terms of the nature of the radical initiators, time, temperature and initial [initiator] (0)/[VDF](0) and [CTA](0)/[VDF](0) molar ratios influenced the yield of the reaction, the obtained average degree of polymerization in number, (DP) over bar (n), of PVDF-I, the defect of VDF-chaining, and the CX2I functionality (where X = H or F). The microstructures of these produced PVDF-I oligomers were characterized by H-1 and F-19 NMR spectroscopy which enabled one to assess the (DP) over bar (n) values and to quantify the head-to-head or tail-to-tail defects of VDF-chainings. A low amount of defect of chaining in PVDF-I when C6F13I was used in contrast to a higher content from HC2F4CH2I. These PVDF-Is exhibited a favored-CH2CF2I functionality from the former CTA which was not observed in the latter one. A good agreement between the targeted and the obtained (DP) over bar (n) values was noted for ITP of VDF in the presence of C6F13I (representative of normal addition) whereas that carried out from HC2F4CH2I (representative of inverse addition) led to experimental (DP) over bar (n) values higher than the targeted ones in all cases. A low conversion of HC2F4CH2I was observed in contrast to that of C6F13I, which shows a better efficiency as the transfer agent.