EFFECTS OF CHAIN STRUCTURE ON THE MELTING CHARACTERISTICS OF POLY(VINYL FLUORIDE)

The effects of configurational disorder and chain branching on the mel ting characteristics of the addition polymer poly(vinyl fluoride) (PVF ) have been investigated. For PVF, the melting point (T(m)) was found to be strongly dependent on polymerization temperature, and only weakl y dependent on polymerization pressure. Structural investigation of th e polymer backbone using F-19 nuclear magnetic resonance analysis reve als that the pronounced increase in T(m) results predominantly from a decrease in chain branching and, to a far lesser extent, from improved main-chain regio-regularity. For PVF with a (tertiary fluorine) branc h-point content above 2.2% (approximately one branch per 45 monomer ad ditions) the melting point is reduced to below 180-degrees-C, whereas for samples with branch-point content less than 0.3% (approximately on e branch per 300 monomer additions) the melting point lies above 205-d egrees-C. Moreover, for the same polymers, the number of head-to-head monomer linkages was found to remain largely constant (= 12.5 +/- 1%).