Homogeneous phase polymerization of vinylidene fluoride in supercritical carbon dioxide

Abstract

For the first time, stabilizer‐free vinylidene fluoride (VDF) homopolymerizations were carried out in homogenous phase with supercritical CO2 using the conventional initiator di‐tert butyl peroxide (DTBP). In‐line FT‐NIR spectroscopy showed that complete monomer conversion may be obtained. Molecular weights were determined via size‐exclusion chromatography and polymer endgroup analysis by 1H‐NMR spectroscopy. The number average molecular weights were below 104 g mol−1 and polydispersities ranged from 3.1 to 5.7 depending on DTBP and VDF concentration. For allowing isothermal reaction, high CO2 contents ranging from 61 to 83 wt % were used. The high‐temperature and high‐pressure conditions required for homogeneous polymerization did not alter the amount of defects in VDF chaining. Scanning electron microscopy indicated that regular stack‐type particles are obtained upon expansion of the homogeneous polymerization mixture. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5626–5635, 2007

Intrinsic viscosity–number average molecular weight relationship for poly(1,4‐butylene adipate) diol

“…The maximal difference is 6.91% and the average one is 3.74%. Compared the values of a and K , just as reported in some literatures,8, 9 the plot (Fig. 5) of log K versus exponent a is linear almost and inversely related.…”

“…There are many ways to determine molecular weight such as end‐group analysis ( M n ),5 gel permeation chromatography (GPC) ( M n , M w , and M z ),1, 6, 7 H‐NMR technique ( M n ),8 membrane osmometry ( M n ),9 light‐scattering ( M w ),9 and viscometry method ( M v ). But most of these ways are time consuming.…”

Iodine transfer copolymerization of vinylidene fluoride and α‐trifluoromethacrylic acid in emulsion process without any surfactants

“…Hence, these high value‐added materials can find applications in many fields of high technology, such as aeronautics,5 microelectronics,6 optics,7, 8 textile finishing,9, 10 in the nuclear industry,11–13 in paints and coatings,14 and lithography 15. These specialty polymers can be produced by radical (co)polymerization of fluorinated monomers in organic solvent and supercritical CO 2 16–21; however, they are commonly made in aqueous processes 1–4, 11–13. As these halogenated monomers are highly hydrophobic, a surfactant must be added to stabilize the emulsion in monodispersed droplets of monomers.…”

Effect of interfacial area on heterogeneous free radical grafting of vinyl monomers in supercritical carbon dioxide: Grafting of acrylic acid on poly(vinylidenefluoride) nanoparticles

“…34 The phase behavior of the ternary mixture of CO 2 , AA, and BPO in the adopted reaction conditions was previously studied by visual observation in a view cell. 36 This means that under operative conditions adopted to perform grafting experiments, an heterogeneous reaction system was obtained constituted by solid PVDF powders contacted with an homogeneous fluid phase formed by the supercritical solvent, BPO and AA. 35 On the other hand to dissolve low molecular weight PVDF (M n 5 3,031 g mol 21 , PDI 5 3.65) in scCO 2 , pressure of 150 MPa and temperature of 140 C were necessary.…”

“…35 On the other hand to dissolve low molecular weight PVDF (M n 5 3,031 g mol 21 , PDI 5 3.65) in scCO 2 , pressure of 150 MPa and temperature of 140 C were necessary. 36 This means that under operative conditions adopted to perform grafting experiments, an heterogeneous reaction system was obtained constituted by solid PVDF powders contacted with an homogeneous fluid phase formed by the supercritical solvent, BPO and AA.…”