PVDF-block copolymers

Therefore, as Mn2(CO)io was never employed in polymerizations of main chain fluorinated monomers, or with inactivated alkyl halides or with perfluoroalkyl iodides, we decided to assess its scope and limitations as photo-coinitiator and to demonstrate that such LjjMt-MtLjj photolyzable transition metal complexes afford the initiation of VDF polymerization directly from a variety of regular and (per)fluorinated alkyl halides (Cl, Br, I) even at rt, thus opening up novel synthetic avenues for the photome-diated synthesis of block and graft copolymers based on FMs. Second, we also set to kinetically explore such polymerization and investigate the possibility of Mn2(CO)io-mediated IDT-VDF-CRP. Third, we aimed to demonstrate the first examples of the synthesis of well-defined PVDF-block copolymers. 

In retrospect, due to the failure of the respective chemistries to activate the stronger and dominant —CF2—CH2—X termini, (as such experiments used high conversion PVDF—I samples, thus containing >80% of the inactive PVDF—CH2—I), it is clear that all previous endeavors were futile and fundamentally incomplete, and that all so-called blocks were in fact always inseparable, ill-defined mixtures of PVDF—CH2—I with PVDF-block copolymers [31,140-144]. Likewise, as the dead PVDF—CH2—I termini accumulate, they are always of lower molecular weight than the dormant/propagating PVDF—CF2—I chain ends. Conceivably, selective precip-itation/fractionation may enable enrichment in the PVDF—CF2—I chain end [28], but this would be inefficient and difficult. Thus, the clean synthesis of pure, well-defined PVDF-block copolymers requires complete activation and/or derivatization of both types of PVDF chain ends, and especially of Cp2CH2-X. 

FIGURE 24 500 MHz IH-NMR spectra of PVDF-I, PVDF-H, and various PVDF-block copolymers. All in dg-acetone except PAN in dg-DMSO. = HjO, = acetone, = DMAC, = DMSO. Reprinted with permission from Reference 51. Copyright 2012 American Chemical Society. 

Thus, performing the activation in the presence of radically polymerizable alkenes leads to the first examples of well-defined AB or ABA-type PVDF-block copolymers with styrene (e, e ), butadiene (f, f, vinyl chloride (g, g ), vinyl acetate (h, h ), methyl acrylate (i, i, i"). and acrylonitrile (j, j ), initiated from both the PVDF halide chain ends. While here Mn2(CO)io simply performs irreversible halide activation, and there is no IDT, control of the block copolymerization can be envisioned by other CRP methods. 

While the concentration of the active —CH2—CF2—I decreases and that of unre-active —CF2—CH2—I PVDF chain ends increases with conversion, their subsequent quantitative activation with Mn2(CO)io affords the first examples of well-defined PVDF-block copolymers with a variety of other classes of monomers, irrespective of the —CH2—CF2—I/—CF2—CH2—I ratio in the PVDF-I sample. 

Polyarylate (PAR)-b-PSt and PAR-b-PMMA for compatibiiizers are described 135,39,40). The addition of PAR-b-PSt (1-10 parts) to 100 parts of a blend of PAR-PSt (7w-3w) resulted in improvement of the tensile and flexural modulus (Fig. 4), and PSt dispersed particles were diminished from 1-5 microns to an order that is undetectable by SEM, indicating the excellent, compatibilizing effect of the block copolymer. The alloy thus formed exert the characteristic of PAR, an engineering plastic, as well as easy processability of PSt. Addition of PAR-b-PMMA (3 or 8 parts) to 100 parts of a blend of PAR-polyvinylidenefluoride (PVDF) (7w-3w) resulted in improved microdispersed state of PVDF due to compatibility of PMMA with PVDF, while segregation of PVDF onto the surface was controlled. 

Non-ionic polymers have also been blended with ionic block copolymers. Poly(vinyl phosphanate)-l7-polystyrene and PS-l -SPS have been blended with PPO. In both cases, improvements were seen in MeOH permeability over that of fhe unmodified block copolymers and conductivity values dropped as a function of increasing PPO confenf. PVDF has been blended wifh SEES in order fo improve its mechanical and chemical stability, but aggregation was found fo be a problem due fo incompafibility between components. However, it was found that a small amount (2 wt%) of a methyl methacrylate-butyl acrylate-methyl methacrylate block copolymer as com-patibilizer not only led to greater homogeneity but also improved mechanical resistance, water management, and conductivity. ... 

Mokrini, A., Huneault, M. A. and Gerard, P. 2006. Partially fluorinated proton exchange membranes based on PVDF-SEBS blends compatibilized with methylmethacrylate block copolymers. Journal of Membrane Science 283 74—83. 

PS PSF PSU PTFE PU PUR PVA PVAL PVB PVC PVCA PVDA PVDC PVDF PVF PVOH SAN SB SBC SBR SMA SMC TA TDI TEFE TPA UF ULDPE UP UR VLDPE ZNC Polystyrene Polysulfone (also PSU) Polysulfone (also PSF) Polytetrafluoroethylene Polyurethane Polyurethane Poly(vinyl acetate) Poly(vinyl alcohol) poly(vinyl butyrate) Poly(vinyl chloride) Poly(vinyl chloride-acetate) Poly(vinylidene acetate) Poly(vinylidene chloride) Poly(vinylidene fluoride) Poly(vinyl fluoride) Poly(vinyl alcohol) Styrene-acrylonitrile copolymer Styrene-butadiene copolymer Styrene block copolymer Styrene butadiene rubber Styrene-maleic anhydride (also SMC) Styrene-maleic anhydride (also SMA) Terephthalic acid (also TPA) Toluene diisocyanate Ethylene-tetrafluoroethylene copolymer Terephthalic acid (also TA) Urea formaldehyde Ultralow-density polyethylene Unsaturated polyester resin Urethane Very low-density polyethylene Ziegler-Natta catalyst... 

As a route for improving the melt-elongational properties of semicrystalline polymers, Siripurapu et al. [7] proposed the blending of amorphous and semicrystalline blends of PS and PVDF nevertheless, their approach showed only limited success. In contrast, Reichelt et al. [29] successfully developed blends of HMS-PP and PP-fe-PE block copolymers. As could be shown, the melt strength increases with the HMS-PP content, while blends rich in HMS-PP also show the lowest densities. 

Destarac and Matyjaszewski et al. showed that a-trichloromethylated pVDF telomers could be used as ATRP macroinitiators to prepare block copolymers with various monomers [250]. The polymerization of VDF was carried out using a peroxide initiator in the presence of chloroform, which produced an a-trichlo-romethyl radical capable of adding to the monomer. The subsequent ATRP of St, MMA, MA, or nBA using these macroinitiators resulted in block copolymers with Mn>6000 and Mw/Mn<1.3. GPC traces verified complete consumption of the macroinitiators [250]. 

To prepare the graft copolymer, a PO (MW = 50 to 1,000 kg/mol) was either dissolved or swollen in an inert hydrocarbon, monomers (>80 wt% of a methacrylic ester, CH2=C(CH3)COOR) and an initiator was added to the heated mixture while stirring. As a result, acrylic branches of a relatively high molecular weight (MW = 20 to 200 kg/mol) were grafted onto the PO macromolecules. The graft copolymer could be used as a compatibilizer-cwm-impact modifier in a variety of polymers selected from between PO, acrylic polymers, SAN, EVAc, PA, PEST, PC, POM, PAr, PVC, ABS, PVDC, cellulosics, polyester-polyether block copolymers, PEA, PEEK, PEI, PES, CPVC, PVDF, PPE, PPS, PSF, TPU, PAI, PCL, polyglutarimide, blends of PEST with PC or PVC [Ilendra et al., 1992, 1993]. 

PAr/ PVDF PAr-b- PMMA PVDF/PMMA is a miscible blend. Addition of PAr to the PAr/PVDF/PAr-b-PMMA resulted in reduction of PVDF T and an increase of PAr T. These effects were m g enhanced by addition of PAr-b-PMMA. Finer dispersion was obtained for higher block copolymer content. Contact angle measurements, showed that was greatly influenced by the presence of block copolymer. Ahn et al., 1994... 

Sun, H., et al., 2015. Synthesis of well-defined amphiphilie block copolymers via AGET ATRP used for hydrophilic modification of PVDF membrane. Journal of Applied Polymer Science. 132(24) n/a-n/a. 

To enhance membrane mechanical and hydro-thermal stability, Jiang et al. prepared a blend of side-chain sulfonated PFCB block copolymer and a PVDF fluoropolymer [129]. The chemical structure of the side-chain sulfonated PFCB ionomer is shown in Scheme 6.32. They evaluated the membrane s fiandamental properties, such as proton conductivity, gas permeability, water uptake, and... 

MOPVC Modified PVC CPVC Chlorinated PVC ASA Acylonitrile-styrene-acrylonitrile block copolymer PVDF Polyvinylidene fluoride ... 

Zhang, Z., Ying, S., and Shi, Z. (1999). Synthesis of fluorine-containing block copolymers via ATRP. 1. Synthesis and characterization of PSt-PVDF-PSt triblock copolymers. Polymer, 40 5) 1341-1345. 

Finally, the best initiators for controlled VDF-IDT photopolymerizations and for high functionality PVDF-I for subsequent chain end derivatization or block copolymer synthesis are based on the semi and perfluorinated initiators. Thus, while good Cl and Br CTAs can at best provide efficient telomerizations [18], uncatalyzed halide DT-CRP occurs only for iodine [15-19]. 

SYNTHESIS OF WELL-DEFINED BLOCK COPOLYMERS FROM PVDF-I... 

As such, while the concentration of active —CH2—CF2—I decreases and that of unreactive —CF2—CH2—I increases with conversion, (Figure 2.3) [51], the total (—CH2—CF2—I -I- —CF2—CH2—I) iodine functionality remains at least 95%, even at larger levels of Mn2(CO)io [51]. This is adequate for block copolymer synthesis, if both halide chain ends can be activated, and this is where the high Mn(CO)5 halide affinity [59] comes into play. Indeed, as seen above, Mn(CO)5" was able to activate not only the CF2—I based initiators, but even the CH3—I, CH3—( 2)5—I, as well as H—CF2—CF2—CH2—I models of the reverse PVDF—CF2—CH2—12,1-chain end... 

SCHEME 83 Schematic illustration of the synthesis of PVDF- -PAAc copolymer hy RAFT-mediated graft polymerization, the preparation of the PVDF-g-PAAc membrane with hving surfaces, and the preparation of the pH- and temperature-sensitive PVDF-g-PAAc-h-PNIPAM microporous membrane via surface-initiated block copolymerization. PVDF, polyfvinyhdene fluoride) AAc, acrylic acid NIPAM, V-isopropylacrylamide. Reprinted with permission from Reference 92. Copyright 2004 American Chemical Society. 

PVDF- -PMcn Block Copolymers Prepared by Controlled Radical Polymerization AN, MAN, and VCN)... 

To develop dielectric polymers with C-CN and C-F groups, the syntheses of poly(vinylidene fluoride)-h-poly(AN, MAN, VCN) (PVDF-h-PMcN) block copolymers (Scheme 20.8), using the iodine transfer polymerization (ITP) of acrylonitrile (AN), methacrylonitrile (MAN), and vinylidene cyanide (VCN), in the presence of PVDF-1, was reported. In a first step, the ITP of vinylidene fluoride (or 1,1-difluoroethylene, VDF) with C6F13I initiated by tcrt-butyl peroxypivalate (TBPPI)... 

SCHEME 20.8 Synthesis of PVDF-fc-PMcK block copolymers by ITP of cyano monomers Mcn [89]. 

Perfluoroalkyl iodides are known to exhibit a weak CF2 -I bond dissociation energy (45 kJ/mol) [97] that enables the C-I bond to be easily broken in various ways thermally, photochemically, biochemically, electrochemically, and with various initiators or catalysts. That is the reason why QFis-I has been chosen as a chain transfer agent (CTA) for this FTP. The full details of the procedure of this ITP are supplied in references [91,96,98]. The synthesis of PVDF-b-PMcN block copolymers was carried out at 75°C, initiated by TBPPI. The FTP process was been reviewed and described in references [91,98]. 

As expected, as the refractive indexes of fluorinated polymers are very low, SEC analysis displayed negative signal assigned to PVDF block response, whereas, the final PVDF-fe-PM(2N block copolymers were identified by positive signals. The values of A/jj (Table 20.6) show that the reactivity of cyano monomers toward the VDF macroradicals can be classified in the following decreasing order AN > MAN > VCN. 

Figure 20.10 displays the DSC thermograms. It is observed a clear change of baseline for all analyzed copolymers. This is attributed to Tg, ranging between 62°C and 86°C (Table 20.6). However, the Tg of PVDF block is not evidenced by DSC... 

TABLE 20.6 Molecular Weights and Thermal Properties of PVDF and PVDF-6-PMcn Block Copolymers [89]... 

FIGURE 20.10 DSC thermograms of PVDF-fc-PMAN, PVDF-fc-PVCN, and PVDF-fc-PAN block copolymers under nitrogen [89]. 

The dielectric spectra were obtained using the samples with thicknesses ranging between 80 and 150 pm, and in the temperature -130°C to 150°C range, except for the PVDF-h-PVCN block copolymer (-130°C to 100°C) [89]. The values of the dielectric permittivities versus temperature (Figure 20.19) show the existence of two relaxations. At room temperature (100 Hz), the values for PVDF homopolymer, PVDF-h-PAN, PVDF-h-MAN, and PVDF-h-PVCN block copolymers are 6.3, 3.9, 5.0, and 5.5 respectively. 

FIGURE 20.19 Dielectric permittivities of various block copolymers and PVDF versus the... 

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