A partially exfoliated bisphenol A polycarbonate nanocomposite has been prepared by using carbonate cyclic oligomers and ditallow dimethyl exchanged montmorillonite (B34). Wide-angle X-ray diffraction (WAXD) indicated that exfoliation of this organically modified layered silicate (OLS) occurs after mixing with the cyclic oligomers in a brabender mixer for 1 h at 180 °C. Subsequent ring-opening polymerization of the cyclic oligomers converted the matrix into linear polymer without disruption of the layer dispersion. Transmission electron microscopy revealed that a partially exfoliated structure was obtained, although no indication of layer correlation was observed in WAXD. If linear polycarbonate was similarly treated with B34 in a brabender mixer, only an intercalated hybrid was obtained. Furthermore, conventional melt or solution processing of the B34 with either linear polycarbonate or cyclic oligomers yielded intercalated nanocomposites with interlayer spacings of 3.27 and 3.6-3.8 nm, respectively. These results demonstrate that consideration of molecular architecture (cyclic vs linear) and kinetics (medium viscosity and shear) is critical for nanocomposite formation.

Lewis acidic, chelating diborane 1 forms stable oxonium acids 2 in the presence of excess MeOH or water. Diborane 1 is shown to be an effective co-initiator for the suspension polymerization of isobutene in aqueous media at sufficiently low temperatures. Poly(isobutene) or butyl rubber is obtained at moderate to high conversion and with Mw < 200 K and PDI approximately 2 under these conditions.

Lewis acidic diborane 1 (J. Am. Chem. Soc. 1999, 121, 3244-3245) is highly effective for both proton- and cationogen-initiated isobutene polymerization in hydrocarbon media at low temperature. Reactions of diborane 1 with cumyl chloride and cumyl methyl ether were studied by variable-temperature 1H and 19F NMR spectroscopy. At low temperatures stable ion pairs 2a and 2b are formed; at higher temperatures these ion-pairs form phenyl-1,3,3-trimethylindan (3) with concomitant release of HCl to form 1 in the case of 2a or degradation of the anion (2b). Reaction between Ph3C-Cl and diborane 1 resulted in the generation of an ion-pair 4 consisting of the Ph3C cation very weakly associated with the chelated, mu-Cl counteranion as revealed by X-ray crystallography.

The use of the chelating diboranes o-C6F4[B(C6F5)2]2 (1) and o-C6F4(9-BC12F8)2 (2: 9-BC12F8 = 1,2,3,4,5,6,7,8-octafluoro-9-borafluorene) for the polymerization of isobutene (IB) in aqueous suspension or in hydrocarbon solution was studied. Polymerizations in aqueous suspension provided polymer of moderate MW and at variable conversion and were dependent on temperature, mode of diborane addition, the presence of surfactant, and the acidity of and nature of the anion present in the aqueous phase. The T dependence of MW over the T range −80 to −20 °C was studied in aqueous suspension, and higher MW polymer was formed at lower T. The hydrolysis and methanolysis of diboranes 1 and 2 was studied by NMR spectroscopy. Reactions of diborane 1 with excess MeOH or water afford solutions containing oxonium acids [o-C6F4{B(C6F5)2}2(μ-OR)][(ROH) n H] (7: R = H, n > 2; 3: R = Me, n = 3). When diborane 1 is present in excess over water or MeOH, degradation of the diborane is observed. In this case the products are o-C6F4{B(C6F5)2}H (5) and (C6F5)2BOH 7 or (C6F5)2BOMe 4, respectively. In the case of diborole 2, o-C6F4(9-BC12F8)B(2-C12F8-2′′-H)(μ-OH)·7H2O (17) and o-C6F4(9-BC12F8)B(2-C12F8-2′′-H)(μ-OMe) (11) were isolated from reactions of 2 with water and MeOH, respectively, and were characterized by X-ray crystallography. None of these degradation products effect IB polymerization in aqueous suspension. As a model for initiation of polymerization, the reaction of diborole 2 with 1,1-diphenylethylene (DPE) was studied. Addition of MeOH at low T results in efficient formation of the ion-pair [Ph2CMe][o-C6F4(9-BC12F8)2(μ-OMe)] via protonation of DPE. Polymerizations in hydrocarbon media were exothermic and rapid and gave quantitative yields of polymer even at very low concentrations of diborane 1. The T dependence of MW was studied in hydrocarbon solution and showed non-Arrhenius behavior. This was explained by competitive chain transfer to monomer at elevated T and chain transfer to molecular water at lower T.

Tris(pentafluorophenyl)gallium (3) and aluminum (7) are active coinitiators for the production of medium‐high molecular weight (MW) polymers of styrene and isobutene (IB) under aqueous reaction conditions. Strong Brønsted acids formed in situ by reaction of these coinitiators with background moisture present in the monomer droplet (5 and 8, respectively) are believed to be responsible for inducing cationic polymerization of these monomers. Of the two, 7 is the most active for IB polymerization in both aqueous media and anhydrous aliphatic solvents. These results are in contradistinction to tris(pentafluorophenyl)boron (2), which is incapable of polymerizing IB in aqueous or aliphatic media. The MWs of the polyisobutenes (PIBs) produced under aqueous conditions by either coinitiator greatly exceed those formed under similar reaction conditions by the strongly acidic chelating diborane (1,2‐C6F4[B(C6F5)2]2, 1) or diborole (1,2‐C6F4[9‐BC12F8]2, 6). Both 3 and 7 are readily synthesized from the corresponding Group 13 halide compounds in conjunction with bis(pentafluorophenyl)zinc (4). Aqueous polymerization of IB dissolved in aliphatic solvents with 3 or 7 can yield PIBs with relatively narrow polydispersities. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Continuous flow methodology for the multi step synthesis of biomass derived aliphatic bicyclic-anhydride monomer. Polymerization with bio-based alcohols results in renewable polyesters with good thermal stability.

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The syntheses of a variety of iminophosphonamide (PN2) ligands (2a−f), the corresponding hydrochloride salts (1a−c), and a number of bis(PN2) dichloride complexes of group 4 (3a−e) and their corresponding dialkyls (5a−e) are described. A novel monosubstituted PN2 “ate” complex 4 was prepared from ligand 2f and Zr(NMe2)4 on treatment with excess Me2NH·HCl. Piano-stool PN2 zirconium dichloride complexes 6a−h were accessible on treatment of CpZr(NMe2)3 (Cp = C5H5, Cp*) with PN2 ligands 2a−e, followed by metathesis with excess Me3SiCl or Me2NH·HCl (6a−g) or at low T with ethereal HCl (6h). Dialkyl derivatives 8a−h could be prepared from 6a−h or directly from ligands 2 and CpMMe3 (Cp = C5H5, Cp*; M = Ti or Zr). The intermediate Cp(PN2)Zr(NMe2)2, precursor to 6h, rearranged to the novel terminal difluoride complexes 7a,b at room temperature. A variety of complexes 3 and 6 or their corresponding alkyl derivatives have been characterized by X-ray crystallography. In addition, the novel “ate” complex 4 and difluoride complexes 7a,b have been structurally characterized in this manner. The structures of 7a,b in the solid state reveal strong, intramolecular coordination of the NMe2 group to the metal center, resulting in eight-coordinate complexes. One of these complexes is fluxional in solution, suggesting rapid exchange of bound versus free NMe2 groups coupled with the formation of coordination stereoisomers.