Copolymerization of vinyl acetate with 1-octene and ethylene by cobalt-mediated radical polymerization

in Journal of Polymer Science Part A-Polymer Chemistry (2007), 45(12), 2532-2542

The cobalt-mediated radical polymerization of vinyl acetate was extended to copolymerization with I-alkenes (ethylene or 1-octene). In agreement with the low amount of I-alkene that could be incorporated ... [more ▼]

The cobalt-mediated radical polymerization of vinyl acetate was extended to copolymerization with I-alkenes (ethylene or 1-octene). In agreement with the low amount of I-alkene that could be incorporated into the copolymer, a gradient structure was predictable, but a. rather low polydispersity was observed. A poly(vinyl acetate)-b-poly(octene) copolymer was also successfully synthesized, leading to a poly (vinyl alcohol)-b-poly(octene) amphiphilic copolymer upon the methanolysis of the poly (vinyl acetate) block. [less ▲]

Controlled radical polymerization of styrene mediated by the C-phenyl-N-tert-butylnitrone/AIBN pair: Kinetics and electron spin resonance analysis

in Journal of Polymer Science Part A-Polymer Chemistry (2007), 45(7), 1219-1235

Kinetics of the free radical polymerization of styrene at 110 degrees C has been investigated in the presence of C-phenyl-N-tert-butylnitrone (PBN) and 2,2'-azobis(isobutyronitrile) (AIBN) after ... [more ▼]

Kinetics of the free radical polymerization of styrene at 110 degrees C has been investigated in the presence of C-phenyl-N-tert-butylnitrone (PBN) and 2,2'-azobis(isobutyronitrile) (AIBN) after prereaction in toluene at 85 degrees C. The effect of the prereaction time and the PBN/AIBN molar ratio on the in situ formation of nitroxides and alkoxyamines (at 85 degrees C), and ultimately on the control of the styrene polymerization at 110 degrees C, has been investigated. As a rule, the styrene radical polymerization is controlled, and the mechanism is one of the classical nitroxide-mediated polymerization. Only one type of nitroxide (low-molecular-mass nitroxide) is formed whatever the prereaction conditions at 85 degrees C, and the equilibrium constant (K) between active and dormant species is 8.7 x 10(-10) mol L-1 at 110 degrees C. At this temperature, the dissociation rate constant (k(d)) is 3.7 x 10(-3) s(-1), the recombination rate constant (k(c)) is 4.3 x 10(6) L mol(-1) s(-1), whereas the activation energy (E-a,E-diss), for the dissociation of the alkoxyamine at the chain-end is similar to 125 kJ mol(-1). Importantly, the propagation rate at 110 degrees C, which does not change significantly with the prereaction time and the PBN/AIBN molar ratio at 85 degrees C, is higher than that for the thermal polymerization at 110 degrees C. This propagation rate directly depends on the equilibrium constant K and on the alkoxyamine and nitroxide concentrations, as well. [less ▲]

Kinetics and electron spin resonance study of the radical polymerization of n-butyl acrylate mediated by a nitroxide precursor: C-phenyl-N-tert-butylnitrone

in Journal of Polymer Science Part A-Polymer Chemistry (2006), 44(21), 6299-6311

The C-phenyl-N-tert-butylnitrone/azobisisobutyronitrile pair is able to impart control to the radical polymerization of n-butyl acrylate as long as a two-step process is implemented, that is, the ... [more ▼]

The C-phenyl-N-tert-butylnitrone/azobisisobutyronitrile pair is able to impart control to the radical polymerization of n-butyl acrylate as long as a two-step process is implemented, that is, the prereaction of the nitrone and the initiator in toluene at 85 degrees C for 4 h followed by the addition and polymerization of n-butyl acrylate at 110 degrees C. The structure of the in situ formed nitroxide has been established from kinetic and electron spin resonance data. The key parameters (the dissociation rate constant, combination rate constant, and equilibrium constant) that govern the process have been evaluated. The equilibrium constant between the dormant and active species is close to 1.6 x 10(-12) mol L-1 at 110 degrees C. The dissociation rate constant and the activation energy for the C-ON bond homolysis are 1.9 x 10(-3) s(-1) and 122 +/- 15 kJ mol(-1), respectively. The rate constant of recombination between the propagating adical and the nitroxide is as high as 1.2 x 10(9) L mol(-1) s(-1). Finally, well-defined poly(n-butyl acrylate)-b-polystyrene block copolymers have been successfully prepared. [less ▲]

Quinone transfer radical polymerization of styrene: Synthesis of the actual initiator

in Journal of Polymer Science Part A-Polymer Chemistry (2006), 44(3), 1233-1244

ortho-Quinones, such as phenanthrenequinone and 3,6-dimethoxyphenanthrenequinone, added with a catalytic amount of metal complexes, impart control to styrene polymerization via the previously reported ... [more ▼]

ortho-Quinones, such as phenanthrenequinone and 3,6-dimethoxyphenanthrenequinone, added with a catalytic amount of metal complexes, impart control to styrene polymerization via the previously reported quinone transfer radical polymerization (QTRP) process. In this study, compounds that mimic the dormant species proposed in the QTRP mechanism have been synthesized and tested as initiators in the presence of cobalt(II) acetylacetonate. These compounds, and particularly 3,6-dimethoxy-10-hydroxy-10-(l-phenyl-ethyl)-phenanthren-9-one, are effective control agents for the radical polymerization of styrene, in agreement with the recently proposed mechanism. Moreover, the induction period, which has been systematically reported in the presence of ortho-quinones, is no longer observed. The end capping of the polystyrene chains by the control agent has been confirmed by H-1 NMR analysis. [less ▲]

Quinone transfer radical polymerization (QTRP) of styrene: Catalysis by different metal complexes

in Journal of Polymer Science Part A-Polymer Chemistry (2005), 43(13), 2723-2733

Styrene has been polymerized by a Quinone Transfer Radical Polymerization (QTRP) based on the redox reaction of an ortho-quinone and a metal catalyst. Several metal acetylacetonates have been tested in ... [more ▼]

Styrene has been polymerized by a Quinone Transfer Radical Polymerization (QTRP) based on the redox reaction of an ortho-quinone and a metal catalyst. Several metal acetylacetonates have been tested in this work. The radical polymerization of styrene is largely controlled when phenanthrenequinone (PhQ) is used with catalytic amounts of Co(acac)(2), Ni(acac)(2), Mn(acac)2 or 3, and Al(acac)(3). As a rule, in the presence of all these metallic complexes, the polystyrene molar mass increases with the monomer conversion, and polydispersity (M-w/M-n) is in the 1.3-1.6 range (at least until 40% monomer conversion). Styrene polymerization has also been resumed by polystyrene chains prepared by QTRP. In the specific case of manganese acetylacetonates, an amine or phosphine ligand has to be added for the control to be effective. Finally, two mechanistic hypotheses have been proposed, depending on whether the oxidation state of the metal can be easily changed or not. [less ▲]

Preparation of supported yttrium alkoxides as catalysts for the polymerization of lactones and oxirane

in Journal of Polymer Science Part A-Polymer Chemistry (2003), 41(4), 569-578

Two methods have been reported that allow yttrium alkoxides to be supported on porous silica and to be used afterward as heterogeneous catalysts in the ring-opening polymerization of oxirane and e ... [more ▼]

Two methods have been reported that allow yttrium alkoxides to be supported on porous silica and to be used afterward as heterogeneous catalysts in the ring-opening polymerization of oxirane and e-caprolactone. In the two methods, [tris(hexamethyldisilyl)-amide]yttrium [Y[N(SiMe3)(2)](3)} is the metal alkoxide precursor. It is directly reacted with the silanol groups of the support, in the first method, and this is followed by alcoholysis of the unreacted amide groups. The flexibility of this method seems to be limited because the grafting density and the structure of the grafted Y alkoxide (less than one alkoxide by metal) are independent of the experimental conditions. In the second method, Y[N(SiMe3)(2)](3) is first reacted with 1 or 2 equiv of alcohol with the formation of the mixed Y alkoxide/amide. The amide functions are used to attach Y to the support. This method is free from side reactions, quite reproducible, and well suited to support one type of active species (monoalkoxide or dialkoxide). Preliminary experiments with e-caprolactone polymerization have confirmed the activity of the supported Y alkoxide, whatever preparation method is used. (C) 2003 Wiley Periodicals, Inc. [less ▲]

Effect of the Solvent Polarity on the Living Ligated Anionic Polymerization of tert-Butyl Methacrylate and Copolymerization with Methyl Methacrylate

in Journal of Polymer Science Part A-Polymer Chemistry (2001), 39(10), 1774-1785

An anionic polymerization of t-butyl methacrylate and a copolymerization with methyl methacrylate were initiated with an organolithium ligated with 10 equiv of LiCl. As a rule, the complexation of the ... [more ▼]

An anionic polymerization of t-butyl methacrylate and a copolymerization with methyl methacrylate were initiated with an organolithium ligated with 10 equiv of LiCl. As a rule, the complexation of the active species by LiCl masked the effect that the polarity of the solvent might have on the molecular structure of the chains. [less ▲]

Reactivity of functional SAN toward coreactive EPR-g-MA at planar interface

in Journal of Polymer Science Part A-Polymer Chemistry (2000), 38(19), 3682-3689

The grafting kinetics of reactive poly(styrene-co-acrylonitrile) (SAN) onto EPR-g-MA was studied under isothermal conditions, at the planar interface of an SAN/ethylene-propylene rubber (EPR) bilayer film ... [more ▼]

The grafting kinetics of reactive poly(styrene-co-acrylonitrile) (SAN) onto EPR-g-MA was studied under isothermal conditions, at the planar interface of an SAN/ethylene-propylene rubber (EPR) bilayer film in relation to the type of reactive groups, NH2 versus carbamate (which is an amine precursor), attached to SAN. The amount of SAN chemically bound to EPR chains at the interface was estimated by selectively washing off the unreacted SAN chains before X-ray photon spectroscopic analysis of the released surface. It is clear that the mutual reactivity of the reactive groups, i.e., the NH2-MA pair versus the carbamate-MA pair, has a decisive effect on the amount of SAN that reacts with EPR-g-MA at the interface. In case of SAN-carb, the grafting reaction is controlled by the thermolysis of the carbamate groups into primary amines. [less ▲]

End-capping of polystyrene by aliphatic primary amine by derivatization of precursor hydroxyl end group

in Journal of Polymer Science Part A-Polymer Chemistry (2000), 38(9), 1618-1629

A new and very efficient route for the synthesis of aliphatic primary amine terminated polystyrene (PS) is reported. In contrast to most known methods, only traditional commercially available reagents are ... [more ▼]

A new and very efficient route for the synthesis of aliphatic primary amine terminated polystyrene (PS) is reported. In contrast to most known methods, only traditional commercially available reagents are used. PS is synthesized by anionic polymerization with a lithium counter ion and the living chains are end-capped by a hydroxyl group upon addition of ethylene oxide followed by protonation. The -hydroxyl end group is tosylated and the tosylate is then reacted with sodium azide. The azide terminal group is finally reduced into primary amine. The different steps of functionalization have been fully characterized by SEC, ToF-SIMS, FTIR, and 1H NMR. The amine content (= 98%) has been determined by acid-base titration with perchloric acid. It clearly shows the efficiency of the synthetic method reported in this article although it is a multistep method. [less ▲]

Macromolecular engineering of polylactones and polylactides. XXV. Synthesis and characterization of bioerodible amphiphilic networks and their use as controlled drug delivery systems

in Journal of Polymer Science Part A-Polymer Chemistry (1999), 37(14), 2401-2411

Well-defined ,-methacryloyl poly--caprolactone (PCL) and poly(d,l)-lactide P(D,L)LA dimacromonomers have been synthesized by living ring-opening polymerization of the parent monomers initiated by ... [more ▼]

Well-defined ,-methacryloyl poly--caprolactone (PCL) and poly(d,l)-lactide P(D,L)LA dimacromonomers have been synthesized by living ring-opening polymerization of the parent monomers initiated by diethylaluminum 2-hydroxyethylmethacrylate (Et2AlO(CH2)2OC(O)C(CH3)CH2) and terminated by reaction of the propagating Al alkoxide groups with methacryloyl chloride. These dimacromonomers have been copolymerized with a hydrophilic comonomer, i.e., 2-hydroxyethylmethacrylate, in bulk at 65°C by using benzoyl peroxide as a free-radical initiator. The swelling ability of the amphiphilic PHEMA/PCL or P(D,L)LA networks has been investigated in both aqueous and organic media. Effect of network composition and molecular weight of the dimacromonomer on the swelling kinetics and the equilibrium solvent uptake has been studied. Lipophilic dexamethasone acetate and the hydrophilic sodium phosphate counterpart have been incorporated into the amphiphilic gels and their release has been studied in relation to the gel characteristics. [less ▲]