References of "Macromolecules"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailPoly(methyl methacrylate)/graphene oxide nanocomposites by a precipitation polymerization process and their dielectric and rheological characterization
Thomassin, Jean-Michel ULg; Trifkovic, Milana; Alkarmo, Walid et al

in Macromolecules (in press)

We report a method for achieving controlled dispersion of graphene oxide (GO) in poly(methyl methacrylate) (PMMA) via the precipitation polymerization process in a water/ methanol mixture. GO acts as a ... [more ▼]

We report a method for achieving controlled dispersion of graphene oxide (GO) in poly(methyl methacrylate) (PMMA) via the precipitation polymerization process in a water/ methanol mixture. GO acts as a surfactant and adsorbs on the interface between polymerized PMMA particles and solvent mixture. Scanning electron and transmission electron microscopy confirmed that the precipitate consists of polymer particles (<1 μm) surrounded by the GO sheets. Compression molding of the precipitate yields a polymer nanocomposite with the GO organized into a regularly spaced 3D network which percolates at 0.2 wt % GO. Simple thermal reduction of the GO sheets dispersed in PMMA at relatively low temperature (210 °C) achieved electrical conductivity higher than 10−2 S/m at 0.4 wt % of GO. Parallel dielectric and rheological characterization demonstrated that the thermal reduction is a quite fast process without significant degradation of the polymer. The study should open up new opportunities in the design of GO-based polymer nanocomposites. [less ▲]

Detailed reference viewed: 34 (7 ULg)
Full Text
Peer Reviewed
See detailStraightforward synthesis of symmetrical multiblock copolymers by simultaneous block extension and radical coupling reactions
Debuigne, Antoine ULg; Detrembleur, Christophe ULg; Jérôme, Christine ULg et al

in Macromolecules (2013), 46(22), 8922-8931

In situ combination of a polymerization step with a coupling reaction is demonstrated to accelerate the synthesis protocols for symmetrical multiblock copolymers. Predici simulations and experiments prove ... [more ▼]

In situ combination of a polymerization step with a coupling reaction is demonstrated to accelerate the synthesis protocols for symmetrical multiblock copolymers. Predici simulations and experiments prove on the example of cobalt-mediated radical polymerization and coupling (CMRP/C) reactions that such synthesis strategy can be very effective and easy to conduct. Treatment of a cobalt-terminated poly(acrylonitrile) precursor with a mixture of acrylate and isoprene led to the rapid polymerization of the acrylate before isoprene-assisted radical coupling of the macroradical chains forming a well-defined poly(acrylonitrile)-b-poly(acrylate)-b-poly(acrylonitrile) triblock. The degree of polymerization of the central block, resulting from the balance between propagation and coupling, could be tuned by adjusting the relative concentration and varying the structure of the acrylate and diene. The same convergent strategy also permits the synthesis of ABCBA-type pentablock copolymer starting from a cobalt-functional diblock. Simultaneous radical polymerization and coupling is thus a powerful macromolecular engineering approach for the straightforward design of symmetrical multiblock copolymers. [less ▲]

Detailed reference viewed: 3 (1 ULg)
Full Text
Peer Reviewed
See detailEffect of head-to-head addition in vinyl acetate controlled radical polymerization: why is Co(acac)2-mediated polymerization so much better?
Morin, Aurélie N.; Detrembleur, Christophe ULg; Jérôme, Christine ULg et al

in Macromolecules (2013), 46(11), 4303-4312

The controlled polymerization of vinyl acetate has been recently achieved by several techniques, but PVAc with targeted Mn and low dispersity up to very high monomer conversions and high degrees of ... [more ▼]

The controlled polymerization of vinyl acetate has been recently achieved by several techniques, but PVAc with targeted Mn and low dispersity up to very high monomer conversions and high degrees of polymerization was only obtained with Co(acac)2 as controlling agent in the so-called CMRP, a type of organometallic mediated radical polymerization (OMRP). Other techniques (including ATRP, ITP, TERP, and RAFT/MADIX) have shown a more or less pronounced slowdown in the polymerization kinetics, which was attributed to the higher strength of the C−X bond between the radical PVAc chain and the trapping agent (X) in the dormant species and to a consequent slower reactivation after a less frequent head-to-head monomer addition. The reason for the CMRP exception is clarified by the present contribution. First, a detailed investigation by 1H, 13C and multiplicity-edited HSQC and DEPT-135 NMR of the PVAc obtained by CMRP, in comparison with a regular polymer made by free radical polymerization under the same conditions, has revealed that Co(acac)2 does not significantly alter the fraction of head-to-head sequences in the polymer backbone and that there is no accumulation of Co(acac)2-capped chains with a head-to-head ω end. Hence, both dormant chains (following the head-to-head and the head-to-tail monomer additions) must be reactivated at similar rates. A DFT study shows that this is possible because the dormant chains are stabilized not only by the C−Co σ bond but also by formation of a chelate ring through coordination of the ω monomer carbonyl group. The head-to-head dormant chain contains an inherently stronger C−Co bond but forms a weaker 6-membered chelate ring, whereas the weaker C−Co bond in the head-to-tail dormant chain is compensated by a stronger 5-membered chelate ring. Combination of the two effects leads to similar activation enthalpies, as verified by DFT calculations using a variety of local, gradient-corrected, hybrid and “ad hoc” functionals (BPW91, B3PW91, BPW91*, M06 and M06L). While the BDE(C−X) of model H-VAc−X molecules [X = Cl, I, MeTe, EtOC(S)S and Co(acac)2] are functional dependent, the BDE difference between head-to-head and head-to-tail dormant chain models is almost functional insensitive, with values of 5−9 kcal/mol for the ATRP, ITP and TERP models, 3−6 for the RAFT/MADIX model, and around zero for CMRP. [less ▲]

Detailed reference viewed: 12 (7 ULg)
Full Text
Peer Reviewed
See detailThermally stable bulk heterojunction solar cells based on cross-linkable acrylate-functionalized polythiophene diblock copolymers
Ouhib, Farid ULg; Tomassetti, Mirco ULg; Manca, Jean et al

in Macromolecules (2013), 46(3), 785-795

We report on the synthesis of new thermally cross-linkable all-conjugated diblock copolymers composed of a poly(3-hexylthiophene) (P3HT) block and an acrylate-functionalized polythiophene block. These ... [more ▼]

We report on the synthesis of new thermally cross-linkable all-conjugated diblock copolymers composed of a poly(3-hexylthiophene) (P3HT) block and an acrylate-functionalized polythiophene block. These copolymers are then used in bulk heterojunction (BHJ) solar cells with [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and their photovoltaic performances are compared with standard P3HT/PCBM devices. Thermal cross-linking of the functional copolymers/PCBM blends is performed to improve the thermal stability of the active layer. BHJ photovoltaic cells with cross-linkable copolymers and PCBM show initial power conversion efficiencies slightly lower than that of P3HT devices. However, solar cells with cross-linkable copolymers retain more than 85% of their initial power efficiency value after 165 h of thermal annealing (accelerated aging test), whereas the same devices with P3HT retain less than 65% of their initial power efficiency. This improvement of the thermal stability of BHJ photovoltaic cells is the result of the polymer network that hampers PCBM diffusion and phase separation, as confirmed with TEM and AFM analysis of the microscopic morphology. Such an improvement is mostly observed when using a cross-linkable P3HT with a short spacer between the acrylate group and the polythiophene backbone. [less ▲]

Detailed reference viewed: 17 (1 ULg)
Full Text
Peer Reviewed
See detailThermally induced coupling of poly(thiophene)-based block copolymers prepared by Grignard metathesis polymerization: a straightforward route toward highly regioregular multiblock conjugated copolymers
Ouhib, Farid ULg; Desbief, Simon; Lazzaroni, Roberto et al

in Macromolecules (2012), 45(17), 6796-6806

We report on a convenient and simple process to prepare highly regioregular poly(thiophene)-based multiblock copolymers by a novel thermally induced coupling reaction. Diblock copolymers of 3 ... [more ▼]

We report on a convenient and simple process to prepare highly regioregular poly(thiophene)-based multiblock copolymers by a novel thermally induced coupling reaction. Diblock copolymers of 3-hexylthiophene (3HT) and 2,5-dibromo-3-(2-(2-tetrahydropyranyl-2-oxy)ethyl)thiophene (THPET) end-capped by a nickel complex (Br-P3HT-b-PTHPET-Ni(dppp)Br) are first prepared using Ni(dppp)Cl2 as catalyst at 30 °C by Grignard metathesis polymerization (GRIM process). The coupling of these α-bromo, ω-Ni(dppp)Br telechelic diblock copolymers then occurs by heating the solution of the copolymer at 80 °C for a few hours without adding any additional reagent. Reactions are complete in only 10 min when heating the copolymer at 120 °C using microwaves. The deprotection of the alcohol groups of PTHPET blocks allows further modifications such as the incorporation of acrylates by esterification. AFM analysis on thin films shows the influence of the nature of side chains (protected alcohol or acrylate), the molecular weight, and the architecture (diblock or multiblock) of the copolymer on the supramolecular organization of the polythiophene chains. [less ▲]

Detailed reference viewed: 35 (6 ULg)
Full Text
Peer Reviewed
See detailMetal-free strategies for the synthesis of functional and well-defined polyphosphoesters
Clement, Benoît ULg; Grignard, Bruno ULg; Koole, Leo et al

in Macromolecules (2012), 45(11), 4476-4486

We report here metal-free strategies using organocatalysis based on supramolecular recognition for the ring-opening polymerization (ROP) of several cyclic phosphate monomers (CPMs) by a variety of ... [more ▼]

We report here metal-free strategies using organocatalysis based on supramolecular recognition for the ring-opening polymerization (ROP) of several cyclic phosphate monomers (CPMs) by a variety of organocatalysts such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazabicyclo[4.4.0]undec-5-ene (TBD), and a bicomponent thiourea−tertiary amine catalyst. Each of these catalysts is efficient to produce linear polyphosphoesters (PPEs) from CPMs but with different sensitivity toward transesterification side reactions. The strong basicity of DBU is sufficient to activate an alcohol initiating the polymerization in the absence of any other cocatalyst. Nevertheless, side chain transfer reactions leading to branched and/or cyclic polymeric structures are observed, especially for high monomer conversion. Unlike DBU, TBD is a dual catalyst activating both the alcohol and the monomer. This dual activation allows shorter polymerization time, but SEC analyses of polyphosphates reveal bimodal molecular weight distribution due to chains coupling. Finally, a mixture of DBU and thiourea (TU) appears by far the most efficient catalyst to carry out fast and controlled polymerization while minimizing transesterification reactions, even at near-complete conversion. Compared with polymerizations carried out with Sn(Oct)2 as a metal catalyst, the control of polymerization is much better so that it is possible to prepare polyphosphoesters (PPEs) with molecular weight close to 70 000 g mol−1 and polydispersity index below 1.10. Simultaneous activation by TU of both CPMs and the alcohol group of the initiator by DBU proves to be an effective and robust ROP catalytic system to synthesize polymers with predictable molecular weight and narrow polydispersity. The chain extension experiments through the use of hydroxy end- capped PPEs as macroinitiators confirm the controlled/living nature of the DBU/TU-catalyzed ROP of CPMs and pave the way to the synthesis of block copolymers based on polyphosphates. [less ▲]

Detailed reference viewed: 69 (23 ULg)
Full Text
Peer Reviewed
See detailSynthesis of 1-vinyl-3-ethylimidazolium-based ionic liquid (co)polymers by cobalt-mediated radical polymerization
Detrembleur, Christophe ULg; Debuigne, Antoine ULg; Hurtgen, Marie ULg et al

in Macromolecules (2011), 44(16), 6397-6404

The cobalt-mediated radical polymerization (CMRP) of 1-vinyl-3-ethylimidazolium bromide (VEtImBr) is described. Polymerizations were performed at 30 °C in solution either in dimethylformamide (DMF) or in ... [more ▼]

The cobalt-mediated radical polymerization (CMRP) of 1-vinyl-3-ethylimidazolium bromide (VEtImBr) is described. Polymerizations were performed at 30 °C in solution either in dimethylformamide (DMF) or in methanol (MeOH) or in a mixture of both solvents, using a preformed alkyl–cobalt(III) adduct, CH3OC(CH3)2CH2–C(CH3)(CN)–(CH2–CHOAc)<4–Co(acac)2, as the mediating agent. Excellent control over molecular weights and dispersities (Mw/Mn 1.05–1.06) was achieved in MeOH, with a linear increase of experimental molecular weights with the monomer conversion. Substituting methanol for DMF induced much faster polymerization process, even under quite high diluted conditions: for instance, about 80% monomer conversion was reached in 30 min in DMF, compared to 10 h in MeOH. However, size exclusion chromatography (SEC) traces of PVEtImBr samples synthesized in DMF revealed a side population in the high molecular weight region, presumably due to the occurrence of irreversible coupling reactions of a small proportion of growing chains. Well-defined diblock copolymers featuring both a poly(vinyl acetate) (PVAc) block and a PVEtImBr-based poly(ionic liquid) block, PVAc-b-PVEtImBr, were next obtained by sequential CMRP of VAc and VEtImBr. To this end, a PVAc-Co(acac)2 was first prepared by CMRP and employed as a macroinitiator for the polymerization of VEtImBr either in methanol or in a mixture of DMF and MeOH (2/1: v/v) at 30 °C. Finally, cobalt-mediated radical coupling (CMRC) of the aforementioned PVAc-b-PVEtImBr diblock copolymers, using isoprene as a simple coupling agent, led to unprecedented and structurally well-defined PVAc-b-PVEtImBr-b-PVAc triblock copolymers. [less ▲]

Detailed reference viewed: 83 (17 ULg)
Full Text
Peer Reviewed
See detailSynthesis and thermal properties of linear amphiphilic diblock copolymers of L-lactide and 2-dimethylaminoethyl methacrylate
Kryuchkov, Maksym A.; Detrembleur, Christophe ULg; Jérôme, Robert ULg et al

in Macromolecules (2011), 44(13), 5209-5217

A well-defined series of nine poly(l-lactide)-b-(2-dimethylaminoethyl methacrylate) (PLLA-b-PDMAEMA) linear diblock copolymers with low polydispersity were prepared by ring-opening polymerization of LLA ... [more ▼]

A well-defined series of nine poly(l-lactide)-b-(2-dimethylaminoethyl methacrylate) (PLLA-b-PDMAEMA) linear diblock copolymers with low polydispersity were prepared by ring-opening polymerization of LLA using 4-isopropylbenzyl alcohol and tin octoate as the initiating system, conversion of the OH-terminated PLLA into Br-terminated macroinitiators (5, 13, and 19 kg/mol), followed by atom transfer radical polymerization of DMAEMA (to obtain one-half, equal, and twice the molecular weight of each PLLA block). Compositional analysis and molecular weight characterization were done using NMR, SEC–LS, TGA, polarimetry, and PDMAEMA quaternization/precipitation to test for residual PLLA homopolymer. DSC investigations indicate that low molecular weight amorphous PLLA or PDMAEMA blocks (less than or equal to ca. 5000 g/mol) are miscible in the second block. Compared to the parent PLLA homopolymers, PLLA crystallization in the block copolymers is significantly retarded, whereas the degree of crystallinity is only mildly affected and melting points are reduced only for the low molecular weight miscible blocks. [less ▲]

Detailed reference viewed: 31 (1 ULg)
Full Text
Peer Reviewed
See detailOrganometallic-mediated radical polymerization: unusual route toward (quasi-) diblock graft copolymers starting from a mixture of monomers of opposed reactivity
Hurtgen, Marie ULg; Debuigne, Antoine ULg; Fustin, Charles-André et al

in Macromolecules (2011), 44(12), 4623-4631

Graft copolymers have been prepared by one-step organometallic-mediated radical polymerization (OMRP) for the first time. Poly(ethylene glycol) acrylate (PEGA) was copolymerized with vinyl acetate (VAc ... [more ▼]

Graft copolymers have been prepared by one-step organometallic-mediated radical polymerization (OMRP) for the first time. Poly(ethylene glycol) acrylate (PEGA) was copolymerized with vinyl acetate (VAc) to yield well-defined P(PEGA-grad-VAc) gradient graft copolymers using bis(acetylacetonato)cobalt(II) as the control agent. The influence of experimental parameters such as the PEGA/VAc molar ratio, the nature of the initiator, and the temperature on the control of the copolymerization was discussed. The use of an excess of cobalt complex appeared as a key parameter to maintain a good level of control when higher contents of acrylate were used in the comonomer feed. The reactivity ratios were estimated and revealed that PEGA was added around 30 times faster than VAc, which gave access to a gradient P(PEGA-grad-VAc) copolymer or to a P(PEGA-grad-VAc)-b-PVAc diblock copolymer when the VAc polymerization was pursued after the full consumption of PEGA. The amphiphilic character of the copolymers makes them prone to self-assemble into micelles in water, as evidenced by dynamic light scattering. [less ▲]

Detailed reference viewed: 46 (12 ULg)
Full Text
Peer Reviewed
See detailEffective cobalt-mediated radical coupling (CMRC) of poly(vinylacetate) and poly(N-vinylpyrrolidone) (co)polymer precursors
Debuigne, Antoine ULg; Poli, Rinaldo; De Winter, Julien et al

in Macromolecules (2010), 43(6), 2801-2813

Cobalt-mediated radical coupling (CMRC) is successfully applied to poly(vinyl acetate) (PVAc) and poly(N-vinylpyrrolidone) (PNVP) precursors for the first time. The coupling process is based on addition ... [more ▼]

Cobalt-mediated radical coupling (CMRC) is successfully applied to poly(vinyl acetate) (PVAc) and poly(N-vinylpyrrolidone) (PNVP) precursors for the first time. The coupling process is based on addition of isoprene onto polymer chains preformed by controlled radical polymerization with cobalt complexes (CMRP). The extents of coupling were high (>90%) to moderate (75-80%) for PVAc and PNVP precursors, respectively. Effects of the length of the polymer precursors and conditions used in the polymerization step on the coupling efficiency are discussed. Mass spectrometry (MS) and nuclear magnetic resonance (NMR) analyses conducted on the coupling products demonstrate the preferential insertion of two isoprene units in the final polymers. The CMRC mechanistic proposal, supported by DFT calculations, is based on this microstructure feature. Finally, illustration of the macromolecular engineering potential of this technique is given by the preparation of symmetrical PVAc-b-PNVP-b-PVAc triblock copolymers starting from the corresponding PVAc-b-PNVP-[Co] diblock copolymer. [less ▲]

Detailed reference viewed: 49 (18 ULg)
Full Text
Peer Reviewed
See detailSolving the problem of bis(acetylacetonato)cobalt(II)-mediated radical polymerization (CMRP) of acrylic esters
Hurtgen, Marie ULg; Debuigne, Antoine ULg; Jérôme, Christine ULg et al

in Macromolecules (2010), 43(2), 886-894

Recent developments in cobalt-mediated radical polymerization (CMRP) and progress in the mechanistic understanding enabled to optimize the copolymerization of n-butyl acrylate (nBA) with vinyl acetate ... [more ▼]

Recent developments in cobalt-mediated radical polymerization (CMRP) and progress in the mechanistic understanding enabled to optimize the copolymerization of n-butyl acrylate (nBA) with vinyl acetate (VAc), as well as to control the homopolymerization of nBA by means of bis(acetylacetonato)cobalt-(II) (Co(acac)2). Critical experimental parameters such as the initiating system, the temperature, and the presence of additives were varied and discussed. Under optimized conditions, an alkylcobalt(III) adduct R0-(CH2-CHOAc)<4-Co(acac)2 (R0=primary radical from the V-70 decomposition) allowed a better control of the nBA/VAc copolymerization than the previously studied V-70/Co(acac)2 pair regarding the molecular weight control and the polydispersities. Importantly, the homopolymerization of nBA was controlled by Co(acac)2 for the first time using the alkylcobalt(III) adduct or the lauroyl peroxide (LPO)/ Co(acac)2 redox pair as initiating system. Typically, poly(n-butyl acrylate) with polydispersity around 1.2 and molar mass as high as 200 000 g/mol was achieved with this cobalt complex. [less ▲]

Detailed reference viewed: 66 (27 ULg)
Full Text
Peer Reviewed
See detailDispersion Atom Transfer Radical Polymerization of vinyl monomers in supercritical carbon dioxide
Grignard, Bruno ULg; Jérôme, Christine ULg; Calberg, Cédric ULg et al

in Macromolecules (2008), 41(22), 8575-8563

Controlled dispersion atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was successfully carried out in supercritical carbon dioxide in the presence of aminated fluoropolymers ... [more ▼]

Controlled dispersion atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was successfully carried out in supercritical carbon dioxide in the presence of aminated fluoropolymers. These materials played the dual role of macroligand for the copper bromide and also steric stabilizer to support formation of polymer microspheres. The livingness of the PMMA beads was confirmed by the one-pot two-step PMMA chain extension and the synthesis of poly(methyl methacrylate)-b-poly(2,2,2-trifluoroethyl methacrylate) (PMMA-b-PFMA) diblock copolymer in scCO2. Successful activator generated by electron transfer (AGET) for ATRP of MMA, using tin ethylhexanoate as a reducing agent, is also discussed, and the concept of dispersion ATRP of MMA was successfully extended to the controlled dispersion polymerization of styrene by ATRP leading to the formation of PS microparticles. Finally, due to the high solubility of the catalyst in scCO2, the purification of PMMA was investigated by supercritical fluid extraction, leading to the preparation of PMMA beads with low residual catalyst traces. [less ▲]

Detailed reference viewed: 51 (8 ULg)
Full Text
Peer Reviewed
See detailSynthesis of highly functionalized poly(alkyl cyanoacrylate) nanoparticles by means of click chemistry
Nicolas, Julien; Bensaid, Fehti; Desmaële, Didier et al

in Macromolecules (2008), 41(22), 8418-8428

A general methodology was proposed to prepare highly functionalized poly(alkyl cyanoacrylate) nanoparticles by means of Huisgen 1,3-dipolar cyclo-addition, the so-called click chemistry. To achieve this ... [more ▼]

A general methodology was proposed to prepare highly functionalized poly(alkyl cyanoacrylate) nanoparticles by means of Huisgen 1,3-dipolar cyclo-addition, the so-called click chemistry. To achieve this goal, different protocols were investigated to obtain azidopoly(ethylene glycol) cyanoacetate of variable molar mass, followed by a Knoevenagel condensation−Michael addition reaction with hexadecyl cyanoacetate to produce a poly[(hexadecyl cyanoacrylate)-co-azidopoly(ethylene glycol) cyanoacrylate] (P(HDCA-co-N3PEGCA)) copolymer, displaying azide functionalities at the extremity of the PEG chains. As a proof of concept, model alkynes were quantitatively coupled either to the P(HDCA-co-N3PEGCA) copolymers in homogeneous medium followed by self-assembly in aqueous solution or directly at the surface of the preformed P(HDCA-co-N3PEGCA) nanoparticles in aqueous dispersed medium, both yielding highly functionalized nanoparticles. This versatile approach, using alkyl cyanoacrylate derivatives, opened the door to ligand-functionalized and biodegradable nanoparticles with “stealth” properties for biomedical applications. [less ▲]

Detailed reference viewed: 79 (10 ULg)
Full Text
Peer Reviewed
See detailAmphiphilic poly(ethylene oxide) macromolecular RAFT agent as a stabilizer and control agent in ab Initio batch emulsion polymerization
Rieger, Jutta ULg; Stoffelbach, François; Bui, Chuong et al

in Macromolecules (2008), 41(12), 4065-4068

Detailed reference viewed: 67 (13 ULg)
Full Text
Peer Reviewed
See detailSynthesis of novel well-defined poly(vinyl acetate)-b-poly(acrylonitrile) and derivatized water-soluble poly(vinyl alcohol)-b-poly(acrylic acid) block copolymers by cobalt-mediated radical polymerization
Debuigne, Antoine ULg; Warnant, Jérôme; Jérôme, Robert ULg et al

in Macromolecules (2008), 41(7), 2353-2360

Poly(vinyl acetate)−Co(acac)2 macroinitiators, prepared by cobalt-mediated radical polymerization of vinyl acetate (VAc), were used to synthesize well-defined poly(vinyl acetate)-b-poly(acrylonitrile ... [more ▼]

Poly(vinyl acetate)−Co(acac)2 macroinitiators, prepared by cobalt-mediated radical polymerization of vinyl acetate (VAc), were used to synthesize well-defined poly(vinyl acetate)-b-poly(acrylonitrile) (PVAc-b-PAN) block copolymers. Different solvents and temperatures were tested for the polymerization of the acrylonitrile segment by cobalt-mediated radical polymerization (CMRP), and copolymers with low polydispersity were obtained provided that dimethylformamide was used as solvent at 0 °C. The mechanism of control was assumed to change from a degenerative chain transfer mechanism for the VAc polymerization to a reversible-termination process for the AN polymerization. The hydrolysis of the ester groups of the PVAc block and the nitrile groups of the PAN sequence of the copolymer by potassium hydroxide in an ethanol/water mixture provided the double hydrophilic and pH-responsive poly(vinyl alcohol)-b-poly(acrylic acid) block copolymer. Finally, the pH responsiveness of these copolymers was demonstrated by DLS pH titration with formation of aggregates at pH < 3. [less ▲]

Detailed reference viewed: 32 (7 ULg)
Full Text
Peer Reviewed
See detailAmphiphilic sun-shaped polymers by grafting macrocyclic copolyesters with PEO
Li, Haiying; Jérôme, Robert ULg; Lecomte, Philippe ULg

in Macromolecules (2008), 41(3), 650-654

An amphiphilic sun-shaped copolymer was successfully prepared by esterification of carboxylic acid terminated PEO with the pendent hydroxyl groups of high molecular weight (M-n = 28 000) cyclic PCL. The ... [more ▼]

An amphiphilic sun-shaped copolymer was successfully prepared by esterification of carboxylic acid terminated PEO with the pendent hydroxyl groups of high molecular weight (M-n = 28 000) cyclic PCL. The cyclic structure of the copolyester originally resulted from the polymerization initiation by a cyclic tin dialkoxide and was ultimately stabilized by the intramolecular cross-linking of a few unsaturated groups. [less ▲]

Detailed reference viewed: 25 (12 ULg)
Full Text
Peer Reviewed
See detailAmphiphilic poly(vinyl acetate)-b-poly(N-vinylpyrrolidone) and novel double hydrophilic poly(vinyl alcohol)-b-poly(N-vinylpyrrolidone) block copolymers prepared by cobalt-mediated radical polymerization
Debuigne, Antoine ULg; Willet, Nicolas ULg; Jérôme, Robert ULg et al

in Macromolecules (2007), 40(20), 7111-7118

Well-defined amphiphilic block copolymers of poly(vinyl acetate) (PVAc) and poly(N-vinylpyrrolidone) (PNVP) were synthesized by cobalt-mediated radical polymerization (CMRP). The NVP polymerization ... [more ▼]

Well-defined amphiphilic block copolymers of poly(vinyl acetate) (PVAc) and poly(N-vinylpyrrolidone) (PNVP) were synthesized by cobalt-mediated radical polymerization (CMRP). The NVP polymerization initiated by poly(vinyl acetate) end-capped by the cobalt(II)acetylacetonate complex met the criteria of controlled polymerization, i.e., first-order kinetic in NVP, increase of the molar mass with the NVP conversion, and narrow molar mass distribution. Therefore, the length of the two blocks can be tuned by the [VAc]/[Co(acac)(2)] and the [NVP]/[PVAc] ratios for the synthesis of the macroinitiator and the polymerization of the second monomer, respectively. These amphiphilic PVAc-b-PNVP block copolymers were easily converted into the double hydrophilic PVOH-b-PNVP counterparts by selective methanolysis of the PVAc block. These two types of copolymers were prone to self-association into micelles in appropriate solvents. [less ▲]

Detailed reference viewed: 32 (5 ULg)
Full Text
Peer Reviewed
See detailSynthesis and evaluation of sterically hindered 1,1-diamantyl nitroxide as a low-temperature mediator for the stable free radical polymerization process
Debuigne, Antoine ULg; Chan-Seng, Delphine; Li, Lichun et al

in Macromolecules (2007), 40(17), 6224-6232

An efficient procedure for the oxidation of 1,1-diadamantylamine with m-chloroperbenzoic acid (m-CPBA) to the corresponding sterically hindered nitroxide in high yield (72%) is reported. The corresponding ... [more ▼]

An efficient procedure for the oxidation of 1,1-diadamantylamine with m-chloroperbenzoic acid (m-CPBA) to the corresponding sterically hindered nitroxide in high yield (72%) is reported. The corresponding styrene-based alkoxyamine was synthesized by an atom transfer radical addition (ATRA) reaction. Because of the bulkiness of the adamantyl substituents, the cleavage of the C−ON bond of the alkoxyamine occurred readily at temperatures below 100 °C. However, in spite of the low bond dissociation temperature of the alkoxyamine, the (co)polymerizations of styrene and n-butyl acrylate proceeded poorly. The results in this paper support the argument that the most important determinant in a nitroxide-mediated polymerization of styrene and acrylate is the ability to control the excess concentration of nitroxide in solution either by an inherent instability of the nitroxide or by the use of additives that destroy the excess nitroxide. Thus, for the 1,1-diadamantyl nitroxide case, and maybe more generally, while a lower C−O bond dissociation energy of an alkoxyamine moiety at the end of the chain may allow lower polymerization temperatures and faster reactions rates, it does not enable polymerizations to proceed to high conversions if the excess nitroxide is not controlled in some manner. [less ▲]

Detailed reference viewed: 12 (2 ULg)
Full Text
Peer Reviewed
See detailStructure and properties of a semifluorinated diblock copolymer modified epoxy blend
Ocando, Connie; Serrano, Elena; Tercjak, Agnieszka et al

in Macromolecules (2007), 40(11), 4068-4074

Novel nanostructured thermosetting materials have been prepared by modification of an epoxy resin with a semifluorinated diblock copolymer, poly(heptadecafluorodecyl acrylate)-b-poly(caprolactone), PaF-b ... [more ▼]

Novel nanostructured thermosetting materials have been prepared by modification of an epoxy resin with a semifluorinated diblock copolymer, poly(heptadecafluorodecyl acrylate)-b-poly(caprolactone), PaF-b-PCL. In a first step, the phase behavior and linear viscoelasticity of PaF-b-PCL were investigated. According to the segregation regime, no order-order transitions were detected, being the order-disorder transition temperature beyond the degradation temperature. Atomic force microscopy (AFM) images of the block copolymer after different thermal treatments revealed that self-assembly takes place into spherical nanodomains, which is consistent with the copolymer composition. This block copolymer was further used to prepare a nanostructured thermoset blend with an epoxy resin. DSC and DMA analysis reveals microphase separation of PaF block from the epoxy-rich phase after curing. The PaF block self-assembled into wormlike and spherical micelles in the thermoset system. This nanostructured blend presented unique surface properties showing high hydrophobicity (upsilon = 109 degrees) and low surface energy (17 mN/m). [less ▲]

Detailed reference viewed: 38 (5 ULg)