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See detailClimbing back up the nucleophilic reactivity scale. Use of cyclosila derivatives as reactivity boosters in anionic polymerization
Zundel, Thomas; Baran, Janusz; Mazurek, Mieczyslaw et al

in Macromolecules (1998), 31(9), 2724-2730

It has been well-known for a very long time that, for anionic homo-polymerization or sequential copolymerization to occur, it is mandatory that the relative nucleophilic reactivity of the initiating ... [more ▼]

It has been well-known for a very long time that, for anionic homo-polymerization or sequential copolymerization to occur, it is mandatory that the relative nucleophilic reactivity of the initiating species be equal to or larger than the one of the (co)monomer. However, the results described in this paper demonstrate that such a classic rule can be circumvented in some cases. Indeed, it is reported for the first time that potassium trimethylsilanolate, and “living” potassium poly(ethylene oxide), both of which are unable to initiate styrene or methyl methacrylate (MMA) polymerization, can be converted from oxyanionic active ends to silyl anionic ones by reacting with cyclic disila derivatives, so allowing the homopolymerization and sequential (co)polymerization of styrene or MMA to proceed in a controlled manner. [less ▲]

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See detailStudy of the propagation center in the anionic polymerization of (meth)acrylic monomers: NMR and MNDO study of the complexes of Di-tert-butyl 2-lithio-2,4,4-trimethylglutarate and of the living poly(tert-butyl methacrylate) oligomers with lithium chloride
Zune, Catherine; Dubois, Philippe ULg; Jérôme, Robert ULg et al

in Macromolecules (1998), 31(9), 2744-2755

Interactions of living oligomers of tert-butyl methacrylate (tBuMA) with a Li counterion and of the model living dimer di-tert-butyl 2-lithio-2,4,4-trimethylglutarate (A) with LiCl (B) were studied in ... [more ▼]

Interactions of living oligomers of tert-butyl methacrylate (tBuMA) with a Li counterion and of the model living dimer di-tert-butyl 2-lithio-2,4,4-trimethylglutarate (A) with LiCl (B) were studied in tetrahydrofuran-d8 (THF-d8) solution by 7Li, 6Li, 1H, and 13C, 1D and 2D, NMR spectroscopy. Di-tert-butyl 2-lithio-2,4,4-trimethylglutarate is shown to form a 1:1 complex with lithium chloride in THF. 1H, 7Li NMR results suggest that a rapid equilibrium between free LiCl and the mixed complex takes place when the molar ratio LiCl:lithiated dimer is higher than 1. From 13C relaxation times, a dimeric aggregation (i.e. A2B2) of the complex is deduced, in full accord with MNDO calculations. Preliminary results are presented for living tBuMA oligomers prepared by initiation with diphenylhexyllithium in the presence of various amounts of lithium chloride. Fast-acquired 13C NMR spectra of the living ends were recorded using 13C-enriched monomer added at the end of the polymerization. Their structure is shown to be affected by the amount of LiCl added and to correspond to an equilibrium between free lithium chloride and a complexed end group. A higher excess of LiCl apparently does not change the nature of the complexed living end. The oligomers exhibit marked self-termination in THF at 273 K. Finally, a correlation of the structure of the living chain ends with the macromolecular parameters of the resulting polymer is attempted. [less ▲]

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See detailStudy of the propagation center in the anionic polymerization of (meth)acrylic monomers: NMR and MO LCAO study of the interaction of Di-tert-butyl 2-lithio-2,4,4-trimethylglutarate and the living poly(tert-butyl methacrylate) oligomers with lithium 2-(2-methoxyethoxy)ethoxide in tetrahydrofuran
Zune, Catherine; Dubois, Philippe ULg; Jérôme, Robert ULg et al

in Macromolecules (1998), 31(9), 2731-2743

Interactions of lithium 2-(2-methoxyethoxy)ethoxide (LiOEEM) with the model dimer di-tert-butyl 2-lithio-2,4,4-trimethylglutarate (A) and the living poly(tert-butyl methacrylate) oligomers (B) were ... [more ▼]

Interactions of lithium 2-(2-methoxyethoxy)ethoxide (LiOEEM) with the model dimer di-tert-butyl 2-lithio-2,4,4-trimethylglutarate (A) and the living poly(tert-butyl methacrylate) oligomers (B) were studied in tetrahydrofuran-d8 at 203−273 K using 1H, 13C, 7Li, and 6Li, 1D and 2D, NMR and ab initio SCF 3-21G and MNDO quantum chemical calculations. LiOEEM is shown to have a strong tendency to self-aggregation, producing dimeric, trimeric, and tetrameric aggregates and competing with its mixed aggregation (or complexation) with A and, in particular, B. When dissolved in THF, LiOEEM as well as its mixtures with A form metastable systems which relax in several days at 258 K into equilibrium. Interaction of LiOEEM with A leads to a system of mixed aggregates LiOEEM1A1, LiOEEM3A1, and possibly LiOEEM2A1 along with the original components, in relative populations depending on the LiOEEM/A molar ratio, temperature, time, and probably other factors of preparation. Probable structures of these complexes are proposed, and the nature of the prevalent bonding is suggested. Experimental results indicate that LiOEEM is unable to convert A completely at moderate excess (up to 4/1 mol/mol). Interaction of LiOEEM with B leads to quite analogous complexes but with even lower yields. There appear to be traces of uncomplexed B even at the LiOEEM/B ratio of 10 mol/mol. This is suggested to produce at least two different kinds of active growth centers in the corresponding ligated anionic polymerization of tert-butyl methacrylate and, consequently, the observed bimodality of the polymeric product. The difference with respect to methyl methacrylate, where LiOEEM ensures an almost ideal living polymerization, is suggested to be due to the steric hindrance of efficient complexation exerted by the tert-butyl group. [less ▲]

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See detailNew ligands for the living isotactic anionic polymerization of methyl methacrylate in toluene at 0°C. 1. Ligation of butyllithium by lithium silanolates
Zundel, Thomas; Teyssié, Philippe; Jérôme, Robert ULg

in Macromolecules (1998), 31(8), 2433-2439

sBuLi and tBuLi have been combined with a new family of ligands, i.e. lithium silanolates, and used as initiators for the ligated anionic polymerization (LAP) of methyl methacrylate (MMA) in toluene at 0 ... [more ▼]

sBuLi and tBuLi have been combined with a new family of ligands, i.e. lithium silanolates, and used as initiators for the ligated anionic polymerization (LAP) of methyl methacrylate (MMA) in toluene at 0 °C. Compared to other known μ-ligands, the accordingly formed Bu(Me2)SiOLi are more efficient stabilizers for the active centers. Under appropriate reaction conditions, a fast polymerization proceeds quantitatively without self-termination at 0 °C and leads to high molecular weight polymer of narrow molecular weight distribution (Mw/Mn < 1.2) and high isotacticity (90% isotactic triads). [less ▲]

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See detailDynamics of poly((dimethylamino)alkyl methacrylate-block-sodium metha-crylate) micelles. Influence of hydrophobicity and molecular architecture on the exchange rate of copolymer molecules
Creutz, Serge; Van Stam, Jan; De Schrijver, Frans C et al

in Macromolecules (1998), 31(3), 681-689

The dynamic stability of the micellar aggregates formed by amphiphilic block copolymers, i.e., poly((dimethylamino)alkyl methacrylate-b-sodium methacrylate), has been investigated by steady-state ... [more ▼]

The dynamic stability of the micellar aggregates formed by amphiphilic block copolymers, i.e., poly((dimethylamino)alkyl methacrylate-b-sodium methacrylate), has been investigated by steady-state fluorescence spectroscopy and size exclusion chromatography. The dynamics of exchange of block copolymer molecules between the micelles, formed in aqueous solution, depend on a manifold of factors, e.g., alkyl substituent in the hydrophobic block, the relation between the hydrophobic and hydrophilic blocks, and the architecture of the block copolymer. All copolymers investigated show a slow unimer exchange with an exchange rate constant on the order of 10-3 s-1, with a difference of a factor of 20 between the fastest and the slowest exchange. It is possible to tune the exchange rate in a controlled way; for instance, an extension or branching of the alkyl chain slows down the exchange rate. The same effect is observed when the hydrophobic/hydrophilic balance of these copolymers is increased or when either the hydrophilic or the hydrophobic moiety of diblocks is divided into two external blocks, leading to a triblock copolymer. [less ▲]

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See detailPoly(2-oxepane-1,5-dione) : a highly crystalline modified poly (epsilon-caprolactone) of a high melting temperature
Tian, Dong; Halleux, Olivier; Dubois, Philippe ULg et al

in Macromolecules (1998), 31(3), 924-927

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See detailControlled radical polymerization of methyl methacrylate initiated by an alkyl halide in the presence of the Wilkinson catalyst
Moineau, Georges; Granel, Claude; Dubois, Philippe ULg et al

in Macromolecules (1998), 31(2), 542-544

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See detailDual living free radical and ring opening polymerizations from a double-headed initiator
Hawker, Craig J; Hedrick, James L; Malmström, Eva E et al

in Macromolecules (1998), 31(2), 213-219

The concept of performing dual living polymerizations from a single initiating molecule with no intermediate activation, or transformation, steps is presented. The compatibility of “living”, or controlled ... [more ▼]

The concept of performing dual living polymerizations from a single initiating molecule with no intermediate activation, or transformation, steps is presented. The compatibility of “living”, or controlled free radical procedures, either nitroxide mediated or atom transfer radical polymerization (ATRP), with the living ring opening polymerization of ε-caprolactone, and vice versa, is demonstrated by the synthesis of a variety of well-defined block copolymers. For example, from a hydroxy-functionalized alkoxyamine, either the living ring opening polymerization of ε-caprolactone, or the “living” free radical polymerization of styrene can be performed leading to narrow polydispersity polymeric initiators. These polymeric initiators can then be used to initiate the living polymerization of the other monomer system without the need for intermediate steps. In a similar way, hydroxy-functionalized ATRP initiators can be used as bifunctional initiators for the polymerization of both ε-caprolactone and a variety of other vinyl monomers. The novel block copolymers that are obtained were shown to have low polydispersities and controllable molecular weights for both of the blocks. [less ▲]

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See detailShear-induced order in aqueous micellar solutions of amphiphilic poly(tert-butylstyrene)-b-poly(Na methacrylate) diblock
Leyh, Bernard ULg; Creutz, S.; Gaspard, J. P. et al

in Macromolecules (1998), 31(26), 9258-9264

Shear-induced order of aqueous micellar solutions of a poly(tert-butylstyrene)-b-poly(sodium methacrylate) diblock (c ) 2.5-15 w/v %) has been investigated by small-angle X-ray scattering. Data collected ... [more ▼]

Shear-induced order of aqueous micellar solutions of a poly(tert-butylstyrene)-b-poly(sodium methacrylate) diblock (c ) 2.5-15 w/v %) has been investigated by small-angle X-ray scattering. Data collected from a Couette cell in both radial and tangential geometries agree with a crystalline ordering of micelles in close packed hexagonal layers perpendicular to the velocity gradient, when c is in the 5-10 w/v % range. The measured interlayer distance is indeed very close to the value expected for a closepacked structure. The experimental data are consistent with a zigzag motion of adjacent planes upon shear. Shear-induced order is, however, restricted to a narrow concentration range just above the concentration for the sol-gel transition. This domain is thought to correspond to a regime where relative layer translation modes are allowed whereas mutual rotation is hindered. [less ▲]

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See detailVersatile and controlled synthesis of star and branched macromolecules by dentritic initiation
Trollsas, Michaël; Hedrick, James L.; Mecerreyes, David et al

in Macromolecules (1997), 30(26), 8508-8511

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See detailSynergism for the improvement of tensile strength in block copolymers of polystyrene and poly(n-butyl methacrylate)
Weidisch, R.; Michler, G. H.; Arnold, M. et al

in Macromolecules (1997), 30(25), 8078-8080

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See detailSmall-angle neutron scattering studies of low polarity telechelic ionomer solutions. 2. Single chain scattering
Karayianni, Eleni; Jérôme, Robert ULg; Cooper, Stuart L

in Macromolecules (1997), 30(24), 7444-7455

A direct probe of the single chain conformation in associating low polarity model telechelic ionomer solutions has been obtained using small-angle neutron scattering. A contrast matching technique was ... [more ▼]

A direct probe of the single chain conformation in associating low polarity model telechelic ionomer solutions has been obtained using small-angle neutron scattering. A contrast matching technique was employed utilizing a solution of hydrogenated and deuterated ionomer chains in a mixture of labeled and unlabeled solvent molecules. The scattering data at all concentrations and ionic levels examined show an excellent fit to the wormlike chain model. Single chain scattering patterns were obtained for two sodium-neutralized carboxy−telechelic polystyrene ionomers that differ by a factor of 2 in their molecular weight, in a concentration range from the dilute to the concentrated solution regime. The single chain dimensions were found to be influenced by both the ionic interactions and the extent of association. Both ionomer systems showed a contraction of the chain dimensions in the dilute solution regime which is more pronounced for the lower molecular weight telechelic ionomer. As concentration increases, the single chain dimensions increase until they reach a plateau value in the concentrated solution regime. This plateau value is very close to the chain dimensions of the ionomer in the bulk, as was found from a previous SANS study on similar ionomer systems. This plateau value chain dimension is also the same as the unperturbed dimension of the nonionic parent polymer in the bulk. The effect of concentration on the ionomer chain dimensions is attributed to the influence of ionic interactions as the nonionic form of the material shows larger chain dimensions in the concentration regime studied. These results indicate that intramolecular interactions with the formation of self loops prevail in the dilute solution regime. Intermolecular interactions with ionic groups connecting to different chains prevail in the concentrated solution regime, as evidenced by an extension of the chain dimensions. [less ▲]

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See detailDifunctional anionic initiator based on 1.3-diisopropenylbenzene. 5. Effect of polar additives and initiator seeding on the synthesis of poly(styrene-b-butadiene-b-styrene) copolymer
Yu, Y. S.; Dubois, Philippe ULg; Teyssié, Philippe et al

in Macromolecules (1997), 30(24), 7356-7362

The initiation of butadiene and styrene polymerization by a pure hydrocarbon soluble difunctional organolithium, 1,3-bis(1-lithio-1,3,3‘-trimethylbutyl)benzene, has been studied in a hydrocarbon solvent ... [more ▼]

The initiation of butadiene and styrene polymerization by a pure hydrocarbon soluble difunctional organolithium, 1,3-bis(1-lithio-1,3,3‘-trimethylbutyl)benzene, has been studied in a hydrocarbon solvent. The initiation occurs in such a way that part of the diadduct remains unreacted. When a second monomer feed along with tetrahydrofuran (THF) is added to the living chains, the residual diadduct is activated to the point where novel chains are formed. Weakly polar additives such as lithium alkoxides and aromatic ether can prevent part of the initiator from being inactive, although these additives are not effective enough to initiate the controlled synthesis of poly(styrene-b-butadiene-b-styrene) (SBS) triblock copolymers. The seeding of the initiator which consists of butadiene oligomerization in the presence of anisole and tBuOLi in cyclohexane, has proved to be very efficient in providing SBS containing 85% 1,4-microstructure polybutadiene (PBD) and with high mechanical properties, e.g., ultimate tensile strength higher than 30 MPa and elongation at a break of 1000%. [less ▲]

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See detailMolecular weight effects on polystyrene fingerprint time-of-flight secondary ion mass spectroscopy (ToF-SIMS) spectra
Vanden Eynde, X.; Bertrand, P.; Jérôme, Robert ULg

in Macromolecules (1997), 30(21), 6407-6416

Monodisperse polystyrenes (PS) of different molecular weights (Mn) synthesized by living anionic polymerization with three types of butyllithium initiator (linear, n; secondary, sec; and tertiary, tert ... [more ▼]

Monodisperse polystyrenes (PS) of different molecular weights (Mn) synthesized by living anionic polymerization with three types of butyllithium initiator (linear, n; secondary, sec; and tertiary, tert) were analyzed by ToF-SIMS (time-of-flight secondary ion mass spectrometry). The influence of the molecular weight on the secondary ion intensities was studied in detail for the fingerprint part of the mass spectra (with m/z < 200). A drastic effect was observed for Mn values below 104, related to the presence of the saturated butyl end group. An extra hydrogen transfer originating from this end group during the secondary ion formation must be invoked to explain the data. Only the first neighbor monomer repeat units seem to be affected. This H exchange increases the intensity of ions containing more hydrogen or needing H transfer for their formation as the tropylium ion (C7H7+ at m/z = 91). The molecular structure of the butyl end group is found to influence greatly not only the intensity of their parent ion but also the PS characteristic ion intensities. Indeed, the tert-butyl end group is seen unable to produce the H transfer observed for the n- and sec-butyl ones. A model is proposed to take the influence of the end group on the PS SIMS fragmentation pattern into account. The parameters of this model allow the quantification of the end group interaction. [less ▲]

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See detailPoly[poly(isobornyl methacrylate-co-methyl methacrylate) (poly(IBMA-co-MMA))-b-polybutadiene-b-poly(IBMA-co-MMA)] Copolymers: synthesis, morphology, and properties
Yu, J. M.; Dubois, Philippe ULg; Jérôme, Robert ULg

in Macromolecules (1997), 30(21), 6536-6543

Anionic random and block copolymerization of isobornyl methacrylate (IBMA) and methyl methacrylate (MMA) has been studied in THF at −78 °C by using (1,1-diphenyl-3,3-dimethylbutyl)lithium (DDBLi) as ... [more ▼]

Anionic random and block copolymerization of isobornyl methacrylate (IBMA) and methyl methacrylate (MMA) has been studied in THF at −78 °C by using (1,1-diphenyl-3,3-dimethylbutyl)lithium (DDBLi) as initiator in the presence of LiCl. The random copolymerization of MMA and IBMA has also been carried out at 0 °C, all the other conditions being kept unchanged. Poly[poly(IBMA)-b-poly(BD)-b-poly(IBMA)] (IBI), poly[poly(IBMA-co-MMA)-b-poly(BD)-b-poly(MMA-co-IBMA)] (I/MBM/I), and poly[poly(IBMA)-b-poly(MMA)-b-poly(BD)-b-poly(MMA)-b-poly(IBMA)] (IMBMI) block copolymers have been synthesized by sequential anionic polymerization of butadiene, MMA, and IBMA initiated by the m-diisopropenylbenzene (m-DIB)/tert-butyllithium (t-BuLi) diadduct. These block copolymers of a monomodal and narrow molecular weight distribution (M̄w/M̄n = 1.1) have been analyzed by size exclusion chromatography (SEC), NMR, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and transmission electron microscopy (TEM). Stereocomplexation of IMBMA and I/MBM/I with iPMMA has also been studied by DSC. Although IBI triblock copolymers show a lamellar morphology even for relatively low hard block content (33 wt %), cylindrical and lamellar morphologies have been observed for the other block copolymers under consideration. These new block copolymers exhibit high ultimate tensile strength (30 MPa), elongation at break (1000%), and upper service temperature (140−200 °C). [less ▲]

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See detailAnionic block copolymerization of 4-vinylpyridine and tert-butyl methacrylate at "elevated" temperature : influence of various additives on the molecular parameters
Creutz, Serge; Teyssié, Philippe; Jérôme, Robert ULg

in Macromolecules (1997), 30(19), 5596-5601

The living anionic polymerization of 4-vinylpyridine (4VP) in 9/1 pyridine/THF at 0 °C has been reported lately (Creutz, S.; Teyssié, Ph.; Jérôme, R. Macromolecules 1997, 30, 1). The success of its block ... [more ▼]

The living anionic polymerization of 4-vinylpyridine (4VP) in 9/1 pyridine/THF at 0 °C has been reported lately (Creutz, S.; Teyssié, Ph.; Jérôme, R. Macromolecules 1997, 30, 1). The success of its block copolymerization with tert-butyl methacrylate (tBMA) has been shown to be dependent on the addition mode, highlighting the difference in reactivity between the two monomers. Moreover, the (co)solvent also strongly influences the fate of that copolymerization. Thus, the impact of various (co)solvents and additives has been investigated more thoroughly, revealing the interesting possibility of modifying the apparent relative reactivities of these two monomers. [less ▲]

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See detailIntramolecular excited-state processes of a halato-telechelic polymer, evaluated by global compartmental analysis of the fluorescence decay surface with the use of model coumpounds
van Stam, Jan; De Schryver, Frans C; Boens, Noël et al

in Macromolecules (1997), 30(19), 5582-5590

The excited-state processes of the halato-telechelic polymer bis[(N,N-dimethyl-N-[3-(1-pyrenyl)propyl]ammonio)trifluoromethanesulfonate]-end-capped poly(tetrahydrofuran) at low concentrations are ... [more ▼]

The excited-state processes of the halato-telechelic polymer bis[(N,N-dimethyl-N-[3-(1-pyrenyl)propyl]ammonio)trifluoromethanesulfonate]-end-capped poly(tetrahydrofuran) at low concentrations are investigated by time-resolved fluorescence. The photophysical processes can be described by an intramolecular three-state excited-state model. Such a system is not identifiable in the absence of a priori information. It is possible to perform a global compartmental analysis of the fluorescence decay surface using the scanning technique, based on model compound data previously obtained [Hermans et al., J. Phys. Chem. 1994, 98, 13583 and Hermans et al. Macromolecules 1995, 28, 3380]. The value boundaries on the rate constant for ring closure of the chain ends show that this process is close to diffusion-controlled. [less ▲]

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See detailMacromolecular engineering of lactones and lactides. 24. Controlled synthesis of (R,S)-β-butyrolactone-b-ε-caprolactone block copolymers by anionic and coordination polymerization
Kurcok, Piotr; Dubois, Philippe ULg; Sikorska, Wanda et al

in Macromolecules (1997), 30(19), 5591-5595

Block copolymers of (R,S)-β-butyrolactone and ε-caprolactone have been synthesized by combining the anionic polymerization of the first monomer with the coordinative ring-opening polymerization of the ... [more ▼]

Block copolymers of (R,S)-β-butyrolactone and ε-caprolactone have been synthesized by combining the anionic polymerization of the first monomer with the coordinative ring-opening polymerization of the second one. The copolymerization yield is close to 100% and the final molecular weight of each sequence can be predicted from the initial monomer-to-initiator molar ratio. The molecular weight distribution of copolymers obtained is quite narrow (Mw/Mn ≤ 1.3). According to NMR and DSC analysis, the polybutyrolactone block is atactic and totally amorphous, in contrast to the polycaprolactone block which is semicrystalline. A partial miscibility of the two blocks in the amorphous phase has however been detected. Thermal and enzymatic degradations of the block copolymers have been investigated. The enzymatic degradation rate promoted by the lipase form Rhizopus arrhizus strongly depends on the copolyester composition and increases with the β-butyrolactone content. [less ▲]

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