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See detailMorphology of ionic aggregates in carboxylato- and sulfonato-telechelic polyisoprenes as investigated by small-angle x-ray scattering
Sobry, Roger ULg; Fontaine, Frédéric; Ledent, Jean et al

in Macromolecules (1998), 31(13), 4240-4252

Twenty seven samples of carboxylato- and sulfonato-telechelic polyisoprenes associated with various cations (Na, K, Rb, Cs, Mg, Ca, Sr, and Ba) have been investigated by small-angle X-ray scattering. The ... [more ▼]

Twenty seven samples of carboxylato- and sulfonato-telechelic polyisoprenes associated with various cations (Na, K, Rb, Cs, Mg, Ca, Sr, and Ba) have been investigated by small-angle X-ray scattering. The Bragg spacing characteristic of the ionic peak is directly proportional to the root-mean-square end-to-end distance (rrms) of the polyisoprene chain. In the series of sulfonato-telechelic polyisoprenes, the Bragg spacing is approximately equal to rrms, whereas in the series of carboxylato-telechelic polyisoprenes it amounts to 21/2 rrms. It also appears that the ionic aggregates are more likely distributed according to a planar hexagonal network. An original method has been used for the tail-end analysis of the SAXS profile, which is based on the general vertex contribution to the Kirste−Porod law. It results that the ionic aggregates are of an angulous shape. Four different functions have been used to account for the interphase profile between the ionic phase and the polymeric matrix. The ionic aggregates would accordingly contain an average of 10 alkali-metal cations with a tetrahedral stacking, whereas six alkaline-earth-metal cations would be organized according to an equilateral prism. The oxygen atoms of the anionic groups mainly contribute to the width of the interface. The additional peaks observed in the upturn of the curve at very low angles are the signature of a superstructure similar to that one previously observed for carboxylato-telechelic poly(tert-butyl acrylate)s. [less ▲]

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See detailNew ligands for the living isotactic anionic polymerization of methyl methacrylate in toluene at 0°C. 2. 7Li NMR analysis of sec-butyllithium ligated by lithium silanolates
Zundel, Thomas; Zune, Catherine; Teyssié, Philippe et al

in Macromolecules (1998), 31(13), 4089-4092

The mixed associated species {xsBuLi, (y − x)sBuMe2SiOLi} formed by reaction of sec-Butyllithium (sBuLi) with octamethylcyclotetrasiloxane (Me2SiO)4 in toluene have been used to initiate the anionic ... [more ▼]

The mixed associated species {xsBuLi, (y − x)sBuMe2SiOLi} formed by reaction of sec-Butyllithium (sBuLi) with octamethylcyclotetrasiloxane (Me2SiO)4 in toluene have been used to initiate the anionic polymerization of methyl methacrylate (MMA) in that solvent at 0 °C. The active species generated by this new type of initiator have been characterized by 7Li NMR at 0 °C. The 7Li NMR spectra of sBuLi and sBuMe2SiOLi mixtures in toluene show that only one single type of {sBuLi, 5sBuMe2SiOLi} mixed species prevails at [sBuMe2SiOLi]/[sBuLi] molar ratios higher than ca. 21, as result of a large excess of {6sBuMe2SiOLi} species. The 7Li NMR has also concluded to the formation of {PMMALi, 5sBuMe2SiOLi} species upon the addition of MMA to that initiator solution, supporting the theory that only one type of ionic species is active during the MMA conversion. These active centers are stable for at least 1 h at 0 °C as confirmed by 7Li NMR. [less ▲]

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See detailHighly functional branched and dendri-graft aliphatic polyesters through ring opening polymerization
Trollsas, Michaël; Hedrick, James L.; Mecerreyes, David et al

in Macromolecules (1998), 31(9), 2756-2763

Highly branched poly(ε-caprolactones) with novel and well-defined molecular architectures have been synthesized by the use of new multifunctional initiators. The ring-opening polymerization methods used ... [more ▼]

Highly branched poly(ε-caprolactones) with novel and well-defined molecular architectures have been synthesized by the use of new multifunctional initiators. The ring-opening polymerization methods used to prepare these new structures allowed accurate control of molecular weight and narrow molecular weight distributions. In addition, the synthesis of even more complex molecular architectures was possible by the use of 1,4,9-trioxaspiro[4.6]-9-undecanone as a comonomer with ε-caprolactone. After copolymerization, complete deacetalization of the polyester chains into the corresponding ketone groups followed by quantitative reduction formed polymers with hydroxyl pendant groups. With this synthetic strategy, significant additional functionality was introduced. In addition, the pendant hydroxyl groups along the chains can serve as macroinitiators for the further initiation of ε-caprolactone to prepare dendri-graft molecular architectures. The new polymers were characterized by 1H NMR, 13C NMR, and size exclusion chromatography (SEC). 13C NMR spectra clearly showed that the hydroxyl groups of the initiators were fully substituted to give polymers with two, four, and six arms. [less ▲]

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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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