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See detailIonic end-capping of (semi)telechelic polymers by mesogens
Gohy, Jean-François; Sobry, Roger ULg; Van den Bossche, Guy ULg et al

in Polymer International (2000), 49(11), 1293-1301

Two methods have been used to end-cap linear polymer chains at one end or at both ends by a mesogen through ionic bonding. These polymers are designated as liquid-crystalline halato(semi)telechelic ... [more ▼]

Two methods have been used to end-cap linear polymer chains at one end or at both ends by a mesogen through ionic bonding. These polymers are designated as liquid-crystalline halato(semi)telechelic polymers (LC H(S)TPs). The first method relies on the ion exchange reaction between the metal counterion of halato(semi)telechelic polymers and an ionic mesogen. The second method is based on the proton transfer from a sulfonic or carboxylic acid end-group to a tertiary aliphatic amine, this approach being controlled by the relative pKa values of the acidic and basic groups. If the pKa difference is not large enough, strong hydrogen-bonding is observed by Fourier-transform infrared (FTIR) spectroscopy rather than proton transfer. The resulting materials have been characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and small-angle X-ray scattering (SAXS). [less ▲]

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See detailSynthesis and characterization of non-covalent liquid crystalline diblock copolymers
Gohy, Jean-François; Antoun, Sayed; Sobry, Roger ULg et al

in Macromolecular Chemistry and Physics (2000), 201(1), 31-41

Poly(dimethylaminoethylmethacrylate)-b-poly(sodium methacrylate) diblocks, (polyDMAEMA-b-polyMA), were synthesized as precursors of liquid crystalline (LC) copolymers. These LC copolymers were prepared by ... [more ▼]

Poly(dimethylaminoethylmethacrylate)-b-poly(sodium methacrylate) diblocks, (polyDMAEMA-b-polyMA), were synthesized as precursors of liquid crystalline (LC) copolymers. These LC copolymers were prepared by pro-ton-transfer between a carboxylic acid-containing meso-gen (A) and the dimethylamino substituent of the poly-DMAEMA block and by electrostatic interactions between the polyMA subunits and an ammonium-contain-ing mesogen (B). When mesogen A is complexed with DMAEMA units, a dramatic enhancement of the meso-phase stability is noted. The mesogenic properties of these LC copolymers were compared to those ones of the parent LC homopolymers, in relation to the copolymer composi-tion. The supramolecular organization of the LC diblock copolymers was studied by small-angle X-ray scattering (SAXS), and smectic mesophases were observed in some LC (co)polymers. For samples containing a major LC block, a smectic mesophase coexists with microphases formed by the second amorphous block. Different organizations, including a body-centered lattice of spheres and a hexagonal array of cylinders, were observed, depending on the investigated copolymers and their composition. When the LC block is the minor component, it forms microdomains too small for a liquid crystalline order to emerge. Moreover, no supramolecular organization of these dispersed microdomains was detected by SAXS. A homogeneous smectic mesophase was observed when the two blocks are bearing liquid crystalline moieties. [less ▲]

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See detailRestriction of mobility in model liquid crystalline ionomers
Gohy, Jean-François; Jérôme, Robert ULg; Van den Bossche, Guy ULg et al

in Macromolecular Chemistry and Physics (1998), 199(10), 2205-2210

Model liquid crystalline ionomers have been analyzed by SAXS both in bulk and in toluene solution. These compounds are referred to as liquid crystalline halatosemitelechelic polystyrenes (LC HSTP's) and ... [more ▼]

Model liquid crystalline ionomers have been analyzed by SAXS both in bulk and in toluene solution. These compounds are referred to as liquid crystalline halatosemitelechelic polystyrenes (LC HSTP's) and consist of low molecular weight polystyrene chains end-capped at one end by a sulfonate group associated to a mesogenic counterion. The results are in agreement with a microphase separation between the polymer chain and the mesogenic counterion. The main characteristic feature of the SAXS profile for the bulk material is the so-called ionic peak, whose position obeys a general law which is in favor of a rod-like organization of the multiplets and which shows that the polymer chains are stretched in the very close vicinity of the mesogenic core, in agreement with the Eisenberg, Hird and Moore model for ionomers. The thickness of this region of restricted mobility has been estimated to 1 nm, which is the order of magnitude of the persistence length of polystyrene. This very local restriction in mobility persists in toluene solution, in contrast to what is observed for the ω-Li-sulfonato-polystyrene precursors. The results also agree with an isotropic distribution of the multiplets in toluene. [less ▲]

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See detailSupramolecular organization of model liquid crystalline ionomers
Gohy, Jean-François; Jérôme, Robert ULg; Van den Bossche, Guy ULg et al

in Macromolecular Chemistry and Physics (1998), 199(9), 1791-1799

A mesogenic cation was associated with low molecular weight carboxylato- and sulfonato(se-mi)telechelic polymers. These compounds were prepared by ion-exchange of the quaternary ammonium group attached to ... [more ▼]

A mesogenic cation was associated with low molecular weight carboxylato- and sulfonato(se-mi)telechelic polymers. These compounds were prepared by ion-exchange of the quaternary ammonium group attached to the mesogen for the metal counterion of the halato(semi)telechelic polymer. The accordingly formed liquid crystalline halato(semi)telechelic polymers (LC H(S)TP's) were analyzed by differential scanning calorimetry (DSC), polarized-light optical microscopy (POM), and small angle X-ray scattering (SAXS). On the basis of these experimental results, a model for the supramolecular organization of the LC H(S)TP's is proposed. The final morphology results from the interplay of two competitive effects: the dipolar interaction of the ion-pairs known for multiplet formation and the propensity of the mesogenic moiety to form mesophases. The outcome of this competition depends on the mobility of the mesogenic counterion, i.e., on the strength of the dipolar interactions, the mobility of the polymer backbone and the mesogen/poly-mer ratio which is controlled by the molecular weight of the polymer. [less ▲]

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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 detailSmall-angle X-ray scattering and small-angle neutron scattering studies of liquid-crystalline halato(semi)telechelic polymers
Sobry, Roger ULg; Van den Bossche, Guy ULg; Fontaine, Frédéric et al

in Journal of Applied Crystallography (1997), 30(6), 1075-1083

Model liquid-crystalline ionomers have been synthesized, which consist of low molecular weight (700-49000) linear ω- and α,ω-sodium sulfonate- and carboxylato-poly(styrenes or isoprenes) selectively end ... [more ▼]

Model liquid-crystalline ionomers have been synthesized, which consist of low molecular weight (700-49000) linear ω- and α,ω-sodium sulfonate- and carboxylato-poly(styrenes or isoprenes) selectively end-capped at one or both end(s) with an ionic mesogenic group. These compounds are referred to as liquid-crystalline halato(semi)telechelic polymers [LC H(S)TPs] A combination of small-angle X-ray scattering and small-angle neutron scattering studies on these LC H(S)TPs clearly shows the usual ionic peak related to interparticle interference between the ionic aggregates and a peak which can be related to the organization of a smectic mesophase. This mesogenic peak is generally masked by the foot of the broad ionic peak. The ionic peak Bragg spacing is much larger in the LC H(S)TP than in the H(S)TP precursor; This increased interaggregate distance results from the hindrance due to the mesogenic organization and from the restricted mobility experienced by the chains closely attached to the mesogen layers. As a rule, the lower the glass transition temperature of the polymeric matrix, the better the definition of the ionic peak, The ionic peak is well defined as long as the temperature is lower than the temperature of transition from solid to smectic phase (32.3 K). At higher temperatures, the ionic peak intensity decreases with increasing temperature. [less ▲]

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