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Wim H. de Jeu

Bio: Wim H. de Jeu is an academic researcher from Solid State Physics Laboratory. The author has contributed to research in topics: Liquid crystal & Phase transition. The author has an hindex of 4, co-authored 5 publications receiving 408 citations.

Papers
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TL;DR: A review of the wide variety of predictions that results from a Landau-type of description of the nematic-isotropic phase transition is given in this paper, which includes a discussion of the nature of the order parameter and of the various types of possible phases.

291 citations

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TL;DR: In this paper, the origin of induced smectic phases (ISP) in binary mixtures of liquid crystals is discussed, and the location of the extrema is calculated as a function of complex concentration and effective, intermolecular interactions.
Abstract: The origin of the occurrence of induced smectic phases (ISP) in binary mixtures of liquid crystals is discussed. First the experimental evidence is reviewed, which leads to a division in strong complexing (electron–donor–acceptor complex as indicated by a charge–transfer band) and weak complexing, where only indirect evidence is available. Within the mean field approximation a theoretical model is given in which the influence of complex formation on the nematic–smectic‐A transition temperature is investigated for ideal orientational order. The ISP mechanism is attributed to the dispersive interactions between the complexes. However, in principle in a two‐component mixture without complexing also ISP can be obtained due to interactions involving permanent dipoles. From fits to experimental phase diagrams and from estimates of parameters it follows that the first mechanism is more likely. Three nonstandard groups of phase diagrams with characteristic maxima of minima are predicted. The location of the extrema is calculated as a function of complex concentration and effective, intermolecular interactions. The model correctly describes presently existing, very rich, experimental data.

64 citations

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TL;DR: In this article, the morphology of a double crystallizable poly(epsilon-caprolactone-b-ethylene oxide) block copolymer has been studied with in situ simultaneously small and wide-angle x-ray scattering as well as atomic force microscopy.
Abstract: The morphology of a highly asymmetric double crystallizable poly(epsilon-caprolactone-b-ethylene oxide) (PCL-b-PEO) block copolymer has been studied with in situ simultaneously small and wide-angle x-ray scattering as well as atomic force microscopy. The molecular masses Mn of the PCL and PEO blocks are 24 000 and 5800, respectively. X-ray scattering and rheological measurements indicate that no microphase separation occurs in the melt. Decreasing the temperature simultaneously triggers off a crystallization of PCL and microphase separation between the PCL and PEO blocks. Coupling and competition between microphase separation and crystallization results in a morphology of PEO spheres surrounded by PCL partially crystallized in lamella. Further decreasing temperature induces the crystallization of PEO spheres, which have a preferred orientation due to the confinements from hard PCL crystalline lamella and from soft amorphous PCL segments in different sides. The final morphology of this highly asymmetric block copolymer is similar to the granular morphology reported for syndiotactic polypropylene and other (co-) polymers. This implies a similar underlying mechanism of coupling and competition of various phase transitions, which is worth further exploration

40 citations

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TL;DR: In this article, the birefringence of mixtures of homologues from the terminally non-polar series of p,p′-dialkylazoxybenzenes has been studied.
Abstract: The birefringence of mixtures of homologues from the terminally non-polar series of p,p′-dialkylazoxybenzenes has been studied. The birefringence is used as a probe of the orientational order parameter, which is coupled to the translational (smectic) order parameter. The tricritical nematic to smectic-A point which results from this coupling is found at a McMillan ratio TAN/TNI= 0.977. This is similar to the values reported for terminally polar systems and is higher than predicated by theory. The critical exponent for the variation of the order parameter across the SA–N phase transition obeys the expected trend.

28 citations

Journal ArticleDOI
TL;DR: In this paper, a theoretical description for antiferroelectric smectic-A phases is proposed, where order parameters are introduced that retain information on the head-tail asymmetry of the constituent molecules and minimum ingredients are given for an averaged model potential.

4 citations


Cited by
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Journal ArticleDOI
B Jerome1
TL;DR: In this paper, a review focusing on nematic liquid crystals is presented, where three main kinds of effects can be distinguished: the perturbation of the liquid crystalline structure close to the surface, the bulk liquid crystal structure is recovered with an orientation which is fixed by the surface and critical adsorption or wetting can occur at surfaces.
Abstract: As their name indicates, liquid crystals simultaneously exhibit some characteristics common to both ordinary isotropic liquids and solid crystals. This ambivalence is also found in the effects of surfaces on these systems which lead to a great diversity of phenomena. These phenomena are reviewed focusing on nematic liquid crystals which have the simplest structure among the many existing types and which have been the most extensively studied. Three main kinds of effects can be distinguished. The first concerns the perturbation of the liquid crystalline structure close to the surface. Beyond this transition region, the bulk liquid crystalline structure is recovered with an orientation which is fixed by the surface: this phenomenon of orientation of liquid crystals by surfaces is the so-called anchoring. Finally, close to bulk phase transitions, critical adsorption or wetting can occur at surfaces as is also seen in isotropic systems.

754 citations

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TL;DR: In this article, the physics of colloidal dispersions in nematic liquid crystals is reviewed and three possible structures are identified and discussed in detail; the dipole, the Saturn-ring and the surface-ring configuration.

579 citations

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TL;DR: In this paper, the self-assembly of block copolymers (BCPs) in the presence of crystallization is reviewed, for BCPs in the bulk, thin films, single crystals and micelles.

320 citations

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TL;DR: A comprehensive overview of phase transition studies can be found in this article, where the authors identify the essential key concepts and points of difficulty associated with the study of phase transitions and discuss the most widely used experimental techniques for measuring these transition properties.

308 citations