| 1. |
- Aad, G, et al.
(författare)
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- 2015
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swepub:Mat__t
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| 2. |
- Niemi, MEK, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 3. |
- Kanai, M, et al.
(författare)
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- 2023
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swepub:Mat__t
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| 4. |
- Trollsås, M., et al.
(författare)
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The influence of the molecular structure on the second-order nonlinear optical properties of pyroelectric liquid crystalline polymers
- 1998
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Ingår i: American Chemical Society Symposium Series (ACS). - Washington, DC : American Chemical Society. - 0097-6156 .- 1947-5918. ; 695, s. 315-327
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Tidskriftsartikel (refereegranskat)abstract
- Pyroelectric Liquid Crystal Polymers (PLCP), a novel class of material with intrinsic polar order developed in our laboratory, are discussed. Thin films (2-4µm) of PLCP were prepared by photopolymerization of ferroelectric liquid crystalline monomers in the chiral smectic C (SmC*) phase. The poly(acrylate) materials have been structurally modified in order to improve their nonlinear optical and thermal properties. Further are their longterm nonlinear optical properties discussed based on results from second harmonic generation (SHG), spontaneous polarization (Ps), and dielectric spectroscopy.
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| 5. |
- Busson, P., et al.
(författare)
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Ferroelectric liquid crystalline dendrimers : Synthesis, thermal behavior, and electrooptical characterization
- 2001
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 34:5, s. 1221-1229
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Tidskriftsartikel (refereegranskat)abstract
- The preparation and characterization of a series of novel ferroelectric liquid crystalline dendrimers are presented. End-capping of 1-, 2-, and 3-generation dendrimers based on 2,2-bis(hydroxymethyl)propionic acid with mesogens gave surface-functionalized liquid crystalline compounds with 6, 12, and 24 mesogen-containing units, respectively. 4 -((R)-1-Methylheptyloxy)phenyl 4-(4 '-[10(hydroxycarbonyl)decyloxyl phenyl)benzoate was synthesized and used as a mesogen-containing unit. The purity and structure of each compound were determined by H-1 NMR spectroscopy, size exclusion chromatography, and elemental analysis. Differential scanning calorimetry and optical microscopy were used to investigate the mesomorphic properties of the mesogen-functionalized dendrimers. The materials displayed a variety of mesophases, including the smectic C* phase. All the liquid crystalline dendrimers showed ferroelectricity, and tilt angle and spontaneous polarization measurements were performed. The obtained results show that the ferroelectric properties of the materials are independent of the generation number of the dendritic scaffold.
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| 6. |
- Busson, P., et al.
(författare)
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Preparation of mesogen-functionalized dendrimers for second-order nonlinear optics
- 2002
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 35:5, s. 1663-1671
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Tidskriftsartikel (refereegranskat)abstract
- Liquid crystalline dendrimers with peripheral mesogen-containing units have been prepared. Multistep synthesis with several selective reactions was used in the preparation of the mesogen-containing molecules, 4-[10-(hydroxycarbonyl)decyloxy]phenyl 4-[4'-(2-(R)-octyloxy)-3'-nitrophenyl]benzo ate and 4-[10-(hydroxycarbonyl)decyloxy]biphenyl 4-[4'-(2-(R)-octyloxy)-3'-nitrophenyl]benzoate. Both molecules possessed an electron-accepting nitro group placed perpendicular to the long axis of the molecules in order to enhance the nonlinear optical activity. A second generation hydroxyl functional aliphatic dendrimer based on the dihydroxy acid, 2,2-bis(hydroxymethyl)propionic acid, was used as dendritic scaffold and was subsequently functionalized with the aforementioned groups. The purity and structure of the two liquid crystalline dendrimers were determined by H-1 NMR spectroscopy, size exclusion chromatography, and elemental analysis. The synthesis of both the mesogen-containing units and the liquid crystalline dendrimers is described in detail. Investigation of the liquid crystalline properties of the materials by differential scanning calorimetry and optical microscopy showed that they exhibited different mesophases, including the chiral smectic C phase. Ferroelectric switching was observed in this tilted phase, and electrooptical properties, including tilt angle and spontaneous polarization measurements, were investigated. Finally, the nonlinear optical properties of one of the materials were preliminary characterized.
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| 7. |
- Fazio, V. S. U., et al.
(författare)
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Enhanced phase-matched second-harmonic generation in a ferroelectric liquid crystal waveguide
- 2001
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Ingår i: Molecular Crystals and Liquid Crystals Science and Technology. - 1058-725X. ; 368, s. 4061-4070
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Tidskriftsartikel (refereegranskat)abstract
- A binary mixture of crosslinkable ferroelectric liquid crystals (FLCs) was used for the design of a channel waveguide. The liquid crystal was aligned in layers parallel to the glass plates (homeotropic) in a sandwich geometry and then the arrangement was permanently fixed by photopolymerization which yielded a polar network possessing a high thermal and mechanical stability. The linear and nonlinear optical properties have been measured and all four independent components of the nonlinear susceptibility tensor d have been determined. The off-resonant d-coefficients are remarkably high and comparable to those of the best known inorganic materials. Phase-matching was achieved by taking advantage of the modal dispersion of the waveguide. A reversal of sign of chi ((2)) at the nodal plane of the electric field distribution of the first-order mode was needed to maximize the overlap. integral between the fundamental and the second-harmonic (SH) light. In samples with chi ((2)) inversion the SH Signal was 1000 larger that in samples without chi ((2)) inversion.
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| 8. |
- Fazio, V. S. U., et al.
(författare)
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Nonlinear optical properties of a channel waveguide produced with crosslinkable ferroelectric liquid crystals
- 2000
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Ingår i: The European Physical Journal E Soft matter. - : Springer Science and Business Media LLC. - 1292-8941 .- 1292-895X. ; 3:3, s. 245-251
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Tidskriftsartikel (refereegranskat)abstract
- A binary mixture of ferroelectric liquid crystals (FLCs) was used for the design of a channel waveguide. The FLCs possess two important functionalities: a chromophore with a high hyperpolarizability beta and photoreactive groups. The smectic liquid crystal is aligned in layers parallel to the glass plates in a sandwich geometry. This alignment offers several advantages, such as that moderate electric fields are sufficient to achieve a high degree of polar order. The arrangement was then permanently fixed by photopolymerization which yielded a polar network possessing a high thermal and mechanical stability which did not show any sign of degradation within the monitored period of several months. The linear and nonlinear optical properties have been measured and all four independent components of the nonlinear susceptibility tensor (d) over bar have been determined. The off-resonant d-coefficients are remarkably high and comparable to those of the best known inorganic materials. The alignment led to an inherent channel waveguide for p-polarized light without additional preparation steps. The photopolymerization did not induce scattering sites in the waveguide and the normalized losses were less than 2 dB/cm. The material offers a great potential for the design of nonlinear optical devices such as frequency doublers of low-power laser diodes.
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| 9. |
- Fazio, V. S. U., et al.
(författare)
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Phase-matched second-harmonic generation in a ferroelectric liquid crystal waveguide
- 2000
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 77:3, s. 319-321
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Tidskriftsartikel (refereegranskat)abstract
- True phase-matched second-harmonic generation in a waveguide of crosslinkable ferroelectric liquid crystals is demonstrated. These materials allow the formation of macroscopically polar structures whose order can be frozen by photopolymerization. Homeotropic alignment was chosen which offers decisive advantages compared to other geometries. All parameters contributing to the conversion efficiency are maximized by deliberately controlling the supramolecular arrangement. The system has the potential to achieve practical level of performances as a frequency doubler for low power laser-diodes.
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| 10. |
- Gustavsson, Per-Erik, et al.
(författare)
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Purification of plasmid DNA with a new type of anion-exchange beads having a non-charged surface
- 2004
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1038:1-2, s. 131-140
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Tidskriftsartikel (refereegranskat)abstract
- We have prepared a new type of anion exchanger, which effectively discriminates between RNA and plasmid DNA. The material is based on a Sephacryl S-500 HR matrix provided with quartenary amine anion-exchange groups. A distinguishing feature of the beads is that a thin (2-3 mum) outer layer of the beads lacks ion-exchange groups. In the synthesis of these beads the vinyl groups in the outer layer of vinylalkyl substituted Sephacryl S-500 HR beads are reacted with bromine. The resulting layer of bromoalkyl groups are hydrolysed, creating an inert outer layer of hydroxyalkyl groups. Finally, bromination and trimethylamine reactions of the inner vinyl groups provide the beads with a core of cationic groups. Large plasmid molecules will not bind to such beads since they are too large to enter the pores and therefore cannot come into contact with the charged matrix in the inner parts of the beads. RNA and protein molecules present in a cleared lysate, on the other hand, readily enter the pores and become adsorbed. A two-column strategy was developed for plasmid purification (recombinant pBluescript, 5.9 kilo base pairs, kbp). The first column was packed with the restricted access anion-exchanger beads (lid beads) and the second column with normal ion-exchange material (same ligand density as the lid beads). Diluted (3 x), cleared lysate was pumped through the tandem columns. The first column was subsequently disconnected from the system and the purified plasmid adsorbed on the second column was eluted in a concentrated form (6x) and with 89% recovery. The two-column procedure removed 99.5% of the RNA and 96% of the proteins. (C) 2004 Elsevier B.V. All rights reserved.
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| 11. |
- Jonas, Örtegren, et al.
(författare)
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Cone motion viscosity and optical second harmonic generation of ferroelectric liquid crystalline dendrimers
- 2001
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Ingår i: Liquid crystals (Print). - : Informa UK Limited. - 0267-8292 .- 1366-5855. ; 28:6, s. 861-868
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Tidskriftsartikel (refereegranskat)abstract
- We report second harmonic generation in a ferroelectric liquid crystalline trimer and ferroelectric liquid crystalline dendrimers of first, second and third generation. Thin cells were filled with the compounds by capillary forces at elevated temperature, and cooled from the surface stabilized ferroelectric state to below the glass transition temperature, while kept in an electric field. The cone motion viscosity and the threshold electric field for unwinding of the helix axis of the chiral tilted smectic mesophases were studied separately at elevated temperature, and these data were used to optimize the preparation of the films. The measured response time was between 0.3 and 3 ms, which corresponds to a cone motion viscosity between 0.5 and 50 Pa s. Second harmonic generation was studied both at elevated temperature with an electric field and at room temperature with and without electric field. The first generation dendrimer exhibited a strong increase in the second order non-linear optical response with time at room temperature. The d(23)-coefficient of this dendrimer was approximately four times larger than for the other macromolecules and was 0.045 pm V-1. The relatively large d-coefficient of the first generation dendrimer is ascribed to crystallization, which improved the orientation of the molecular dipoles.
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| 12. |
- Ortegren, J., et al.
(författare)
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Dielectric relaxation of liquid crystalline dendrimers and liquid crystalline polymers with pendant nitro groups
- 2001
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 42:25, s. 10027-10033
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Tidskriftsartikel (refereegranskat)abstract
- The dielectric relaxation was determined in a time-domain spectrometer between 100 and 295 K and from 0.1 to 1000 Hz for series of dendritic liquid crystalline polymers with scaffolds based on 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) of generations 0-3 with 4-((R)-1-methylheptyloxy)phenyl 4-{4'-[10-(hydroxy-carbonyl)decyloxy]-phenyl} benzoate as mesogen and for the second generation of dendrimers with 4-[10-(hydroxycarbonyl)decyloxy]-biphenyl 4-[4'-(2-(R)-octyloxy)-3-nitrophenyl] benzoate as mesogen. Dielectric data are also reported for a side-chain liquid crystalline polymer based on {4''-[(R)-(-)-2-octyloxyl-3-nitro-phenyl 4-(4'-(11-acryloyl-oxyundecyloxy)phenyl}benzoate. The low temperature subglass process (gamma) assigned to the spacer group was essentially insensitive to molecular architecture and to the presence of a pendant nitro group in the mesogen. The high temperature sub-glass process (beta) assigned to a 180 degrees flip of part of mesogen was only moderately sensitive to the molecular architecture. The introduction of a pendant nitro group in the mesogen led to a substantial increase in both activation energy and relaxation strength. The results suggest that the phenylene ring with the pendant nitro group participates in the beta process.
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| 13. |
- Ortegren, J., et al.
(författare)
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Improved thermal stability of pyroelectric polymers by crosslinking of ferroelectric liquid crystals
- 2001
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1089-5647 .- 1520-6106 .- 1520-5207. ; 105:42, s. 10223-10227
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Tidskriftsartikel (refereegranskat)abstract
- Monofunctional ferroelectric liquid crystalline monomers and a blend of monofunctional/lbifunctional ferroelectric liquid crystalline monomers were photopolymerized, yielding a side-chain liquid crystalline polymer and a cross-linked polymer, respectively. The cross-linked polymer exhibited higher thermal stability than the side-chain liquid crystalline polymer and was pyroelectric up to 170 degreesC, whereas the side-chain liquid crystalline polymer lost most of its pyroelectricity at 38 degreesC. It is shown by electrooptic and birefringence measurements that cross-linking in the unwound SmC* phase prevented the reoccurrence of the helical superstructure.
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