Aloir A Merlo | Universidade Federal do Rio Grande do Sul (original) (raw)
Papers by Aloir A Merlo
Macromolecular Symposia, 2005
ABSTRACT
Journal of The Brazilian Chemical Society, 2001
... Aloir A. Merlo*, Olga MS Ritter, Fabiano V. Pereira, Carolina H. Vieira and Nádya P. da Silve... more ... Aloir A. Merlo*, Olga MS Ritter, Fabiano V. Pereira, Carolina H. Vieira and Nádya P. da Silveira*. ...Bento Gonçalves, 9500, Campus do Vale, 91501 970, Porto Alegre - RS, Brazil. ... quirais líquido cristalinos com cadeia lateral derivados do (S)-(-)2-metil-1-butanol são descritos. ...
Polymer Bulletin, 1999
Summary The synthesis and phase behavior of three homopolymers with liquid crystalline side-cha... more Summary The synthesis and phase behavior of three homopolymers with liquid crystalline side-chains is described. These new homopolymers show a dependence of the phase transition temperatures on the molecular weight. The synthesized material exhibits typical mesomorphism-nematic, smectic A and C. We compare the mesomorphic behavior of the homopolymers of the different liquid crystals polyacrylates. In addition, a dynamic and static
Tetrahedron Letters, 2011
A collection of isoxazoles derivatives has been efficiently synthesized in three steps. The oxima... more A collection of isoxazoles derivatives has been efficiently synthesized in three steps. The oximation reaction of aldehydes followed by nitrile oxide [3+2] 1,3-dipolar cycloaddition and MnO 2 -oxidation reaction furnished the title compounds which were purified by simple filtration on celite Ò .
Tetrahedron, 2008
A homologous series of the new N-heterotolans 8aed were synthesized using two cross-coupling reac... more A homologous series of the new N-heterotolans 8aed were synthesized using two cross-coupling reactions mediated by copper and palladium/copper. The final compounds present the phenyl-pyridyl framework connected by the acetylene group. The evaluation of thermal properties for this series is described. All compounds exhibit the smectic A and X mesophase. For comparison were also synthesized compounds 10, 12, and 14. Their LC properties are reported.
Synthetic Communications, 1993
Química Nova, 2001
... R mes corresponde às unidades 4'-n-alcoxibifenilas e 5-n-alcóxi-(2-fenil)pirimidinas, re... more ... R mes corresponde às unidades 4'-n-alcoxibifenilas e 5-n-alcóxi-(2-fenil)pirimidinas, respectivamente. ... Cryst. Liq. Cryst. 1991, 209, 349 [ Links ]. 28. Goodby, JW; Waugh, MA; Stein, SM; Chin, E.; Pindak, R.; Patel, JS; J. Am. Chem. Soc. 1989, 111, 8119. [ Links ]. 29. ...
Polymer, 2002
The solution behaviour of a new mesogenic side group polyacrylate in tetrahydrofuran and toluene ... more The solution behaviour of a new mesogenic side group polyacrylate in tetrahydrofuran and toluene has been investigated by static and dynamic light scattering. In the dilute regime the polymer behaves as typical polydisperse linear chains in good solvent and the dynamics is dominated by a single fast mode. Cluster formation was detected starting at a concentration around 50gl−1. It seems to be independent of the solvent as well as of polymer molecular weight. In the semidilute regime, the behaviour of the reduced osmotic modulus leads to the conclusion that repulsion between the chains is stronger than in linear macromolecules. The appearance of larger clusters was revealed above a characteristic concentration and is slightly dependent on the polyacrylate molecular weight. The dynamics was generally characterised by a fast mode related to the cooperative diffusion and by a slow mode associated with large clusters. The existence of a network of multiconnected clusters is envisaged wit...
Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, 1994
... T. R. TAYLOR and TEODOSIO KROlN Departamento de Fisica, Universidade Federal de Santa Catarin... more ... T. R. TAYLOR and TEODOSIO KROlN Departamento de Fisica, Universidade Federal de Santa Catarina; 88.000 Florianopolis, SC, Brazil ... The transition temperatures for all compounds were determined by optical mi-croscopy using a Leitz Ortholux Polarizing Microscope in ...
Liquid Crystals, 2008
The mesophase behaviour of a side‐chain liquid crystalline polyacrylate (LCP) grown by drying a s... more The mesophase behaviour of a side‐chain liquid crystalline polyacrylate (LCP) grown by drying a solution has been investigated. This LCP, characterised by a short spacer (four carbon atoms) and a long tail (10 carbon atoms), displays, at increasing temperatures, SmC and SmAd phases. The effect of the mean molecular weight, i.e. the mean number of side chains per polyacrylate main
Liquid Crystals, 2000
Two homologous series, 4¾ -(4-n-alkoxybenzoyloxy)-4-substituted 3-nitrotolans (Ia-d) and 4¾ -(4-n... more Two homologous series, 4¾ -(4-n-alkoxybenzoyloxy)-4-substituted 3-nitrotolans (Ia-d) and 4¾ -(4-n-alkoxybenzoyloxy)-4-substituted tolans ( IIa-c), with substituents (S)-2-methyl-1-butyl and n-alkyl, were synthesized by Sonogashira's coupling. Their mesomorphic behaviour is reported. The thermal stability of the series II is higher than that of series I. Series I melting points and clearing points are lower than those of series II. None of the chiral tolans or m-nitrotolans have an enantiotropic smectic C phase. When the chiral chains are changed to n-alkyl groups in compounds Ia,b and IIa, an enantiotropic smectic C phase is seen. All compounds have a nematic or cholesteric phase, and two homologues of series II present a monotropic smectic C phase with mosaic texture. The mesophases were characterized using optical polarized light microscopy and diOE erential scanning calorimetry.
Liquid Crystals, 2008
... a , Guilherme D. Vilela a , Paulo H. Schneider a , Olga MS Ritter b & Aloir A. Merlo a * ... more ... a , Guilherme D. Vilela a , Paulo H. Schneider a , Olga MS Ritter b & Aloir A. Merlo a * pages 833-840. ... 8: 47???51. (a); (b) Walba, DM; Keller, P.; Parmar, DS; Clark, NA; Wand, MD J. Am. Chem. Soc. 1989, 111, 8273???8274; (c) Yoshizawa, A.; Nakata, M.; Yamaguchi, A. Liq. Cryst. ...
Liquid Crystals, 2004
Starting from (2)-menthone, a new chiral building block useful for liquid crystal preparation was... more Starting from (2)-menthone, a new chiral building block useful for liquid crystal preparation was synthesized. This chiral moiety was attached to selected phenols under mild conditions by esterification. Rigid cores of tolanebenzoates and phenylbenzoates were prepared using the palladium cross-coupling reaction or by traditional liquid crystal synthesis methods. This convergent approach ended with a second esterification or palladium cross-coupling reaction to furnish new liquid crystal materials with smectic A, smectic C* and N* phases, as well as blue phases (BP). Thermal behavior, and the effect of chiral moiety branches and molecular packing in the smectic phases, have been investigated using differential scanning calorimetry, optical microscopy and X-ray diffraction.
Liquid Crystals, 2002
ABSTRACT The synthesis of chiral side chain liquid crystalline polyacrylates with a two-stereogen... more ABSTRACT The synthesis of chiral side chain liquid crystalline polyacrylates with a two-stereogenic centre from L-α-aminoacid is described. The chiral tail is 2-chloroalcohol obtained from L-isoleucine and the spacer group has either four or eleven methylene units. The mesogenic moiety is derived from phenyl benzoate. The stereochemistry of the key intermediate (2S,3S)-(+)-4- [1-(2-chloro-3-methyl)pentyloxy]phenyl benzoate (6) obtained by a Mitsunobu reaction was established by single crystal X-ray analysis. This result indicates that the nucleophilic displacement of chiral diazonium salts proceeds with overall retention of configuration. The liquid crystalline behaviour of polyacrylates P13 and P14 was investigated by DSC, optical microscopy, small angle X-ray scattering and depolarized light scattering. The polyacrylate P13, with eleven methylene units in the spacer, exhibits a chiral smectic A phase whereas the polyacrylate P14, with a spacer containing four methylene units, displays a chiral nematic phase.
Liquid Crystals, 2010
The synthesis and mesomorphic properties of new liquid-crystalline 3,5-disubstituted isoxazolines... more The synthesis and mesomorphic properties of new liquid-crystalline 3,5-disubstituted isoxazolines are presented and discussed. These isoxazoline derivatives have been synthesised by reacting oximes with the appropriate 4-substituted styrene dipolarophiles in the presence of N-...
Liquid Crystals, 2012
A simple and efficient procedure for the synthesis of a new class of organoselenium liquid crysta... more A simple and efficient procedure for the synthesis of a new class of organoselenium liquid crystal compounds was developed. The coupling of aryl bromides with elemental selenium was catalysed using copper oxide nanopowder in the presence of potassium hydroxide employing dimethyl sulfoxide as the solvent. This is the first report of the synthesis and characterisation of liquid crystal-based diselenides. Their
Liquid Crystals, 2012
Four liquid crystals (LC) 3,7a-bis(4-alkyloxyphenyl)-7,7a-dihydro-6H-isoxazolo[2,3-d][1,2,4]oxadi... more Four liquid crystals (LC) 3,7a-bis(4-alkyloxyphenyl)-7,7a-dihydro-6H-isoxazolo[2,3-d][1,2,4]oxadiazol-6-yl)acetic acid (7a–d) were synthesised and the mesomorphic behaviour reported. The LCs were characterised as 2:1 bisadducts, which were obtained from a double [3 + 2] 1,3-dipolar cycloaddition. In the first step, the cycloaddition of 4-alkyloxyphenylnitrile oxide (4a–d) and vinylacetic acid (5) gave the initial unobserved 1:1 cycloadducts 2-[3-(4-alkyloxyphenyl)-4,5-dihydroisoxazol-5-yl]acetic acid (6a–d). In the second step, the addition of
Liquid Crystals, 2004
Small angle X-ray scattering was used to examine the new chiral side chain liquid crystalline pol... more Small angle X-ray scattering was used to examine the new chiral side chain liquid crystalline polyacrylates (P4M and P11M) and their mixtures (2 wt %) in the low molar mass nematogenics 4′-n-pentyl-4-cyanobiphenyl (5CB) and 4′-octyl-4-cyanobiphenyl (8CB). Complementary data were obtained by polarizing optical microscopy. In agreement with previous studies, the mesophases of the bulk polymers show a dependence on the aliphatic spacers
Journal of Thermal Analysis and Calorimetry, 2005
Journal of the Brazilian Chemical Society, 2006
The influence of the chemical structure of the mesogenic groups and the length of the spacer grou... more The influence of the chemical structure of the mesogenic groups and the length of the spacer groups on the phase behavior in a series of side-chain liquid crystalline polyacrylates (SCLCP) have been studied using Small Angle X-ray Scattering (SAXS) and Polarized Optical Microscopy (POM). Analyses of the mesophase arrangement in unaligned and aligned samples by magnetic field are reported. The role of the spacer length on the local packing and on the thickness of the layers encountered in the SmA and SmC mesophases is elucidated. The tilt angles θ of the mesogenic cores related to the normal of the layers in the SmC mesophases are measured. A study about the degree of order as a function of temperature for the smectic polymers was possible using SAXS measurements. A particular arrangement in one of the studied SCLCPs is related to the coexistence of two different phases.
Macromolecular Symposia, 2005
ABSTRACT
Journal of The Brazilian Chemical Society, 2001
... Aloir A. Merlo*, Olga MS Ritter, Fabiano V. Pereira, Carolina H. Vieira and Nádya P. da Silve... more ... Aloir A. Merlo*, Olga MS Ritter, Fabiano V. Pereira, Carolina H. Vieira and Nádya P. da Silveira*. ...Bento Gonçalves, 9500, Campus do Vale, 91501 970, Porto Alegre - RS, Brazil. ... quirais líquido cristalinos com cadeia lateral derivados do (S)-(-)2-metil-1-butanol são descritos. ...
Polymer Bulletin, 1999
Summary The synthesis and phase behavior of three homopolymers with liquid crystalline side-cha... more Summary The synthesis and phase behavior of three homopolymers with liquid crystalline side-chains is described. These new homopolymers show a dependence of the phase transition temperatures on the molecular weight. The synthesized material exhibits typical mesomorphism-nematic, smectic A and C. We compare the mesomorphic behavior of the homopolymers of the different liquid crystals polyacrylates. In addition, a dynamic and static
Tetrahedron Letters, 2011
A collection of isoxazoles derivatives has been efficiently synthesized in three steps. The oxima... more A collection of isoxazoles derivatives has been efficiently synthesized in three steps. The oximation reaction of aldehydes followed by nitrile oxide [3+2] 1,3-dipolar cycloaddition and MnO 2 -oxidation reaction furnished the title compounds which were purified by simple filtration on celite Ò .
Tetrahedron, 2008
A homologous series of the new N-heterotolans 8aed were synthesized using two cross-coupling reac... more A homologous series of the new N-heterotolans 8aed were synthesized using two cross-coupling reactions mediated by copper and palladium/copper. The final compounds present the phenyl-pyridyl framework connected by the acetylene group. The evaluation of thermal properties for this series is described. All compounds exhibit the smectic A and X mesophase. For comparison were also synthesized compounds 10, 12, and 14. Their LC properties are reported.
Synthetic Communications, 1993
Química Nova, 2001
... R mes corresponde às unidades 4'-n-alcoxibifenilas e 5-n-alcóxi-(2-fenil)pirimidinas, re... more ... R mes corresponde às unidades 4'-n-alcoxibifenilas e 5-n-alcóxi-(2-fenil)pirimidinas, respectivamente. ... Cryst. Liq. Cryst. 1991, 209, 349 [ Links ]. 28. Goodby, JW; Waugh, MA; Stein, SM; Chin, E.; Pindak, R.; Patel, JS; J. Am. Chem. Soc. 1989, 111, 8119. [ Links ]. 29. ...
Polymer, 2002
The solution behaviour of a new mesogenic side group polyacrylate in tetrahydrofuran and toluene ... more The solution behaviour of a new mesogenic side group polyacrylate in tetrahydrofuran and toluene has been investigated by static and dynamic light scattering. In the dilute regime the polymer behaves as typical polydisperse linear chains in good solvent and the dynamics is dominated by a single fast mode. Cluster formation was detected starting at a concentration around 50gl−1. It seems to be independent of the solvent as well as of polymer molecular weight. In the semidilute regime, the behaviour of the reduced osmotic modulus leads to the conclusion that repulsion between the chains is stronger than in linear macromolecules. The appearance of larger clusters was revealed above a characteristic concentration and is slightly dependent on the polyacrylate molecular weight. The dynamics was generally characterised by a fast mode related to the cooperative diffusion and by a slow mode associated with large clusters. The existence of a network of multiconnected clusters is envisaged wit...
Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, 1994
... T. R. TAYLOR and TEODOSIO KROlN Departamento de Fisica, Universidade Federal de Santa Catarin... more ... T. R. TAYLOR and TEODOSIO KROlN Departamento de Fisica, Universidade Federal de Santa Catarina; 88.000 Florianopolis, SC, Brazil ... The transition temperatures for all compounds were determined by optical mi-croscopy using a Leitz Ortholux Polarizing Microscope in ...
Liquid Crystals, 2008
The mesophase behaviour of a side‐chain liquid crystalline polyacrylate (LCP) grown by drying a s... more The mesophase behaviour of a side‐chain liquid crystalline polyacrylate (LCP) grown by drying a solution has been investigated. This LCP, characterised by a short spacer (four carbon atoms) and a long tail (10 carbon atoms), displays, at increasing temperatures, SmC and SmAd phases. The effect of the mean molecular weight, i.e. the mean number of side chains per polyacrylate main
Liquid Crystals, 2000
Two homologous series, 4¾ -(4-n-alkoxybenzoyloxy)-4-substituted 3-nitrotolans (Ia-d) and 4¾ -(4-n... more Two homologous series, 4¾ -(4-n-alkoxybenzoyloxy)-4-substituted 3-nitrotolans (Ia-d) and 4¾ -(4-n-alkoxybenzoyloxy)-4-substituted tolans ( IIa-c), with substituents (S)-2-methyl-1-butyl and n-alkyl, were synthesized by Sonogashira's coupling. Their mesomorphic behaviour is reported. The thermal stability of the series II is higher than that of series I. Series I melting points and clearing points are lower than those of series II. None of the chiral tolans or m-nitrotolans have an enantiotropic smectic C phase. When the chiral chains are changed to n-alkyl groups in compounds Ia,b and IIa, an enantiotropic smectic C phase is seen. All compounds have a nematic or cholesteric phase, and two homologues of series II present a monotropic smectic C phase with mosaic texture. The mesophases were characterized using optical polarized light microscopy and diOE erential scanning calorimetry.
Liquid Crystals, 2008
... a , Guilherme D. Vilela a , Paulo H. Schneider a , Olga MS Ritter b & Aloir A. Merlo a * ... more ... a , Guilherme D. Vilela a , Paulo H. Schneider a , Olga MS Ritter b & Aloir A. Merlo a * pages 833-840. ... 8: 47???51. (a); (b) Walba, DM; Keller, P.; Parmar, DS; Clark, NA; Wand, MD J. Am. Chem. Soc. 1989, 111, 8273???8274; (c) Yoshizawa, A.; Nakata, M.; Yamaguchi, A. Liq. Cryst. ...
Liquid Crystals, 2004
Starting from (2)-menthone, a new chiral building block useful for liquid crystal preparation was... more Starting from (2)-menthone, a new chiral building block useful for liquid crystal preparation was synthesized. This chiral moiety was attached to selected phenols under mild conditions by esterification. Rigid cores of tolanebenzoates and phenylbenzoates were prepared using the palladium cross-coupling reaction or by traditional liquid crystal synthesis methods. This convergent approach ended with a second esterification or palladium cross-coupling reaction to furnish new liquid crystal materials with smectic A, smectic C* and N* phases, as well as blue phases (BP). Thermal behavior, and the effect of chiral moiety branches and molecular packing in the smectic phases, have been investigated using differential scanning calorimetry, optical microscopy and X-ray diffraction.
Liquid Crystals, 2002
ABSTRACT The synthesis of chiral side chain liquid crystalline polyacrylates with a two-stereogen... more ABSTRACT The synthesis of chiral side chain liquid crystalline polyacrylates with a two-stereogenic centre from L-α-aminoacid is described. The chiral tail is 2-chloroalcohol obtained from L-isoleucine and the spacer group has either four or eleven methylene units. The mesogenic moiety is derived from phenyl benzoate. The stereochemistry of the key intermediate (2S,3S)-(+)-4- [1-(2-chloro-3-methyl)pentyloxy]phenyl benzoate (6) obtained by a Mitsunobu reaction was established by single crystal X-ray analysis. This result indicates that the nucleophilic displacement of chiral diazonium salts proceeds with overall retention of configuration. The liquid crystalline behaviour of polyacrylates P13 and P14 was investigated by DSC, optical microscopy, small angle X-ray scattering and depolarized light scattering. The polyacrylate P13, with eleven methylene units in the spacer, exhibits a chiral smectic A phase whereas the polyacrylate P14, with a spacer containing four methylene units, displays a chiral nematic phase.
Liquid Crystals, 2010
The synthesis and mesomorphic properties of new liquid-crystalline 3,5-disubstituted isoxazolines... more The synthesis and mesomorphic properties of new liquid-crystalline 3,5-disubstituted isoxazolines are presented and discussed. These isoxazoline derivatives have been synthesised by reacting oximes with the appropriate 4-substituted styrene dipolarophiles in the presence of N-...
Liquid Crystals, 2012
A simple and efficient procedure for the synthesis of a new class of organoselenium liquid crysta... more A simple and efficient procedure for the synthesis of a new class of organoselenium liquid crystal compounds was developed. The coupling of aryl bromides with elemental selenium was catalysed using copper oxide nanopowder in the presence of potassium hydroxide employing dimethyl sulfoxide as the solvent. This is the first report of the synthesis and characterisation of liquid crystal-based diselenides. Their
Liquid Crystals, 2012
Four liquid crystals (LC) 3,7a-bis(4-alkyloxyphenyl)-7,7a-dihydro-6H-isoxazolo[2,3-d][1,2,4]oxadi... more Four liquid crystals (LC) 3,7a-bis(4-alkyloxyphenyl)-7,7a-dihydro-6H-isoxazolo[2,3-d][1,2,4]oxadiazol-6-yl)acetic acid (7a–d) were synthesised and the mesomorphic behaviour reported. The LCs were characterised as 2:1 bisadducts, which were obtained from a double [3 + 2] 1,3-dipolar cycloaddition. In the first step, the cycloaddition of 4-alkyloxyphenylnitrile oxide (4a–d) and vinylacetic acid (5) gave the initial unobserved 1:1 cycloadducts 2-[3-(4-alkyloxyphenyl)-4,5-dihydroisoxazol-5-yl]acetic acid (6a–d). In the second step, the addition of
Liquid Crystals, 2004
Small angle X-ray scattering was used to examine the new chiral side chain liquid crystalline pol... more Small angle X-ray scattering was used to examine the new chiral side chain liquid crystalline polyacrylates (P4M and P11M) and their mixtures (2 wt %) in the low molar mass nematogenics 4′-n-pentyl-4-cyanobiphenyl (5CB) and 4′-octyl-4-cyanobiphenyl (8CB). Complementary data were obtained by polarizing optical microscopy. In agreement with previous studies, the mesophases of the bulk polymers show a dependence on the aliphatic spacers
Journal of Thermal Analysis and Calorimetry, 2005
Journal of the Brazilian Chemical Society, 2006
The influence of the chemical structure of the mesogenic groups and the length of the spacer grou... more The influence of the chemical structure of the mesogenic groups and the length of the spacer groups on the phase behavior in a series of side-chain liquid crystalline polyacrylates (SCLCP) have been studied using Small Angle X-ray Scattering (SAXS) and Polarized Optical Microscopy (POM). Analyses of the mesophase arrangement in unaligned and aligned samples by magnetic field are reported. The role of the spacer length on the local packing and on the thickness of the layers encountered in the SmA and SmC mesophases is elucidated. The tilt angles θ of the mesogenic cores related to the normal of the layers in the SmC mesophases are measured. A study about the degree of order as a function of temperature for the smectic polymers was possible using SAXS measurements. A particular arrangement in one of the studied SCLCPs is related to the coexistence of two different phases.