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End-on and side-on nematic liquid crystal dendrimers

End-on and side-on nematic liquid crystal dendrimers
End-on and side-on nematic liquid crystal dendrimers
A group of nematic materials based on poly(propyleneimine) dendrimers (PPI) containing two types of mesogenic subunits were synthesized. The presence of different types of mesogenic group, the topology of the attachment to the core (end-on and side-on), and the chemical nature of the linking connection to the PPI scaffold (imine or amide) were used to tailor the mesomorphic properties. The materials were characterized by a variety of techniques including H-1, C-13 NMR spectroscopy, GPC, MALDI-TOF MS, DSC, POM, and X-ray diffraction. The crystalline state, when it exists, was found to be suppressed for most of the materials once they had undergone the first transition to the isotropic phase. The majority of the compounds exhibited glass transitions near to or lower than room temperature and an accompanying wide temperature range mesophase. All of the side-on dendrimers synthesized exhibit a nematic mesophase whereas end-on dendrimers exhibit different mesophases depending on the length of the terminal chain of the mesogenic unit (nematic for n = 2, 4, 5). The H-2 NMR technique was used to investigate the symmetry of the nematic phase formed by the side-on dendrimers (G = 3). These studies revealed that the symmetry of the nematic phase is uniaxial. They also allow the investigation of the orientational order of the phase and the rate of field-induced director alignment.
induced director dynamics, smectic-a phase, mesogenic groups, chain polymers, dependence, series
9386-9394
Pastor, Laura
e641fed7-8b09-4516-abf3-7c951ad03652
Barberá, Joaquín
91d0773b-0111-4049-b471-03bcce29243f
McKenna, Mark
edd4f7c6-1646-4311-b2d6-5c3af0e5eb3e
Marcos, Mercedes
139ea1fa-ee62-4f3e-8ddb-36596cfbdbad
Martín-Rapún, Rafael
006e3911-303b-454d-8a93-d0c8e78fbebd
Serrano, José Luis
493d6d6f-8e7c-4bee-83bc-645b980c9e01
Luckhurst, Geoffrey R.
7807d1c6-54a1-414f-9abe-22de4d9c30f7
Mainal, Azizah
d39ab96f-1277-445b-9f73-8e5133bc67e4
Pastor, Laura
e641fed7-8b09-4516-abf3-7c951ad03652
Barberá, Joaquín
91d0773b-0111-4049-b471-03bcce29243f
McKenna, Mark
edd4f7c6-1646-4311-b2d6-5c3af0e5eb3e
Marcos, Mercedes
139ea1fa-ee62-4f3e-8ddb-36596cfbdbad
Martín-Rapún, Rafael
006e3911-303b-454d-8a93-d0c8e78fbebd
Serrano, José Luis
493d6d6f-8e7c-4bee-83bc-645b980c9e01
Luckhurst, Geoffrey R.
7807d1c6-54a1-414f-9abe-22de4d9c30f7
Mainal, Azizah
d39ab96f-1277-445b-9f73-8e5133bc67e4

Pastor, Laura, Barberá, Joaquín, McKenna, Mark, Marcos, Mercedes, Martín-Rapún, Rafael, Serrano, José Luis, Luckhurst, Geoffrey R. and Mainal, Azizah (2004) End-on and side-on nematic liquid crystal dendrimers. Macromolecules, 37 (25), 9386-9394. (doi:10.1021/ma048450p).

Record type: Article

Abstract

A group of nematic materials based on poly(propyleneimine) dendrimers (PPI) containing two types of mesogenic subunits were synthesized. The presence of different types of mesogenic group, the topology of the attachment to the core (end-on and side-on), and the chemical nature of the linking connection to the PPI scaffold (imine or amide) were used to tailor the mesomorphic properties. The materials were characterized by a variety of techniques including H-1, C-13 NMR spectroscopy, GPC, MALDI-TOF MS, DSC, POM, and X-ray diffraction. The crystalline state, when it exists, was found to be suppressed for most of the materials once they had undergone the first transition to the isotropic phase. The majority of the compounds exhibited glass transitions near to or lower than room temperature and an accompanying wide temperature range mesophase. All of the side-on dendrimers synthesized exhibit a nematic mesophase whereas end-on dendrimers exhibit different mesophases depending on the length of the terminal chain of the mesogenic unit (nematic for n = 2, 4, 5). The H-2 NMR technique was used to investigate the symmetry of the nematic phase formed by the side-on dendrimers (G = 3). These studies revealed that the symmetry of the nematic phase is uniaxial. They also allow the investigation of the orientational order of the phase and the rate of field-induced director alignment.

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More information

Published date: 14 December 2004
Keywords: induced director dynamics, smectic-a phase, mesogenic groups, chain polymers, dependence, series

Identifiers

Local EPrints ID: 20880
URI: http://eprints.soton.ac.uk/id/eprint/20880
PURE UUID: 20dc8043-1bae-45a9-87be-2bfa1ccd9e23

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Date deposited: 02 Mar 2006
Last modified: 15 Mar 2024 06:26

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Contributors

Author: Laura Pastor
Author: Joaquín Barberá
Author: Mark McKenna
Author: Mercedes Marcos
Author: Rafael Martín-Rapún
Author: José Luis Serrano
Author: Geoffrey R. Luckhurst
Author: Azizah Mainal

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