3.10 - Nitroxide-Mediated Polymerization

Rigid polymer backbones have often been considered to be detrimental to the packing of mesogenic pendants, and polyacetylenes have generally been regarded as unpromising materials for light-emitting applications. Our group, however, has succeeded in creating a series of liquid-crystalline polyacetylenes with rigid backbones and a variety of light-emitting polyacetylenes with luminescent chromophores. Here we demonstrate that the rigid polyacetylene skeleton can play a constructive role in guiding the alignments of mesogenic pendants and prove that polyacetylenes can be highly emissive with photoluminescence quantum yields of up to 98% and electroluminescence performances comparable or superior to those of the best blue-light-emitting polymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2607–2629, 2003

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/pola.10802

Liquid‐crystalline and light‐emitting polyacetylenes

A free radical initiated optically active vinyl polymer with memory of chirality after removal of the inducing stereogenic center

We report the synthesis and characterization of a series of novel mesogen- jacketed liquid-crystalline polymers, poly(2,5-bis(4 0 -alkoxycarbonylphenyl)styrene)s (1-m, where m is the number of carbon atoms in the alkyl tails), along with the corre- sponding monomers, 2,5-bis(4 0 -alkoxycarbonylphenyl)styrenes (2-m), and their precur- sors, 2,5-bis(4 0 -alkoxycarbonylphenyl)toluenes (3-m). The influence of the tail length on the thermotropic properties of the two types of low-molecular-mass compounds and macromolecules was investigated with a combination of differential scanning calorime- try, polarized optical microscopy, and wide-angle X-ray diffraction techniques. Except for compound 3-3, which exhibited a monotropic nematic phase, all members of the low-molar-mass molecules developed no mesophase during both heating and cooling processes. The glass-transition temperatures of the polymers decreased as the tail lengths increased. The 5% weight loss temperatures of all the polymers under a nitro- gen atmosphere were above 360 8C, indicating quite high thermal stability. Although polymers 1-1 and 1-2 were non-liquid-crystalline, columnar nematic phases were observed for the remaining homopolymers with longer alkyl tails. The mesophases of 1-3 to 1-9 that developed at high temperatures remained upon cooling to room temper- ature, whereas those of 1-10 to 1-12 disappeared during the cooling process. V C 2007

Synthesis and characterization of a thermotropic liquid‐crystalline poly[2,5‐bis(4′‐alkoxycarbonylphenyl) styrene]

A novel combined main-chain/side-chain liquid crystalline polymer based on mesogen-jacketed liquid crystal polymers (MJLCPs) containing two biphenyls per mesogenic core of MJLCPs main chain, poly(2,5-bis{[6-(4-butoxy-4'-oxy-biphenyl)hexyl]oxycarbonyl)styrene) (P1-P8) was successfully synthesized via atom transfer radical polymerization (ATRP). The chemical structure of the monomer was confirmed by elemental analysis, 1 H NMR, and 13 C NMR. The molecular characterizations of the polymer with different molecular weights (P1-P8) were performed with 1 H NMR, gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). Their phase transitions and liquid-crystalline behaviors of the polymers were investigated by differential scanning calorimetry (DSC) and polarized optical microscope (POM). We found that the polymers P1-P8 exhibited similar behavior with three different liquid crystalline phases upon heating to or cooling in addition to isotropic state, which should be related to the complex liquid crystal property of the side-chain and the main-chain. Moreover, the transition temperatures of liquid crystalline phases of P1-P8 are found to be dependent on the molecular weight.

Design, synthesis, and characterization of a combined main‐chain/side‐chain liquid crystalline polymer based on mesogen‐jacketed liquid crystal polymer via atom transfer radical polymerization

A series of novel reactive liquid crystals, 2,5-bis(4'-alkoxy-phenyl)styrene, was designed and synthesized to prepare stereoregular mesogen-jacketed liquid crystal polymers (MJLCPs). These monomers are different from their analogous studied previously in that they do not contain polar linkages such as ester or/and amide group and therefore are expected to polymerize easily both by radical and ionic polymerization. The preliminary studies show that the resulting polymers have higher glass transition temperature (Tg) and much better thermal stability than their analogous.

Synthesis and polymerization of 2,5-Bis(4′-alkoxy-phenyl)styrene for mesogen-jacketed liquid crystal polymers

The first TEMPO-mediated 'living' free radical polymerization of liquid crystallinemonomer, 2, 5-bis[(4-methoxyphenyl)oxycarbonyl]styrene(MPCS), was carried out at 130℃ withBPO as an initiator. The molecular weight of the polymer can be varied from rather low values to highvalues while maintaining narrow polydispersity. It was observed that the polymerization of MPCSproceeded much faster than that of styrene. A tentative explanation for this fast polymerization wassuggested.

Nitroxide-mediated free radical synthesis of mesogen-jacketed liquid crystal polymers *

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Synthesis and polymerization of 2,5-Bis(4′-alkoxy-phenyl)styrene for mesogen-jacketed liquid crystal polymers

Nitroxide-mediated free radical synthesis of mesogen-jacketed liquid crystal polymers *