Side-chain liquid-crystalline polyacrylates

SW Chang, AK Li, CW Liao, and CS Hsu, Polarized blue emission based on a side chain liquid crystalline polyacrylate containing hw-tolane side groups, Jpn. J. Appl. Phys., 41 1374-1378, 2002. 

The first demonstration of azobenzene polymers for holographic storage was made by Wendorff and coworkers who utilized side-chain liquid crystalline polyacrylates (see Fig. 6.14) comprising terminal cyano-substituted azobenzene connected via a hexyloxy tether to an acrylate backbone [45,46],... 

Correia etal. also reported the surface tension [8] and temperature-dependent behavior [9] of a side-chain liquid crystalline polyacrylate (poly( 3-[4-(4-... 

Structure-Dependent Alignment of Side-Chain Liquid-Crystalline Polyacrylates on Anisotropic Surfaces... 

P6CN 6 93 of the investigated side-chain liquid-crystalline polyacrylates. 

The concept of a side chain liquid crystal polymer has been demonstrated in a number of laboratories and is well documented in the literature (J ). Most of the side chain liquid crystalline polymers reported to date contain polysiloxane, polyacrylate or polymethacrylate main chains. More recent studies on the effect of backbone flexibility now include the use of flexible poly(ethylene oxide) or more rigid poly( a-chloroacrylate) chains. 

The study by Percec, Tomazos and Willingham (15) looked at the influence of polymer backbone flexibility on the phase transition temperatures of side chain liquid crystalline polymethacrylate, polyacrylate, polymethylsiloxane and polyphosphazene containing a stilbene side chain. Upon cooling from the isotropic state, golymer IV displays a monotropic nematic mesophase between 106 and 64 C. In this study, the polymers with the more rigid backbones displayed enantiotropic liquid crystalline behavior, whereas the polymers with the flexible backbones, including the siloxane and the polyphosphazene, displayed monotropic nematic mesophases. The examples in this study demonstrated how kinetically controlled side chain crystallization influences the thermodynamically controlled mesomorphic phase through the flexibility of the polymer backbone. 

Ringsdorf and coworkers [71] have shown that it is possible to induce liquid crystalline phases, namely discotic-columnar mesophases, by doping amorphous polymers containing disk-shaped electron donors, in either the side chain or the main chain, with a low molar mass electron acceptor, as shown in Figure 3.31. The resulting complexes can be considered as diskcomb PLCs and disk PLCs, respectively [5]. The electron-rich moiety is a triphenylene unit and the electron acceptors are fluorenone derivatives. When 20-25 mol% of 2,4, 7-trinitrofluorenone (TNF) is added to the side chain polymethacrylate or polyacrylate... 

Tabrizian, M., Bunel, C., Vairon, J. P, Friedrich, C., and Noel, C., Liquid-crystalline polyacrylates containing biphenyl and chiral terminal groups in the side chain. 1. Influence of the spacer length on the liquid-crystal behaviour, Makromol. Chem., 194, 689-704 (1993). 

We chose a polyacrylate with liquid crystalline side chains as shown in Fig. 4. The family of this polymer with different alkyl spacers has been prepared by Ringsdorf and coworkers(25). Recently, they reported an interesting application of the following polymers for image recording(26-28) by means of the photoinduced phase transition principle. 

An initial approach to supramolecular H-bonded mesogenic polymer complexes involves a polyacrylate with 4-oxybenzoic acid moieties via a hexamethylene spacer 29 [26]. The 1 1 complexation of the side chain of the polymer and stilbazole 3 n - 2) (nematic, 168-216 °C) results in the formation of an extended supramolecular mesogen in the side chain (Fig. 11). Side-chain polymer complex 30 exhibits a nematic phase up to 252 °C, which shows that a significantly stabilized mesophase is achieved by the complexation of two different components. Liquid-crystalline properties have been examined for the series of complexes formed between polyacrylates and trans-4-alkoxy-4 -stilbazoles [33, 78]. Figure 12 shows transition temperatures against the carbon number of the alkyl chain for the series of complexes 31 [33]. They exhibit thermally stable smectic liquid-crystalline phases. For example, smectic E, B, and A phases are observed until 192 °C after the glass transition at 38 °C for the complex with m = 6 [78a]. 

Polysiloxanes, polyacrylates, and polymethacrylates are usually used as main-chain components, and alkoxy- or cyano-substitut biphenyls as mesogenic groups. We reported a novel side-chain smectic liquid crystalline polyoxetane with cyano- or fluoro- substituted biphenyl as mesogenic group, and pointed out die importance of the flexibility of the main-chain and the structure of mesogen on the liquid crystalline structure 28-30),... 

The liquid crystalline side chain polymers investigated have either a polysiloxane (compounds SiCl and SIGN) or a polyacrylic (compound AcCN) polymer chain. These are coupled via flexible spacers with the mesogenic p-substituted benzoic acid phenylester groups. SiCl and SiCN are copolymers with p-methoxy components in excess. 

Poly(4 -dialkylamino-4-nitrostilbene acrylate-b-methyl methacrylate) Poly(4 -dlalkylamlno-4-nltrostilbene methacrylate-b-methyl methacrylate) Polyacrylates with NLO active side chains wide range of M up to 186 000 many soluble in methylene chloride or THF two samples show liquid crystallinity microscopy and thermal analysis discussed. [179]... 

Physical cross-linking is easily incorporated into the structures of supramolecular side-chain polymers by using bi- or multifunctional molecules [9,31,93]. The complexation of the functionalized polyacrylates, a stilbazole, and bipyridine molecules form supramolecular side-chain cross-linked polymer 37 (Figure 27) [31,93]. Bis-imidazolyl compounds are also used for such cross-linking [105]. Reversible association-dissociation of the hydrogen bonding leads to the reversible thermal order-disorder transitions, which is an important feature of supramolecular materials. Liquid-crystalline main-chain supramolecular networks have been prepared from multifunctional components [32,123-126], which will be described in Section IV. 

Kato, T, Kihara, H., Uryu, T, Fujishima, A., Frechet, J. M. J. (1992), Molecular self-assembly of liquid-crystalline side-chain polymers through intermolecular hydrogen-bonding - polymeric complexes bruit from a polyacrylate and stilbazoles. Macromolecules, 25,6836-41. 

The induction or stabilization of liquid-crystalline phases in binary CT systems, where the donor and the acceptor compounds are rod-shaped, has been utilized in the design of polymers to enhance their mesomorphic properties the combination of mesomorphic properties and those of polymeric systems, e.g., glassy behavior, has attracted interest due to possible applications, for example, in the field of nonlinear optics. Side-chain copolymers with a polyester or polyacrylate backbone containing 4-me-thoxyazobenzene and 4-cyanoazobenzene units, for example, show the formation of an SmA phase with an enhanced mesomorphic temperature range [30]. Similar behavior is observed for copolystyrene derivatives carrying electron-rich donor units (4-methoxy-... 

The author s group chose polyacrylate [102, 103], polyoxyethylene [104, 105], polysiloxane [103], and a polyacrylate/polysiloxane hybrid polymer [106] as the main chain according to the design in Fig. 1.26b-e. We attached various kinds of side-chain structures onto polymer main chains described above and checked the physical properties of these side-chain-type ferroelectric liquid crystalline polymers (FLCPs). 

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