Spacer polyacrylates

Table I demonstrates that most liquid crystalline polymers lacking a spacer are formed from a flexible polyacrylate backbone. In contrast, the methyl substituent in polymethacrylate backbones both reduce main chain mobility and imposes additional steric barriers to mesophase formation. Therefore, successful liquid crystalline formation of polymethacrylates has been achieved only...

Note 3 Examples of polymer backbones are polyacrylates, polymethacrylates, and polysiloxanes the spacers are usually oligomethylene, oligo(oxyethylene), or oligosiloxane. 

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. 

It is not necessary to carry out synthesis, if the triggering photochromic compound has good affinity to the polymer matrix. A mixture of the polyacrylate with BMAB which exhibits an excellent function as trigger is equally photoresponsive. While the monomer model compound (i.e. the acrylate before polymerization) does not provide a liquid crystalline phase, the polymer shows a clear nematic - isotropic transition at ca. 61 °C and the glass transition temperature at 24 °C as shown in Fig. 4. Tj j depends very much on the length of the alkyl spacer. In comparison with the... 

We have discussed the influence of the flexibility of the polymer backbone on the mesophase formation by examples of polyacrylates and polymethacrylates. More flexible polymers should have a stronger tendency to form more stable mesophases. Nevertheless, smectic liquid crystalline phases are the most common mesophases formed, if they do indeed form, by polymers in which no flexible spacers are used to connect main chain and... 

Flexible spacer and mesogenic unit Polymethacrylate ( 3.51 ) Polyacrylate ((3.52)) Polysiloxane ((3.53))... 

Fig. 5,11. Order distribution-functions of various parts of a polyacrylate with side-chain mesogen (phenylene-4-hydroxybenzoate) separated by a flexible spacer (hexamethylene). Determined from the angular dependence of the deuterium NMR line-shape. Presented by H. W. Spiess, Dechema Tagung 1987, see also Refs. The angle p is defined between the ma etic field and the...

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]. 

Many reviews [1-3] of SCLCPs describe the structure of the backbone (main chain), the spacer (flexible linkage), and the side group (mesogenic unit) of the SCLCP. For example, the most widely used backbones include polyacrylates or polymethacrylates, polysiloxanes, and polyphosphazenes po-ly-ct-chloroacrylates, itaconates, and ethylene oxides have also been reported. 

The general structure of a homopolymer is shown in Fig. 1. Most of the SmC LCPs synthesized so far are derived from polyacrylate, polymethacrylate, or polymethylsi-loxane backbones. Some polyoxyethylenes [7] as well as some poly vinylethers [8] have also been prepared. The mesogenic core structures, the tails, and the spacers generally used to obtain SmC LCPs are respectively summarized in Figs. 2-4. 

Study of the variation of the spacer length in polyacrylates V-n has shown that the spontaneous polarization increases when the spacer is shortened [21]. This could be... 

SmC polyacrylate XIV, having a chiral center in its spacer (Fig. 21), also shows, at... 

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. 

Fig. 4. Stiff, main and side chain high-molecular weight thermo- and lyotropics (left to right and top to bottom) aromatic polyamides,10 cellulose triacetate,H azoxybenzene polymers with flexible main chain spacers,12 polyacrylates with flexible side chain spacers,13 polysiloxanes with a combination of flexible main and side chain parts.1 >13... 

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