Spacer groups flexible

In this paper two new polymerized vesicle systems have been presented. The first lipid can be polymerized in vesicle through UV irradiation. Because the second lipid contains a flexible spacer group it can be prepolymerized in benzene and then converted to vesicles by ultrasonication in water. The polymerization improves the stabilities of the synthetic liposomes. Since there is a acetal linkage between the... 

The first generation NLO polymers were side chain polymers, usually made by copolymerisation of a monomer bearing the chromophore bridged by a flexible spacer group with a co-monomer, commonly methacrylates. This is a flexible process allowing a wide range of co-polymers to be made. A typical example of this type of polymer is the methyl methacrylate azo dye co-polymer (5.9). 

Polymers with 6H4SNSNSC6H4- or -C6H4SNSNS CeUiSNSNSCeUi segments separated by flexible spacer groups have also been synthesized. These insulators are converted to semiconductors (see Semiconductors) when doped with Br2. 

Finally, it is possible that side chains in polymers with very long side chains occur in mesomorphous structures, whereas the main chain is amorphous below the glass transition temperature, and behaves like a normal liquid above it. This type of behavior is observed when the movements of the main and side chains are decoupled by flexible spacer groups joining them together. An example of this is a poly(methacrylate) with the monomeric unit ... 

In this paper three kinds of polymers will be considered (polymers 1, 2 and 3) in which mesogenic groups are either attached to the flexible backbone via flexible spacer groups (polymers 1 and 2) or directly without spacer groups. The polymers studied are shown in table 1. 

Polymers with flexible spacer groups. Polymers obtained by precipitation or by casting films from solutions were found to be amorphous as shown by X-ray and microscopical observations. The DSC data revealed that on heating up the samples for the first time a stepwise increase of the specific heat occurred which could be attributed to a glass transition. Thus at room temperature the as received samples were in the isotropic glassy state, apparently no liquid crystalline solutions exist. 

Polymers without flexible spacer groups. The DSC curves of t he polymer 3 indicated the existence of a liquid crystalline glassy state at room temperature. The polymer was found to be smectic. Two melting peaks were observed in the temperature range between 300 and 310 deg. C. These peaks are not as easily observed as in the case of the polymers discussed above, since the decomposition takes place in the same temperature range. The occurrence of exothermic peaks on cooling nevertheless indicates that reversible melting and crystallization processes take place. 

Polymers with flexible spacer groups. Smectic or nematic polymers were obtained depending on the nature of the substituent R in the case of polymers 1 (Table 2). It has to be pointed out that the structures at temperatures above the glass transition temperatures are equilibrium structures, since thermodynamically stable liquid crystalline phases exist. This is in contrast to most systems studied until now where only liquid crystalline structures were obtained ... 

In the case of the polymers 2 smectic structures were observed for the homopolymers, that is for polymers in which the flexible spacer group was constant. 

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