Side chain PLCs

Surface alignment may also have a positive effect on the alignment on side chain PLCs, particularly in combination with other alignment methods [86,94,117]. 

Unlike main chain PLCs, the mesogenic units in side chain PLCs are located not in the polymer backbone but in the side chains. The dynamics of a side chain PLC is therefore determined by the behavior of both the backbone and the mesogenic groups as well as the coupling between them. Neutron scattering studies [43,44] reveal that the polymer... 

Benguigui and co workers [16,17] are the only group which has measured the ultrasonic modulus and absorption of side chain PLC. The PLC studied is a polymethylsiloxane with the following chemical structure ... 

For side chain PLCs there are two orienting molecular elements which can influence the elastic properties the mesogenic groups and the monomer units of the polymer backbone. The fact that is... 

Kruger and coworkers [13-15] have employed the Brillouin scattering technique to determine the stiffness constants of three side chain PLCs with a polymethacrylate backbone. The chemical structures of these PLCs are shown in Figure 14.33 while the transition temperatures and stiffness constants are given in Table 14.11. For these measurements. 

There have been very few studies of the acoustic absorption of PLCs, probably because of the difficulty in interpreting the data. To date, absorption measurements have been carried out mainly to reveal the relaxation peak associated with the glass transition in side chain PLCs. 

Before the classification in [25] was proposed, one talked about main-chain and side-chain PLCs. It is clear from looking at classes such as a, p, -y, and that the name main-chain is far from sufficient, since it includes... 

Fig. 5.20. Some simple topologies of polymer liquid crystals (PLCs) derived from calamltic and discotic mesogenic cores main-chain PLCs, copolymers with core and flexible spacer alternating side-chain PLCs with mesogenic cores attached by flexible spacers to the main chain of a conventional polymer and dendritic (or star-shaped) stmctures with mesogens emanating from a central core via flexible spacers.

The rate of production of DAG in the cell does not occur linearly with time, but rather it is biphasic. The first peak is rapid and transient and coincides with the formation of IP3 and the release of Ca2+ this DAG is therefore derived from the PI-PLC catalyzed hydrolysis of phosphatidylinositols [1]. There is then an extended period of enhanced DAG production that is now known to be derived from the more abundant phospholipid phosphatidylcholine (PC), which has a different composition of fatty acid side chains [9]. Although DAG may be generated directly from PC through the action of PC-PLC, it can also be formed indirectly from PC. In this pathway, PC is first hydrolyzed by PLD to give choline and phosphatidic acid, which is then converted to DAG by the action of a phos-phatidic acid phosphatase [10,11 ]. 

The length of the acyl side chains of a phosphatidylcholine derivative have significant effects upon the rate with which PLC i( catalyzes the hydrolysis of... 

Although the stabilizing interactions between the amino acid side chains of PLC/j, and the choline headgroup are readily apparent in the PLC fc-phosphonate inhibitor complex, it is more difficult to identify contacts between the protein and the acyl chains of the inhibitor [45]. In part this is because thermal motion in the acyl side chains, especially the sn-1 chain, renders them somewhat disordered. Consequently, the measured distances between the side chain carbons... 

Fig. 12. Reaction mechanism of oxaldie 1 catalyzed decarboxylation of oxaloacetate.The organization of several flanking lysine residues depresses the plC of the catalytically active Lys side chain. The free amino terminal of the folded peptide is the most reactive residue because its plC is depressed by the positive end of the helix dipole...

There is approximately a dozen of classes of PLCs known today, differing in location (in the backbone, in the side-chain, etc.) and shape ( rod, cross, disc, etc.) of the mesogenic groups. The first comprehensive systematical classification was proposed in (26) and somewhat amplified later (Brostow, W. Polymer 1990, in press), see also (22). 

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