Amorphous—liquid-crystalline side-chain

Amorphous—Liquid-Crystalline Side-Chain AB Block Copolymers Synthesis and Morphology... 

The amorphous segment of microphase-separated amorphous/liquid crystalline block copolymers may influence the ordering of the mesogens at the interface, as well as the size and discreteness of that interface. Living copolymerizations are therefore being used to determine the effect of the morphology and domain size on the thermotropic behavior of side-chain liquid crystalline block copolymers. 

The LSCEs represent a new class of macromolecular systems distinguished by macroscopically uniform anisotropy. The concept of LSCE can be furthermore extended to other synthesis routes and to the densely crosslinked systems. Macroscopic uniaxially oriented films can be formed by mechanical force, alignment surface [30], magnetic and electric fields [31], polarized light [32], etc., and then crosslinked to form an anisotropic network (LC network is abbreviated as LCN) if the mixture components contain polymerizable or crosslink-able bifunctional monomers (Figure 9.13). Alternatively, amorphous or liquid crystalline side-group and/or main-chain polymers incorporating additional... 

Whereas poly(9,9-dihexylfluorene) (PDHF, 195) is generally considered as amorphous, PF with longer octyl side chains, PFO 196, is crystalline material. Many PFs — dioctyl (PFO 196 [228,230,231]) or 2-ethyl hexyl) (197 [232]) as well as some fluorene copolymers [233] exhibit liquid crystalline behavior, opening a possibility to fabricate polarized LEDs [224,234,235] (Chart 2.45). 

The first approach has successfully been applied to the study of amorphous as well as to macroscopically ordered solids. Examples of applications include the determination of backbone geometries in fibrous proteins [4] or the determination of protein-backbone, side-chain, and bound-ligand orientation with respect to the membrane normal in membrane-bound proteins [5-8]. Membranes, bilayers, bicelles, or liposomes are neither solid nor liquid systems but have aspects of both and are sometimes liquid crystalline. In most of these systems, time-independent anisotropic interactions play an important role,... 

Komiya et al. described the living ROMP synthesis of AB-type block copolymers that contain side chain liquid crystalline polymer blocks and amorphous blocks [62]. Norbornene (NBE), 5-cyano-2-norbornene (NBCN) and methyl-tetracyclododecene (MTD) were used for the amorphous polymer blocks, while I-n (n=3,6) were used for the SCLCP block (see Fig. 9). Initiator 1 was used for the ROMP. Block copolymers with monomer ratios from 75/25 to 20/80 (amor-... 

These results corroborate the experimentally measured data and predict torsional barriers. Furthermore, the calculations provide a detailed picture at the molecular level of the available isomeric states and show that the mobility of the side chains at temperatures below Tg should differ from that at temperatures above Tg for some cases. Additional experiments will test our conclusion. The theoretical description of the isomeric states provides grounds for predicting the crystalline and amorphous forms of the polymeric materials in the solid and liquid states. 

Novel vinyl liquid crystalline (l.c.) polymers were synthesized with the UV-sensitive p-methoxycinnamate chromophore incorporated into the side chain of the polymers. The objective of this synthesis was to determine if a molecularly organized environment could influence the yield of a chemical reaction in the solid state. The investigation into the photochemical and physical processes of these thin films revealed that the photodimerization of the p-methoxycinnamate moieties was very sensitive to their geometrical arrangement in the polymer matrix. The relative quantum yield of cyclobutane formation increased by a factor of approximately 8 for the l.c. p-methoxycinnamate film compared to its amorphous analog. This quantum yield approaches the theoretical limit for this system. 

It is difficult to grow a good organic crystal film and a Langimur-Blogette film of up to 1 micron thickness. However, polymers have a wide choice and can be tailored to meet the above requirements. The polymers may be side chain liquid crystalline polymers, ferroelectric liquid crystalline polymers and amorphous polymers. Among them the side chain liquid crystalline polymers have drawn more attention. 

The development of H-bonded complexes is now considered. An influence of UV irradiation on optical properties of low-molecular-weight azobenzene-con-taining material (Fig. 2.4b) has been investigated (Aoki et ah, 2000) on the basis of such interactions. The first observation of photoinduced optical anisotropy in H-bonded complexes of azobenzene dyes and copolymers (Fig. 2.4b) has been recently demonstrated (Medvedev et ah, 2005). In this case, the induced anisotropy was stable, and the maximum dichroic ratio of 2 has been observed. A kinetics of the induction of birefringence (maximum value of ca. 0.01) in one of these complexes is shown in Fig. 2.5. An influence of H-bonding on the mesomorphic and photoorientation properties was recently demonstrated (Cui and Zhao, 2004). In this approach, the amorphous azopyridine side-chain polymer was converted into liquid crystalline polymers through self-assembly with a series of commercially available, aliphatic, and aromatic carboxylic acids (Fig. 2.4d). 

Adams J, Gronski W. 1989. LC side chain AB block copolymers with an amorphous A block and a liquid crystalline B block. Macromol Rapid Commun 10 553 557. 

Amorphous-Side-Chain Liquid Crystalline Block Copolymers. 52... 

Polymers with side chain structure similar to that of low molecular weight liquid crystalline compounds can achieve various levels of organization in the bulk. These polymers are sometimes formed by polymerization of vinyl monomers that themselves exhibit mesomorphic behavior. In other cases, they can be obtained from monomers that do not form liquid crystalline states. At one extreme the structure of the polymer is highly organized, approaching that of crystalline polymers and giving rise to a number of x-ray diffraction peaks. At the other extreme the polymer chains are disorganized, with x-ray diffraction patterns that resemble those from amorphous polymers. 

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