Crosslinked LCP

Thermosetting LCPs have been reviewed [11]. Crosslinked LCPs may be divided into two categories Thermosetting LCP or LC thermosets. 

On the other hand, single-wall CNTs (SWCNTs) can efficiently absorb and convert photon energy into thermal energy and have excellent thermal conductivities. Thus, they can act as a nanoscale heat source and thermal conduction pathway to heat the crosslinked LCP matrix effectively [51]. Furthermore, the resultant crosslinked PLCP/SWCNT nanocomposites exhibited effective photoactuation not only by white light but by near-IR irradiation as well [52]. Such nanocomposites were used to direct sun-driven artificial heliotropism for solar energy harvesting [53]. 

The first, and until now apparently the only, cellulose derivative converted into a permanently crosslinked LCP network is hydroxypropyl cellulose (HPC) [272-276]. The HPC chains were either first derivatized with groups crosslink-able in a second step by photoinitiation [272,274,276] or were directly reacted with di- or higher-functional crosslinking moiety [273,275] to produce a crosslinked network. Typical bridging groups connecting saccharide rings in adjacent chains, may be ... 

LCP radiation crosslinkable resins for articles that strain-recover upon heating Toy et al., 1994... 

Crosslinking through the side group leads to elastomeric LCPs with interesting properties due to the coupling of the elastic prop-... 

SmC LCPs can retain their mesomorphic properties when their side chains are diluted by functional groups like dyes [57], crosslinkable moieties [20], or NLO chro-... 

Recently, we have developed a real time pulsed NMR(RTPNMR) system(2) controlled by a microcomputer as shown in Figure 3 to study dynamics of structure formation in polymer systems. It has been successfully applied to study crystallization process (3), gelation process(4) and so on. In this paper, application of RTPNMR for characterization of curing process of epoxy resins, polymerization crosslinking process of diacetylenes, and orientation process of liquid crystalline polymers(LCPs) under magnetic field are described. Papers related to the detailed analysis of these data will appear in the near future. EXPERIMENTAL... 

Because of the unique photodeformable behavior of LCPs, a variety of soft actuators such as flexible inchworm walkers [34], plastic motors [35] and high-frequency oscillators [36] have been designed. For these soft photo-driven acm-ators based on LCPs, many factors determine the photo-driven behaviors of actuators, including the wavelength, polarization direction and intensity of the light source, and inherent parameters of actuators such as the concentration of azobenzene moieties, the crosslinking density and the molecular arrangement within actuators. Besides, their mechanical properties, conductivity and overall physical attributes should also be taken into consideration for practical applications (see in Fig. 10.2). 

Figure 9.1 Schematic representation of different types of LC elastomers (LCE) from (a) side chain, (b) main chain, and (c) combined (main chain/side chain) LCPs crosslinking points are circled.

FIGURE 7.24 Photoresponse of crosslinked photoinert LCPs doped with azobenzene dye. An action resembling that of flatfish was observed. 

Here, we shall first describe networks containing stiff mesogenic groups in the main chain, connected to one another and crosslinked by flexible spacers and junctions. We then describe similar networks in which the junctions are stifi branchpoints. After these, networks with flexible main chains and stiff mesogenic pendants will be discussed. These are also divisible into two networks in which the junctions consist of flexible units and networks in which flexible chains are connected to one another by means of stiff mesogenic units reacted at both ends. There exist in the literature several LCP networks containing two kinds of mesogens or two kinds of junctions or crosslinks. These are not amenable yet to theoretical description and will not be specifically discussed. 

The branchpoint substitution level on the HMMM nucleus depends on the cure conditions [116,117]. The presence of unreacted hydroxy groups in the crosslinked networks [114] indicates, however, that not all the functionalities were reacted. Network segments left dangling loose on one end, and segments twice as long as the precursor oligomers and containing a melamine residue in their center, are both present as defects in these LCP networks. 

In the LCPs of the present category, the flexible main-chains belong to two groups polysiloxanes [119-122] and acrylates or methacrylates [110, 123,125, 126]. The polysiloxane polymers were crosslinked by divinyl(dimethylsiloxane) telomers [119] or by groups such as [124]... 

A different LCP network falling in the present category was recently reported [129]. In this case, a mesogenic group serves as both mesogen and crosslinking agent for a substantially flexible diepoxy ... 

Even stiffer chains than aromatic polyamides were built into networks with flexible crosslinking residues. A specially synthesized polyisocyanate copolymer was prepared by Aharoni [278] containing 25% 1-decenyl- and 75% n-octyl-isocyanate residues. This LCP was then lightly crosslinked by heating in solution in the presence of a free radical initiator (AIBN) to produce a gelled insoluble network. A characteristic structure appears as ... 

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