Side-chain polymers nonlinear optics

Liquid crystal polymers are also used in electrooptic displays. Side-chain polymers are quite suitable for this purpose, but usually involve much larger elastic and viscous constants, which slow the response of the device (33). The chiral smectic C phase is perhaps best suited for a polymer field effect device. The abiHty to attach dichroic or fluorescent dyes as a proportion of the side groups opens the door to appHcations not easily achieved with low molecular weight Hquid crystals. Polymers with smectic phases have also been used to create laser writable devices (30). The laser can address areas a few micrometers wide, changing a clear state to a strong scattering state or vice versa. Future uses of Hquid crystal polymers may include data storage devices. Polymers with nonlinear optical properties may also become important for device appHcations. 

Van der Vorst CPJM, Picken SJ (1996) Electric field poling of nonlinear optical side chain polymers. In Shibaev VP (ed) Polym Electroopt photoopt Act Media. Springer, Berlin Heidelberg New York, p 173... 

Van der Vorst CPJM and Picken SB, "Electric Field Poling of Nonlinear Optical Side Chain Polymers", in Shibaev VP (Ed.) "Polymers as Electro-optical and Photo-optical Active Media", Springer Verlag, Berlin, 1996, Chap. 5 "Electric Field Poling of Acceptor-Donor Molecules", J Opt Soc Am B 7 (1990) 320. 

Wendorff, J. H., and Eich, M. Nonlinear optical phenomena in liquid crystalline side chain polymers. Mol. Cryst. Liq. Cryst. 169, 133 (1989). 

As discussed earlier, while the scale of the fillers is substantially different, nanocomposite materials concepts and technology are very similar to those of conventional composite materials. This is clearly demonstrated in the case of new thermosets for nonlinear optical (NLO) applications, " " where nanocomposite of liquid crystalline thermosets, IPNs, and simple filled thermosets are evaluated. Tripathy et al. discussed four different ways to prepare nonlinear optical polymers. (1) The polymer matrix is doped with NLO moieties in a guest/host system (2) In side-chain polymer systems, NLO polymers with active moieties are covalently bonded as pendant groups (3) In the main chain polymer, the chromo-phores are incorporated as parts of the main polymer backbone to enhance the temporal stability of the NLO properties and (4) Stability of the optical noninearity in sol-gel-based thermosets is related to... 

D. W. Kim, H. Moon, S. Y. Park, and S. II Hong. Synthesis of photoconducting nonlinear optical side-chain polymers containing carbazole derivatives. React. Funct. Polym., 42(l) 73-86, September 1999. 

C. P. J.M. van der Vorst, D.J. Picken, Electric Field Poling of Nonlinear Optical Side Chain Polymers, in V. P. Shibaev (ed.). Polymers as Electrooptical and Photo-optical Active Media, Springer, Berlin (1996). 

Cooperative effects of the monomer units along the polymer backbone may result in a nonlinear relation between the specific optical rotation and the enantiomeric excess (ee) of chiral units present in the polymer [91]. For stiff helical isocyanates, these cooperative effects have led to observations referred to as majority-rules. The role of cooperative effects in chiral rr-PATs has also been examined using a series of PTs containing various ratios of chiral and achiral side chains. Data show that the cooperative interaction between the side chains affects the optical activity in a nonlinear fashion, while the majority-rules principle is applicable to chiral rr-PATs, the magnitude is less pronounced than with helical main-chain isocyanates [91]. 

Extensive studies have been made on poled NLO guest-host systems . The limited solubility of the NLO species in a host matrix and the thermal relaxation of the induced nonlinear optical activity of the poled polymeric films are major disadvantages. Side chain polymers have attracted attention since a large number of NLO molecules may be covalently attached to the polymer chain and the problem of phase segregation of the NLO component is alleviated. In this article, we present the second and third order NLO properties of a new class of guest-host system which possess excellent doping features and photoreactive characteristics. 

Hayden, L.M., Sauter, G.F., Ore, F.R., and Pasillas, P.L. (1990) Second-order nonlinear optical measurements in guest-host and side-chain polymers. 

These materials are compatible with semiconductor technology. Low-oost thin films or waveguiding structures of polymers can be fabricated easily by fomiliar spincoating processes which meet the requirements of integrated nonlinear optics. Polymers and. in particular, side-chain polymers, liquid crystalline or amorphous ones, offer a high potential for molecular engioeering. 

A nonlinear side-chain polymer-based MZ interferometer has been reported [143], in which the channel definition was achieved through the change in refractive index caused by poling. A field of 100 MV m at a temperature of 90 °C yielded an index change of 0.06, sufficient to provide lateral confinement. Modulation at frequencies up to 1 kHz were achieved with drive voltage levels indicative of an electro-optic coefficient of 2.8mV ... 

Side-chain polymers are significantly more stable to electric field poling-induced nonlinear optical effects than those of guest-host polymers, but still suffer from slow relaxation of field-induced noncentrosymmetric alignment and, hence, the nonlinearity. 

Optically active polymers are potentially very useful in areas such as asymmetric catalysis, nonlinear optics, polarized photo and electroluminescence, and enantioselective separation and sensing.26 Transition metal coupling polymerization has also been applied to the synthesis of these polymers.27 For example, from the Ni(II)-catalyzed polymerization, a regioregular head-to-tail polymer 32 was obtained (Scheme 9.17).28 This polymer is optically active because of the optically active chiral side chains. 

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