Side chain polymers synthesis

Melucci, M., G. Barbarella, M. Zambianchi, M. Benzi, F. Biscarini, M. Cavallini, A. Bongini, S. Fabbroni, M. Mazzea, M. Anni, and G. Gigli. 2004. Poly(alpha-vinyl-omega-alkyloligothiophene) side-chain polymers. Synthesis, fluorescence, and morphology. Macromolecules 37 5692-5702. 

M. Rahahn, A.-D. Schliiter, G. Wegner, and W.J. Feast, Soluble poly(p-phcnylcne)s. 1. Extension of the Yamamoto synthesis to dibromobenzenes substituted with flexible side chains, Polymer, 30 1054-1059, 1989. 

S. Dailey, W.J. Feast, R.J. Peace, I.C. Sage, S. Till, and E.L. Wood, Synthesis and device characterization of side-chain polymer electron transport materials for organic semiconducting applications, J. Mater. Chem., 11 2238-2243, 2001. 

The systematic synthesis of non amphiphilic l.c.-side chain polymers and detailed physico-chemical investigations are discussed. The phase behavior and structure ofnematic, cholesteric and smectic polymers are described. Their optical properties and the state of order of cholesteric and nematic polymers are analysed in comparison to conventional low molar mass liquid crystals. The phase transition into the glassy state and optical characterization of the anisotropic glasses having liquid crystalline structures are examined. 

The synthesis of amphilic l.c.-side chain polymers and their phase behavior in aqueous solutions verifies that these polymers exhibit hexagonal, cubic and lamellar phases in analogy to the monomeric systems. 

Non Amphiphilic L.C. Side Chain Polymers 2.1 Model Considerations and Synthesis... 

A broad variety of l.c. polymers is conceivable because of the wide range of well known mesogenic molecules, e.g. tabulated in the book of Dcmus27), and the different types of polymers. Further variations are possible by copolymers or systems, where each monomer unit carries more than one mesogenic moiety ( en bloc systems28)). Furthermore the synthesis of linear, branched and crosslinked systems has to be mentioned. Because of this broad variety a manifold influence on the phase behavior of the systems via the chemical constitution is feasible. In the following chapter we will discuss some basic considerations on the phase behavior of l.c.-side chain polymers. 

The schema in Fig. 37 a indicates the synthesis route for elastomers. It is most convenient to start with well characterized linear l.c. side chain polymers, which additionally contain reactive centers. These centers may be located within the polymer backbone or as substituents of the mesogenic side chains. In a suitable reaction, or... 

Kawakami Y, Yu SP, Abe T (1992) Synthesis and gas permeability of aromatic polyamide and polyimide having oligodimethylsiloxane in main chain or in side chain. Polym J (Tokyo) 24( 10) 1129... 

Synthesis, Characterization, and Photochemistry of a Cinnamate-Containing Liquid-Crystalline Side-Chain Polymer... 

There are in general two ways to synthesize side chain polymers, polymerization of peptide-functional monomers or introduction of the peptide moiety afterwards, by grafting. The latter technique is based on the synthesis of polymers containing some form of functionality in the side chain, normally an activated ester moiety, which can further react with a peptide. The most commonly used method for the polymerization of monomers containing active esters is free radical polymerization. In particular many activated acrylate esters have been polymerized in this manner [12] (Table 1) for use in a wide variety of applications, from the preparation of polymer drug conjugates [13,14] to supports for solid phase peptide synthesis [15,16]. 

FIGURE 4.21 Example of the synthesis of a side-chain polymer using Diels-Alder postfunctionalization. 

During the last years most efforts at preparing LCPs have focused on the use of rod-like mesogens. Only very recently has the synthesis of mesomorphic polymers with disclike units (see Fig. 1) been reported [29,30]. Likewise, combing main-chain/ side-chain polymers (see Fig. 1), comprising structural aspects of both types of LCPs, have only recently become known [31]. 

BIG Bignotti, F., Pence, M., Sartore, L., Peroni, I. Mendichi, R., and Casolaro, M., Synthesis, characterisation and solution behaviour of thermo- and pH-responsive polymers bearing L-leneine residues in the side chains, Polymer, 41, 8247, 2000. 

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. 

Murata, H., Sanda, R, and Endo, T., Synthesis and Radical Polymerization of a Novel Acrylamide Having an a-Helical Peptide Structure in the Side Chain, /. Polym. Sci Part A Polym. Chem., 36,1679,1998. 

Until now there was no obvious correlation found between the monomer structure and the resulting pol qner phase. No.theorr retical structural conditions were described which would result in a liquid crystalline polymer with a definite ordered phase e.g. with a nematic a smectic or a cholesteric phase as in conventional liquid crystals. Although previous examples have established (8 9) the existence of enantiotropic liquid crystalline side chain polymers additional considerations are in order for a systematic synthesis of such polymers. 

Synthesis of side chain polymers is commonly performed by one of two routes — an example of route i) as described on the following page is shown below ... 

C. Noel and J. Virlet, "DSC, Miscibility and X-ray Studies of the Thermotropic Liquid Crystalline Polyesters with Aromatic Moieties and Flexible Spacers in the Main Chain", in "Liquid Crystals and Ordered Fluid, A. Griffin and A. Johnson eds., Plenvim Press, New-York, vol. 1+, 1+01 (198I+) Finkelmann, "Synthesis, Structure, and Properties of Liquid Crystalline Side Chain Polymers", in "Polymeric Liquid Crystals", A. Ciferri, W.R. Krigbaum and R.B. Meyer eds. Academic Press, New-York (I982)... 

Xie J, Peng WY, Li G, Jiang JM. Synthesis and characterization of poly(aryl ether ketone)s with fluorinated phenyl in the side chain. Polym Bull 201 l 67(l) 45-56. 

Goldoni, R, R.A.J. Janssen, and E.W. Meijer. 1999. Synthesis and characterization of new copolymers of thiophene and vinylene Poly(thienylenevinylene)s and poly(terthienylenevinylene)s with thioether side chains. / Polym Sci A 37 4629-4639. 

Benicewicz, B.C., and R. Chen. 2000. Synthesis and characterization of polymers with oKgoanOine side chains. Polym Prepr Am Chem Soc Div Polym Chem 41 (2) 1733. 

The poly(4-carboxy-2,2 -bithiophene) can be prepared by direct chemical or electrochemical polymerization of 4-carboxy-2,2 -bithiophene (Figure 4.34) [51]. Hutchison et al. have suggested that this approach reduces undesirable side reactions and allows facile incorporation of strong electron-withdrawing side chains. Chemical synthesis was carried out using anhydrous ferric chloride in chloroform. The electrochemical polymerization was carried out in propylene-carbonate-containing tetra-butyl ammonium hexafluorophosphate. The conductivity of a pressed pellet of chemically synthesized polymer was approximately 10 " S/cm and the polymer was water soluble in its neutral form. 

Zhang, W. Shiotsuki, M. Masuda, T., Synthesis and Properties of Polymer Brush Consisting of Poly(phenylacetylene) Main Chain and Poly(dimethylsiloxane) Side Chains. Polymer 2007, (48), 2548-2553. Aranguren, M. I., Crystallization of Polydimethylsiloxane Effect of Silica Filler and Curing. Polymer 1998,39,4897-4903. 

Podhajecka, K., K. Ptochazka, and D. HourdeL 2007. Synthesis and viscoelastic behavior of water-soluble polymtns modified with strong hydrophobic side chains. Polymer 48(6) 1586-1595. 

In this chapter we shall only be concerned with electro-optic and thermo-optic switching effects in thermotropic side-chain polymer liquid crystals. We will consider briefly the synthesis and structure of such compounds and show how the nematic, cholesteric and smectic phases arise. Since the optical properties of each of these phases are different, and may be altered depending on alignment within the phase, each gives rise to different electro-optic effects. If these are coupled to the use of dye additives or substituents, then it will be realized that a wide range of electro-optic devices based on dichroism or fluorescence as well as birefringence or scattering power may be fabricated. These will be considered and discussed in terms of their performance and potential applications. Finally, possible uses of polymer-low molar mass liquid crystal solutions will be considered in terms of electro-optic device applications. 

The most general preparative procedures used in the synthesis of side-chain polymer liquid crystals are (a) homopolymerization or copolymerization of the mesogenic (or non-mesogenic) groups themselves or (b) attachment of the mesogenic units via a reactive site to an existing polymer backbone. As shown schematically in Fig. 2, for either route, the nett effect is a semi-flexible backbone with pendant side-groups. A, B, C, etc. 

As already mentioned, four types of chemical structures are known for ferroelectric LC polymers side-chain polymers, main-chain polymers, combined ones, and cross-linked polymers, i.e., ferroelectric LC elastomers. All of them contain rodlike mesogenic moieties (Fig. la) but not disklike ones (Fig. lb). From the first publications to date, most research work has been carried out on side-chain polymers about 240 side-chain FLCPs versus 5 main-chain FLCPs [10]. Synthesis of the two other types of polymers under discussion is often related to the procedures used for side-chain FLCPs e.g., preparation of cross-linkable side-chain polymers is usually the first step in the synthesis of ferroelectric LC elastomers. That is the reason for the prior discussion of the synthesis of side-chain FLCPs. 

As mentioned earlier, ferroelectric LC elastomers were first synthesized by Zentel et al. [94-96] the synthesis and properties of LC elastomers are reviewed by Gleim and Finkelmann [97]. One of the synthetic routes to ferroelectric LC elastomers is preparation of side-chain polymers (Fig. 10) or combined polymers (Fig. 12b) containing active groups in side chains, with further cross-linking. The ultraviolet (UV) light-induced radical polymerization of acrylamide or acrylate active groups has been used in the former case [83,95,98] and hydrosilation addition in the latter case [94]. 

Aharoni S M (1993) Synthesis of comb-like graft copolyamides with rigid aromatic main-chains and long flexible side-chains, Polym Bull 30 149-153. 

Nagase Y, Nakajima S, Oku M, Iwasaki Y, Ishihara K. Synthesis and properties of segmented poly(urethane-urea)s containing phosphorylcholine moiety in the side chain. Polym J 2008 40(12) 1149-52. 

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