Polymers/Polymerization azobenzene-containing polymer

For comparison, a statistical copolymer was synthesized by a common free radical polymerization of hydroxyethyl methacrylate (HEMA) and styrene with AIBN as initiator, followed by a polymeranalogous reaction to the azobenzene-containing polymer (Afn 33,000g mol, PDI 1.6). The copolymer, comprising 28wt% of azobenzene side-groups, exhibits a Tg at 88°C, but no liquid crystalline behavior was observed. 

Kang JW, Kim MJ, Kim JP, Yoo SJ, Lee JS, Kim DY, Kim JJ. Polymeric wavelength filters fabricated using holographic surface relief gratings on azobenzene containing polymer films. 2003. Appl Phys Lett 80 3823 3825. 

Zhang Y, Cheng Z, Chen X, Zhang W, Wu J, 23m J, Zhu X. 2007. Synthesis and photoresponsive behaviors of well defined azobenzene containing polymers via RAFT polymerization. Macromolecules 40 4809 4817. 

Xu, I, Zhang, W, Zhou,N., Zhu, J., Cheng, Z., Xu, Y. and Zhu, X. (2008) Synthesis of azobenzene-containing polymers via RAFT polymerization and investigation on intense fluorescence from aggregates of azobenzene-containing amphiphilic diblock copolymers ,/. Polym. Sci. Polym. Chem., 46,5652. 

Figure 11.3. Two methods for the synthesis of azobenzene thermopiastic eiasto-mers (a) grafting of an azobenzene-containing side-chain iiquid crystaiiine polymer (azo-SCLCP) onto the thermoplastic styrene-butadiene-styrene (SBS) tribiock copoiymer using radical polymerization, and (b) tribiock copoiymer composed of a rubbery centrai block and two azobenzene SCLCP end blocks synthesized using atom transfer radical polymerization (ATRP).

Tang X, Gao L, Fan X, Zhou QF. 2007. ABA type amphiphilic triblock copolymers containing p ethoxy azobenzene via atom transfer radical polymerization synthesis, characterization, and properties. J Polym Sci Part A Polym Chem 45 2225 2234. 

Tang XD, Gao LC, Fan XH, Zhou QF (2007) Controlled grafting of ethyl cellulose with azobenzene-containing polymethacrylates via atom transfer radical polymerization. J Polym Sci Polym Chem 45 1653-1660... 

Also, when copolymers of polystyrene and 4-(methacryloyl-amino)azobenzene containing 2.2-6.5% of the latter are irradiated in a cyclohexane soluticMi with 15 flashes of 347 nm of Ught. The polymeric chains contract [221], This occurs at a high rate per second as a consequence of isomerization. At a later stage, several hundred seconds after the flash, there is evidence of polymer aggregation and precipitation [221], In addition, when azobenzene residues are introduced into the main chain of poly(dimethylsiloxane), reversible solution viscosity changes can be obtained by irradiation with ultraviolet light [221],... 

Another approach to liquid crystalline alignment is based on photoisomerization of azo compounds in polymeric materials or as part of the polymer strueture. In recent years, investigation of the use of azobenzene-containing... 

With the emergence of photonics for telecommunication applications, there have been extensive activities related to the development of polymeric materials to this end. Several reviews are available on the synthesis and fabrication of polymer-based molecular wires and switches [67a-g]. In addition, a number of studies on azobenzene-containing... 

This chapter focuses on this particular family of photochromic systems. As presented elsewhere in this book, azobenzene-containing materials experience reorganizations at different length scales in response to light of the appropriate wavelength. The photochemistry of azobenzene molecules will be described. The main types of azobenzene polymeric architectures will be presented as well as associated synthetic methods. A brief overview of the photoresponse of azobenzene polymers when exposed to linearly polarized light in their absorption bands will be presented. Special emphasis will be... 

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