Macromol. Chem. Phys. 21/2009

Azobenzene‐Containing Polymers for Surface Relief Gratings

“…[16,17] For our systems we expect a higher mobility for the starshaped polymers since for the invidual side chains the critical molecular weight for entanglement is not reached while this is the case for the linear polymer. [6] It is difficult to put these results into the context of the existing theories and to judge the role of entanglements in mechanism of the surface relief formation. Probably more experiments are necessary or the theories describing the photoinduced formation of surface relief gratings have to be extended.…”

“…[7,8] Applying appropriate conditions for the ATRP, in particular by choosing the right catalyst system, well defined star copolymers can be obtained and no star-star coupling is observed. [6] Furthermore, copolymerization with methyl methacrylate reduced the density of functional chains and with that the tendency for aggregation. The functionalization of the prepolymers was accomplished by esterification of the OH-groups using 2-(4-(4-cyanophenylazo)-phenoxy)acetylchloride in a polymeranalogous reaction.…”

“…[4,5] For preparation of branched prepolymers 4-, 6-and 12-arm initiators have been used in the ATRP according to a literature procedure. [6][7][8] The copolymerization of HEMA with n-butyl methacrylate and isobornyl methacrylate for adjusting the glass transition temperature was performed in a similar manner as the copolymerisation with methyl methacrylate. [4,5] Characterization Molecular weights and molecular weight distributions were measured by SEC/ MALLS combination in THF (membrane filtered and degassed) containing LiBr (0.1 mol/L) on two PL-gel 5mm mixed-C columns (Polymer Laboratories, VARIAN) at 80 8C and a flow rate of 0.5 mL/min.…”

“…The glass transition temperatures of the polymers are almost identical. [6] Thin films of the polymers were prepared and surface reliefs were written into the films. The kinetics as well as the modulation depths reached for the polymers of this series were very similar (s. Table 2).…”

“…In this way the chromophore content, type, and linking can be adjusted. With this method well defined azobenzene-containing (co)polymers were obtained, varying only in the molecular weight, [4] the chromophore content, [5] the glass transition temperature or the architecture (branched or linear) [6] and the influence of these parameters on the formation of SRG was studied.…”