کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5182452 | 1380990 | 2012 | 11 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Rational design, syntheses, characterization and solution behavior of amphiphilic azobenzene-containing linear-dendritic block copolymers Rational design, syntheses, characterization and solution behavior of amphiphilic azobenzene-containing linear-dendritic block copolymers](/preview/png/5182452.png)
In this paper, based on the synthesis of precursor linear-dendritic block copolymers (LDBCs) with a linear poly(ethylene glycol) (PEG) block of molecular weight around 2000 and dendritic polyamidoamine (PAMAM) segments of generation G0 to G3, a series of azobenzene-containing amphiphilic LDBCs mPEG-dendr[PAMAM-(AZO)n] (n = 2, 4, 8, 16) have been successfully prepared in moderate yields 45-60%, through complete Michael addition between the peripheral amine groups of dendritic segment and the reactive azobenzene acrylate mesogen units bearing octyloxy tails and flexible decylmethylene spacers. The purified copolymers have been characterized and confirmed by NMR, FT-IR, MALDI-TOF MS, and GPC showing narrow molecular weight distribution in the range 1.09-1.20. A generation-dependent polymeric micellar aggregation behavior of thus obtained amphiphilic LDBCs from nanofibers of uniform diameter around 20 nm to nanospheres/oval sheets, vesicles, and porous large compound micelles (LCMs) of micrometer size has been demonstrated in selective solvent mixture of dioxane/water. Furthermore, photoisomerization transformation of these azobenzene-containing LDBCs and their kinetics of reversible trans-cis-trans photochemical transitions in THF solution have also been investigated, the measured trans-cis photoisomerization rate constant 0.0240 sâ1 for G3 copolymer is twice of the 0.0127 sâ1 determined for the precursor azobenzene compound, manifesting a kind of promising photoresponsive copolymer materials.
Journal: Polymer - Volume 53, Issue 2, 24 January 2012, Pages 359-369