Tuning Polymer Thickness: Synthesis and Scaling Theory of Homologous Series of Dendronized Polymers
作者：Yifei Guo, Jacco D. van Beek, Baozhong Zhang, Martin Colussi, Peter Walde, Afang Zhang,* Martin ....
關鍵字：Dendronized polymer, attach-to route, single molecule, simulation
論文來源：期刊
具體來源：J. Am. Chem. Soc. 2009, 131, 11841–11854
發表時間：2009年
The thickness of dendronized polymers can be tuned by varying their generation g and the dendron functionality X. Systematic studies of this effect require (i) synthetic ability to produce large samples of high quality polymers with systematic variation of g, X and of the backbone polymerization degree N, (ii) a theoretical model relating the solvent swollen polymer diameter, r, and persistence length, λ, to g and X. This article presents an optimized synthetic method and a simple theoretical model. Our theory approach, based on the Boris-Rubinstein model of dendrimers predicts r ∼ n1/4g1/2 and λ ∼ n2 where n ) [(X - 1)g - 1]/(X - 2) is the number of monomers in a dendron. The average monomer concentration in the branched side chains of a dendronized polymer increases with g in qualitative contrast to bottle brushes whose side chains are linear. The stepwise, attach-to, synthesis of X ) 3 dendronized polymers yielded gram amounts of g ) 1-4 polymers with N ≈ 1000 and N ≈ 7000 as compared to earlier maxima of 0.1 g amounts and of N ≈ 1000. The method can be modified to dendrons of different X. The conversion fraction at each attach-to step, as quantified by converting unreacted groups with UV labels, was 99.3% to 99.8%. Atomic force microscopy on mixed polymer samples allows to distinguish between chains of different g and suggests an apparent height difference of 0.85 nm per generation as well as an increase of persistence length with g. We suggest synthetic directions to allow confrontation with theory.