Conformation of Cylindrical Brushes in Solution: Effect of Side Chain Length
详细信息 查看全文
- 作者：Bin Zhang ; Franziska Grö ; hn ; Jan Skov Pedersen ; K. Fischer ; M. Schmidt
- 刊名：Macromolecules
- 出版年：2006
- 出版时间：November 28, 2006
- 年：2006
- 卷：39
- 期：24
- 页码：8440 - 8450
- 全文大小：467K
- 年卷期：v.39,no.24(November 28, 2006)
- ISSN：1520-5835
文摘
The conformation of cylindrical brush polymers with a polymethacrylate main and polystyreneside chains (6 
33, with 
the number-average degree of polymerization of the side chains) were studiedby combined light and small-angle neutron scattering experiments. The results reveal that the main chain stiffnessexpressed in terms of the Kuhn statistical segment length, lk, increases with side chain length but does not followscaling predictions which most probably is due to the limited length of the side chains investigated experimentally.In this respect the present work addresses the transition regime from flexible coils to stiff cylindrical brushes asa function of side chain length. In detail, the increase of lk is stronger in toluene, a very good solvent for the sidechains, than in the poor solvent cyclohexane and does not level off for the longest side chains investigated (
= 33). In contrast to earlier work, the cylinder length per main chain monomer is found to be independent of sidechain length but to depend slightly on the solvent quality, i.e., lm = 0.241 nm in toluene and lm = 0.207 nm incyclohexane. The value determined in toluene is close to the maximum value of lm = 0.25 nm expected for afully stretched vinylic main chain, whereas the smaller value for lm in cyclohexane suggests a local coiling of themain chain, most probably caused by less repulsive interactions between the side chains. The discrepancy tosome earlier scattering experiments could be resolved, but the origin of frequently reported much smaller cylinderlengths derived by atomic force microscopy remains unclear.
33, with the number-average degree of polymerization of the side chains) were studiedby combined light and small-angle neutron scattering experiments. The results reveal that the main chain stiffnessexpressed in terms of the Kuhn statistical segment length, lk, increases with side chain length but does not followscaling predictions which most probably is due to the limited length of the side chains investigated experimentally.In this respect the present work addresses the transition regime from flexible coils to stiff cylindrical brushes asa function of side chain length. In detail, the increase of lk is stronger in toluene, a very good solvent for the sidechains, than in the poor solvent cyclohexane and does not level off for the longest side chains investigated (= 33). In contrast to earlier work, the cylinder length per main chain monomer is found to be independent of sidechain length but to depend slightly on the solvent quality, i.e., lm = 0.241 nm in toluene and lm = 0.207 nm incyclohexane. The value determined in toluene is close to the maximum value of lm = 0.25 nm expected for afully stretched vinylic main chain, whereas the smaller value for lm in cyclohexane suggests a local coiling of themain chain, most probably caused by less repulsive interactions between the side chains. The discrepancy tosome earlier scattering experiments could be resolved, but the origin of frequently reported much smaller cylinderlengths derived by atomic force microscopy remains unclear.