刚性超分子聚合物的厚度转换
Laurent Bouteiller1, Olivier Colombani, Frédéric Lortie
1Laboratoire de Chimie des Polymères, UMR 7610, CNRS, Université Pierre et Marie Curie, 4 place Jussieu, 75252 Paris Cedex 05, France. bouteil@ccr.jussieu.fr
Journal of the American Chemical Society
|June 16, 2005
概括
低分子量 bisurea 自组装成厚或薄的纤维,改变溶液粘度. 这种可逆,合作的结构开关是可调的,为响应性材料设计提供了潜力.
科学领域:
- 超分子化学 超分子化学
- 材料科学是一种材料科学.
背景情况:
- 低分子量 bisurea 化合物可以通过键自组装.
- 溶剂的特性和度影响自组装行为.
研究的目的:
- 为了研究在非极性溶剂中低分子量 bisurea 的自我组装.
- 描述形成的不同结构及其对溶液性质的影响.
- 探索引发可逆结构转型的因素.
主要方法:
- 基于 bisurea 自组合的基于溶液的研究.
- 粘度测量以探测结构变化.
- 温度和溶剂组成的变化,以诱导过渡.
主要成果:
- 观察到两种不同的高分子量结构 (厚细丝).
- 对于厚细丝 (低温,高度) 的粘度很高. 和薄纤维的低 (高温,低度. ) 的情况.
- 结构之间的高度合作,可逆转变发生在5°C范围内,可通过溶剂或成分调节.
结论:
- 该 bisurea 系统展示了一个可调节的,通过自组装驱动的合作结构开关.
- 这种过渡对温度,度和溶剂环境都很敏感.
- 这些发现对于设计具有可控制性质的响应性材料非常有价值.
相关概念视频
Polymers: Defining Molecular Weight
Unlike small molecules with definite molecular weights, polymers are a mixture of individual polymer chains of varying lengths, each with a unique molecular weight. So, the molecular weight of a polymer is expressed as an average value based on the average size of the polymer chains. The two most common forms of averages used for polymers are the number average molecular weight and weight average molecular weight.
The number average molecular weight (Mn) is the summation of the number...
The number average molecular weight (Mn) is the summation of the number...
Polymers: Molecular Weight Distribution
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Polymers are classified as linear or branched on the basis of their chain architecture. The polymer chains in linear polymers have a long chain-like structure with minimal to no branching at all. Even if a polymer features large substituent groups on the monomer, which appear as branches to the skeleton, it is not considered a branched polymer. A branched polymer contains secondary polymer chains that arise from the main polymer chain. The branching occurs when the polymer growth shifts from...
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Unlike ionic or small covalent molecules, polymers do not form crystalline solids due to the diffusion limitations of their long-chain structures. However, polymers contain microscopic crystalline domains separated by amorphous domains.
Crystalline domains are the regions where polymer chains are aligned in an orderly manner and held together in proximity by intermolecular forces. For example, chains in the crystalline domains of polyethylene and nylon are bound together by van der Waals...
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Step-growth or condensation polymerization is a stepwise reaction of bi or multifunctional monomers to form long-chain polymers. As all the monomers are reactive, most of the monomers are consumed at the early stages of the reaction to form small chains of reactive oligomers, which then combine to form long polymer chains in the late stages. Hence, the reaction has to proceed for a long time to achieve high molecular weight polymers.
Many natural and synthetic polymers are produced by...
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Molecular Weight of Step-Growth Polymers
Step growth polymerization involves bi or multifunctional monomers. Bifunctional monomers react to form linear step growth polymers, whereas multifunctional monomers react to form non-linear or branched polymers.
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...


