在没有特定的单体-单体相互作用的合成聚合物的多链螺旋中识别分子重量
Jiro Kumaki1, Takehiro Kawauchi, Koichi Ute
1Japan Science and Technology Agency (JST), Department of Chemical Science and Technology, Faculty and School of Engineering, Japan. kumaki@yz.yamagata-u.ac.jp
Journal of the American Chemical Society
|May 1, 2008
概括
聚甲酸的立体复合体形成三链螺旋. 分子长度决定螺旋长度,分子重量识别通过拓螺旋结构发生,而不是特定的相互作用.
科学领域:
- 聚合物科学 聚合物科学
- 超分子化学 超分子化学
- 材料科学 材料科学 材料科学
背景情况:
- 立体规律的异性和同性聚甲酸 (it-PMMA和st-PMMA) 通过范德瓦尔斯相互作用形成立体复合体 (SC).
- 在商品聚合物中,SC形成是螺旋式超分子结构的罕见例子.
研究的目的:
- 研究由具有不同分子量和分布的均it-和st-PMMAs形成的SCs的详细结构.
- 确定分子量及其分布对SC结构的影响.
主要方法:
- 使用具有狭窄分子量分布的均it-和st-PMMA制备SCs.
- 高分辨率原子力显微镜 (AFM) 分析SC结构.
主要成果:
- 互补的it-和st-PMMA的较长分子链决定了SC的总长度.
- 较短的聚合物链结合在一起,以补充或覆盖较长的链.
- 观测支持三链螺旋结构模型 (一个st-PMMA螺旋体内的两个it-PMMA链).
- 在it-PMMA螺旋结构中证明了分子重量识别 ("分子排序").
结论:
- 三链螺旋模型适用于SCs在广泛的分子重量范围内.
- 分子重量识别可以通过由范德瓦尔斯力驱动的拓螺旋结构实现,独立于特定的单体相互作用.
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
For any given polymer, the weight average molecular weight (Mw) is higher than, if not equal to, the number average molecular weight (Mn). The only situation in which the weight average molecular weight and the number average molecular weight are equal is when a polymer consists only of chains with equal molecular weight. However, this never happens in a synthetic polymer, since it is difficult to control the polymerization process up to a molecular level with accuracy to a hundred percent.
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...
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Polymer samples typically consist of macromolecular chains with a distribution of lengths, resulting in a range of molar masses rather than a single discrete value. Conventional descriptors such as the number-average molar mass and weight-average molar mass quantify this distribution but do not fully capture polymer behavior in solution..The viscosity-average molar mass provides a more realistic description of polymer behavior in solution because it accounts for the enhanced contribution of...
Determination of Molar Masses of Polymers I
Polymerization produces macromolecules with a range of chain lengths due to the random nature of molecular growth processes. As chains form and terminate at different stages, a single polymer sample contains molecules of varying sizes rather than a uniform structure. This variability is described using average molar masses and distribution-related parameters, which together provide a comprehensive understanding of polymer characteristics.The distribution of molar masses plays a critical role in...
Polymers
The word polymer is derived from the Greek words “poly” which means “many” and “mer” which means “parts”. Polymers are long chains of molecules composed of repeating units of smaller molecules, known as monomers. They either occur naturally, such as DNA and proteins, or can be constructed synthetically, like plastics. They have varied structural characteristics, such as linear chains, branched chains, or complex networks, that contribute to the properties that they exhibit. Additionally,...


