连接的纳米封闭对玻璃过渡温度,脆弱性和聚乙烯薄膜中的染料转化扩散性的影响取决于分子重量
Tong Wei1, Logan M Fenimore1, Tian Lan2
1Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois 60208, USA.
The Journal of chemical physics
|October 15, 2025
概括
低分子量聚乙烯薄膜的脆弱性和染料扩散不受纳米级限制的影响,与高分子量薄膜不同. 玻璃过渡温度的降低仅发生在50nm以下,而不依赖于分子量.
科学领域:
- 聚合物科学 聚合物科学
- 材料科学 材料科学 材料科学
- 物理化学 物理化学
背景情况:
- 与散装材料相比,纳米封闭聚合物薄膜表现出改变的特性,如玻璃过渡温度 (Tg),脆弱性和扩散性.
- 之前的研究表明,受限对聚合物脆弱性的影响与Tg和染料扩散率的变化之间存在联系.
研究的目的:
- 为了研究纳米级封闭对极低分子量 (MW) 聚烯 (PS) 薄膜的脆弱性和染料扩散性的影响.
- 为了测试这个假设,限制对脆弱性的影响与Tg和染料扩散性的影响相关.
主要方法:
- Ellipsometry 用于测量薄膜厚度和光学性能.
- 基于非辐射能量转移 (NRET) 的光测量探测了染料扩散性.
- 聚乙烯薄膜的分子量约为6kg/mol,在各种限制级别进行了研究.
主要成果:
- 在低MWPS薄膜中的脆弱性和染料扩散性保持不变,直到~100nm的限制.
- 高MWPS薄膜显示,随着限制,脆弱性和扩散性显著降低.
- 玻璃过渡温度 (Tg) 的降低仅在~50纳米厚度以下观察到,不论MW.
- 低MWPS的α-放松时间分布并没有随着监禁而缩小.
结论:
- 脆弱性决定了聚合物动态对纳米尺度限制的敏感性.
- 连接封闭效应与聚合物动态的拟议框架得到了验证.
- 与高MW聚合物相比,低MW聚合物表现出明显的限制行为,特别是关于脆弱性和扩散性.
相关概念视频
Molecular Weight of Step-Growth Polymers
2.7K
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...
2.7K
Polymer Classification: Crystallinity
3.8K
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...
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...
3.8K
Polymer Classification: Stereospecificity
3.1K
Polymerization generates chiral centers along the entire backbone of a polymer chain. Accordingly, the stereochemistry of the substituent group has a significant effect on polymer properties. Polymers formed from monosubstituted alkene monomers feature chiral carbons at every alternate position in the polymer backbone. Relative to the predominant orientation of substituents at the adjacent chiral carbons, the polymer can exist in three different configurations: isotactic, syndiotactic, and...
3.1K
Polymers: Molecular Weight Distribution
4.7K
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.
4.7K
Polymers: Defining Molecular Weight
3.7K
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...
3.7K


