AI Article Synopsis
- The surface properties of polymer blends can be influenced by the presence of shorter chain components, which can affect their performance in specific applications.
- Observations using a technique called SL-MALDI-ToF-MS revealed that even polymers that seem to have uniform molecular weight show a tendency for shorter chains to accumulate at the surface.
- For instance, 6 kDa polystyrene has a surface molecular weight about 300 Da lower than its bulk counterpart, while 7 kDa poly(methyl methacrylate) shows a shift of around 500 Da, aligning with predictions from mean-field theory.
Article Abstract
The preference for a shorter chain component at a polymer blend surface impacts surface properties key to application-specific performance. While such segregation is known for blends containing low molecular weight additives or systems with large polydispersity, it has not been reported for anionically polymerized polymers that are viewed, in practice, as monodisperse. Observations with surface layer matrix-assisted laser desorption ionization time-of-flight mass spectrometry (SL-MALDI-ToF-MS), which distinguishes surface species without labeling and provides the entire molecular weight distribution, demonstrate that entropically driven surface enrichment of shorter chains occurs even in low polydispersity materials. For 6 kDa polystyrene the number-average molecular weight () at the surface is ca. 300 Da (5%) lower than that in the bulk, and for 7 kDa poly(methyl methacryalate) the shift is ca. 500 Da. These observations are in qualitative agreement with results from a mean-field theory that considers a homopolymer melt with a molecular-weight distribution matched to the experiments.
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| http://dx.doi.org/10.1021/acsmacrolett.7b00993 | DOI Listing |
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