2016/02/12 by S. Mostafa Sabzevari, Sabzevari, S. Mostafa, Joshua D. McGraw +3
Chemical Engineering · Engineering · #FOS: Physical sciences #Fluid Dynamics and Thin Films #Lattice Boltzmann Simulation Studies #Rheology and Fluid Dynamics Studies #Soft Condensed Matter (cond-mat.soft)
paper · pdf · doi:10.48550/arxiv.1602.04109
openalex publication_date 2016/02/12 · openalex created_date 2022/08/22 · openalex updated_date 2026/07/28
We investigate the effect of short chains on slip of highly entangled\npolystyrenes (PS) during thin film dewetting from non-wetting fluorinated\nsurfaces. Binary and ternary mixtures were prepared from monodisperse PS with\nweight average molecular weights 5 < M_ textrmw < 490 kg/mol. Flow dynamics\nand rim morphology of dewetting holes were captured using optical and atomic\nforce microscopy. Slip properties are assessed in the framework of hydrodynamic\nmodels describing the rim height profile of dewetting holes. We show that short\nchains with M_ textrmw below the polymer critical molecular weight for\nentanglements, M_ textrmc, can play an important role in slip of highly\nentangled polymers. Among mixtures of the same M_ textrmw, those containing\nchains with M<M_ textrmc exhibit larger slip lengths as the number average\nmolecular weight, M_ textrmn, decreases. The slip enhancement effect is\nonly applicable when chains with M<M_ textrmc are mixed with highly\nentangled chains such that the content of the long chain component,\n\φ_ textrmL, is dominant (\φ_ textrmL<0.5). These results suggest\nthat short chains affect slip of highly entangled polymers on non-wetting\nsurfaces due to the physical or chemical disparities of end groups, and any\nassociated dynamical effect their presence may have, as compared to the\nbackbone units. The enhanced slip in this regard is attributed to the impact of\nchain end groups or short chain enrichment on the effective interfacial\nfriction coefficient. Accordingly, for entangled PS, a higher concentration of\nend groups or short chains at the interface results in a lower effective\nfriction coefficient which consequently enhances the slip length.\n