Graduate student Xinru Huang and Prof. Connie Roth demonstrate that chains tethered to substrates at low grafting densities locally increase the glass transition temperature by 50 Kelvin

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Roth Lab Research

Optimizing the Grafting Density of Tethered Chains to Alter the Local Glass Transition Temperature of Polystyrene near Silica Substrates: The Advantage of Mushrooms over Brushes

Physics PhD graduate student Xinru Huang and Professor Connie Roth have used a localized fluorescence method to experimentally measure the local glass transition temperature Tg near substrates with end-tethered chains.  An optimum grafting density was observed that resulted in a maximum increase in local Tg next to the substrate of 49 ± 2 K.  Surprisingly this maximum increase was found to occur at low grafting densities well within the “mushroom-to-brush” transition regime corresponding to a volume fraction of tethered chains near the substrate of only ~10%.  The profile in local Tg(z) as a function of distance from the interface was also measured and found to extend out to a distance of z ≈ 100-125 nm before bulk Tg of the material was recovered.  These results provide insight into how chain-grafted nanoparticles can be utilized to strengthen and reinforce polymer nanocomposites.  

This research was published in the ACS Macro Letters:
Xinru Huang and Connie B. Roth, ACS Macro Letters 2018, 7, 269-274. 
DOI: 10.1021/acsmacrolett.8b00019