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

roth image

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

https://pubs.acs.org/doi/10.1021/acsmacrolett.8b00019

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