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Glass transition temperature of single-chain polystyrene particles end-grafted to oxide-coated silicon.
- Source :
-
Journal of Chemical Physics . 2/14/2020, Vol. 152 Issue 6, p1-9. 9p. 1 Diagram, 1 Chart, 6 Graphs. - Publication Year :
- 2020
-
Abstract
- A method based on the PeakForce QNM atomic force microscopic (AFM) adhesion measurement is employed to investigate the glassy dynamics of polystyrene (PS) single-chain particles end-grafted to SiO2—Si substrates with different diameters, D0, of 3.4 nm–8.8 nm and molar masses, Mn, of 8–123 kg/mol. As temperature was increased, the adhesion force, Fad, experienced by the AFM tip on pulling off the single chains after loading demonstrated a stepwise increase at an elevated temperature, which we identified to be Tg based on previous works. Our result shows that Tg of our grafted single chains increases with Mn in a manner consistent with the Fox–Flory equation, but the coefficient quantifying the Mn dependence of Tg is only (36 ± 6)% the value of bulk PS. In addition, the value of Tg in the Mn → ∞ limit is about 25 °C below the bulk Tg but more than 15 °C above that of (untethered) PS nanoparticles with D0 ≈ 100 nm suspended in a solution. Our findings are consistent with Tg of our single chains being dominated by simultaneous effects of the interfaces, which depress Tg, and end-grafting, which enhances Tg. The latter is believed to exert its influence on the glass transition dynamics by a mechanism reliant on chain connectivity and does not vary with chain length. [ABSTRACT FROM AUTHOR]
- Subjects :
- *POLYSTYRENE
*GLASS transitions
*ADHESION
*MOLAR mass
*NUCLEAR forces (Physics)
Subjects
Details
- Language :
- English
- ISSN :
- 00219606
- Volume :
- 152
- Issue :
- 6
- Database :
- Academic Search Index
- Journal :
- Journal of Chemical Physics
- Publication Type :
- Academic Journal
- Accession number :
- 141756922
- Full Text :
- https://doi.org/10.1063/1.5140627