Reduced Glass Transition Temperatures in Thin Polymer Films: Surface Effect or Artifact?

被引:134
作者
Baeumchen, O. [1 ,2 ]
McGraw, J. D. [1 ,2 ]
Forrest, J. A. [3 ,4 ]
Dalnoki-Veress, K. [1 ,2 ]
机构
[1] McMaster Univ, Dept Phys & Astron, Hamilton, ON L8S 4M1, Canada
[2] McMaster Univ, Brockhouse Inst Mat Res, Hamilton, ON L8S 4M1, Canada
[3] Univ Waterloo, Dept Phys & Astron, Waterloo, ON N2L 3G1, Canada
[4] Univ Waterloo, Guelph Waterloo Phys Inst, Waterloo, ON N2L 3G1, Canada
基金
加拿大自然科学与工程研究理事会;
关键词
POLYSTYRENE FILMS; DYNAMICS; REDUCTIONS; BEHAVIOR; CONFINEMENT; DEPRESSION; MOTION; LAYERS; SCALE;
D O I
10.1103/PhysRevLett.109.055701
中图分类号
O4 [物理学];
学科分类号
0702 ;
摘要
We have examined the direct effect of manipulating the number of free surfaces on the measured glass transition temperature T-g of thin polystyrene films. Thin films in the range 35 nm < h < 114 nm with molecular weights of 592 kg/mol and 1144 kg/mol were studied. Ellipsometry was used to determine the temperature dependence of the thickness and refractive index of freestanding films. By noting the change in slope in each of these quantities, a T-g value can be assigned in quantitative agreement with previously reported results. For thin freestanding films this value is reduced from that of the bulk. The exact same films are then transferred to a Si substrate and the T-g of the resulting supported film was determined. The T-g values of the now supported films are the same as the bulk value and the same as previous reports of similar supported films. These experiments unambiguously show that free interfaces are the dominant cause of the T-g reductions for the film thicknesses studied.
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页数:5
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