Films of amorphous polystyrene (PS) with a weight-average molecular weight (
Mw) of 225 × 10
3 g/mol were bonded in a T-peel test geometry, and the fracture energy (
G) of a PS/PS interface was measured at the ambient temperature as a function of the healing time (
th) and healing temperature (
Th).
G was found to develop with (
th)
1/2 at
Th =
Tg-bulk − 33 °C (where
Tg-bulk is the glass-transition temperature of the bulk sample), and log
G was found to develop with 1/
Th at
Tg-bulk − 43 °C ≤
Th ≤
Tg-bulk − 23 °C. The smallest measured value of
G = 1.4 J/m
2 was at least one order of magnitude larger than the work of adhesion required to reversibly separate the PS surfaces. These three observations indicated that the development of
G at the PS/PS interface in the temperature range investigated (<
Tg-bulk) was controlled by the diffusion of chain segments feasible above the glass-transition temperature of the interfacial layer, in agreement with our previous findings for fracture stress development at several polymer/polymer interfaces well below
Tg-bulk. Close values of
G = 8–9 J/m
2 were measured for the symmetric interfaces of polydisperse PS [
Mw = 225 × 10
3, weight-average molecular weight/number-average molecular weight (
Mw/
Mn) = 3] and monodisperse PS (
Mw = 200 × 10
3,
Mw/
Mn = 1.04) after healing at
Th =
Tg-bulk − 33 °C for 24 h. This implies that the self-bonding of high-molecular-weight PS at such relatively low temperatures is not governed by polydispersity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1861–1867, 2004
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