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In situ AFM study of near‐surface crystallization in PET and PEN
Author(s) -
Shinotsuka Kei,
Assender Hazel
Publication year - 2016
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.44269
Subject(s) - crystallization , materials science , polyester , glass transition , contact angle , substrate (aquarium) , polymer , thin film , polyethylene terephthalate , morphology (biology) , composite material , crystallography , polymer chemistry , chemical engineering , nanotechnology , chemistry , oceanography , biology , engineering , genetics , geology
The surface crystallization behavior of poly(ethylene terephthalate) (PET) and poly(ethylene 2,6‐naphthalate) (PEN) spin‐coated thin films was compared by means of atomic force microscopy (AFM) with an in situ heating stage. As the films were heated up stepwise, characteristic surface crystals appeared at a crystallization temperature ( T c ) in the near‐surface region which is about 15 °C under the bulk T c , and were replaced by bulk crystals when the temperature was increased to the bulk T c . In the case of films whose thickness is less than 70 nm (PET) and 60 nm (PEN), significant increases in the bulk T c were observed. Scanning force microscopy (SFM) force‐distance curve measurements showed that the glass transition temperature ( T g ) of the near‐surface region of PET and PEN were 22.0 and 26.6 °C below their bulk T g (obtained by DSC). After the onset of surface crystallization, edge‐on and flat‐on crystals appeared at the free surface of PET and PEN thin films, whose morphologies are very different to those of the bulk crystals. Although the same general behavior was observed for both polyesters, there are significant differences both the influence of the surface and substrate on the transition temperatures, and in morphology of the surface crystals. These phenomena are discussed in terms of the differences in the mobility of polymer chains near the surface. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133 , 44269.