Transition temperature of poly(methyl methacrylate) determined by time-of-flight secondary ion mass spectrometry and contact angle measurements

Yi Fu; Yiu-Ting R Lau; Lu-Tao Weng; Kai-Mo Ng; Chi-Ming Chan

doi:10.1016/j.jcis.2017.05.120

Transition temperature of poly(methyl methacrylate) determined by time-of-flight secondary ion mass spectrometry and contact angle measurements

J Colloid Interface Sci. 2017 Oct 15:504:758-764. doi: 10.1016/j.jcis.2017.05.120. Epub 2017 Jun 1.

Authors

Yi Fu¹, Yiu-Ting R Lau¹, Lu-Tao Weng², Kai-Mo Ng³, Chi-Ming Chan⁴

Affiliations

¹ Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
² Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong; Materials Characterization and Preparation Facility, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
³ Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong; Advanced Engineering Materials Facility, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
⁴ Department of Chemical and Biomolecular Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong; Division of Environment, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong. Electronic address: kecmchan@ust.hk.

PMID: 28623701
DOI: 10.1016/j.jcis.2017.05.120

Abstract

The surface chain conformations of poly(methyl methacrylate) (PMMA) at different temperatures were extensively studied by time-of-flight secondary ion mass spectrometry (ToF-SIMS). Similar to our previous experimental studies on polystyrene (PS) and poly(2, 3, 4, 5, 6-pentafluorostyrene) (5FPS), a transition temperature (T_T) could be identified through the principal component analysis (PCA) of the ToF-SIMS spectra obtained from the PMMA samples annealed at different temperatures. Interestingly, our results show that the T_T depended on molecular weight and was about 50-60˚C below the bulk glass transition temperature (T_g) and therefore could possibly be related to the surface glass transition temperature (T_g^S). These results were confirmed by contact angle measurements. ToF-SIMS results showed higher peak intensities of several low-mass oxygen-containing positive ions, hydrocarbon positive ions and OCH₃^- negative ion at higher temperatures, which can be interpreted by a higher surface concentration of methoxy groups at the surface.

Keywords: Contact angle measurements; PMMA; Principal component analysis; Surface structure; ToF-SIMS.