Quantitative Analysis of Near Surfaces Three-Dimensional Orientation of Polymer Chains in PET and PEN Films Using Polarized ATR FTIR Spectroscopy MIHO MOMOSE, 1 SHINJI ANDO 2 1 Material Research Laboratory, Teijin Limited, Asahigaoka, Hino, Tokyo 191-8512, Japan 2 Department of Chemistry and Materials Science, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8552, Japan Received 1 September 2009; revised 3 January 2010; accepted 12 January 2010 DOI: 10.1002/polb.21958 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Polarized attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy was utilized to character- ize the three-dimensional orientation of polymer chains near highly anisotropic surfaces generated by uniaxial drawing. A ver- satile method was proposed to analyze the molecular orientation of the polymers by combining the experimental refractive indices and optimized contact pressure by an anvil for solving the optical contact problem. This method is effective even when changes in the molecular orientation along the thickness direc- tion caused by drawing are remarkable. In addition, this method enables quantitative comparison of the molecular orientation among different polymers in the same coordinate system. From the molecular orientation analysis of poly (ethylene terephtha- late) (PET) and poly (ethylene naphthalate) (PEN), it was revealed that this method has a broader range of applications with high accuracy in estimating the molecular orientation of polymers compared with the conventional methods. The significant changes in the molecular orientation caused by uniaxial and biaxial drawing of PET and PEN films were quantitatively ana- lyzed, and the reasons for the significant in-plane orientation of PEN chains on the film plane are discussed. In addition, the dif- ference in the molecular orientation between both sides of the films was also demonstrated. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 870–879, 2010 KEYWORDS: Fourier transform infrared (FTIR); FTIR; orientation; polyesters; refractive index; spectroscopy; structural charac- terization INTRODUCTION Characterization of molecular orientations in polymer films is an important key for production and practi- cal applications because polymer films are generally formed under anisotropic conditions, such as inflation or extrusion molding using dies. Several methods have been used for the characterization of molecular orientation in polymers, such as wide-angle X-ray diffraction (WAXD), broad-line NMR, polarized fluorescence, polarized Raman and infrared (IR) spectroscopy. WAXD can be used to estimate orientation functions only in the crystalline components in polymers, and broad-line NMR requires a precise knowledge of the molecular conformations taking place during drawing. In contrast, polarized Raman and IR spectroscopies have advan- tages in estimating both the crystal and amorphous orienta- tions in polymers. The theoretical basis and applications for molecular orientation analysis using polarized vibrational spectroscopy were developed and summarized by Ward and coworkers. 1,2 Polarized attenuated total reflection (ATR) Fourier trans- formed (FT) IR spectroscopy is one of the most useful tool for characterizing the chemical composition and conforma- tional structures near polymer surfaces. In particular, the three-dimensional orientation analysis of polymer chains can be systematically performed by combining polarized IR spec- troscopy with the ATR method. The theoretical and practical basis of this method were laid by Flournoy and Schaffers, 3,4 and it has been applied to the analysis of the molecular ori- entation in polypropylene. 4,5 In this method, the contact between the sample and the crystal is frequently changed during measurement, which is called the contact problem. When an infrared absorption band exists, which is not affected by structural factors, such as orientation, crystalliza- tion, and the refractive index, the contact problem is over- come. The method for using such nondichroic reference bands is referred to as a ‘‘single-peak reference’’ (SPR), and it has been successfully used to obtain the three- dimensional orientations for uniaxially drawn poly(ethylene terephthalate) (PET), 6–11 and poly(trimethyleneterephtha- late) (PTT). 12–14 However, this method is inapplicable to samples that lack inherent reference bands like PEN and polyimides. Hence, we analyzed the orientations of aromatic polyimide films by using their refractive indices 15–17 in which three principal values were estimated from the in- plane birefringence and the average refractive indices. Correspondence to: M. Momose (E-mail: m.momose@teijin.co.jp) Journal of Polymer Science: Part B: Polymer Physics, Vol. 48, 870–879 (2010) V C 2010 Wiley Periodicals, Inc. 870 INTERSCIENCE.WILEY.COM/JOURNAL/JPOLB