Characterization of Polymer Blends with FTIR Spectroscopy

Characterization of Polymer Blends with FTIR Spectroscopy 

Characterization of Polymer Blends Miscibility, Morphology, and Interfaces, First Edition. 

Polymer blends exhibit good mechanical properties which are directly related to the adhesion between the constituent polymers, their interaction, and their miscibility. Interactions take place at the interface of the polymers phases to provide good adhesion moreover, the better the miscibility, the smaller is the size of the interface. An understanding of the factors that affect the miscibility of polymer mixtures is of fundamental importance. It is also essential to have a clear understanding of the basic physical and chemical properties of the constituents associated with this large class of materials. 

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Fourier-transform infrared (FTIR) spectroscopy is an invaluable characterization technique used to confirm the chemical structure of a polymer, particularly through the observation of vibrational transitions associated with specific functional groups [185,186]. The technique has been extensively used for the characterization of polymer blends and several reviews have appeared in the literature [187-190]. FTIR measurements can help identify the mechanism of interaction between the components of a polymer blend. For example, FTIR studies carried out by Hsu and coworkers [191] have shown that the favorable interaction between PS and PVME can be monitored through the C—H out-of-plane vibration of the phenyl ring at 698 cm in PS and the COCH3 vibration of PVME (doublet at 1085 and 1107 cm ). Changes in the position and intensity of the IR bands can be used to monitor changes in miscibility behavior ]192, 193]. 

Most utility polymeric articles available today contain multiphase polymeric systems comprised of semi-crystalline polymers, copolymers, polymers in solution with low molar mass compounds, physical laminates or blends. The primary aim of using multicomponent systems is to mould the properties available from a single polymer to another set of desirable material properties. The property development process is complex and depends not only on the properties of the polymer(s) and other components but also on the formation process of the system which determines the developed microstmcture, and component interaction after formation. Moreover, the process of polymer composite formation and the stability of the composite is a function of environmental parameters, e.g., temperature, presence of other species etc. The chemical composition and some insight into the microscopic structure of constituents in a polymer composite can be directly obtained using Infrared (IR) spectroscopy. In addition, a variety of instrumental and sampling configurations for spectroscopic measurements combine to make irrfra-red spectroscopy a versatile characterization technique for the analysis of the formation processes of polymeric systems, their local structure and/or dynamics to relate to property development under different environmental conditions. In particular, Fourier transform infrared (FTIR) spectroscopy is a well-established technique to characterize polymers [1, 2]. 

In polymer processing, whether it is a blending, annealing or diffusion process, it is vital to characterize the chemical composition and spatial distribution of the materials involved. Fourier transform infrared (FTIR) spectroscopy has traditionally been used as a powerful nondestructive material identification method, as well as an important tool to study intermolecular interactions and different polymer morphologies. With the introduction of infrared (IR) microscopes and array detectors, chemical imaging using FTIR spectroscopy has become an established tool in polymer analysis. 

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