Polymers infrared absorption

Infrared Spectra of Grafted Bamboo. It has been demonstrated that the occurrence of graft copolymerization of methyl methacrylate onto bamboo can be accertained by the presence of characteristic absorptions of polymer branches in the infrared spectrum (17-19), in addition to the weight increased in bamboo samples. In this study, similar procedures were conducted for the grafting of acrylonitrile. The formation of graft copolymer could easily be detected by the... 

Infrared spectroscopy, including Fourier-transform infrared (FTIR) spectroscopy, is one of the oldest and most widely used analytical techniques in adhesion-related research. Transmission infrared spectroscopy has been used to identify compounds used in formulating adhesives and to follow curing reactions. Attenuated total reflection (ATR) (see Infrared spectroscopy attenuated total reflection) has been used to probe the surface composition of polymers that have been surface modified by an etching process or by deposition of a film. More recently, reflection-absorption infrared spectroscopy (see Infrared spectroscopy RAIR) has been used to characterize thin films on the surfaces of reflecting substrates. 

Condensation of the phenylethynyl-tetraamine with m-bis (p -phenoxyphenylglyoxalyl)benzene in m-cresol, afforded prepolymer A. The prepolymer exhibited a Tg of 215 C by TMA and a strong DTA exotherm maximizing at 2 5°C. Thermal treatment of the prepolymer at 2U5°C overnight resulted in its conversion to the fused benzanthracene polymer B as evidenced by absence of the DTA exotherm and the acetylene absorption band in the infrared. Polymer B, after the 2 5 C cure, showed a Tg of 365 C which represents a 120 C advancement in Tg over the cure temperature. 

Chart 1.3 Regions of strong solvent absorptions in the near 10 Chart 21.1 Infrared - polymer flowchart 1 279... 

One interesting aspect of the application of IR spectroscopy relates to thin (micrometer) and ultrathin (<50 nm) polymer films, polymer surfaces, and polymer-substrate interfaces [23]. So-called external reflection methods can be used to determine the important properties of thin films (comprising monolayers and multilayers) such as thickness, anisotropy, molecular orientation, and composition. The most frequently applied methods include IR ellipsometry (IRE) [63-67] and IR reflection absorption spectroscopy (IRRAS), which may also be referred to as reflection absorption infrared spectroscopy (RAIRS) [1,23]. 

Figure 2.19 Reflection absorption infrared 0.18 mbar (condition I) and 0.05 mbar spectroscopy (IRRAS). Absorption spectra of (condition 11). Adapted with permission from polymer films formed by plasma deposition Ref. [70] 2003, Elsevier, of hexamethyidisilane on a metal substrate at...

A solubihty parameter of 24.5-24.7 MPa / [12.0-12.1 (cal/cm ) ] has been calculated for PVF using room temperature swelling data (69). The polymer lost solvent to evaporation more rapidly than free solvent alone when exposed to air. This was ascribed to reestabUshment of favorable dipole—dipole interactions within the polymer. Infrared spectral shifts for poly(methyl methacrylate) in PVF have been interpreted as evidence of favorable acid—base interactions involving the H from CHF units (70). This is consistent with the greater absorption of pyridine than methyl acetate despite a closer solubihty parameter match with methyl acetate. 

The role of specific interactions in the plasticization of PVC has been proposed from work on specific interactions of esters in solvents (eg, hydrogenated chlorocarbons) (13), work on blends of polyesters with PVC (14—19), and work on plasticized PVC itself (20—23). Modes of iateraction between the carbonyl functionaHty of the plasticizer ester or polyester were proposed, mostly on the basis of results from Fourier transform infrared spectroscopy (ftir). Shifts in the absorption frequency of the carbonyl group of the plasticizer ester to lower wave number, indicative of a reduction in polarity (ie, some iateraction between this functionaHty and the polymer) have been reported (20—22). Work performed with dibutyl phthalate (22) suggests an optimum concentration at which such iateractions are maximized. Spectral shifts are in the range 3—8 cm . Similar shifts have also been reported in blends of PVC with polyesters (14—20), again showing a concentration dependence of the shift to lower wave number of the ester carbonyl absorption frequency. 

Analytical and Test Methods. Most of the analytical and test methods described for THF and PTHF are appHcable to OX and POX with only minor modifications (346). Infrared and nmr are useful aids in the characterization of oxetanes and their polymers. The oxetane ring shows absorption between 960 and 980 cm , regardless of substituents on the ring (282). Dinitro oxetane (DNOX) has its absorption at 1000 cm . In addition, H-nmr chemical shifts for CH2 groups in OX and POX are typically at 4.0—4.8 5 and 3.5—4.7 5, respectively (6,347,348) C-nmr is especially useful for characterizing the microstmcture of polyoxetanes. 

Surface analysis has made enormous contributions to the field of adhesion science. It enabled investigators to probe fundamental aspects of adhesion such as the composition of anodic oxides on metals, the surface composition of polymers that have been pretreated by etching, the nature of reactions occurring at the interface between a primer and a substrate or between a primer and an adhesive, and the orientation of molecules adsorbed onto substrates. Surface analysis has also enabled adhesion scientists to determine the mechanisms responsible for failure of adhesive bonds, especially after exposure to aggressive environments. The objective of this chapter is to review the principals of surface analysis techniques including attenuated total reflection (ATR) and reflection-absorption (RAIR) infrared spectroscopy. X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and secondary ion mass spectrometry (SIMS) and to present examples of the application of each technique to important problems in adhesion science. 

As indicated above, the penetration depth is on the order of a micrometer. That means that in ATR, absorption of infrared radiation mostly occurs within a distance 8 of the surface and ATR is not as surface sensitive as some other surface analysis techniques. However, ATR, like all forms of infrared spectroscopy, is very sensitive to functional groups and is a powerful technique for characterizing the surface regions of polymers. 

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