Copolymers Raman spectroscopy

Recent studies on PEO-PPO, PEO-PBO di- and triblock copolymers include the works of Bahadur et al. [121], who examined the role of various additives on the micellization behavior, of Guo et al. [122], who used FT-Raman spectroscopy to study the hydration and conformation as a function of temperature, of Booth and coworkers [ 123], who were mainly interested in PEO-PBO block copolymers with long PEO sequences, and of Hamley et al., who used in situ AFM measurements in water to characterize the morphology of PEO-PPO micelles [56,57]. 

Wenz and colleagues at Bayer Polymers Inc. describe the use of Raman spectroscopy to determine the reaction end point for the emulsion production of ABS graft copolymer [197]. Early termination reduces product yield and results in an extra product purification step termination too late reduces product quality. 

Bauer et al. describe the use of a noncontact probe coupled by fiber optics to an FT-Raman system to measure the percentage of dry extractibles and styrene monomer in a styrene/butadiene latex emulsion polymerization reaction using PLS models [201]. Elizalde et al. have examined the use of Raman spectroscopy to monitor the emulsion polymerization of n-butyl acrylate with methyl methacrylate under starved, or low monomer [202], and with high soUds-content [203] conditions. In both cases, models could be built to predict multiple properties, including solids content, residual monomer, and cumulative copolymer composition. Another study compared reaction calorimetry and Raman spectroscopy for monitoring n-butyl acrylate/methyl methacrylate and for vinyl acetate/butyl acrylate, under conditions of normal and instantaneous conversion [204], Both techniques performed well for normal conversion conditions and for overall conversion estimate, but Raman spectroscopy was better at estimating free monomer concentration and instantaneous conversion rate. However, the authors also point out that in certain situations, alternative techniques such as calorimetry can be cheaper, faster, and often easier to maintain accurate models for than Raman spectroscopy, hi a subsequent article, Elizalde et al. found that updating calibration models after... 

Since the late 1960 s a few papers have demonstrated compositional analysis of various polymer systans by Raman spectroscopy. For example, Boerio and Yuann (U) developed a method of analysis for copolymers of glycidyl methacrylate with methyl methacrylate and styrene. Sloane and Bramston-Cook (5) analyzed the terpolymer system poly(methyl methacrylate-co-butadiene-co-styrene). The composition of copolymers of styrene-ethylene dimethacrylate and styrene-divinylbenzene was determined by Stokr et (6). Finally, Water (7) demonstrated that Raman spectroscopy could determine the amount of residual monomer in poly(methyl methacrylate) to the % level. This was subsequently lowered to less than 0.1% (8). In spite of its many advantages, the potential of Raman spectroscopy for the analysis of polymer systems has never been fully exploited. 

Figure 6. Mole percent methyl methacrylate incorporated in poly(methyl)meth-acrylate-co-3-oximino-2-butanone methacrylate) copolymers as a function of monomer feed composition determined by Raman spectroscopy. Key -----------ideality...

Attempts to elucidate the polymerization or copolymerization kinetics of ethynyl and maleimide-functionalized monomers have been undertaken via vibrational spectroscopy (137). The thermal polymerization of A-(3-ethynyl-phenyl) maleimide (the structure is given in Fig. 48) was studied via IR and Raman spectroscopy. This model compound is interesting because it carries maleimide and ethynyl groups attached to the same aromatic ring. Kinetic studies indicate that both the acetylene and maleimide group react at the same rate, which strongly suggests the formation of a copolymer rather than a mixture of homopolymers. 

This study illustrates a particular use of FT-Raman spectroscopy (Section 2.4.2) to monitor an emulsion polymerization of an acrylic/methacrylic copolymer. There are four reaction components to an emulsion polymerization water-immiscible monomer, water, initiator, and emulsifier. During the reaction process, the monomers become solubilized by the emulsifier. Polymerization reactions were carried using three monomers BA (butyl acrylate), MMA (methyl methacrylate), and AMA (allyl methacrylate). Figure 7-1 shows the FT-Raman spectra of the pure monomers, with the strong vC=C bands highlighted at 1,650 and 1,630 cm-1. The reaction was made at 74°C. As the polymerization proceeded, the disappearance of the C=C vibration could be followed, as illustrated in Fig. 7-2, which shows a plot of the concentration of the vC=C bonds in the emulsion with reaction time. After two hours of the monomer feed, 5% of the unreacted double bonds remained. As the... 

One can conclude that the microindentation technique allows the strain-induced polymorphic transition in PBT to be followed. The observed rather abrupt variation in H (within 2-4% of external deformation) makes the method competitive with respect to sensitivity to other commonly used techniques such as WAXS, infrared spectroscopy, Raman spectroscopy, etc. (Tashiro Tadokoro, 1987). Furthermore, by applying the additivity law it is possible to calculate the microhardness of completely crystalline PBT, comprising crystallites of the /6-type, as = 122 MPa. This technique can also be used to examine the stress-induced polymorphic behaviour of PBT in copolymers and blends as will be demonstrated in the following sections. 

Raman spectroscopy is sensitive to polymer conformation. For example, a polymer blend of polybutadiene-polystyrene in which polybutadiene is used to increase toughness of the polystyrene can be examined by Raman microscopy to identify its heterogeneity. Polybutadiene has three isomer conformations (cis-1,4, trans-1,4 and syndiotactic-1,2). These three types of isomers can be identified from C=C stretching modes as shown in Figure 9.36. The Raman spectra of the copolymer indicate the difference in amounts of isomer types at the edge and the center of the polybutadiene-polystyrene sample. Relative amounts of these isomer types affect the mechanical properties of the copolymer. 

Figure 9.44 Comparison of IR and Raman spectra of copolymer ethylene-vinyl acetate (EVA). EVA is distinguished by the C=Cbands. (Reproduced from M. J. Pelletier, Analytical Applications of Raman Spectroscopy, Blackwell Science, Oxford. 1999 Blackwell Publishing.)...

Fourier-Transform Raman Spectroscopy (FTR) was used to characterize a homologous series of aliphatic poly(anhydrides), poly(carboxyphenoxy)al-kanes, and copolymers of carboxyphenoxy propane (CPP) and sebacic acid. All anhydrides show two diagnostic carbonyl bands, the aliphatic polymers has the carbonyl pairing at 1803/1739 cm 1, and the aromatic polymers have the band pair at 1764 and 1712 cm -1. All the homo- and copolymers showed methylene bands due to deformation, stretching, rocking and twisting the spectra for the... 

This chapter covers the applications of Fourier transform infrared (FTIR) and Raman spectroscopy to the characterization of water-soluble polymers. The structural analysis of poly(oxyethylene), poly ethylene glycol), poly methacrylic acid), and poly acrylic acid), and the interactions of selected polymers with solvents and surfactants are presented. Structural features of these compounds in the crystalline and melt states are compared with their structural features upon dissolution in aqueous solvents. Special emphasis is given to the recent studies of the interactions between water-soluble polymers or copolymers and solvents or surfactants. New experimental approaches and the sensitivities of both FTIR and Raman spectroscopy to monitor such interactions are presented. 

The theory of IR (or FTIR) and Raman spectroscopy has been reviewed in several monographs (i-3) and various general references on Raman spectroscopy (3-6). The objective of this review is to survey the spectroscopic results obtained for various water-soluble polymers and to evaluate recent experimental techniques. In particular, this chapter will focus on the studies of selected water-soluble polymers and copolymers and their interactions with solvents and surfactants. 

Nuclear magnetic resonance (NMR) spectroscopy is a popular direct measurement technique that provides quantitative information about the chemical structure of copolymers. and isotopes are the two commonly employed nuclei, but other isotopes ( N, F, F, Si, and P) can be used depending on the comonomers. Other spectroscopic techniques (e.g., infrared, ultraviolet, and Raman spectroscopy) are also used [129-132]. 

Katti, K. S., Sikdar, D., Katti, D. R., Ghosh, P. Verma. D. (2006). Molecular interactions in intercalated organically modified clay andclay-polycaprolactam nanocomposites Experiments and modeling. Polymer, Vol. 47, No. 1, pp. 403-414 Kister, G., Cassanas, G. Vert, M. (1998). Structure and morphology of solid lactide-glycolide copolymers from n.m.r., infra-red and Raman spectroscopy. Polymer, Vol. 39, No. 15, pp. 3335-3340... 

References to the characterization of emulsion polymers with IR or Raman spectroscopy are not numerous, and IR is used only in very specific cases. Only very few cases of the determination of copolymer composition with IR have been reported. An example where IR is utilized concerns the analysis of poly(methyl acrylate(MA)-co-styrene (S)) copolymers in chloroform at a concentration of 10% w/v [51]. Hergeth and Lange [52] used IR and Raman spectroscopy to study the stracture of core-shell latex particles of poly(vinyl acetate)(PVAc)-polystyrene (PS), and also obtained information about die interfacial layer between the two polymer phases. 

It is necessary to be able to identify and quantify the additives in polymers and vibrational spectroscopy is a particularly useful approach to this problem. Compared with traditional chemical analyses, vibrational methods are nondestructive and are time-and cost-effective as well as more precise. A large number of examples exist in the literature. For example, antistatic agents (polyethylene glycol (PEG) in polyethylene (PE)) can be detected directly using FTIR sampling (367). An IR spectroscopic technique for the analysis of stabilisers (2, 6-di-tert-butyM-methylphenol) in PE and ethylene-vinyl acetate (EVA) copolymer has been described (368). It is possible to quantify the amount of external and internal lubricants (stearic acid in polystyrene (PS)) (371). Fillers in polymers can also be analysed (white rice husk ash (predominantly silica in polypropylene (PP)) (268). Raman spectroscopy has been used to detect residual monomer in solid polymethyl methacrylate (PMMA) samples (326). 

Near-infrared diffuse reflectance spectra were measured by use of a rotating drawer for pellets of 12 kinds of ethylene-vinyl acetate copolymers with vinyl acetate comonomer varying in the 7-44 wt% range. An attempt was made to predict the melting points of these copolymers. The potential of near-infrared spectroscopy with that of Raman spectroscopy in the discrimination of copolymers and the prediction of their properties was given. 23 refs. 

The polybutadiene microstructures of a number of copolymers of butadiene and acrylonitrile were studied by quantitative Raman spectroscopy and a comparison was made with IR studies of these copolymers. The intensities of the v(C C) and the v(CN) bands were also used to determine the amount of each monomer in the copolymer. 24 refs. 

All spectroscopic methods allowing the identification of chemical structures and the quantitative determination of identified chemical functions can be used to determine the composition of a copolymer. Nuclear magnetic resonance is by far the most used method for this purpose, but infrared and Raman spectroscopy can also be used. 

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