Skip to main content

Über dieses Buch

This book is a collection of selected papers presented at the symposium titled "In situ Spectroscopy in Monomer and Polymer Synthesis," held at the April, 2001 ACS National Meeting in San Diego, California, USA. The co-organizers of this symposium were Timothy Long, Judit E. Puskas, Robson F. Storey, and J. Andrews. In situ spectroscopic monitoring is gaining popularity both in academia and industry. FfIR monitoring is used most frequently, but UV-visible, raman, and NMR spectroscopy are also important. This book concentrates mostly on FfIR monitoring, both in the near and mid-infrared ranges. The first chapter is a short general overview of FfIR spectroscopy, followed by the symposium contribu­ tions. We thought that this would be especially useful for student readers. We hope that the book will present a state-of-the-art overview of research related to in situ spectroscopic monitoring. -Judit E. Puskas ix Acknowledgments This book would not have been possible without the dedicated effort of the chapter contributors and the symposium committee: Professor Judit E. Puskas Professor Timothy Long Professor Robson F. Storey Professor J. Andrews The symposium was financially supported by: ACS-Petroleum Research Fund REMSPEC Co. Wyatt Technology Co.



Introduction to Real Time Infrared Spectroscopic Monitoring

This paper gives a general overview of infrared (IR) spectroscopy, serving as a foreword to this book on real-time spectroscopic monitoring. After a short discussion of the theoretical background of IR spectroscopy, sampling methods, data collection and analysis and remote sensing methods will be reviewed. This paper is intended for students and new researchers in this field. We hope that it will be a useful first-hand reference.
Sohel Shaikh, Sara van Zanden, Judit E. Puskas

The Allure of “Molecular Videos”: In situ Infrared Spectroscopy of Polymerization Processes

In situ infrared spectroscopy permits the real-time elucidation of polymerization kinetics and mechanisms for a wide range of polymerization processes. Both near- and mid-infrared spectroscopy have been utilized for the investigation of living ionic polymerizations. The essential determinations of pseudo first order polymerization kinetics that are consistent with living mechanisms and monomer conversion profiles facilitated the discovery of novel block and star copolymers. Real time determination of polymerization rates for stable free radical polymerizations of styrene and 2-vinylnaphthalene has provided significant insight regarding nitroxide mediation in free radical polymerization processes. Free radical alternating copolymerization of norbornenes with maleic anhydride was also investigated and In situ mid-infrared spectroscopic analysis has been vital for mechanistic studies of this copolymerization process. In addition, mid-infrared spectroscopy of melt phase polyester polymerizations via acidolysis allowed the identification of suitable polycondensation catalysts and the nature of the heterogeneous polymerization environment at 300 °C.
A. J. Pasquale, J. R. Lizotte, D. T. Williamson, T. E. Long

Real-time Fiber Optic Monitoring of Solution and Suspension Polymerization Processes

A novel fiber optic mid-IR probe equipped with an Attenuated Total Reflectance (ATR) and a transmission (TR) head was developed for the real-time monitoring of polymerization processes and ancillary reactions. The TR head can monitor very low concentrations (0.1 mmol/L). The probe was used to monitor both homogeneous living carbocationic isobutylene, styrene and p-tert/-butylstyrene homopolymerizations and sequential block copolymerizations, phenylacetylene polymerization, ring opening metathesis polymerization (ROMP) of 1,5- cyclooctadiene, and heterogeneous carbocationic isobutylene-isoprene copolymerizations by following the disappearance or appearance of IR bands characteristic of the monomers and polymers. Due to the sensitivity of the TR probe, overtone signals could also be monitored. Reactions related to the polymerization processes such as initiation, isomerization and complexation were also monitored. The novel monitoring methods gave insight into the mechanism and kinetics of the relevant processes, providing a powerful tool for macromolecular engineering.
Judit E. Puskas, Armin J. Michel, L. Bryan Brister, Eraclis Tzaras, Gregory Marr, Monika Hoffman, Karin Weiss

Investigation of High Temperature Isobutylene Polymerizations Utilizing Real-Time ATR-FTIR Spectroscopy

Mechanistic Considerations
We have conducted a series of kinetic investigations on controlled cationic isobutylene (IB) polymerizations at high temperature, i.e., -10°C, monitored using in situ ATR-FTIR spectroscopy (ReactIR 1000, ASI Applied Systems,Inc.). The polymerizations were carried out in chlorinated solvents with boron trichloride as Lewis acid catalyst, and in the presence of the Lewis base (LB)2,4-lutidine, 2,6-lutidine, or 2,6-di-tert-butylpyridine, or the common-ionpre cursor, tetra-n-butyl ammonium chloride. Our goal was to produce nearly monodisperse polyisobutylene (PIB) with precise control over molecular weight and macromolecular architecture, including end groups. FTIR revealed subtle details of the polymerization at low monomer conversion that would have proved difficult to detect through the use of traditional, gravimetric analysis. NMR characterization of aliquots revealed a reversible, chain end dehydrochlorination reaction, which occurs at low monomer conversions. In situ NMR experiments were conducted to further the mechanism of this reaction.
Casey D. Stokes, Robson F. Storey

Application of FT-NIR Spectroscopy for Monitoring the Kinetics of Living Polymerizations

Fourier-transform near infrared (FT-NIR) spectroscopy in combination with a fiber optic probe was successfully used to monitor the living cationic polymerization of isobutylene (IB) and the living anionic polymerization of ethylene oxide (EO) and butadiene (B). After the development of online monitoring techniques for the living anionic polymerizations of styrene (S) and isoprene in the near infrared range (NIR), methods were developed that allow to follow the polymerization of IB and S in the mid-infrared (MIR) range. It was believed that NIR could not be used for IB due to overlapping signals. In this paper we show that even in the NIR specific signals of the monomer can be used for monitoring conversion without using deconvolution methods in IB as well as EO and B polymerizations. In the case of EO a temperature dependent induction period was found with sec-butyllithium and the phosphazene base t-BuP4 as initiating system.
M. G. Lanzendörfer, H. Schmalz, V. Abetz, A. H. E. Müller

Spectroscopic Techniques for Continuous Monitoring of Emulsion Polymerization Reactions

Emulsion polymerization is a process of considerable industrial importance for which the development of adequate systems for real time monitoring continues to be an active area of research. Ultraviolet-visible, (UV-Vis), multi- wavelength transmission and reflectance spectroscopy are two suitable configurations for monitoring emulsion polymerization reactors. This paper presents the summary of a set of experimental results obtained applying these spectroscopic techniques to the analysis of polymer lattices and monomer colloidal dispersions. Continuously sampled multi-wavelength transmission measurements have been achieved using a patented parallel sampling and dilution system coupled with a miniaturized spectrometer and interpreted in terms of the particle size distribution and the chemical composition on the basis of Mie theory. in-line monitoring is achieved with reflection spectroscopy measurements. To assess the sensitivity of the latter, several reflectance configurations with commercially available probes have been tested. The analysis capabilities are demonstrated through the characterization polystyrene latex standards of known particle size distribution. On-line measurement techniques are demonstrated with the continuous monitoring of batch, and seeded emulsion polymerization reactions.
A. M. Cardenas-Valencia, V. Shastry, L. H. Garcia-Rubio

Kinetic Study of Photoinitiated Polymerization Reactions by Real-Time Infrared Spectroscopy

The photoinitiated polymerization of different types of multifunctional monomers has been investigated in situ by real-time infrared (RTIR) spectroscopy. Monomer conversion versus time curves have been recorded in systems where the liquid to solid phase change occurs within seconds. Some important kinetic parameters have been determined for such ultrafast reactions namely the kinetic chain length, the growth rate of polymer chains and the rate constants of the propagation and termination reactions. The influence of chemical and physical factors has been examined for both radical-type (acrylate) and cationic type (epoxide, vinyl ethe) polymerizations. RTIR spectroscopy proved particularly useful to study the polymerization of monomer mixtures as it allows one to monitor in situ the disappearance of each monomer.
Christian Decker, Frédéric Masson, Catherine Bianchi

In Situ NMR Monitoring of Living Radical Polymerization

Reaction Kinetics and Catalyst Evolution
Copper mediated living radical polymerization has been investigated by on- line 1H NMR spectroscopy. The reaction was followed by in-situ 1H NMR spectroscopy that results in accurate information on the polymerization. An example is given whereby living radical polymerizations is studied in the presence of ethylene glycol groups in monomer, initiator and solvent. Methyl ether poly (ethylene glycol) macroinitiators of various sizes are shown to initiate living polymerization of methacrylates, but exhibit poor initiator efficiency. The living radical polymerization of methyl ether poly(ethylene glycol) methacrylate macromonomers is demonstrated and the unusual high rate of polymerization observed is compared to that of the polymerizations with ethylene glycol containing macroinitiators. The 1H NMR study of the catalyst complex in the presence of ethylene glycol groups leads us to conclude that there is possible competitive co-ordination at the copper between ligand and ethylene glycol groups. This influences the Cu(I) / Cu(II) equilibrium, resulting in the high observed polymerization rate.
Sébastien Perrier, David M. Haddleton

Real-Time Monitoring of Isocyanate Chemistry using a Fiber-Optic FTIR Probe

Mid-IR fiber optics provides a convenient way to monitor many kinds of chemical reactions in situ and in real time. Isocyanate chemistry, both in the solution phase and in the form of urethane foams and binders, lends itself well to this approach. It is shown in this paper that the calibration of mid-IR fiber optics is simple and transferable between probes and probe heads, and that useful information about reaction rates and extent of cure can be obtained by simple peak area measurements in many cases.
Mary A. Thomson, Peter J. Melling

Real-Time Monitoring of the Components in PVC Melt Compounds Using NIR Spectroscopy During Extrusion

The composition of industrial PVC mixtures was monitored during extrusion on a twin screw extruder by in-line NIR spectroscopy. We investigated a PVC mixture with the following composition: PVC (76%), recycled PVC material (10%), impact-resistant modifier (5%), lubricant (4%), TiO2 (3%), CaCO3 (2%). We varied the content of the modifier from 4.1 to 6.5% and the content of the lubricant from 2.8 to 4.5%. We developed a PLS model with a calibration and a validation set. The standard errors of prediction (SEP) for the validation set are 0.18% for the modifier and 0.13% for the lubricant. After that, we made a real-time prediction for PVC mixtures not included in the calibration and validation with SEP's of 0.28% for the modifier and 0.26% for the lubricant. These accuracy’s are efficient enough for an industrial process control.
D. Fischer

In Situ Analysis of the Thermal Elimination Reaction in the Synthesis of Poly(p-phenylene vinylene)(PPV) and PPV Derivatives

In situ spectroscopy is an important tool to characterize polymers synthesized via a precursor route. Highly conjugated polymers such as poly(p-phenylene vinylene) (PPV) and PPV derivatives are commonly prepared from a precursor polymer because the final polymers are very insoluble and intractable. Preparation in the precursor form enables the polymer materials to be cast as films. The PPV polymers are obtained from the precursor forms using a thermal elimination reaction. The exact conditions of the reaction are important as they influence the properties of the resultant polymer. The details of this thermal elimination reaction have been analyzed using thermal gravimetric analysis (TGA) coupled with infrared analysis of the evolved gas products. In situ infrared spectroscopy of the precursor films during thermal conversion to the polymers has provided further details about the elimination reaction. We have characterized PPV synthesized from a tetrahydrothiophenium monomer (sulfonium precursor route) nd via the xanthate precursor route. PPV derivatives under study include poly (2,5- dimethoxy-p-phenylene vinylene) and poly(phenoxy phenylene vinylene).
Georgia A. Arbuckle-Keil, Yolanda Liszewski, James Wilking, Bing Hsieh

Carbonylation of Methanol over Supported Rhodium Catalysts

Kinetic and FT-IR Spectroscopic Investigations
Rhodium on different supports was found to be the most active and selective among supported transition metal catalysts for the vapor phase carbonylation of methanol and hydrocarboxylation of ethylene. High catalyst activities and good selectivities were obtained for the carbonylation of methanol over carbon supported rhodium catalysts in tubular reactor. A detailed parameter study of the carbonylation reaction, led to the experimental establishment of the kinetic equation. Fourier transform infrared (FT-IR) transmission spectroscopy was used to verify the validity of homogeneous methanol carbonylation mechanisms for two-phase (vapor-solid) applications. FT-IR spectra of adsorbed species obtained on RhCl3/Cab-O-Sil 5 catalyst treated successively with CO1 CH3I and CH3OH gave valuable information on the reaction mechanism. The absorption band appearing at 1717–1723 cm-1 after adsorption of CH3I on the catalyst surface is close to the acetyl C=O stretching freq (1708–1711 and 1723 cm’-1) obtained under homogeneous conditions, proving that the surface complex of type [Rh(CO)2AclxLv]’ (Ac = CH3CO-, L = OH- H20, SiO-, and x + y = 3) can be assumed as reaction intermediate, and the similarity of the mechanisms in both liquid and vapor-solid reaction conditions as well.
Jeno Bódis


Weitere Informationen