Polymer Degradation Studies

Thermal degradation studies have been carried out by MALDI and NMR on SEC 

Chen and co-workers [6] used GPC-MALDI-ToF-MS to determine the nature of end-group blue light emitting copolymers and confirmed the usefulness of such techniques for synthetic polymer structure analysis. The results showed that these synthetic polymers possessed various end groups and even contained macrocycles. 

Tillier and co-workers [49] carried out structural molecular weight and end-group studies on copolyesters of polyethylene terephthalate (PET) and e-caprolactone using GEC and MALDI-ToF-MS. The measurement of molar mass by MALDI-ToF-MS was shown to be inapplicable in the case of polymers exhibiting a polydispersivity index (1 ), greater than 1.10 such as PET and others. 

Hydroxy and carboxy end-groups, and oxydiethylene units are already present in the initial PEG and are obviously present in final copolyester. The vinyl ester function of the E series can be formed by a degradation reaction during heating (Equation 5.7)  

It is interesting to note that, although vinyl ester end-groups cannot be detected in the H-NMR spectra due to their very low concentration, vinyl ester-terminated macromolecules are very easily observed in the MALDI-ToF mass spectra. 

DTA used in conjunction with mass spectrometry has been used to measure energy changes caused by phase transformations in polymers [16-19]. Fernandez [19] used DTA to determine the activation energy of the degradation of styrene-nitrostyrene copolymers. This technique in conjunction with TGA has also been used to examine the influence of allyl glycidylester in its copolymer with dimethylaminoethyl methacrylate on the thermo-oxidative degradation of the copolymer [20]. 

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TG-DTA Characterisation of carbon black [149], flammability evaluation [64], polymer degradation studies [65], ageing studies [70-72], product control [77, 81], combustion performance [83], safety evaluation [83], antioxidation activity [68], pyrolysis of rubbers [82], thermal stability [67, 69, 76, 77], interfacial junctions in viscoelastic composites [78], weathering [72], vulcanisation [73], oxidative behaviour [79], materials evaluation [80], failure analyses [81],... 

Bodzay, B., Marosfoi, B. B., Igricz, T., Bocz, K., and Marosi, G. 2009. Polymer degradation studies using Laser pyrolysis-FTIR microanalysis. Journal of Analytical and Applied Pyrolysis 85 313-320. 

Pyrolysis-Gas Chromatography-Mass Spectrometry Techniques for Polymer Degradation Studies... 

These two examples demonstrate both the value of FTIR-EGA for studying both mechanical and thermal degradation and the potential for erroneous results arising from the effects of mechanical degradation on subsequent polymer degradation studies. 

Because of the more practical aspect of polymer stability in the numerous proposed uses of intrinsically conducting polymers, including polyaniline and its relatives, and the more fimdamental interest in the chemistry of processes that change the chemical identity and various solid state properties of the polymers, degradation studies are warranted. These studies focussed initially on the mere rate of degradation (which may be of very practical interest). Wth purely electrochemical measiuements, Kobayashi et al. [512,513] showed that the two peaks in qrclic voltammograms of PANI di-... 

Gel permeation chromatography (GPC), particularly in its multidetection version, is now a mature and well-accepted technique for MW characterization. The capability of GPC to determine changes throughout the MWD, in addition to the different MW averages, opens new possibilities for polymer degradation studies. The scission probability as a function of position along the molecular chain, for instance, could be inferred from the MWD of degraded polymer [12). 

Another technique of great importance in polymer degradation studies is one based on pyrolysis followed by a detailed examination of decomposition products by gas chromatography and mass spectrometry (Chapters 1 and 14). Such studies can provide a detailed picture of the degradation process. 

MS represent a well-established and traditionally used method to examine polymer degradation. Several classical methods have proved very successful at studying polymer degradation mechanisms (e.g. IR and UV/visible spectroscopies, NMR, SEC). This chapter wants to answer the question What does mass spectrometry have to offer additionally in polymer degradation studies ... 

Concentration profiles were measured using microtomed slices and FTIR microspectroscopy.Similar methods are used for determination of other additives in polymers (e.g., UV stabilizers in polymer degradation studies). Further studies using this method should provide data, which confirm that slicing conditions (especially temperature) do not introduce error. This method, if developed to its full capabilities, has full potential to produce data not affected by conditions of measurement. 

Fig. 5.47—Pressure vs. percent core length for polymer-degradation studies.

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