Abstract
Thermal degradation behavior of polymers derived from monomers with a polar group was investigated by thermogravimetry interfaced to mass spectrometry (TG-MS) to see its applicability to the investigation on thermal degradations of polymers. The polymers studied were poly(methyl methacrylate) (PMMA), poly(methyl acrylate) (PMA), and polyacrylamide (PAM). Decomposition products of PMMA consist exclusively of methyl methacrylate monomers that were formed through random scissions of main chains followed by depolymerization. Initiation temperature of the random scission of PMMA was strongly influenced by its micro-structures, such as head-to-head and head-to-tail linkages and vinyl terminated chain ends, which suggests that subtle difference of polymer structures can be elucidated by TG-MS studies. This could be the characteristic feature of TG-MS that differentiates from other analytical method. During thermal degradation of PMA, unbuttoning reactions, some portion of unzipping reactions, and random scission of main and side chains occurred to afford a wide variety of products including monomers, oligomers, and some other unknown substances. Intra- and intermolecular imidation reactions between the side chain amide groups proceeded to yield glutarimide rings through main chains and crosslinking, respectively, during the initial stage of heat-treatments of PAM. Then, various low molecular weight compounds such as glutarimide and its analogues were formed by the decomposition on further heat-treatment at elevated temperature. The thermal degradation mechanism of these polymers was discussed in terms of the ceiling temperature of the monomers from which these polymers were derived. The results obtained were in good accordance with those reported using other analytical methods, which indicates that TG-MS could be one of the useful techniques for the investigation of thermal degradations of polymers.
