This article presents an experimental study of the spontaneous thermal homopolymerization of methyl acrylate (MA) and n-butyl acrylate (nBA) in the absence of any known added initiators at 120 and 140 C in a batch reactor. The effects of the solvent type, oxygen level, and reaction temperature on the monomer conversion and polymer average molecular weights were investigated. Three solvents, dimethyl sulfoxide (DMSO; polar, aprotic), cyclohexanone (polar, aprotic), and xylene (nonpolar) were used. The spontaneous thermal polymerization of MA and nBA in DMSO resulted in a lower conversion and higher average molecular weights in comparison to polymerization in cyclohexanone and xylene under the same conditions. The highest final conversion of both monomers was obtained in cyclohexanone. The high polymerization rate in cyclohexanone was most likely due to an additional initiation mechanism where cyclohexanone complexed with the monomer to generate free radicals. Bubbling air through the mixture led to a higher monomer conversion during the early stage of the polymerization and a lower polymer average molecular weight in xylene and cyclohexanone; this indicated the existence of a distinct behavior between the air-and nitrogen-purged systems. Matrixassisted laser desorption/ionization time-of-flight analysis of the polymer samples taken from nitrogen-bubbled batches did not reveal fragments from initiating impurities. On the basis of the identified families of peaks, monomer self-initiation is suggested as the principal mode of initiation in the spontaneous thermal polymerization of MA and nBA at temperatures above 100 C.

MALDI-TOF mass spectrometry has been employed to examine polymers generated via acyclic diene metathesis (ADMET) polymerization using a ruthenium metathesis catalyst at 50 °C, a study which targets the analysis of ADMET polymers having amino acid pendant groups placed at specific positions along the polyolefin backbone. The MALDI spectra clearly delineate olefin isomerization chemistry which competes with propagation when catalyst 2 is employed, the result being loss of precise control of polymer structure. The distribution of peaks in the MALDI spectra matches the distribution pattern of gas chromatography (GC) peaks obtained for other ADMET polymers, leading to the following conclusions. First, structural isomerization and metathesis occur concurrently rather than in any kind of sequence. Second, the relative amount of isomerized chains produced dominates over the amount of nonisomerized products. In contrast to GC, MALDI analysis unequivocally identifies the mass of the oligomeric chains, allowing for increased confidence in assignment of the possible chain structures.

Mass spectrometry has become an essential tool in delineating the structural properties of a new series of amino acid functionalized acyclic diene metathesis (ADMET) polymers known as bioolefins. These measurements, coupled with the measurement of the polymers chemical and physical properties, assist in the determination of their utility as biomaterials. In the present study, a set of five polymers with different bulk size and electronic properties were chosen for structural analyses by MALDI-TOF, MALDI-FTICR, and DIOS-TOF. The obtained data show that due to the competing metathesis and isomerization during ADMET, depending on their structural properties, the olefins display different selectivity toward main metathesis or isomerized products.