Date of Award
Master of Arts
Dr. George Lowry
Masters Thesis-Open Access
The heat of polymerization (∆Hp) of α-methylstyrene (AMS) has been a source of study for many years. The structure of AMS is shown in Figure 1.
The first quantitative work was done by Roberts and Jessup.1 Their values were more positive than those theoretically calculated by Flory2 and compared with ∆Hp data of other systems. This was not totally unexpected and could be satisfactorily explained on the basis of steric hindrance and loss of resonance energy of conjugation. This steric hindrance arose from "head-to-tail" polymerization of the 1, 1-disubstituted ethylene structure.3 Their data also displayed a ∆Hp dependence on the degree of polymerization (DP). Roberts and Jessup's explanation that the DP was the predominant variable in the functionality of ∆Hp was not completely accepted. Since Roberts and Jessup first published their work in 1951, there have been several reports in the literature with new values for ∆Hp and new explanations for the apparent DP p dependence.4, 5, 6, 7, 8 There are discrepancies in the more recently reported ∆Hp data and, in general, the differences were not within the range of experimental error. All of these studies were either incomplete, conjectural or included a variety of approximations and corrections.
The original outline for this thesis proposed an experimental method for finding the ∆Hp of oligomeric α-methylstyrene (AMS) without applying major corrections. The plan of attack called for synthesizing very low molecular weight oligomers and analyzing the monodisperse samples. By analyzing only low molecular weight monodisperse polymers, assumptions involving molecular weight distribution and glass transition contributions would be unnecessary. However, the unavailability of a preparative gel permeation chromatography (GPC) instrument for our use prevented separation of the oligomer into the pure monodisperse samples. Therefore, analytical GPC was substituted which dictated that corrections involving the molecular weight distribution would have to be applied to the ∆Hp data.
Humbert, "Heats of Combustion of Alpha-Methylstyrene Oligomers" (1972). Master's Theses. 4371.