Off-campus UMass Amherst users: To download campus access dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.

Non-UMass Amherst users: Please talk to your librarian about requesting this dissertation through interlibrary loan.

Dissertations that have an embargo placed on them will not be available to anyone until the embargo expires.

Date of Award


Access Type

Open Access Dissertation

Document type


Degree Name

Doctor of Philosophy (PhD)

Degree Program

Polymer Science and Engineering


The mechanism of molecular weight limitation in the anionic polymerization of 1 , 3-cyclohexadiene has been studied using nmr and gas chromatographic techniques to detect and characterize benzene as a low molecular weight reaction byproduct of polymerization. This benzene is thought to occur by aromatization of cyclohexadienyl anions formed originally by abstraction of allylic protons from the monomer by the propagating polymeric carbanion. Such aromatization is part of a degradative chain transfer reaction sequence which limits molecular weight and conversion. Polycyclohexadiene endgroups were studied by ultraviolet spectroscopy which indicated that aromatization of the intermediate cyclohexadienyl anion occurred in complete preference to the alternative possibility of chain reinitiation by the cyclohexadienyl anion, a process leading to molecular weight, but not conversion, limitation. The latter alternative requires one cyclohexadienyl terminal group to be present for each polymer chain reinitiated; if present, such groups should be readily detectable in the ultraviolet spectrum but were not observed.