The synthesis of molecularly designed poly(propylene oxide) was accomplished by using aluminum porphyrin initiator/catalysts to prepare controlled molecular weights, narrow molecular weight distributions, topologies, and functionalities. Poly(propylene oxide) has been an important intermediate in macromolecular synthesis. However, lack of control via the conventional potassium hydroxide initiated synthetic method limits the applications of this polymer. In the synthesis of poly(propylene oxide) by using aluminum porphyrin catalyst system, polymerization occurred by exclusive cleavage of the epoxide methylene oxygen bond via nucleophilic attack. This type of ring opening polymerization yields to head to tail configuration with asymmetric monomers. The aluminum porphyrin allowed the synthesis of poly(propylene oxide) with a high molecular weight of ca. 100,000 g/mole and narrow molecular weight distribution, indicating a living nature of this system. A variety of reactive functional end groups, including both primary and secondary hydroxyl and amine could be incorporated in the polymer chains through the modification of the original catalyst with chain transfer agents such as bisphenol A or p-nitro phenol. These reagents also permitted very significant reductions in the required concentration of the catalyst. The well defined poly(propylene oxide)s allowed the systematic study of effects of functional end groups on thermal degradation behavior. Interestingly, aromatic amine and aromatic nitro end groups significantly improved the thermal stability, whereas the presence of unsaturated end groups caused very adverse effects. Some of the functionally terminated poly(propylene oxide)s were utilized in the synthesis of block and segmented copolymers to examine the well defined structures as characterized by spectroscopic analysis. The aluminum porphyrin catalyst system was also used to produce statistical copolymers of propylene oxide and allyl glycidyl ether or caprolactone. / Ph. D.