The research presented herein, addresses key issues of homogeneous Group 4 single-site coordination polymerization (CP) catalysts for the production of polyolefins and polyolefin-like materials. Specifically, this research moves beyond the one-catalyst one-material' paradigm to afford an array of amorphous polyolefin materials with high Tg from a single monomer. The multitude of microstructurally distinct materials available from a single starting olefin is attributed to stereoengineering: a technique, which reduces stereoblock length in a highly controlled fashion while retaining regioselectivity. The precatalysts employed in this work are previously reported Group 4 CS-symmetric or C1-symmetric pentamethylmonocyclopentadienyl amidinate complexes with the general formula {(η5-C5R5)M[N(R1)C(R2)N(R3)]-(Me2)} (M = Zr, Hf, R = alkyl, Me = methyl), which are activated by cocatalysts such as N,N-dimethylanilinium tetrakis(pentafluorophenyl)-borate ([PhNMe2H][B(C6F5)4]). Living CP of 1,6-heptadiene and stereoengineering of the subsequent poly(methylenecycloalkane)s with the above complexes reveal a variety of stereochemically controlled, yet amorphous, poly(methylene-1,3-cyclohexane) (PMCH) materials with Tg values as high as 101 °C. Similar polymerization techniques have been applied, for the first time with Sita group complexes, towards the CP of the heteroatom-olefins such as diallyldimethylsilane (DAS). The controlled CP and stereoengineering of DAS resulted in amorphous poly(3,5-methylene-1,1-dimethyl-1-silacyclohexane) materials with Tg values as high as 127 °C. The living character and tunable stereoblock lengths of PMCH provided the opportunity to explore the high Tg polyolefin as the hard' domain (A segment) in pure polyolefin AB block copolymers, BCPs. Specifically, amorphous AB diblock copolymers were synthesized using poly(1-hexene) as the soft' B block to afford a series of microphase-separated morphologies without the deleterious effects of crystallization. Microphase-separated morphologies for were also observed for ABA triblock copolymers using atactic polypropylene as the soft' segment (B block) and primary component. The latter BCPs were found to exhibit thermoplastic elastomeric properties. The work described in this document provides a foundation for the further expansion of the currently-limited pool of monomers to include heteroatom-olefins for CP with the aforementioned Group 4 transition metal complexes. Moreover, the formation of well-defined pure polyolefin block copolymers serve as an important contribution to the development of new polyolefin architectures.