The technique of high resolution solid state carbon-13 NMR, achieved with magic angle spinning (MAS) and high power 13c-1H dipolar decoupling and cross polarization, was applied to a number of multicomponent polymer systems. Specific problems which were addressed are: (1) the nature of domain structure and molecular motion of two thermoplastic elastomer systems, including a series of styrene isoprene-styrene linear triblock copolymers (SIS’s) of various compositions, molecular weights and sample histories, and a poly(ester)- urethane based on poly(1,4-butylene adipate) and 4,4¹ -diphenylmethane diisocyanate, (2) the compatibility at the molecular level of polymer blends containing poly{vinylidene fluoride) (PVF2), including solution and mechanical blends with poly{methyl methacrylate) {PMMA}, poly(vinyl acetate} (PVAc) and poly(vinyl methyl ether) (PVME). For the thermoplastic copolymers, higher degree of phase separation between the hard and soft domains was indicated by two facts: First, ¹³C resonances of either domain could be selectively observed with different experimental conditions. Second, there was a one-component, first-order, spin-lattice relaxation behavior of the ¹³C nuclei in the soft domains. For the SIS copolymers, results of T₁ and T₂* determinations (beth with MAS) suggest that molecular motion, in terms of frequency, was independent of composition, molecular weight and selective casting solvents. However, from static spectra, molecular motion of the isoprene blocks was found to be more anisotropic for the samples cast from a poor solvent for polyisoprene {MEK) in contrast to samples cast from a good solvent of polyisoprene (hexane). For the polymer blends of poly(vinylidene fluoride), the level of molecular intermixing was reflected through the degree of ¹³C NMR signal attenuations of the non-PVF₂ polymers. These attenuations are mainly due to undecoupled intermolecular ¹³C-¹⁹F dipolar interactions. With a MAS rate of 2KHz, resolution of the intimacy of mixing between the two constituent polymers in the blends was estimated to be in the range of 3 to 4 angstroms. Varying degrees of NMR signal attenuations among the individual chemically different carbons of a polymer support a postulation of weak intermolecular 'acid-base' association between the acidic protons of PVF₂ and basic carbonyl groups in the case of both the PMMA and PVAc. / Ph. D.