Dynamics and structure of benzyl ether dendritic macromolecules

Dendrimers are perfectly branched polymers that mimic the structure of trees. The purpose of this thesis was to study the solid state behavior of the dendrimers, their exact linear analogs, and dendrimer-based block copolymers. Understanding the solid state behavior of the dendritic macromolecules will lead to more applications that take advantage of the unique structure of the dendrimers.; Natural-abundance 13C solid-state NMR was used to study the dynamics of dendritic macromolecules through T₁, T_1ρ , and Dipolar Rotational Spin Echo (DRSE) experiments. From the combination of experiments, it was determined that the terminal ring units of the dendrimers were undergoing 180° ring flips. The most dramatic difference observed was between the crystalline and amorphous forms of the exact linear analog, where crystallinity greatly reduced the ring motion.; In order to understand the role dendrimers play in crystallizable block copolymers, we synthesized a library of well-defined block copolymers composed of benzyl ether dendrimer and poly(ethylene glycol). These copolymers have lower melting temperature and lower heat of fusion changes, as observed by modulated DSC, with increasing weight percentage of dendrimer content. Cross-polarized optical microscopy showed more nucleation events in the crystallization of the block copolymers as the dendrimer block(s) gets bigger. These changes in the degree of crystallinity imply that the dendrimer blocks are acting as nucleation events, and the increasing difficulty in accommodating the large dendrimers into the growing crystal. Finally, when benzyl ether dendrimer content exceeds 50–55% of the total copolymer the crystallization of PEG is severely impaired and the copolymer is amorphous.; Lastly, to separate the effects of the monomer from those of the structure of the block copolymers, we have synthesized benzyl ether dendrimer-linear architectural copolymers where the monomer units are the same. By modulated DSC we demonstrated that the crystallization of the linear block can be impeded by the globular block in much the same way as poly(ethylene glycol). Once again, the globular dendrimer disrupted the ability of the linear block to undergo crystallization when the dendrimer content is roughly 50% or above.