Functional groups attached, motion

Functional groups attached to solvent-swollen polymer chains exhibit free rotational motion as indicated by electron spin resonance rotational correlation times 132-134) These studies using nitroxide spin labels covalently bound to polystyrene matrices indicated that the mobility of the substituent is a function of the cross-link density and degree of swelling. The rotational correlation time of nitroxide within 2% cross-linked beads was about 100 times shorter in dichloromethane or benzene than in ethanol, and 2-3 times longer than nitroxide bound to non-cross-linked polystyrene. The latter observation shows that the heterogeneous reaction involving 2% cross-linked polystyrene is 2-3 times slower than the same reaction in solution. 

Most organic molecules consist of hydrocarbon skeletons with functional groups attached. We began a study of these skeletons with a discussion of the names and structures of alkanes, hydrocarbons that lack fnnctional groups. We presented concepts of molecular motion and their associated energy changes. These ideas will underlie the behavior of molecules of all types, and we will retnm to them frequently. 

Targeted attachment of molecules and/or functional groups to nanostructures Demonstrated autonomous motion in nanoparticles... 

We have so far assumed that the nuclei are at rest in fixed positions with respect to each other. When molecular motion, — which in polymers will be chiefly group rotation —, takes place, the variables in equation (2) become functions of time1. If we assume for our present discussion that r is constant and only 6 varies with time (as would be true, for example, for the interaction of protons attached to the same carbon atom or to the same benzene ring), then the time averaged local field will be given... 

---