ABSTRACT
In theta solvents, excluded volume effects vanish and flexible molecular chains behave as phantom chains (1). The characteristic ratio Cn — (r2)0/A72, where (r2)0 is the mean square end-to-end distance of a
chain with N bonds each of average length /, depends on short-range inter actions and consequently is conditioned by the chemical structure. Each molecular chain on average occupies in these conditions a spherical region of radius R = [(r2)0]l/2. In good solvents the net interaction between the polymer segments is repulsive and the excluded volume parameter v is posi tive and large. In these conditions, the radius of the coil (or the spherical domain of the chains) increases. In general, R ~ N v, the value of v being 0.6 in good solvents (1,2).
