Dense star polymers having two dimensional molecular diameter

A dense star polymer which is a dendrimer represented by the formula:

• wherein .circle.I is a polyfunctional core, Z.sub.c is a functional group bonded to the core and a X group of the first generation, N.sub.c is the number of functional group bonded to the core, X.sup.i is a monofunctional tail of a repeating unit Y.sup.i of the i generation which is bonded to Y.sup.i and a Z group of the i-1 generation, Z.sup.i is a functional group bonded to Y.sup.i and a X group of the i+1 generation, N.sup.i is a number of at least 2 which corresponds to the multiplicity of the polyfunctional head of Y.sup.i, is the product function, N.sup.i-1 is a number of at least 2 which corresponds to the multiplicity of the polyfunctional head of Y.sup.i-1 wherein Y.sup.i-1 is a repeating unit of the Y.sup.i-1 generation, X.sup.t is the monofunctional tail of a repeating unit Y.sup.t of the terminal generation, Z.sup.t is a terminating group bonded to Y.sup.t, N.sup.t is zero or a number which corresponds to the number of Z.sup.t groups bonded to one Y.sup.t group, i represents a number of a particular generation in a series from 1 to a number from 1 to t-1, provided that (1) all X.sup.i Y.sup.i (Z.sup.i).sub.N i are the same within a generation and may be the same or different in different generations and (2) all X.sup.t Y.sup.t (Z.sup.t).sub.N t of the terminal generation are the same.