(York Univ.)

One of the many places in which lattice animals and their relatives
arise

is in the modelling of the physical properties of polymers. Most work

in this area has concentrated on polymers made up of a single type

of building block (or monomer), and many results (both exact and

numerical) are known.

Not all polymers are homogeneous, and many interesting polymers (such
as

DNA) are made up of two or more types of monomers with different

properties. There are far fewer exact results for models of inhomogeneous

polymers (or co-polymers) and many basic questions about their
behaviour

remain unanswered.

I will give a LIGHT introduction to some basic statistical mechanics
and

phase transitions, before proceeding onto some combinatorial models
of

polymers, some recent exact solutions, and the application of a little

number theory.