Making Initial configurations of polymers



 Hi:
 Is there any software (free or otherwise) out there which can build the
 initial chain of PMMA, given bond lengths and bond angles?
 Iam looking for a united atom model initial chain.
 And also once one chain is made , what is the best way to proceed to make
 the initial configuration of the system?( I usually make duplicates, put
 them all in the box together and apply some repulsive potential to introduce
 excluded volume but that takes quite a while)?
 Thanks
 Vani