Making Initial configurations of polymers

 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)?