An inert non-crystalline cryoprotectant oil was needed as a non-incoherent scattering matrix for neutron studies of solvent containing crystalline materials. This led us to prepare perdeuterated polyethylpropylene (PEP) with a molar mass around 1100 g/mol. On route to this material an improved method for the preparation of isoprene-d(8) starting from calcium carbide and acetone-d(6) was devised. Subsequent anionic polymerization using t-butyl lithium as initiator resulted in an oligomeric perdeuterated polyisoprene (PI) with an average chain length of approx. 15 monomer units and Mw/Mn: 1.1. This polymer was deuterated with D-2 and Pd/C (10%) in cyclohexane to yield the desired perdeutero polymer (PEP-d). The polymer fulfill the important properties that it does not crystallize at low temperature and has a low neutron scattering efficiency.