Techniques are described for use by a pacemaker or implantable cardioverterdefibrillator or other implantable medical device. It provides and uses a precursor polymer of formula below: in which n is a whole number, R1 and R2, identical or different, represent independently an alkyl group, and R3 represents an amino group, a hydrogen atom, an alkyl, a cycloalkyl or a boryl. A thermal fluid system from said engine is configured to circulate fluid, which may be engine coolant, through the second volume and transfer heat from the fluid through the first closed chamber and vaporize said liquid fuel. A low temperature heating circuit is used for protection in cold conditions.